Foramina of Middle Cranial Fossa

Optic Canal	CN II, ophthalmic artery, central retinal vein
Superior Orbital Fissure	CN III, IV, VI, ophthalmic vein
Foramen Rotundum	CN V2 ( maxillary br.)
Foramen Ovale	CN V3 (mandibular br.)
Foramen Spinosum	middle meningeal artery
Foramen Lacerum	nothing

* all structures pass through sphenoid bone

Foramina of Posterior Cranial Fossa

Internal auditory meatus	CN VII, VIII
Jugular foramen	CN IX, X, XI, jugular vein
Hypoglossal canal	CN XII
Foramen magnum	spinal root of CN XI, brain stem , vertebral artery

* all structures pass through temporal & occipital bone

Passage of Cranial Nerves

CN I	Cribriform plate
CN II	Optic canal
CN III, IV, V1, VI	Superior orbital fissure
CN V2	Foramen rotundum
CN V3	Foramen ovale
CN VII, VIII	Internal auditory meatus
CN IX, X, XI	Jugular foramen

Mastication muscles

3 muscles to close jaw : masseter, temporalis, medial pterygoid
1 muscle to open jaw : lateral pterygoid
All are innervated by CN V3

3 Structures in Carotid sheath

V : internal jugular vein ( lateral )
A : common carotid artery ( medial )
N : vagus nerve ( posterior )

Diaphragm
Embryology	septum transversum pleutoperitoneal folds dorsal mesentery of esophagus body wall
Passage	At T 8	Inferior vena cava
	At T10	esophagus, vagus
	At T12	aorta, thoracic duct, azygous vein
Innervation	C3,4,5 : Referred pain to shoulder

8 Layers of Abdomianl wall	Spermatic cord
Skin
Fascia ( Camper's & Scarpa's )	Dartos muscle & Colles' fascia
Ext. Oblique muscles	Ext. spermatic fascia & superficial inguinal ring
Int. Oblique muscles	Cremaster muscle & conjoint tendon
Transeverse abdominalis	No contribution except to conjoint tendon
Transverse facisa	Internal spermatic fascia & deep inguinal ring
Extraperitoneal fat
Peritoneum	Tunica vaginalis testis & processus vaginalis

Inguinal Hernia
Direct Hernia	Protrude through inguinal ( Hasselbach's) triangle Bulge directly through abdominal wall medial to inf. epigastric artery Goes through the superficial inguinal ring only
Indirect Hernia	Due to failure of closure of processus vaginalis Enters deep inguinal ring lateral to inf. epigastric artery Goes through deep & superficial inguinal ring, and into scrotum
Hasselbach's triangle	Inguinal ligament Inferior epigastric artery Lateral border of rectus abdominalis

Clinical Landmarks
Ischial spine	Pudendal nerve block
McBurney's point	Appendix 2/3 of the way between umblicus & Superior iliac spine
Iliac crest	Lumbar pucture

Hand Muscle : Thenar - Hypothenar
Thenar	Opponens pollicis Abductor pollicis brevis Flexor pollicis brevis
Hypothenar	Opponens digiti minimi Abductor digiti minimi Flexor digiti minimi

Contents of femoral sheath

lateral to medial

femoral nerve, artery, vein, lymphatics

femoral nerve lies outside femoral sheath

femoral canal contains deep inguinal lymph node

Unhappy triad of Knee injury

Common for football injury ( by clipping from the side )
Injury of medial collateral ligament, medial meniscus, anterior cruciate ligament

Anterior Drawer sign : indicate tearing of ant. crucate ligament

Muscle name with Palate

Innervation by Vagus nerve , but tensor veli palatini --> CN V3

KLM sounds
Kuh- kuh-kuh	test palatal elevation	vagus nerve
La- la- la	test tongue	hypoglossal nerve
Mi- mi- mi	test lips	facial nerve

Muscle name with ~Glossus

Innervation of hypoglossal nerve, but palatoglossus --> vagal nerve

Cervical rib

An embriological defect ; can compress subcalvian artery and inferior trunk of branchial plexus (C8, T1), resulting in thoracic outlet syndrome

Atrophy of the thenar and hypothenar eminences
Atrophy of the interosseous muscle
Sensory deficits on the medial side of the forearm and hand
Disappearance of the radial pulse upon moving the head toward the opposite side

Medial nerve injury
Motor deficit	no loss of power in any of arm muscle loss of forearm pronation, wrist, and finger flexion several thumb movement, thenar atrophy
Sensory deficit	loss of sense in lateral palm, over thumb, radial 2 finger

Ulnar nerve injury
Motor deficit	impaired wrist flexion & adduction impaired adduction of thumb & ulnar 2 fingers

Radial nerve injury
Motor deficit	triceps brachi ( triceps reflex ) brachioradialis ( brachioradialis reflex ) extensor carpi radialis longus
Sensory deficit	posterior brachial cutaneous dorsal antebrachial cutaneous

Axillary nerve injury
Motor deficit	loss of deltoid action

Musculocutaneous nerve injury

Motor deficit

loss of function of coracobrachialis, biceps & brachialis muscle ( biceps reflex )

affect flextion at the shoulder (coracobrachialis & biceps brachii)
flexion at elbow (brachialis , biceps brachii )
supination of forearm ( biceps brachii )

Sensory deficit

below elbow, continue as lateral cutaneous nerve of forearm
no distribution to hand

Erb- Duchenne palsy
Cause	Traction or tear of the superior trunk of the brachial plexus (C5 & C6 roots) ; follows falling down on shoulder or trauma during delivery
Findings	limb hangs by side ( paralysis of abductors ) medially rotated ( paralysis of lateral rotators ) forearm is pronated ( loss of biceps )

Nerve injury in lower limbs
Common peroneal nerve	loss of dorsiflexion ( foot drop )
Tibial nerve	loss of plantar flexion
Femoral nerve	loss of knee jerk
Obturator nerve	loss of hip adduction

Pectinate line
Above the line	internal hekmorrhoid ( not painful ), adenocarcinoma visceral innervation, blood supply, and lymphatic drainage
Below the line	external hemorrhoid ( painful ), squamous cell ca, Somatic innervation, blood supply & lymphatic drainage

Portal - systemic anastomosis
Esophageal varices	left gastric --- azygous
Hemorrhoid	superior --- middle / inferior rectal
Caput medusae	paraumbilical --- inferior epigastric

Recurrent laryngeal nerve
Supplies all intrinsic muscles of the larynx except the cricothyroid muscle.
Left recurrent laryngeal nerve	wraps around the aortic arch and the ligamentum arteriosum
Right recurrent laryngeal nerve	wraps around right subclavian artery.
Damages results in hoarseness as a complication of thyroid surgery.

Lung relations

Right lung has three lobes. Left has two lobes and Lingula ( homologue of right middle lobe ).
Right lung more common site are for inhaled foreign body owing to less acute angle of right main stem bronchus

Relation of pulmonary artery to the bronchus at each lung hilus : RALS ( Right-Anteior, Left-Superior )

Bronchial & Pulmonary artery run with airways in the center, veins and lymphatics drain along the border

Course of ureter

pass under artery & under ductus deferens

Autonomic innervation of penis
Erection	by parasympathetic nervous system ( Point )
Emission	by sympathetic innervation ( Shoot )
Ejaculation	by somatic & visceral nerves

Ligaments of the uterus

pubocervical, transverse cervical ( cardinal ), sacrocervical ligaments, round ligament of uterus, round ligament of ovary
round ligament of uterus : homologous to gubernaculum testis; run from labia majora to uterus
round ligament of ovary : run from uterus to ovary
broad ligament contains the round ligaments of the uterus, the round ligaments of the ovary, the uterine tubes, the epoophoron and multiple lymphatic vessels & nerve fibers

NEUROANATOMY REVIEW

Special stain

Eosin	Acidic, anionic dye. binding to acidophilic tissue ( protein with high content of basic amino acid , high mitochondria ),Stain smooth ER
Hematoxylin	Basic, cationic dye, binding to basophilic nucleic acid ( rough ER has high RNA content --> basophilic )
Methylene blue, Toluidine blue	Stain DNA, RNA, ribosome, heparin-containing granule
PAS	Stain glycogen & basement membrane
Silver	Stain neuron process (Alzheimer's plaque, tangle) & reticular fibers, Also Pneumocystis carinii & Legionella
Congo red	Amyloid ( apple green birefringence under polarized light )
Prussian blue	Iron ( memory : Russia --> iron curtain )

RER

the site of synthesis of secretory protein, append N-linked oligosaccharide to many protein.
Mucus-secreting goblet cell of small intestine and antibody- secreting plasma cells are rich in RER.

SER

the site of synthesis of steroid & secretion, detoxication site of drug,toxic substance.
Liver hepatocytes and steroid hormone producing cells of the adrenal cortex are rich in SER.
EM view : lipid droplet appear as spherical inclusion without limiting membrane.

Functions of Golgi body

Distribution center of proteins and lipids from ER to the plasma membrane, lysosomes, and secretory vesicles.
Modification of A.A & Protein

Modified N-oligosaccharides on asparagine
Adds O-oligosaccharides to serine and threonine residues
Addition of mannose - 6- phosphate to specific lysosomal proteins, which targets the protein to the lysosome.

Proteoglycan assembly from proteoglycan core proteins
Sulfatation of sugars in proteoglycans and selected tyrosine on proteins

TYPES OF COLLAGEN

Type 1 : bone, tendon, skin, fascia, late wound repair, cornea
Type 2 : cartilage ( including hyaline ), vitreous body, nucleus pulposis
Type 3 ( reticulin ) : skin, vessel, uterous, fetal tissue, granualtion tissue
Type 4 : basement membrane or basal lamina

Nissl Bodies

Nissl bodies in neurons = rough ER
Not found in axon or axon hillock
Synthesize enzymes ( e.g. cholline acetate transferase ) & neuropeptides

Peripheral nerve coats
Endoneurium	wrap single nerve fiber
Perineurium	permeability barrier - surround fascicle of nerve fiber must be coapted in microsurgery for limb replantation
Epineurium	dense connective tissue - surround entire nerve ( contain vessel )

Nerve endings
Meissner's corpuscles	small & encapsulated sensory receptor in skin of palm, sole, digit light discriminatory touch in hairless skin
Pacinian corpuscles	large & encapsulated sensory receptor in deep layer of skin at ligament, joint capsule, serous membrane, mesentery pressure, coarse touch, vibration, tension

Supportive cell of CNS & PNS
Astrocyte	physical support, repair, K⁺metabolism
Microglia	phagocytosis
Oligodendroglia	synthesis of central myelin
Schwann cell	synthesis of peripheral myelin
Ependymal cell	inner lining of ventricle

Microglia

CNS phagocytes.
Mesodermal origin.
Not readily discernible in Nissel stain
Have small irregular nuclei & relatively little cytoplasm
In tissue damage, transform into large ameboid phagocytic cell
HIV infected microglia fuse to form multinucleated giant cell in the CNS

Oligodendroglia

Function to myelinate multiple CNS axons.
In Nissel stain, appear as small nuclei with dark chromatin & little cytoplasm
Predominat type of giant cell in White matter
These cells are destroyed Multiple sclerosis

Schwann cells

Function to myelinate PNS axons.
Unlike oligodendroglia, a single Schwann cell myelinates only PNS axon
Schwann cells promote axonal regeneration

Type of axocrine gland
Apocrine	secretion with loss of cytoplasm from apical side ( e.g., sweet )
Eccrine /merocrine	by exocytosis ( e.g., protein )
Holocrine	secretion with destruction of cell ( e.g. sebaceous gland )

Epidermis layer ( from base to surface )

Stratum Germinativum
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum

Choroid

1. Pigmented layer between retina and sclera
2. Blood supply to retina, contains dark pigment which absorbs stray light pass by retina

Cones	Rods
Cones are for Color and their outer segment are continous with the plasma membrane, unlike rods. Cones have a sharp tip ( acuity )	have Rhodopsin, have a high sensitivity due to multipla rods synapsing on the bipolar cell ( convergence)
Bright & acute vision ( color, concentrated in fovea )	Night vision ( no color ; many more than cones ; none in the fovea )
Comprise inner & outer segments connected by -- modofied cilium : Outer segment disks continous with plasma membrane	Comprise inner & outer segment connected by -- modified cilium : Outer segment disks not continous with plasma membrane
Contain idopsin pigment, red green blue specific	contain rhodopsin

