Anatomy physiology review

Ancient anatomy

begins at least as early as 1600 BC, the date of publication of an Egyptian anatomical papyrus that has survied to this day; this treatise identifies a number of organs and shows a basic knowledge of blood vessels.

The earliest medical scientist of whose works any great part survives today is Hippocrates, a Greek physician active in the late 5th and early 4th centuries BC (460-377 BC). His work demonstrates a basic understanding of musculoskeletal structure, and the beginnings of understanding of certain organs, such as the kidneys. Much of his work, however, and much of that of his students and followers later, relies on speculation rather than empirical observation of the body.

In the 4th century BC, Aristotle and several contemporaries produced a more empirically founded system, based on dissection of animals; works produced around this time are the first to identify the difference between arteries and veins, and the relations between organs are described more accurately than in previous works.

The first use of human cadavers for anatomical research occurred later in the 4th century BC, when Herophilos and Erasistratus performed dissections of cadavers in Alexandria under the auspices of the Ptolemaic dynasty. Herophilos in particular developed a body of anatomical knowledge much more informed by the actual structure of the human body than previous works had been.

Galen

The final major anatomist of ancient times was Galen, active in the 2nd century AD. He compiled much of the knowledge obtained by previous writers, and furthered the inquiry into the function of organs by performing vivisection on animals. His collection of drawings, based mostly on dog anatomy, would hold as a "Gray's Anatomy of the ancient world" for 1500 years. The original text is long gone, and his work was only known to the Rennaissance doctors through the careful custody of Arabic medicine, since the Church destroyed it as heresy. Hampered by the same religious restrictions as anatomists for centuries after him, Galen assumed that anatomical structures in dogs were the same as for humans.

Modern anatomy

Anatomical research in the past hundred years has taken advantage of technological developments and growing understanding of sciences such as evolutionary and molecular biology to create a thorough understanding of the body's organs and structures. While disciplines such as endocrinology have explained the purpose of glands that previous anatomists could not explain, medical devices such as MRI machines and CAT scanners have enabled researchers to study the organs of living people. Progress today in anatomy is centered in the field of molecular biology, as the macroscopic aspects of the field have now been catalogued and addressed.

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Muscle (from Latin musculus "little mouse" ) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Its function is to produce force and cause motion, either locomotion or movement within internal organs. Much of muscle contraction occurs without conscious thought and is necessary for survival, like the contraction of the heart, or peristalsis (which pushes food through the digestive system). Voluntary muscle contraction is used to move the body, and can be finely controlled, like movements of the finger or gross movements like the quadriceps muscle of the thigh. There are 2 types of muscle movement, slow twitch and fast twitch. Slow twitch movements act for a long time but not very fast, whilst fast twitch movements act quickly, but not for a very long time.

Agonist A muscle that causes motion.

AntagonistA muscle that can move the joint opposite to the movement produced by the agonist.

Target The primary muscle intended for exercise.

Synergist A muscle that assists another muscle to accomplish a movement.

StabilizerA muscle that contracts with no significant movement

Origin (b): muscle attatchment that moves least, generally more proximal.
Insertion (a): muscle attatchment that moves most, generally more distal.
Abduction: Lateral movement away from the midline of the body
Adduction: Medial movement toward the midline of the body
Circumduction: circular movement (combining flexion, extension, adduction, and abduction) with no shaft rotation
Extension: Straightening the joint resulting in an increase of angle
Eversion: Moving sole of foot away from medial plane
Flexion: Bending the joint resulting in a decrease of angle
Hyperextension: extending the joint beyond anatomical position
Inversion: Moving sole of foot toward medial plane
Pronation: Internal rotation resulting in appendage facing downward
Protrusion: Moving anteriorly (eg: chin out)
Supination: External rotation resulting in appendage facing upward
Retrusion: Moving posteriorly (eg: chin in)
Rotation: Rotary movement around the longitudinal axis of the bone

The cell is the structural and functional unit of all living organisms, and is sometimes called the "building block of life."Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion or 10¹⁴ cells; a typical cell size is 10 µm; a typical cell mass is 1 nanogram.) The largest known cell is an ostrich egg.

The cell theory, first developed in 1839 by Schleiden and Schwann, states that all organisms are composed of one or more cells. All cells come from preexisting cells. Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

The word cell comes from the Latin cellula, a small room. The name was chosen by Robert Hooke when he compared the cork cells he saw to the small rooms monks lived in.

[http://en.wikipedia.org/wiki/Cell_(biology) ]

Skeletal muscle is made up of thousands of cylindrical muscle fibers often running all the way from origin to insertion. The fibers are bound together by connective tissue through which run blood vessels and nerves.

Each muscle fibers contains:

an array of myofibrils that are stacked lengthwise and run the entire length of the fiber.
mitochondria
an extensive smooth endoplasmic reticulum (SER)
many nuclei.

The multiple nuclei arise from the fact that each muscle fiber develops from the fusion of many cells (called myoblasts).

The number of fibers is probably fixed early in life. This is regulated by myostatin, a cytokine that is synthesized in muscle cells (and circulates as a hormone later in life). Myostatin suppresses skeletal muscle development. Cattle and mice with inactivating mutations in their myostatin genes develop much larger muscles. Some athletes and other remarkably strong people have been found to carry one mutant myostatin gene. These discoveries have already led to the growth of an illicit market in drugs supposedly able to suppress myostatin.

In adults, increased strength and muscle mass comes about through an increase in the thickness of the individual fibers and increase in the amount of connective tissue. In the mouse, at least, fibers increase in size by attracting more myoblasts to fuse with them. The fibers attract more myoblasts by releasing the cytokine interleukin 4 (IL-4). Anything that lowers the level of myostatin also leads to an increase in fiber size.

Because a muscle fiber is not a single cell, its parts are often given special names such as

sarcolemma for plasma membrane
sarcoplasmic reticulum for endoplasmic reticulum
sarcosome for mitochondrion
sarcoplasm for cytoplasm

although this tends to obscure the essential similarity in structure and function of these structures and those found in other cells

Secretory Mechanisms

The secretory cells can release their secretory products by one of three mechanisms.

	Merocrine secretion corresponds to the process of exocytosis. Vesicles open onto the surface of the cell, and the secretory product is discharged from the cell without any further loss of cell substance.
	Apocrine secretion designates a mechanism in which part of the apical cytoplasm of the cells is lost together with the secretory product