Inner Ear
Perilymph	similar to ECF, Na+ rich, exists in osseous labyrinth
Endolymph	similar to ICF, K+ rich, exists in membranous labyrinth made by stria vascularis

Thymus

Site of T-cell maturation. Encapsulated. From epithelium of 3rd branchial pouches. Lymphocytes of mesenchymal origin. Cortex is dense with immature T cells ; medulla is pale with mature
T cells and epithelial reticular cells and contains Hassall's corpuscles.
Positive and negative selection occurs at the corticomedullary junction

Lymph Node
A secondary lymphoid organ that has many afferents, one or more efferents. Encapsulated. With trabeculae. Functions are nonspecific filtration by macro phages, storage / proliferation of B and T cells, Ab products
Follicle	Site of B-cell localization and proliferation In outer cortex. primary folllicles are dense and dormant. secondary follicles have pale central germinal central and are active.
Medulla	Consists of medullary cords ( closely packed lymphocytes and plasma cells) and medullary sinuses communicate with efferent lymphatics and contains reticular cells and macrophages.
Paracortex	Houses T cells. Region of cortex between follicles and medulla. Contains high endothelial venules through which T and B cells enter from blood. In an extreme cellular immature response, paracortex becomes greatly enlarged. Not well developed in patients with DiGeorge's syndrome

ENTERIC PLEXUS

Myenteric plexus

Auerbach's plexus, some parasympathetic terminal effector neuron ;
exists between inner & outer layer of GI tract smooth muscle ; controls motility

Submucosal plexus

Meissner's plexus, some parasymphathetic terminal effector neuron; exists between mucosa and inner layer of GI tract smooth muscle ; controls secretions

Brunner's gland

secrete Alklaine mucus . Located in submucosa of duodenum
( the only GI submucosal gland ) doudenal ulcers cause hypertrophy

Peyer's patch

Unencapsulated lymphoid tissue found in lamina propria and submucosa of intestine
Covered by single layer of cuboidal enterocytes. ( no globlet celll ) with specialized M cells interspersed.
M cells take up antigen.
Stimulated B cells leave Peyer's patch and travel through lymph and blood to lamina propria of intestinem where they differentiate to Ig A- secreting plasma cells.
Ig A receives protective secretory piece, then is transported across epithelium to gut to deal with intraluminal Ag

Sinusoids of liver

Irregular ' capillaries ' with round pores 100-200 nm in diameter.
No basement membrane. Allows macromolecules of plasma full access to surface of liver cells through space of Disse

Sinusoids of spleen

Long, vascular channels in red pulp. With fenestrated ' barrel hoop ' basement membrane.
Macrophages found nearby.
Red pulp --> T cell, White pulp --> B cell

Pancreas endocrine celll types

Islets of Langerhans : collections of endocrine cells
( most numerous in tail of pancreas )
¥á = glicagon, ¥â = insulin, ¥ä = somatostatin.

Airway cells

Cliliated cells extend to the respiratory branchioles ; goblet cells extend only to the terminal bronchioles

Type I cell ( 97% of alveolar surface ) line the alveoli

Type II cell ( 3% ) secrete pulmonary surfactant ( dipalmitoylphosphatidylcholine )
--> lowers the alveolar surface tension

* lecithin : spingomyelin ratio > 1.5 --> fetal lung maturation

Glomerular basement membrane

Formed from fused endothelial & podocyte basement membrane
Coated with negatively charged heparan sulfate
Responsible for actual filtration of plasma according to net charge & size
In Nephrotic syndrome, negative charge is lost ( e.g., plasma protein is lost)

Juxtaglomerular apparatus

Juxta = close by , JGA is defined GFR via renin-angiotensin system
JGA = JG cell ( modified smooth muscle of afferent arteriole ) + macula densa (Na+ sensor, part of distal convoluted tubule )
JG cell lower renal blood pressure , secrete renin or erythropoietin when Na+ delivery is decreased through distal tubule

Posterior pituitary ( neurohypophysis )

Receive hypothalamic projection from supraoptic ( ADH ) & paraventricular (Oxytocin) nuclei
( oxys = quick , tocos = birth )

Adrenal cortex

zone G ( glomerulosa ) ; mineral corticoid ( aldosterone )
zone F ( fasciculate ) ; glucorticoid ( cortisol )
zone R ( reticularis ) ; cortisol & some sex hormone ( androgene , DHEA )

Adrenal medulla

secretes Epi & NE from Chromaffin cell
In Adults, most common adrenal medulla tumor is Pheochromocytoma
In Childs, most common adrenal medulla tumor is Neuroblastoma

HISTOLOGY REVIEW

Spermatogenesis

Full development takes 2 months.
Spermatogenesis in semineferous tubule.
Spermatogonia --> primary spermatocyte --> 2ndary spermatocyte -->
spermatid ( spermiogenesis ) --> spermatozoa
acrosome : from Golgi apparatus
flagellum (tail ) : from one of the centriole
middle piece (neck) : has mitochondria

Meiosis & Ovulation

Primary oocyte starts meiosis during fetal life, completes meiosis I before ovulation
Meiosis I is arrested in prophase for years until ovulation
Meiosis II is arrested in metaphase until fertilization

Rule of 2's for 2nd week of development

2 germ layers ( bilaminar disc ) : epiblast / hypoblast
2 cavities ( amniotic, yolk sac )
2 placental components ( cytotrophoblast, syncytiotrophoblast )

Embryonic derivatives

Ectoderm	epidermis (including hair, nail ), nervous system, adrenal medulla, pituitary
Mesoderm	connective tissue, muscle, bone, cardiovascular organ, lymphatics, urogenital structure, serous lining of body cavities, spleen,adrenal cortex
Endoderm	gut tube epithelium & derivatives ( Ex : lung, pancreas )
Notocord	nucleus pulposus of the intervertebral disc

Neural crest derivatives

ANS, dorsal root ganglia, melanocyte, chromaffin cell of adrenal medulla,
enterochromaffin cell, pia, celiac ganglia, Schwann cell, odontoblast,
parafollicular cell of thyroid ( * Dura ---> mesodermal origin )

Amniotic fluid abnormalities

Polyhydramnios	> 1.5- 2 liter of amniotic fliud associated with esophageal / duodenal atresia / anencephaly
Oligohydramnios	< 0.5 liter associated with bilateral renal agenesis or posterior urethral valve ( in males )
* Potter's syndrome	bilateral renal agenesis --> oligohydramnios --> limb deformity, facial deformity, pulmonary hypoplasia

Ear development
Bone	incus & malleus : 1st arch stapes : 2nd arch
Muscles	Tensor tympani ( V3 ) : 1st arch Stapedius ( VII ) : 2nd arch
Others	external auditory meatus : 1st cleft tympanic membrane , E-tube : 1st pouch

Pharyngeal pouch derivatives
1st pouch	endoderm lined structure of ear
3rd pouch	3 structure ( thymus, left & right inferior parathyroid )
1st pouch	middle ear cavity , E-tube, mastoid air cell
2nd pouch	epithelial lining of palatine tonsil
3rd pouch(dorsal wing)	inferior parathyroid
4th pouch(ventral wing)	superior parathyroid
5th pouch	ultimobranchial body --> thyroid C-cell

Heart embryology
Embryonic structure	Give rise to
Bulbous cordis	RV &aortic outflow tract
Primitive ventricle	LV ( except for aortic outflow tract )
Truncus arteriosus	ascending aorta & pulmonary trunk
Primitive atria	auricular appendage
Left horn of sinus venosus	coronary sinus
Right horn of sinus venosus	smooth part of right artium

Aortic arch derivatives

1st part of maxilary artery
2nd stpedial & hyoid artery
3rd common carotid artery & proximal part of internal carotid artery
4th       to systemic artery
            left : aortic arch
            right : proximal part of right subclavian artery
6th to pulmonary & pulmonary to systemic shunt ( ductus arteriosus )
proximal part of pulmonary artery & (on the left only )ductus arteriosus

Embryologic lining abnormality
Cyst	spherical epithelium lined cavity
Pseudocyst	spherical cavity without epithelial lining
Sinus	blind ending duct or space opening externally or internally
Fistula	abnormal patent canal which open bilateral ending
Atresia	Closure of normal body opening or tubular organ

Fetal erythropoiesis
Yolk sac	3-8 week
Spleen	9-28 week
Bone marrow	28 weeks onward

Umbilical cord

Contains 2 umbilical arteries, which return deoxygenated blood from the fetus, and 1 umbilical vein, which supplies oxygenated blood from the placenta to the fetus

Fetal - Postnatal derivatives
Umbilical vein	ligamentum teres hepatis
Umbilical arteries	medial umbilical ligaments
Ductus arteriosus	ligamentum arteriosum
Ductus venosus	ligamentum venosum
Foramen ovale	fossa ovalis
Allantois, Urachus	median umbilical ligament
Notochord	nucleus pulposus

Meckel's diverticulum

Persistenceof the vitelline duct or yolk stalk.
May contain ectopic acid - secreting mucosa and/ or pancreatic tissue.
Most common congenital anomaly of the GI tract.
Can cause bleeding or obstruction near the terminal ileum.
Contrast with omphalomesenteric cyst = cystic dilatation of vitelline duct

Cleft lip and Cleft palate
Cleft lip	failure of fusion of the maxillary and medial nasal processes
Cleft palate	failure of fusion of the lateral palatine processes, the nasal septum, and / or the median palatine process

Tongue development & innervation
anterior 2/3 ( pain via CN V3, taste via CN VII )	from 1st branchial arch
posterior 1/3 ( pain & taste mainly via CN IX, extreme posterior via CN X )	from 3rd and 4th arches
Motor intervention is via CN XII

Pancrea embryology

Derived from foregut.
Ventral pancreatic bud : become head, uncinate process ( lower 1/2 of head ), main duct
Dorsal pancreatic duct : become body, tail , isthmus, accessory duct

Branchial derivatives	Cartilage	Muscle	Nerve
Branchial arch 1	Meckel's cartilage : Mandible, Malleus, incus , sphenoMandibular ligament	Muscles of Mastication ( temporalis, Masseter, lateral and Medial pterygoid ) Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini	CN V3
Branchial arch 2	Reiter's cartilage : Stapes, Styloid process, lesser horn of hyoid, Stylohyoid lig.	Muscles of facial expression : Stapedius, Stylohyoid, posterior belly of digastric.	CN VII
Branchial arch 3	greater horn of hyoid	Stylopharyngeus	CN IX
Branchial arch 4-6	thyroid , cricoid, arytenoids, corniculate, cuneiform	Muscle (4th arch) : most pharyngeal constrictors, cricothyroid, levator Muscle (6th arch) : intrinsic muscles of larynx	4th arch - CN X 6th arch - CN X ( recurrent laryngeal branch)
Branchial cleft derivatives 1st cleft develops into external auditory meatus 2nd through 4th clefts form temporary cervical sinuses which are obliterated by proliferation of 2nd arch mesenchyme

Branchial apparatus : origin

Branchial clefts derived from ectoderm
Branchial arches derived from mesoderm and neural crests
Branchial pouches derived from endoderm

CAP covers outside from inside

Congenital penile abnormalities
Hypospadias	Abnormal opening of penile urethra on infeior ( ventral ) side of penis due to failure of urethral folds to close
Epispadia	Abnormal opening of penile urethra on superior (dorsal) side of penis due to faulty positioning of genital tubercle

Genital ducts
Mesonephric ( wolffian ) duct	Develops into Seminal vesicles, Epididymis, Ejaculatory duct & deferens
Paramesonephric ( mullerian ) duct	Develops into fallopian tube, uterus and part of vagina
Bicornuate uterus results from incomplete fusion fo the paramesonephric ducts. Mulleirian inhibiting substance secreted by testes suppresses development of paramesonephric ducts in male

Male / Female genital homologues
Corpus spongiosum	vestibular bulbs
Bulbourethral glands ( of Cowper )	greater vestibular glands ( of Bartholin)
Prostate gland	urethral and paraurethral glands ( of Skene )
Glans penis	clitoris
Ventral shaft of the penis	labia minora
Scrotum	labia majora

Thyroid develpoment

Thyroid diverticulum arises from floor of primitive pharynx, descends into neck.
Connected to tongue by thyroglossal ducts, which normally disappears but may persist as pyramidal lobe of thyroid.
Foramen cecum is normal remmant of thyroglossal duct.
Most common ectopic thyroid tissue site is the tongue.

EMBRYOLOGY REVIEW

THE SKULL AND SCALP

DEVELOPMENT OF THE SKULL

A) NEUROCRANIUM

SKULL BASE : ENCHONDRAL OSSIFICATION

Brain and cranial nerves develop before the skull --> chondrocranium develops : form around the nerves (foramina).
chondrocranium ossification.
spheno-occipital synchondrosis : The last piece of ossification between the sphenoid body and the occipital bone ( the epiphyseal growth plate in length of the skull base : ossification at age 25 )

CALVARIAL BONE : INTRAMEMBRANOUS OSSIFICATION

The calvarium ossification from separate centers and formation of sutures ( completion at about 3 years)
6 fontanelles at the intersection of two sutures : the anterior fontanelle ( BREGMA ) stays open until the middle of the 2nd year.
Craniostenosis is the failure for the skull to expand due to malformed suture

B) VISCEROCRANIUM : Facial bones are partly basal and partly calvarial bones so they ossify both by intramembranous and endochondral ossification.

ENCHONDRAL VISCEROCRANIUM : middle ear ossicles, styloid process of temporal bone, greater horn/ inferior body of hyoid and laryngeal cartilages
MEMBRANOUS VISCEROCRANIUM : maxillary and mandibular prominence

CALVARIAL BONES

The frontal bone ossification from 2 centers ( right and left frontal bones at birth). --> metopic suture --> one large frontal bone.
The parietal bones are separated by the sagittal suture and from the frontal bone by the coronal suture.
The anterior fontanelle ( bregema ) between them.
The parietal bones and the occipital bone meet at the posterior fontanelle (lambda), lambdoid suture.
The side wall of the skull is completed by the squamous part of the temporal bone and the greater wing of the sphenoid bone, at the pterion. It is located 4 cm above the midpoint of the zygomatic arch and is the site of surgical exploration for the middle meningeal artery. ( bifurication of MMA at this point )
The flat bones of the skull : frontal, parietal, temporal and occipital

diploë (cancellous bone containing red bone marrow) between 2 layers of compact bone.

The bones are drained by diploic veins (usually 4 on each side) which open into the nearest convenient venous sinus.
The flat bones of the skull are also pierced by emissary foramina transmitting emissary veins connecting veins of the scalp with the dural venous sinuses inside the skull (possible route for infection): may be seen in the parietal or the temporal bone posterior to the external auditory meatus.

cf. Roentgenographically, there are some points of differential diagnosis with skull fracture :

the sutures (possibly metopic suture),
the diploic veins,
the middle meningeal artery.

The occipital bone: the external occipital protuberance is located inferior to lambda. The superior nuchal lines run lateral from the external occipital protuberance and the inferior nuchal lines are situated inferiorly.

THE CRANIAL FOSSAE

1) ANTERIOR CRANIAL FOSSA :

Orbital plate of the frontal bone
Lesser wing of the sphenoid bone
The cribriform plate of the ethmoid with the crista galli transmits olfactory nerves from the upper part of the nasal cavity -- possible route for infection or CSF escape in skull fractures ( CSF Rhinorrhea ).
Optic canal for transmission of optic nerve ( & ophthalmic artery, central retinal vein ).
Anterior clinoid processes projecting posteriorly to the posterior clinoid processes of the sphenoid bone.

2) MIDDLE CRANIAL FOSSA :

is formed by the greater wing of the sphenoid bone and petrous temporal bone.
The most posterior tip of the greater wing contains the foramen spinosum ( middle meningeal artery ).
Anteriorly to the foramen spinosum is the foramen ovale ( manidbular branch of trigemianal nerve, lesser petrosal nerve, accessory meningeal artery ) and then the foramen rotundum ( maxillary branch of trigemianla nerve ). The foramen rotundum leads to the pterygopalatine fossa.
The superior orbital fissure is a gap between the lesser wing and the greater wing of the sphenoid leading to the orbit, just lateral to and below the optic nerve. ( CN III, IV, V-1, VI, ophthalmic vein )
The body of the sphenoid bone contains the hypophyseal fossa for the pituitary gland. This fossa is also called the sella turcica and it is shaped like a 4-poster bed. Its maximum length is 14mm and its depth is 8mm. Measurements are important because pituitary tumors cause ballooning of the sella.
The foramen lacerum is located lateroposterior to the sella. ( internal carotid artery & nerve plexus )

3) POSTERIOR CRANIAL FOSSA

the foramen magnum for the lower end of the medulla, spinal CN XI, vertebral artery.
The clivus, anterior to the foramen magnum, which leads up to the body of the sphenoid bone.
The transverse sinus
The sigmoid sinus which ends at the jugular foramen. ( CN IX, X, XI, jugular vein )
The hypoglossal canal (anterior condylar) canal and the posterior condylar canal. ( CN XII )
The internal auditory meatus on the posterior aspect of petrous temporal bone. ( CN VII, VIII, labyrinth. a. )
The arcuate eminence on the petrous portion of the temporal bone, marking the position of the superior semicircular canal.

* The right jugular foramen is thus usually larger than the left. ( The superior sagittal sinus is continuous with the right transverse sinus whereas the smaller straight sinus is continuous with the left transverse sinus. )

THE EXTERIOR OF THE BASE OF THE SKULL

The spine of the sphenoid bone near the foramen spinosum.
The jugular foramen is occupied by the jugular bulb (for expansion of the internal jugular vein) in life.
The styloid process, the mastoid process and the stylomastoid foramen between the 2 processes. (Facial n.)
Anterior to the jugular foramen and in the petrous portion of the temporal bone lies the carotid canal.
The spine of the sphenoid bone lies medial to the mandibular fossa. The mandibular fossa articulates with the head of the mandible to form the temporomandibular (TMJ) joint.
The foramen ovale lies at the base of the lateral pterygoid plate.
The medial pterygoid plate (with the pterygoid hamulus at its base) and the lateral pterygoid plate are parts of the sphenoid bone.
The inferior orbital fissure leads anteriorly from the pterygoid region to the orbit.
The hard palate is formed by the palatine process of the maxilla and by the horizontal plate of the palatine bone. There are 3 foramina in the horizontal plate ( the larger being the greater palatine foramen, others being lessee palatine foramen and incisive foramen ).
The vomer bone in the posterior opening (the choanae) of the nasal cavity is attached by a fibrous joint to the undersurface of the body of the sphenoid.

* THE COURSE OF INTERNAL CAROTID ARTERY :

enters the carotid canal,
runs anteromedially to the foramen lacerum
and then runs superoanteriorly to enter the cranium through the internal orifice of the foramen lacerum.
It then turns anteriorly and lies on the side of the sella turcica. It now lies in the cavernous sinus.
It then turns superoposteriorly, medial to the anterior clinoid process and breaks up into 3 branches.

SCALP

S = skin
C = connective tissue
A = aponeurosis referring to the Galea aponeurotica (epicranial aponeurosis). This aponeurosis belongs to the occipitofrontalis muscle located antero- and posteriorly.
L = loose areolar space, this is a plane of cleavage for injury and the spread of blood : contains emissary veins
P = periosteum ( or pericranium )

BLOOD VESSELS & NERVES:

Anastomoses in the scalp ( from anterior to posterior ):

Supratrochlear artery
Supraorbital artery
Superficial temporal artery
Posterior auricular artery
Occipital artery

Emissary veins (valveless) may spread infections from the scalp to the intracranial cavity. Normal blood flow is from inside to outside of the skull.
Nerves innervation of the scalp ( from anterior to posterior ):

2 branches from the ophthalmic division of the trigeminal nerve (cranial nerve V): the supratrochlear and suprorbital nerves
1 branch from the maxillary division of the trigeminal nerve: the zygomaticotemporal nerve
1 branch from the mandibular division of the trigeminal nerve: the auriculo temporal nerve

Branches of the trigeminal nerve lie anterior to the external ear or auricle

Posterior to the auricle:

The lesser occipiral nerve (C2,3)
The greater occipital nerve (C2)
The third occipital nerve (C3)

THE FACE

THE SKELETON OF THE FACE

Structures in the orbit

the superior orbital fissure
the optic canal
The greater and lesser wings of the sphenoid.
The zygomatic bone and the (hollow) maxilla are in the lateral wall of the orbit.
The ethmoid bone and the small fragile lacrimal bone are in the medial wall .

The supraorbital, infraorbital and mental foramina, lie on a vertical line and transmit the ophthalmic, maxillary and mandibular divisions of the trigeminal (Vth cranial) nerve.
Zygoma: frontal, maxillary and temporal processes
Mandible:

Body : fusion of right and left sides at 2 years

Alveolar process for teeth
Mandibular foramen and canal lie medial to the mandibular angle. They contain the inferior alveolar nerve ( CN-V3) and vessels

2 rami

Coronoid process
Condylar process with head (in temporomandibular joint) and neck
Mandibular notch
Lingula for attachment of the sphenomandibular ligament

FACIAL MUSCULATURE

2 groups of muscle on the face:

muscles of facial expression : by the facial nerve ( Cranial nerve VII )
muscles of mastication : by the mandibular division of the trigeminal nerve.( CN V-3 )
Muscles of facial expression : dilators and sphincters around orifices in the face region.
Around the eye:

The sphincter : orbicularis oculi

a palpebral part (closes eye gently)
an orbital part : blends in with the anterior belly of occipitofrontalis (closing the eye forcibly). The orbital part causes radiating skin wrinkles from the lateral corner of the eye ( crow's feet ).

The dilator : levator palpebrae superioris innervated by the oculomotor nerve ( CN III ) and postganglionic sympathetic fibers from the superior cervical ganglion.

Around the mouth:

The sphincter : orbicularis oris ( closes the lips but can also protrude the lips as in whistling.)
The dilators :

Levator labii superioris alaeque nasi ("Grace"), Levator labii superioris, Levator anguli oris, Zygomaticus minor, Zygomaticus major, Platysma (risorius), Depressor anguli oris, Depressor labii inferioris, Mentalis

The buccinator : the main muscle of the cheek and it keeps the cheeks in contact with the gums so that food does not accumulate in the vestibule of the mouth.

*Bell's Palsy : lesions of the facial nerve ( CN VII )

Drooling of saliva & tearing : paralysis of the 2 main orbicularis muscles. Paralysis of buccinator will lead to accumulation of food in the vestibule.
Test by asking patients to screw up the eye (loss of muscle tone causes the normal skin folds to disappear on the side of the lesion), to smile or to whistle.
Muscles must be supported during recovery or they will stretch under gravity and cause a permanent asymmetry of the face.

Muscles of mastication : developed from the first branchial arch / innervated by branches from the anterior branch of the mandibular division of the trigeminal nerve
The masseter muscle attaches to the zygomatic arch and the outer surface of the mandible near the angle. It is composed of a superficial and deep part. The masseter closes the jaw and is innervated by the masseteric nerves passing through the mandibular notch.
The temporalis muscle attaches from the lateral side of the skull below the temporal line to coronoid process and anterior border of the ramus of the mandible almost as far as the third molar tooth. The temporalis muscle closes the jaw and is innervated by the deep temporal nerves.
The lateral pterygoid muscle attaches from the lateral surface of the lateral pterygoid plate to the neck of mandible and the intraarticular disc of the temporomandibular joint. It is the only muscle in this group to open the jaw.
The medial pterygoid is attached from the medial surface of the lateral pterygoid plate to the deep surface of the mandible (at the angle of the mandible) opposite to the attachment of the masseter muscle. The angle of the mandible thus lies between these 2 muscles. The medial pterygoid muscle closes the jaw.
Both pterygoid muscles are innervated by the pterygoid nerves.

BLOOD VESSELS:

The facial artery

Passes over the lower border of mandible at the anterior border of the masseter : groove for facial artery.
A tortuous course (for facial movement ), first to the angle of the mouth ( angular artery ) and then up at the side of the nose to the medial angle of the eye.
gives off upper and lower labial branches with numerous branches. Free anastomoses across the midline.

The facial vein

A straighter path and communicates with deeper veins such as veins of the orbit (leading to the cavernous sinus within the skull : so danger zone of face --> central face ) near the medial canthus and the pterygoid venous plexus.

The superficial temporal artery

A branch of the external carotid artery. it ascends in front of the tragus of the ear. Above the ear it divides into anterior and posterior branches. It anastomoses with the facial artery.

PAROTID GLAND ( The gland of mumps )

Enclosed in a split layer of deep cervical fascia .
The medial thickening in this capsule forms the stylomandibular ligament.
The duct : leaves the anterior border, crosses the masseter muscle, turns around the anterior border of the muscle and pierces the buccinator muscle to enter the mouth opposite the 2nd upper molar tooth.
3 important structures passes through the parotid gland from superficial to deep: the facial nerve, the retromandibular vein and the external carotid artery.

FACIAL NERVE

from stylomastoid foramen,
gives off posterior auricular branch to occipital belly of occipitofrontalis,
divides within the parotid gland forming an intraglandular network,
5 branches emerge from the anterior border of the gland: temporal, zygomatic, buccal, marginal mandibular and cervical.
*Marginal mandibular branch runs below the border of the mandible to supply muscles of chin. ( Incision should always be made a finger's width below it. )

RETROMANDIBULAR VEIN

formed in the gland by the union of the maxillary and superficial temporal veins,
emerges from the gland near the angle of the mandible
divides into 2 with the anterior branch joining the facial vein and draining into the internal jugular vein,
the posterior branch joins with the small posterior auricular vein to form the external jugular vein.

EXTERNAL CAROTID ARTERY

divides in the parotid gland into the maxillary and superficial temporal arteries,
The maxillary artery runs deep to the neck of mandible to enter the infratemporal region,
The superficial temporal artery lies in front of the ear and divides into anterior and posterior branches.
Cf. Branches of external carotid artery : superior thyroid, ascending pharyngeal, lingual facial, occipital, postauricualr, superficial temporal, maxillary arteries

THE DEEP FACIAL REIGION & PAROTID

The PAROTID BED is formed:

Posteriorly by the mastoid process and the origins of the sternocleidomastoideus and posterior belly of the digastric;
Medially by the styloid process of the temporal bone and the stylohyoid muscle. Styloglossus and stylopharyngeus are also medial to the parotid bed within the lateral pharyngeal space;
Anteriorly by the sphenomandibular and stylomandibular ligaments as well as the fasciae of the medial pterygoid and masseter muscles;
Superiorly by the zygomatic arch;
Inferiorly by the posterior belly of the digastric.
*The deep cervical fascia

envelop of the parotid gland : weakest between the styloid process and spine of the sphenoid.

Infections may spread from the parotid fascia into the lateral pharyngeal space which communicates with the retropharyngeal space between the pharynx and prevertebral musculature.
Infections may track inferiorly through the neck and into the thorax, along the course of the carotid sheath, between visceral and prevertebral fasciae.

Innervation by the lesser petrosal branch (secretomotor) of the glossopharyngeal nerve( CN IXth ).

Sympathetic innervation is from the superior cervical ganglion via the arteries and it controls the saliva.
Parasympathetic : Preganglionic parasympathetic fibers from the tympanic plexus in the middle ear ---- enter the middle cranial fossa by a hiatus on the anterior aspect of the petrous bone ---- run through the periosteal dura and exit the middle cranial fossa through the foramen ovale with V3. --- The preganglionic fibers synapse in the otic ganglion on the medial aspect of V3 --- The postganglionic fibers join with the auriculotemporal nerve to run to the parotid gland. --- The auriculotemporal nerve thus carries secretomotor fibers of IXth and sensory fibers of V3 for pain in the gland.

THE INFRATEMPORAL REGION

Lateral wall: medial aspect of ramus of the mandible
Anterior wall:

body and tuberosity of the maxilla, deep to zygoma and zygomatic process of the maxilla.
The pterygomaxillary fissure may be seen in the medial aspect of this anterior wall, opening into the more medial pterygopalatine fossa.
The inferior orbital fissure may also be seen.
Inferior to the pterygomaxillary fissure is the hamulus serving as attachment point for the pterygomandibular raphé. It serves as the common site of origin for the buccinator and the superior constrictor muscle and runs from the hamulus to the upper 1/5 of the mylohyoid line.

Medial wall:

lateral pterygoid plate,
superior constrictor muscle,
levator and tensor palati muscles.

Roof of the infratemporal fossa :

the greater wing of the sphenoid anteriorly
and the squamous portion of the temporal bone posteriorly.

Infratemporal crest :

on the undersurface of the greater wing of the sphenoid
serves as an attachment site for the upper head of the lateral pterygoid.

Foramen ovale :transmission of V3 and the lesser petrosal nerve (from IXth) from the middle cranial fossa to the infratemporal fossa;
Foramen spinosum : transmission of the middle meningeal artery from the infratemporal fossa to the middle cranial fossa.

CONTENTS OF THE INFRATEMPORAL FOSSA

Lateral pterygoid muscle.

This muscle has 2 heads
from the infratemporal crest to the capsule of the interarticulating disc of the TMJ
from the lateral aspect of the lateral pterygoid plate to the neck of the mandible.

(*Protrusive actions of the lateral pterygoid muscle are used to test V3: deviation is TOWARDS the side of the lesion.)

Maxillary artery

lateral to the lateral pterygoid muscle.
From the external carotid artery in the parotid gland, the artery enters the posterior aspect of the infratemporal fossa by passing deep to the neck of the mandibular condyle.
It crosses the lateral side of the lateral pterygoid muscle and enters the pterygomaxillary fissure.
It is divided into a first (mandibular) part, second (pterygoid) part and third (pterygopalatine) part.

5 branches of the mandibular division of the maxillary artery

The middle meningeal artery ( foramen spinosum : the principal artery to periosteal cranial dura )
The inferior alveolar artery ( mandibular foramen : supplies the teeth and the mandible.)
The deep auricular artery ( supplies the auditory meatus )
The anterior tympanic artery ( accompanies the chorda tympani through the petrotympanic fissure) to reach the middle ear.
The accessory meningeal branch ( foramen ovale : supplies the trigeminal ganglion & dura. )

5 branches of the pterygoid portion of the artery : supplying mastication muscles in the infratemporal fossa

2 deep temporal branches, a masseteric branch, a pterygoid branch and a buccal branch.

Pterygoid venous plexus

follows the maxillary artery in the infratemporal fossa, lying mostly lateral to the artery.
This is a route for infection: the veins have connections with the cavernous sinus via the deep facial, inferior ophthalmic and emissary veins in the sphenoid bone.
Veins of the head have NO valves.

Mandibular division of the trigeminal nerve

I. Anterior division:

Masseteric branches
Posterior and anterior temporal branches to the temporalis muscle
The nerve to the medial pterygoid
The nerve to the lateral pterygoid
The buccal nerve

The buccal nerve :

passes between the 2 heads of the lateral pterygoid muscle.
continues into the cheek on the lateral surface of the buccinator muscle.
is the terminal branch of the anterior division
is sensory to the mucosa of the inside of the cheek and the lower gums around the molar teeth.
does not supply the motor innervation of the buccinator.

II. Posterior division:

Auriculotemporal nerve:

The initial segment encircles the middle meningeal artery and receives postganglionic parasympathetic fibers from the otic ganglion which are secretomotor to the parotid gland.
Passes medial to the head of the mandibular condyle and sends a sensory branch to the TMJ.
Enters the deep portion of the parotid gland giving sensory branches as well as parasympathetic postganglionic fibers from the otic ganglion.
Its terminal portion accompanies the superficial temporal artery and innervates the upper half of pinna of the ear and part of the temporal region (Pain and general sensation).

Inferior alveolar (dental) nerve

From the foramen ovale to the mandibular foramen on the medial aspect of the ramus of the mandible, lying between the medial and lateral pterygoid muscles and just posterior to the lingual nerve.
The branch to mylohyoid and to the anterior belly of the digastric : the only branch in the infratemporal fossa.
It first lies in the mylohyoid groove, and then on the inferior aspect of the mylohyoid to reach the digastric muscle.
In the ramus of the mandible : entirely sensory to lower teeth, lower gums and the mucosa of the lower lips.
On exit through mental nerve : innervate the mucosa and gum adjacent to the lower lip.

Lingual nerve

lies anterior to the inferior alveolar nerve and remains medial to mandible.
receives the chorda tympani in the infratemporal fossa. The chorda tympani reaches the infratemporal fossa via the petrotympanic fissure. The chorda tympani contains preganglionic parasympathetic secretomotor fibers of VII from the tympanic plexus and special sensory fibers for taste from the anterior 2/3 of the tongue. The taste fibers have their cell bodies in the geniculate ganglion of VII.
Terminal distribution of the lingual nerve and associated fibers which mediate general sensation (pain, touch temperature and pressure) is to the floor of the mouth and the anterior 2/3 of the tongue.

cf. Mandibular block technique: injection of anesthetic in the fascial compartment defined by the fascial covering of the medial pterygoid and the medial aspect of the ramus of the mandible. The anesthetic diffuses to the lingual and inferior alveolar nerves.

TEMPOROMANDIBULAR JOINT(TMJ)

Head of mandible
Mandibular fossa and articular tubercle of the temporal bone
Synovial joint with intraarticular disc dividing joint

lower compartment (hinge rotation for mandibular head)
upper compartment (sliding joint for protrusion)

Major supportive elements of the TMJ: MUSCLES OF MASTICATION
Minor supportive elements of the TMJ:

Lateral temporomandibular ligament (thickening of the joint capsule)
Stylomandibular ligament (between parotid and submandibular glands)
Sphenomandibular ligament

Movements of the mandible:

Elevation
Depression
Protrusion
Retraction

INTRACRANIAL CAVITY, MENINGES AND CRANIAL NERVES

INTRACRANIAL BLOOD VESSELS:

Venous sinuses : the veins have rigid walls composed of dura to avoid collapse of the veins during systole .
Intracranial arteries : thin walls because when the arteries are distended during systole, the effect is counteracted by a rise in intracranial pressure. However, the arteries are prone to localized distension (aneurysm)& hemorrhage.

MENINGES

Dura mater (pachymeninx)
Arachnoid
The subarachnoid space (continues through the foramen magnum, around the spinal cord.)
Pia mater (closely adherent to the brain) : *Arachnoid and pia mater are also called leptomeninges.

DURA MATER

2 layers:

An outer fibrous layer
An inner serous layer (to form the venous sinuses )

The dura is supplied by small arteries and the middle meningeal artery. The vein runs with the artery.
Intracranial extension of the dura mater:

The falx cerebri with the superior sagittal sinus, starts at the crista galli.
The tentorium cerebelli incompletely roofs over the posterior cranial fossa.
At this level , the midbrain runs superiorly through the opening to join with the diencephalon. The sharp edges of dura may have fatal consequences when the brain is displaced by force or a space-occupying lesion. ( tentorial herniation )

CSF & VENOUS SYSTEM

The arachnoid villi drain CSF from the subarachnoid space to the venous sinuses. ( With age, the arachnoid villi become clumped together to form the arachnoid granulations.)
Superior sagittal sinus to the right transverse sinus to the sigmoid sinus to the internal jugular vein.
Inferior sagittal sinus : in the free edge of the falx cerebri and receives part of the drainage of the great cerebral vein (of Galen) and becomes the straight sinus. ---> left transverse sinus, left sigmoid sinus and left internal jugular vein. ( The right jugular foramen is usually bigger than the left. )
Cavernous sinuses

on either side of the sella turcica (pituitary gland):
Anteriorly, the superior and inferior opthalmic veins open into them.
Posteriorly, minor venous sinuses (superior and inferior petrosal sinuses) also open into them. The inferior petrosal sinus communicates at its other end with the internal jugular vein at the jugular foramen.
The cavernous sinuses are joined across the midline by intercavernous sinuses lying anterior and posterior to the pituitary gland. The pituitary fossa is roofed in by the diaphragma sellae through which runs the pituitary stalk. Superoanteriorly, lies the optic chiasma.
Veins from the lower parts of the brain also drain into the cavernous sinuses.
The cavernous sinus contains cranial nerves III,IV, V, and VI, and the internal carotid artery.

ARTERIAL SUPPLY OF THE BRAIN

Internal carotid artery

turns superiorly after passing through the cavernous sinus.
it then gives out the opthalmic artery (which runs into the optic canal with the optic nerve),
terminates as the anterior and middle cerebral arteries and the posterior communicating artery.
Before it breaks up into terminal branches, it gives out small branches to the pituitary gland and adjacent structures.

Vertebral artery

through the foramen magnum and gives off:
anterior & posterior spinal artery
posterior inferior cerebellar artery
basilar artery : lies ventral to the pons, on the clivus and give off :

branches to the brainstem,
anterior inferior cerebellar artery
terminates as the superior cerebellar and posterior cerebral arteries.

Terminal branches of the internal carotid and the vertebral arteries form the circle of Willis.

CRANIAL NERVES

GENERAL ARRANGEMENT OF THE CRANIAL NERVES

MOTOR INNERVATION : The cell bodies for the motor fibers of all cranial nerves are located in the respective brainstem nuclei (lower motor neurons).

SENSORY INNERVATION : The cell bodies for the sensory fibers of all cranial nerves are located in the parasympathetic ganglia (see below) or special sensory organs.

SYMPATHETIC INNERVATION : The sympathetic fibers mostly run along the internal and external carotid arteries to get to their target organs.

SUPERIOR CERVICAL GANGLION: The highest sympathetic chain ganglia, which contains synapses for all the major sympathetic fibers for the head and neck region.
External Carotid Artery: Post-Ganglionic sympathetics run along the external carotid to supply the salivary glands and lower face.
Internal Carotid Artery: Larger portion of sympathetics run along internal carotid, forming the internal carotid plexus.
INTERNAL CAROTID PLEXUS: In cavernous sinus

· Deep Petrosal Nerve: Given off of the internal carotid plexus within the cavernous sinus. From there it goes to Pterygopalatine Fossa and onto nose, palate, and lacrimal glands.

· Sympathetic Root of Ciliary Ganglion: The internal carotid plexus also sends a sympathetic branch to the Ciliary Ganglion, where it then goes on to form the Long Ciliary Nerve, which will innervate the dilator pupillae muscle of the eye.

PARASYMPATHETIC INNERVATION : All Parasympathetic motor innervation to the head synapses exactly once, in one of the four cranial ganglia listed below. All of these ganglia are distributed along branches of the Trigeminal Nerve (V).

CILIARY GANGLION: parasympathetics from Oculomotor Nerve (III)

Located in the posterior of the orbit.
GVE (Parasympathetic) innervation is to:

Ciliary Muscles (for Accommodation)
Sphincter of the Pupil (constriction, or miosis).

It hangs off of the Ophthalmic Branch of the Trigeminal Nerve (V¹)

PTERYGOPALATINE GANGLION: parasympathetics from Facial Nerve (VII)

Located in the Pterygopalatine Fossa in the posterior part of sphenoid bone.
GVE (Parasympathetic) innervation is to:

Nose
Palate
Lacrimal Glands

It hangs off of the Maxillary Branch of the Trigeminal Nerve (V²).

SUBMANDIBULAR GANGLION: Carries parasympathetics from Facial Nerve (VII)

Located below and lateral to the tongue.
GVE (Parasympathetic) innervation is to:

Submandibular Gland
Sublingual Gland

It hangs off of the Mandibular Branch of the Trigeminal Nerve (V³).

OTIC GANGLION: Carries parasympathetics from Glossopharyngeal Nerve (IX)

Located in Intratemporal Fossa, just below Foramen Ovale.
GVE (Parasympathetic) innervation is to the Parotid Salivary Gland.
It hangs off of the Mandibular Branch of the Trigeminal Nerve (V³)

VAGUS NERVE (CN X)

There is no parasympathetic ganglion in the head for the vagus nerve.
Sends parasympathetic innervation to the thoracic and abdominal viscera.

CRANIAL NERVE I: OLFACTORY NERVE

OLFACTORY MUCOSA: olfactory nerves in the superior nasal cavity. : pierce the Cribriform Plate of the Ethmoid Bone and lead to OLFACTORY TRACTS. ( SKULL FRACTURES: Can shear olfactory nerves at the cribriform plate, impairing sense of smell. The damage can be unilateral. ) / TESTING THE NERVE: Wave peppermint under the nostril, testing each nostril separately.

CRANIAL NERVE II: OPTIC NERVE

OPTIC CHIASM: The convergence of the two optic nerves.

It occurs at the sella turcica, on the body of the sphenoid bone, right at the Pituitary Gland.
Fibers from the medial side of each eye cross at the Optic Chiasm, to join the Optic Tract on the opposite side.

So medial fibers from the Left Eye will go to the right side of the brain, and medial fibers from the right eye will go to the left side of the brain.
These fibers are carrying peripheral visual information for both respective eyes.

Fibers from the lateral side of each eye do not cross at the Optic Chiasm, but instead join the Optic Tract directly on their own side.
TUNNEL VISION: Indicates a lesion at the optic chiasm. Medial fibers have been impinged upon, destroying peripheral vision in both eyes.

Pituitary Tumor can impinge on the optic chiasm, causing tunnel vision.

OPTIC TRACT: That portion extending between the Optic Chiasm and the Lateral Geniculate Nucleus in the brainstem. This portion of nerve is not properly called the Optic Nerve.

CRANIAL NERVE III: OCULOMOTOR NERVE

SUPERIOR DIVISION: Somatic innervation to the superior rectus and levator palpebrae muscles.
INFERIOR DIVISION: Somatic innervation to the medial and inferior rectus muscles.

The inferior division also carries Parasympathetic Fibers, via the Short Ciliary Nerve, to the Sphincter Pupillae and Ciliary Muscles (constrict eye and accommodate for near vision).

* * UNILATERAL LESION OF OCULOMOTOR NERVE :

"Lateral Strabismus" = The eyeball will point downward and outward.

Unchecked tension of the Lateral Rectus (CN VI) will abduct it (pull it outward)
Unchecked tension of the Superior Oblique (CN IV) will pull the eye down and outward -- not upward.

"Ptosis" = The eyelid will droop.

This is due to lost innervation of the Levator Palpebrae muscle.
There may be tonic tension of the Frontalis Muscle as well, in order to compensate for drooping eyelid.

"Mydriasis" = The pupil will be dilated.

Due to lost innervation of the Sphincter Pupillae.

Accommodation of the lens will be lost.

Due to lost innervation to Ciliary Muscle.

CRANIAL NERVE IV: TROCHLEAR NERVE

PATHWAY IN BRAIN:

originates from the opposite of the brain.
exits from the dorsal side of the cranium, so it has a very long path.
associated with the eye, that doesn't enter the orbit through a tendinous ring.

CAVERNOUS SINUS: It runs in the cavernous sinus. If there is ever brain hemorrhage, pressure from excess CSF can damage the Abducens nerve.
INJURY: Injury to the Trochlear Nerve or Superior Oblique Muscle will cause someone to tilt their head slightly in compensation.

CRANIAL NERVE V: TRIGEMINAL NERVE

Crosses the petrous temporal bone, carrying with it a diverticulum of dura (cavum trigeminale or Meckel's cave) from the posterior cranial fossa
TRIGEMINAL GANGLION: It contains the sensory cell bodies for the Trigeminal Nerve. It contains no synapses.

The Motor cell bodies are in the Masticator Nucleus within the pons.

V¹ -- OPHTHALMIC NERVE -- Purely Sensory Nerve.

It runs through the lateral wall of the Cavernous Sinus.
It exits through Superior Orbital Fissure to enter the orbit.
Associated Ganglion: CILIARY GANGLION. It carries parasympathetic motor fibers from the Oculomotor Nerve (CN III), which go on to innervate extrinsic eye muscles.

V² -- MAXILLARY NERVE -- Purely Sensory Nerve.

It runs through the lateral wall of the cavernous sinus.
It exits through Foramen Rotundum, in the Greater Wing of the Sphenoid.
Associated Ganglion: PTERYGOPALATINE GANGLION. It carries parasympathetic motor fibers from the Facial Nerve (CN VII), which goes on to innervate muscles of facial expression.

V³ -- MANDIBULAR NERVE-- Mixed nerve. The only branch of the Trigeminal to carry any motor innervation.

It exits through Foramen Ovale, in the Greater Wing of the Sphenoid.
Associated Ganglia:

OTIC GANGLION: Carries parasympathetic motor fibers from the Glossopharyngeal Nerve (CN IX), which go on to innervate the Parotid Salivary Gland. / located in the Infratemporal Fossa
SUBMANDIBULAR GANGLION: Carries parasympathetic motor fibers from the Facial Nerve (CN VII), which go onto innervate the Submandibular and Sublingual glands.

Motor Innervation: Muscles of mastication; Anterior belly of digastric and mylohyoid; Tensor tympani and tensor veli palati.
Sensory Innervation: It sends up a meningeal branch to innervate part of the meninges.

TIC DOULOUREUX: A severe split second pain in the cutaneous region of the Trigeminal nerve.

Pains runs through Mandibular and Maxillary divisions, i.e. region around mouth.

MENINGEAL BRANCHES: All branches of Trigeminal send some meningeal branches to the meninges of the brain. If something is irritating the meninges, the pain information will be sent back through the Trigeminal.

In all cases, meningeal branch will be given off before each branch exits its respective foramen.

CRANIAL NERVE VI: ABDUCENS NERVE

CAVERNOUS SINUS: It runs in the cavernous sinus. If there is ever brain hemorrhage, pressure from excess CSF can damage the Abducens nerve.
STRABISMUS: The inability to direct both eyes toward the same object.
INJURY TO ABDUCENS: The eye on the affected side rotates inward (adducts), due to the unopposed action of the medial rectus muscle.

CRANIAL NERVE VII: FACIAL NERVE

3 Main Functions:

Innervate the Muscles of Facial Expression
Supply special sense of taste to anterior 2/3 of tongue, via Chorda Tympani Nerve.
To innervate all facial glands (salivary, nasal, lacrimal), EXCEPT the Parotid
There is also a small area of somatic sensation carried by the facial nerve, around the ear canal ear drum.

GENICULATE GANGLION : houses the cell bodies for all fibers of the Facial Nerve. It has no synapses.
PATHWAYS OF THE FACIAL NERVE: All fibers of the facial nerve exit the cranium at the INTERNAL ACOUSTIC MEATUS in the middle ear. From there, all fibers (except sensory to the ear) go to the GENICULATE GANGLION. From there, the nerve splits into two parts: a special-efferent motor division (to innervate facial-expression muscles) and a parasympathetic motor division (to innervate glands)

Motor Fibers of Facial Expression (SVE): They all bend downward and all head out the Stylomastoid Foramen and then pass through the Parotid Gland (but they do not innervate it). Then they divide into five branches.

All of these muscles are derived from the second branchial arch.

TEMPORAL BRANCH -- Frontal Muscles
ZYGOMATIC BRANCH -- Orbicularis Oculi
BUCCAL BRANCH -- Buccinator, Orbicularis Oris, Zygomaticus
MANDIBULAR BRANCH -- Orbicularis Oris, Depressor Labii Inferiores
CERVICAL BRANCH -- Platysma

Parasympathetic Secretomotor Fibers (GVE): They split into the Chorda Tympani and Greater Petrosal nerves, and head in two different directions.

PATHWAY OF CHORDA TYMPANI : Through Middle Ear ---> Out the Petrotympanic Fissure ---> Joins up with the Lingual Nerve ---> Submandibular Ganglion, where it synapses ---> Sublingual and Submandibular Salivary Glands

So ultimate innervation is secretomotor innervation to Submandibular and Sublingual glands.

PATHWAY OF GREATER PETROSAL: Middle Ear ---> Out the Greater Petrosal Hiatus ---> back in through the foramen lacerum ---> Join with sympathetics from Deep Petrosal Nerve to form the Nerve of Pterygoid Canal ---> Pterygopalatine Ganglion, where it synapses ---> Nasal mucosa and Lacrimal Glands.

So, ultimate innervation is secretomotor innervation to lacrimal glands and nasal mucosa.

BELL'S PALSY: Paralysis of the Facial Nerve for no obvious reason (loss of SVE motor innervation of the Facial Nerve)

Commonly occurs if the nerve gets impeded or inflamed at the Stylomastoid Foramen.

Facial paralysis results on the side affected. Patients will be unable to close eyelids, they will drool, and they will have a contorted face due to unopposed muscles on other side.

An injury here would not affect parasympathetic secretomotor innervation (those are given off before the stylomastoid foramen) -- it would only affect muscles of facial expression.
Loss of buccinator muscle can lead to difficulty eating.
Inability to close eyelid results in damage to cornea due to dryness of the eye, due to no innervation of palpebral part of orbicularis oculi.

CRANIAL NERVE VIII: VESTIBULOCOCHLEAR NERVE

VESTIBULAR NERVE: for the semicircular canals, utricle, & saccule; responsible for dynamic & static balance.
COCHLEAR NERVE: Innervates the cochlea and is responsible for hearing.
INTERNAL ACOUSTIC MEATUS: Cranial Nerve VIII exits out the internal acoustic meatus, along with the Facial Nerve.
ACOUSTIC NEUROMAS: A neuroma from a Schwann Cell in the Vestibulocochlear may impinge upon the Vestibular and Cochlear nerves in the Internal Acoustic Meatus. If it is large enough, it may impinge on the Facial Nerve, too.

CRANIAL NERVE IX: GLOSSOPHARYNGEAL NERVE

5 Functions of Glossopharyngeal Nerve

Innervates Stylopharyngeus Muscle.
Special sense of taste to posterior 1/3 of tongue
General sensation to posterior 1/3 of tongue, lateral oropharyngeal wall, part of soft palate
Parasympathetic secretomotor to Parotid Gland
Visceral Sensation from the Baroreceptors ("blood-pressure" receptors) at the Carotid Body (Sinus), at the bifurcation of the Carotids. ; carry special chemoreceptors and stretch receptors. They provide feedback to the heart to control heart rate and modulate blood pressure.

TYMPANIC NERVE: Is given off at the Jugular Foramen from the Glossopharyngeal. It carries Parasympathetic innervation to the Parotid, via the Lesser Petrosal.

It travels through the middle ear (inside the cranium), where it forms the Tympanic Plexus.
It exits the cranium at the Lesser Petrosal Hiatus of the Temporal bone.
After it exits back out, it is known as the Lesser Petrosal Nerve.
Lesser Petrosal Nerve: The continuation of the Tympanic; it synapses at the Otic Ganglion and then continues to carry parasympathetic innervation to the Parotid Gland.

GAG REFLEX: Glossopharyngeal can be tested by eliciting a gag reflex. Touch the posterior 1/3 of tongue or palate region to elicit response.

One should also be able to see symmetric raising of the soft palate during swallowing to verify functionality of the nerve.

OVERALL PATH OF GLOSSOPHARYNGEAL NERVE TO PHARYNX

Through JUGULAR FORAMEN
Down posterior wall of pharynx to innervate the stylopharyngeus muscle
Penetrate gap between Superior and Middle Pharyngeal Constrictors, adhered to the Stylopharyngeus muscle.
Finally, innervation to the posterior 1/3 of tongue.

CRANIAL NERVE X: VAGUS NERVE

THE INNERVATIONS

BRANCHIAL MOTOR (SVE): All muscles of the larynx, pharynx, and palate, EXCEPT the Stylopharyngeus (IX) and Tensor Palati (V3).

In this role, the Vagus is "stealing" some of the innervation from the Spinal Accessory (XI). Hence in this case the Vagus is actually innervating striated rather than smooth muscle.

VISCERAL MOTOR (GVE): Parasympathetics to the Thoracic and Abdominal viscera.( Carotid massage & Vagotomy )

The Vagus serves no Parasympathetic function in the head and neck region -- only the thorax and abdomen.

VISCERAL SENSORY (GVA): Sensory info from tongue, pharynx and larynx, heart and lungs, CAROTID SINUS (along with CN IX), stomach and intestine.
GENERAL SENSORY (GSA): General sensory from larynx, pharynx, and a small portion of the outer ear and tympanic membrane.

General Sensory innervation may include the eardrum itself. These individuals may elicit a gag reflex when cleaning their ears -- due to sensory response from the Vagus ( Anold nerve )

SPECIAL SENSORY (SVA): Maybe a few taste buds carry taste information via the Vagus.

TACHYCARDIA: To treat tachycardia, you can give the patient a Carotid Body Massage, at the bifurcation of the Carotids, in attempt to stimulate the visceral sensory components of the Vagus and Glossopharyngeal, to try to slow heart rate by increasing the Vagal stimulation of the heart.

UNILATERAL LESIONS OF THE VAGUS: Lesions of the vagus lead to the following symptoms.

Hoarseness, due to lost laryngeal function on the affected side.
Difficulty Swallowing, due to inability to elevate the soft palate on the affected side. This also makes the soft palate droop on that side.
The uvula tends to deviate toward the unaffected (intact) side, due to droop of the soft palate on the affected side. ( If the uvula deviates toward the left, then damage is to the right Vagus nerve. )

SUPERIOR VAGUS GANGLION: within the Jugular Foramen. It houses somatic sensory cell bodies of the Vagus nerve.
INFERIOR VAGUS GANGLION: right beneath the Jugular Foramen, right outside the skull. It houses visceral sensory cell bodies for the Vagus nerve.

CRANIAL NERVE XI: SPINAL ACCESSORY NERVE

Two Roots

Spinal Root: Gives SVE (Branchial) innervation to Sternocleidomastoid and Trapezius muscles.
Cervical Root: Quickly joins up with Vagus (and could be considered part of Vagus) to form the Recurrent Laryngeal Nerve.

NERVE GRAFTS: The function of Spinal Accessory is somewhat redundant.

It can be used to replace innervation lost by other muscles. The nerve can be redirected to the muscles of facial expression, e.g., and patients can learn to use the new pathway with physical therapy.

DAMAGE TO SPINAL ACCESSORY:

Shoulder Droop, due to lost innervation to upper part of Trapezius.
Difficulty in turning head, due to lost innervation to Sternocleidomastoid -- but other muscles serve this function as well.

MOTOR CELL BODIES: in the spinal cord (C1-C5).

Fibers run up the spinal cord and into the cranium through the Foramen Magnum, and then back out the posterior cranial fossa through the Jugular Foramen.

CRANIAL NERVE XII: HYPOGLOSSAL NERVE

INNERVATION: All intrinsic and extrinsic musculature of the tongue, EXCEPT the Palatoglossus which is innervated by the Vagus.
PATH: It exits the posterior cranial fossa through the Hypoglossal Canal, which is anterior to the Occipital Condyles.

It may pass through the Carotid Sheath or on either side of it.
It passes toward the tongue medial to the posterior belly of the Digastric muscle.
Upper portions of the Ansa Cervicales will hang off the Hypoglossal in order to reach the strap muscles, but the fibers do not intermix.

DAMAGE TO HYPOGLOSSAL:

It would be difficult to stick tongue out.
The tongue would deviate toward the non-functional side, due to functional muscles protruding it in that direction.

If tongue deviates to the left, then damage is to the left hypoglossal nerve.

EYE AND ORBIT

THE BONY ORBIT

Borders

Superior : orbital plate of Frontal bone and small part of Lesser Wing of the sphenoid
Lateral : Greater wing of the sphenoid and frontal process of the Zygomatic bone

Lateral walls are almost 90 from each other.

Medial : Orbital lamina of the ethmoid bone and lacrimal bones.

Medial walls approximately parallel to each other.

Inferior : Maxillary bone.

FORAMINA

1. SUPERIOR ORBITAL FISSURE: Between the lesser and greater wings of the sphenoid bone.

It transmits the Superior Ophthalmic Vein.
It transmits all innervation to the orbit, EXCEPT the Optic Nerve (II): Oculomotor (III), Trochlear (IV), Opthalmic (V¹), and Abducens (VI)

2. OPTIC CANAL: In the Lesser Wing of Sphenoid, superomedial to the superior orbital fissure.

It transmits the Optic Nerve (II)
It transmits the Ophthalmic Artery, a branch from the Internal Carotid.

3. INFERIOR ORBITAL FISSURE: Carries the Maxillary Nerve (V²) along the bottom surface of the orbit.

4. INFRAORBITAL FORAMEN: The lower medial corner of the orbit, in the orbital part of the maxillary bone.

It transmits the Infraorbital Nerve (V²) out of the orbit.
It transmits the Infraorbital Artery -- an anastomotic branch between the Angular and Maxillary Aa. (both of which are off the External Carotid).

5. ETHMOID FORAMEN: Anterior and posterior foramina in the medial wall, transmitting structures that are going from orbit to the ethmoid air sinuses and nose:

Anterior and Posterior Ethmoid Arteries, from Opthalmic Artery
Anterior and Posterior Ethmoid Nerves, from Nasociliary Nerve (V¹)

THE MUSCLES

COMMON ANNULAR TENDON: The common ring-shaped origin of the extrinsic eye muscles (except for the inferior oblique muscle). It surrounds both the Optic Canal and Superior Orbital Fissure.

The common tendon actually sits medial and not exclusively posterior to the eyeball.
All four rectus muscles originate from the tendon itself.
The two oblique muscles have origins near the tendon but not in it.
The interior of the cone is filled with fat and contains the optic nerve.

EXTRINSIC MUSCLES

The lateral rectus (LR)is an abductor
The medial rectus (MR)turns the eyeball medially. Left and right medial recti muscles contract simultaneously to cause convergence of the gaze (for focusing on a near object).
The superior rectus (SR) turns the eyeball superiorly and medially.
The inferior rectus (IR) turns the eyeball inferiorly and medially.
The superior oblique (SO) runs along the medial wall to reach the trochlea. It then loops posteriorly through a fascial sling before being attached to the eyeball. It turns eyeball inferiorly and laterally.
The inferior oblique (IO) arises from the floor of the orbit and travels laterally below the eyeball, attaching to the eyeball laterally. It turns the eyeball superiorly and laterally.
Extraocular Movements :

Looking straight up: SR and IO
Looking straight down: IR and SO
Looking left: left LR and right MR

LEVATOR PALPEBRAE SUPERIORIS

Superior to the cone, outside of it.
It is supplied both by the 3rd cranial nerve & sympathetic nerves (loss of either innervation will lead to ptosis).

BLOOD VESSELS

Ophthalmic artery : from the internal carotid artery.
Central retinal artery

from the ophthalmic artery
is only blood supply to neural retina : enters the optic nerve
divides within the eye into nasal and temporal branches c/ veins.

Dorsal nasal and Supratrochlear arteries : the ophthalmic artery travels anteriorly along the medial wall of the orbit and ends by dividing into , emerging onto the face.
Other branches of the ophthalmic artery in the orbit are

The lacrimal artery, which follows the lateral wall of the orbit, supplies the lacrimal gland and ends on the face by supplying the eyelids.
The long (2) and short (many) posterior ciliary arteries which enter the eyeball to supply the choroid. The short arteries supply the back of the eyeball. The long arteries enter the back of the eyeball but will break up into branches only at the corneoscleral junction. The long and/or short posterior ciliary arteries may give out an anterior ciliary artery to the front of the eyeball.
The supraorbital artery lies below the roof of the orbit and supplies the scalp.
The anterior and posterior ethmoidal arteries enter canals in the ethmoid bone to supply the ethmoidal air cells and the posterior ethmoidal artery continues into the nasal cavity.

Veins accompany all the arteries but they drain into the superior and inferior ophthalmic veins which communicate with the cavernous sinus and the pterygoid plexus of veins.

NERVES

CN IV : enters the orbit above the fibrous ring (outside of the muscular cone), crosses to the medial side and enters the upper border of the superior oblique muscle.
CN VI : enters within the ring and immediately turns laterally to enter the lateral rectus.
CN III : divides into 2 divisions lying above and below the nasociliary nerve within the cone:

The superior branch : to the superior rectus & the levator palpebrae superioris.
The inferior branch : to the medial rectus, the inferior rectus & the inferior oblique muscles. The nerve to the inferior oblique carries parasympathetic fibers from the Edinger-Westphal nucleus in the midbrain. They travel in a branch to the ciliary ganglion, synapse and the short ciliary nerves travel to the back of the eyeball. They supply the ciliaris muscle and the sphincter pupillae.

Ophthalmic division of the trigeminal nerve (sensory): the frontal and lacrimal nerves enter the orbit above the fibrous ring and the nasociliary within it.

Frontal nerve : lying on the levator palpebrae superioris. It divides into the supraorbital and supratrochlear nerves leaving the orbit at its upper border and supplies the scalp.
Lacrimal nerve : along the lateral orbit wall to the eyelids ; also carries parasympathetic secretomotor fibers to the lacrimal gland.
Nasociliary nerve : short ciliary nerves are derived from the ciliary ganglion, not the nasociliary nerve & the lacrimal nerve is a separate branch from the ophthalmic division.

gives off 2 long ciliary nerves which carries sympathetic fibers to the dilator pupillae and sensory fibers to the cornea.
Along the medial wall , the nasociliary nerve gives out a posterior ethmoidal nerve and ends by turning into the anterior ethmoidal nerve, giving off a small infratrochlear nerve.

GROSS MORPHOLOGY

External Features:

CONJUNCTIVA: Palpebral Conjunctiva,Bulbar Conjunctiva,Superior & Inferior Conjunctival Fornix
CANTHUS: Medial and Lateral.

Outer Layer of Eyeball

BULBAR SHEATH (TENON'S CAPSULE): A connective-tissue capsule enclosing, right outside the sclera.

Medial and Lateral Check Ligaments: These ligaments are extensions of the Bulbar Sheath. They connect to the medial and lateral periorbita (periosteum) of the orbit, to hold the eyeball in place.

SCLERA: Dense white connective tissue continuous with the dura mater of the optic nerve and brain.

The oculomotor muscles insert into the sclera.

CORNEA: The clear central part of the sclera, anterior to the pupil and iris. ; continuous with the sclera.

The cornea is avascular, but there are pain fibers from the Ophthalmic N. (V¹)
The cornea receives O₂ from the air, thus contact lenses should be gas permeable.
Cornea transplants can be done successfully (an immunologically privileged site).

ANTERIOR CHAMBER between the cornea and the iris, filled with Aqueous Humor.
CANAL OF SCHLEMM: Drains the aqueous humor out of the anterior chamber into the venous blood.

Middle Layer of Eyeball

CHOROID: Highly vascular compartment (containing ciliary arteries) ; between the sclera & the retina proper.
PUPIL: The opening of the iris, which allows light into the eye.
IRIS: Pigmented part of the eyeball, surrounding the pupil.

Contains the 2 intrinsic ciliary muscles: Dilator Muscle (sympathetic) & Sphincter Muscle (parasympathetic)

LENS: deformable and has a natural curvature ; modulated by zonular fibers ciliary muscle.

Presbyopia: The loss of the ability of accomodation. The lens becomes less elastic with old age, resulting in far-sightedness.
The more the lens is rounded up, the closer up it can focus.

CILIARY BODY: Produces aqueous humor, which is secreted into the anterior chamber.
CILIARY MUSCLE: contracts zonular fibers ---> allow lens to increase its natural curvature ---> accomodation for near-vision.
ZONULAR FIBERS: Also known as Suspensory ligaments of the lens ; connect the lens to the ciliary bodies.

Tension of zonular fibers make the lens slightly flattened, to allow it to gaze at distant objects.
ACCOMMODATION: Ciliary muscle contracts ---> Zonular fibers lose tension by pulling toward the anterior chamber of the eye ---> the lens increases its curvature ---> light is more highly refracted ---> close-up objects come into focus.

Inner Layer of Eyeball:

VITREOUS BODY: Filled with gelatinous proteoglycans, vitreous humor, in the posterior chamber of the eye.
RETINA

NEURAL RETINA
PIGMENTED RETINA

EYELID ANATOMY

CILIA: Eyelashes.

CILIARY GLANDS: Sebaceous Glands that lubricate the eyelashes.

Sty: Infection of the sebaceous ciliary glands, usually resulting from obstruction.

TARSAL PLATE: Connective tissue core of the eyelid.

Two muscles insert on the tarsal plate to control the eyelid:

Tarsal Muscle (smooth)
Levator Palpebrae Superiores

Palpebral part of Orbicularis Oculi also helps to raise the eyelid, but its insertion is superior to the tarsal plate.
Medial and Lateral Palpebral Ligaments
TARSAL GLANDS: Secrete fatty lubricants

Chalazion: An infection of the tarsal glands.

ORBITAL SEPTUM: Extends up from tarsal plate and hooks onto the bony border of the orbit. It effectively separates very anterior part from the rest of the orbit.

Lacrimal Apparatus:

Lacrimal Gland: The superior and lateral part of the orbit, consisting of two parts: An orbital and palpebral part.

They secrete tears into the superior conjunctival fornix of the eye.
Tears go over the cornea of the eye every time you blink or close your eyelid.

Lacrimal Caruncle: Medial Canthus of the eye, the location of the Lacrimal Lake, where tears accumulate after they have coated the surface of the cornea.
Lacrimal Puncti: Two openings in the Lacrimal Papilla (bumps), on either side of the Lacrimal Caruncle. These holes take up tears by a vacuum motion every time you blink.
Lacrimal Canaliculus: The canal that conducts tears from the Lacrimal Puncti to the Lacrimal Sac.
Lacrimal Sac: Directly proximal to the Nasolacrimal Duct. Tears pool up here until they are ejected into the nasolacrimal duct and onto the nose.
Nasolacrimal Duct: The duct which allows tears to conduct from the eye to the nose. Crying and tearing causes sniffling due to overflow of the nasolacrimal duct.
Overall flow of tears: Lacrimal Gland ------> 8 to 10 lacrimal ducts ------> Superior Conjunctival Fornix ------> surface of cornea ------> Lacrimal Lake ------> Lacrimal Puncti ------> Lacrimal Canaliculi ------> Lacrimal Sac ------> Nasolacrimal Duct ------> Nasal Cavity, under the Inferior Turbinate.

THE EAR AND THE TEMPORAL BONE

The EXTERNAL EAR:

Auricle: elastic cartilage, continuous with cartilage of external acoustic meatus and lobule (loose connective tissue).
External acoustic meatus

The innervation of the skin of the ear:

Superior portion : innervated by V3 via the auriculotemporal nerve;
Inferior portion including lobule : innervated by fibers of the greater auricular nerve from the cervical plexus (C 2, 3);
External acoustic meatus and the skin surrounding the opening (concha) : innervated by X for general sensation.

Neurological examination of the skin of ear can determine the status of the upper spinal cord (C 2, 3), the medulla (X) and the pons (V).

The external acoustic meatus:

from the concha to the tympanic membrane.
Lateral cartilaginous 1/3 (lined with hair, sebaceous glands and ceruminous glands)
Medial bony 2/3 (thin stratified squamous epithelium, also lining external surface of tympanic membrane).
The auricular branch of the vagus (X) provides the sensory innervation.

The MIDDLE EAR or TYMPANUM

Sound waves create vibrations on the tympanic membrane moving the 3 bony ossicles (malleus, incus and stapes) which in turn vibrate the oval window (fenestra vestibuli) on the medial wall of the middle ear: this is an amplification system.

The middle ear is a modified bony sinus in the petrous portion of the temporal bone. It communicates with the mastoid air cells through the aditus and with the nasopharynx through the auditory tube.

The tympanic cavity and its walls:

The roof : a thin layer of petrous temporal bone separating the middle cranial fossa from the middle ear.

The space below the roof is the epitympanic recess for the articular joint of the head of the malleus and body of the incus.

The floor : rests upon the superior jugular bulb.

Where the internal carotid artery (moving anteriorly) diverges from the internal jugular vein (moving posteriorly), the cranial nerves IX and X send branches into the bony tympanic floor.

The lateral wall : closed by the tympanic membrane.
Roof and floor converge anteriorly to form the auditory tube which is divided by the processus cochlearis into:

superior compartment : contain the tensor tympani muscle. The tensor tympani inserts into the handle of the malleus.
lower compartment : joins with the cartilaginous portion of the auditory tube.

The ascending carotid artery is associated with the anterior wall of the tympanic cavity, separated by a thin layer of bone.

Pulsations may be heard by the patient in some clinical disorders.

The posterior wall : contains a tunnel, the aditus, connecting to the mastoid antrum.

Fluid from the mastoid air cells drain via the aditus into the tympanic cavity and then into the auditory tube and the nasopharynx.
Fluid may collect within the tympanic cavity if the auditory tube is obstructed due to an upper respiratory airway infection.
The VIIth cranial nerve enters the posterior wall below the aditus and exits from the base of the temporal bone via the stylomastoid foramen.
The chorda tympani arises from the facial nerve within the posterior wall of the middle ear, courses over the eardrum along the lateral wall, exits via the petrotympanic fissure into the infratemporal fossa.
The pyramid is also located in the posterior wall. The apex of the pyramid has an orifice through which the tendon of the stapedius passes to insert on the neck of the stapes..
The stapedius acts to retract the stapes from the oval window and reflexively attenuates loud sound. It is innervated by cranial VII and Bell's palsied patients may complain of sensitivity to loud sounds (hyperacusis).

The medial wall : faces the inner ear contained within the petrous portion of the temporal bone.

It has the promontory at its center, overlying the first turn of the cochlea. Within the mucosa covering the promontory is the tympanic plexus where fibers of VII, IX and X intermingle. Through this plexus will pass:

sensory fibers to the external and middle ear
and preganglionic parasympathetic fibers for the greater and lesser petrosal nerves.

Posterior and superior to the promontory are the oval window, the canal for the facial (VIIth cranial) nerve and the prominence of the lateral semicircular canal.

The shape of the oval window matches the footplate of the stapes.
The canal of facial nerve is horizontal and connects the internal auditory meatus to the descending canal of VII in the posterior wall.

Posterior and inferior to the promontory is the round window or fenestra cochleae, closed by a membrane.

The tympanic membrane

is circular
is set in a sulcus in the tympanic bone
is oriented laterally, anteriorly and inferiorly ("catches sounds from the ground as one advances").
is lined with epidermis (ectodermal) laterally and mucous membrane (endodermal) medially.
The handle of the malleus is attached to the tympanic membrane.
The superior pars flaccida of the eardrum attaches to the lateral process of the malleus.
The chorda tympani lies posterior to this pars flaccida and must be avoided in puncturing the eardrum to drain the middle ear.

3 bony ossicles : 2 synovial joints ( between malleus and incus; between incus and stapes; may be affected by otosclerosis resulting in deafness ):

Malleus: head, neck, manubrium with lateral process and inferior tip. Anterior process of the malleus is attached to a stabilizing ligament.
Incus: Body of the incus articulates with the malleus.

Short crus attaches via a ligament to the posterior wall of the epitympanic recess.
Long crus is vertically oriented and descends into the tympanic cavity. It has a lenticular process which articulates with the head of the stapes.

Stapes: head, neck, posterior and anterior limbs and footplate attached to oval window by annular ligament.
The role of the middle ear is to transfer sounds from air to fluid (perilymph):

Vibratory surface of eardrum is 55 mm2 .
Footplate is 3.2 mm2 .
Hydraulic ratio between membrane and footplate is 17:1.

Muscles of the ossicles: contraction of either attenuate sound by decreasing the movement of ossicles.

1) Tensor tympani in the auditory canal runs around the processus cochleariformis to attach to the handle of the malleus: contraction tenses the eardrum by pulling medially. It is innervated by a branch of V3 as it exits foramen ovale.
2) Stapedius in the pyramid of the posterior wall, inserts into the neck of the stapes. Contraction pulls the foot plate away from the oval window to dampen the sound. It is innervated by VII.

The INNER EAR is a bony labyrinth containing a membranous labyrinth.

The bony labyrinth consists of: the cochlea, the vestibule and the semicircular canals.
1) Cochlea: snail shell with 2.5 turns. Vibrations from the perilymph of the vestibule is communicated to the fluids of the cochlea stimulating the hearing receptors of the inner ear.
2) Vestibule lies between the cochlea and semicircular canals, communicating with both chambers. It communicates with the tympanic cavity via the oval window.
3) 3 semicircular canals: anterior (superior), posterior and lateral (horizontal). They lie in 3 planes like the corner of a room. Their function is to maintain balance.
The membranous labyrinth is surrounded by perilymph and is formed by the cochlear duct, saccule, utricle and 3 semicircular canal ducts.
The ductus endolymphaticus passes from saccule and utricle through a canal in the petrous bone to a fissure lateral to the internal auditory meatus. It acts as a safety expansion, the endolymphatic sac being placed extradurally.
Fluid waves from the perilymph are communicated to the endolymph of the cochlear duct for hearing.
Angular acceleration of endolymph in semicircular canals shifts the endolymph in the semicircular ducts and stimulate the vestibular receptors in the ampulla of the semicircular canal.
Utricle (for detecting movements in the sagittal plane) and saccule (for detecting movements in the coronal plane) are for head movements detection. This is based on gravitational forces acting on their receptor mechanisms.

VIIIth cranial (Vestibulocochlear) nerve:

Test hearing by using a tuning fork placed against the mastoid process:

If the eardrum and bony ossicles are impaired, then the bony conduction should be heard normally. But if VIII is impaired then total deafness is the result.
Test balance by having patient stand with feet together and eyes closed. If the vestibular portion of VIII is defective then the patient will fall to the lesioned side.

The blood supply of the inner ear enters the internal acoustic meatus with VII and VIII: This labyrinthine artery is a branch of the anterior inferior cerebellar artery. It may be affected by strokes in the vertebral arterial system.

VIIth cranial (Facial) nerve:

is the nerve of the 2nd pharyngeal arch to the muscles of facial expression, stylohyoid, posterior belly of the digastric and stapedius.
also carries nervus intermedius for taste (special sensory) and preganglionic parasympathetic fibers to all glands of the face except parotid gland.
runs through the internal auditory meatus with VIII,
lies above VIII in the canal, above the vestibule of the bony labyrinth,
bends on the medial wall of the middle ear and forms the genu with the geniculate ganglion,
and courses to the posterior wall to descend through the facial canal and exit through the stylomastoid foramen.
The geniculate ganglion contain the cell bodies for the taste fibers. There is no synapse in the geniculate ganglion.
The greater (superficial) petrosal nerve branches from the geniculate ganglion, pierces the anterior wall of tympanic cavity, enters the middle cranial fossa. It carries taste fibers for the palate, and secretomotor fibers for glands in the roof of the oral cavity, the nasal cavity and the orbit.
The descending part of VII gives off motor branch to stapedius and chorda tympani.
Chorda tympani runs between the handle of malleus and vertical process of incus to exit into the infratemporal fossa via the petrotympanic fissure. It carries taste fibers from the anterior 2/3 of the tongue and secretomotor fibers to the submandibular ganglion.
Unilateral facial muscles paralysis:

1) for loss of taste in the anterior 2/3 of tongue for chorda tympani.
2) for hyperacusis to test the nerve to stapedius.
3) for lack of lacrimation on one side for the greater (superficial) petrosal nerve. If this is present, it will result in dessication of cornea, ulceration and blindness. Dessication of cornea will result in pain carried by V1.
If all 3 signs are present then the lesion is between the brainstem and the geniculate ganglion.
Bell's palsy usually affects only branches of the facial nerve (VII) below the stylomastoid foramen.

LYMPHATIC DRAINAGE OF THE HEAD AND NECK

Lymph nodes in the head and neck are organized into 2 groups:

A terminal (collecting)group : deep cervical group

is related to the carotid sheath
All lymph vessels from the head and neck drain directly to this group or indirectly via the

Intermediary, outlying groups

The jugular trunk　

is formed by efferents of the deep cervical group
drains on the right into the right lymphatic duct or at the junction between the internal jugular and subclavian vein.
drains on the left into the thoracic duct or joins the internal jugular or subclavian vein.

The deep cervical lymphatic nodes :

1) Superior deep cervical nodes

which can be found next to the upper portion of the internal jugular vein.
and most lie deep to the sternocleidomastoid muscle.
drain to the lower inferior group or directly to the jugular trunk.

The jugulodigastric group : for lymphatic drainage of the tongue ; in a triangle bordered by the posterior belly of the digastric muscle, the facial and internal jugular veins.

2) Inferior deep cervical lymph nodes are related to:

the deep surface of the SCM muscle
the lower portion of the internal jugular vein
the brachial plexus and subclavian vessels

The jugulo-omohyoid node ( at the level of the intermediate tendon of the omohyoid ) : lymphatic drainage of the tongue.

The inferior deep cervical lymph nodes drain into the jugular lymph trunk.

LYMPHATIC SYSTEM OF SUPERFICIAL HEAD & NECK

2 types of drainage exist:

Drainage by vessels afferent to local groups of nodes which in turn drain to the deep cervical nodes.
Direct drainage to deep cervical nodes.

Superficial drainage groups

1) In the head:

occipital
retroarticular (mastoid)
parotid
buccal (facial)

2) In the neck:

submandibular
submental
anterior cervical
superficial cervical

Lymphatic drainage of scalp and ear

Submandibular nodes receive drainage from the frontal region above the root of the nose.

Superficial parotid nodes (anterior to tragus, superficial and deep to parotid fascia) receive drainage from :

rest of the forehead,
temporal region,
upper half of the lateral auricular aspect
anterior wall of the external acoustic meatus
lateral vessels from the eyelids and skin of the zygomatic region

Efferent vessels drain to the upper deep cervical nodes.

Upper deep cervical nodes and retroauricular nodes receive drainage from:

a strip of scalp above the auricle
the upper half of the cranial aspect and margin of the auricle
the posterior wall of the external acoustic meatus

The retroauricular nodes are found:

superficial to the mastoid attachment of the sternocleidomastoid muscle
deep to the auricularis posterior
They drain to the upper deep cervical nodes

Superficial cervical or upper deep cervical nodes receive drainage from :

auricular lobule
floor of the auditory meatus
skin over the mandibular angle
skin over the lower parotid region

Superficial cervical nodes:

are distributed along the external jugular vein superficial to sternocleidomastoid
have efferents:

going around the anterior border of the sternocleidomastoid to the upper deep cervical nodes
following the external jugular vein to the lower deep cervical nodes in the subclavian triangle.

The occipital scalp is drained:

partly to the occipital nodes.
partly by a vessel along the posterior border of sternocleidomastoid to the lower deep cervical nodes.

The occipital nodes are mainly found superficial to the upper attachment of trapezius and occasionally in the superior angle of the posterior triangle of the neck.

Lymphatic drainage of the face

Lymph vessels draining the eyelid and conjunctiva:

start in a subcutaneous and deep plexus around the tarsal plates.
divided into lateral and medial vessels

Lymph vessels from eyelids and conjunctiva are organized into:

1) Lateral vessels :

drain the whole thickness of both eyelids (except for the medial parts)
drain all of the conjunctiva
run to the superficial parotid nodes and deep nodes embedded in the parotid gland.
also receive lymph from the middle ear.

2) Medial vessels:

drain the whole thickness of the medial parts of the lids.
drain the caruncular lacrimalis.
run to the submandibular nodes.

Submandibular nodes

lie deep to the cervical fascia, in the submandibular triangle.
are usually 3 in number:

one at the anterior pole of the submandibular gland.
two on either side of the facial artery as it reaches the mandible.
Other nodes may be embedded in the submandibular gland or deep to it.

drain a wide area from the :

submental nodes
buccal nodes
lingual nodes

drain to the upper and lower deep cervical nodes.
drain directly the:

external nose
cheeks
upper lip and lateral part of the lower lips
the mucosa of lips and cheeks
A few buccal nodes may be present near the facial vein and they also drain to the submandibular nodes.

The skin over the root of the nose and central forehead drains partly to the parotid nodes and partly to the submandibular nodes.

The lateral part of the cheek drains to the parotid nodes.

Submental nodes

are located on the mylohyoid, between the anterior bellies of the digastric muscles.
receive bilateral afferents.
have efferents running to the submandibular and jugulo-omohyoid nodes.

Lymphatic drainage of the neck

Superficial vessels run:

around the sternocleidomastoid, to the superior or inferior deep cervical nodes.
over the sternocleidomastoid and the posterior triangle, to the superficial cervical and occipital nodes.

The superior region of the anterior triangle drains to the submandibular and submental nodes.

The anterior cervical skin below the hyoid bone drains to the anterior cervical lymph nodes near the anterior jugular veins.

Efferents go to the deep cervical nodes bilaterally (infrahyoid, prelaryngeal and pretracheal groups).

An anterior cervical node may often be found in the suprasternal space

LYMPHATIC SYSTEM OF DEEP HEAD AND NECK

Deep nodes are organized into

Superior deep cervical nodes
Inferior deep cervical nodes
Retropharyngeal nodes
Paratracheal nodes
Infrahyoid, prelaryngeal and pretracheal nodes.
Lingual nodes.

The retropharyngeal nodes:

are formed by a median and 2 lateral groups. The lateral group is found bilaterally, anterior to the lateral process of the atlas, along the border of the longus capitis muscle.
lie between the pharyngeal and prevertebral fasciae.
receive afferents from the nasopharynx, eustachian tube and joints between the occipital bone, C1 and C2 vertebrae.
drain to the upper deep cervical nodes.

Paratracheal nodes

lie on either side of the trachea and esophagus, along the recurrent laryngeal nerves.
drain to the upper and lower deep cervical nodes.

Infrahoid, prelaryngeal and pretracheal nodes are located deep to the cervical fascia.

infrahyoid nodes are anterior to the thyrohyoid membrane.
prelaryngeal nodes are on the conus elasticus and cricothryoid ligament.
pretracheal nodes are anterior to the trachea near the inferior thyroid veins.

The infrahyoid nodes:

drain afferents from the anterior cervical nodes.
drain to the deep cervical nodes.

Lingual nodes

form an inconstant group.
are found on the external surface of the hyoglossus, and between the genioglossi.
drain to the upper cervical nodes.

Lymphatic drainage of nasal cavity and nasopharynx

The anterior region of the nasal cavity drains superficially to the submandibular nodes.
rest of nasal cavity, paranasal sinuses, nasopharynx and pharyngeal end of the auditory tube drain via the retrophrayngeal nodes or directly to the upper deep cervical nodes.
the posterior nasal floor drains to the parotid nodes.

Lymphatic drainage of the middle ear.

The mucosa of the tympanic membrane and the antrum drain to the parotid or upper deep cervical lymph nodes.
The tympanic end of the auditory tube drain to the deep cervical lymph nodes.

Lymphatic drainage of the larynx.

Laryngeal lymphatic vessels:

form superior and inferior groups, at the level of the vocal fold,
anastomose on the posterior wall.

1) Superior vessels run with the superior laryngeal vessels to the upper deep cervical nodes.

2) Inferior vessels run:

between the cricoid cartilage and the first tracheal ring to the inferior deep cervical nodes.
or through the cricothyroid ligament to the pretracheal and prelaryngeal nodes.

Lymphatic drainage of the trachea

A dense network of lymphatic vessels (tracheal plexus) is present in the tracheal wall.

This tracheal plexus drains to:

the pretracheal nodes
the paratracheal nodes
or directly to the inferior deep cervical nodes.

Lymphatic drainage of the thyroid gland

Lymphatic vessels from the thyroid gland communicate with the:

prelaryngeal nodes (above thyroid isthmus) via the tracheal plexus,
pretracheal nodes,
paratracheal nodes,
brachiocephalic nodes (in superior mediastinum),
deep cervical nodes via the superior thyroid vessels,
and directly to the thoracic duct.

Lymphatic drainage of the mouth

Gingiva drain to the submandibular nodes.
Soft and hard palate drain to the superior deep cervical nodes and the retropharyngeal nodes.
Anterior part of the floor of the mouth drains via the submental nodes or directly to the superior deep cervical nodes.
Rest of the floor of the mouth drains to the submandibular and superior deep cervical nodes.

Lymphatic drainage of the teeth

Lymphatics from the teeth pass to the submandibular and deep cervical nodes.

Lymphatic drainage of the tonsil

The lymphatic drainage of the tonsil drains to the superior deep cervical nodes:

most to the jugulodigastric node.
some to the small nodes on the lateral aspect of the internal jugular vein.

Lymphatic drainage of the tongue

The lingual mucosal plexus is continuous with the intramuscular plexus.

The anterior 2/3 of the tongue drains into the marginal and central vessels.
The posterior 1/3 of the tongue drains into the dorsal lymph vessels.

Marginal vessels of the tongue

arise from the tip of the tongue and frenulum.
drain bilaterally to the:

submental nodes,
jugulo-omohyoid node,
anterior or middle submandibular node,
jugulo-digastric nodes.

Central vessels of the tongue follow the lingual vein to drain to:

deep cervical nodes (jugulodigastric and juguloomohyoid nodes).
submandibular nodes.

Dorsal vessels of the tongue

join with the marginal vessels
drain into the jugulodigastric node or juguloomohyoid node

Lymphatic drainage of the pharynx and cervical part of the esophagus

passes:

through the retropharyngeal or paratracheal nodes
or directly to the deep cervical nodes.

The epiglottis drains to the infrahyoid nodes.

Danil hammoudi.md

Sinoe Medical Association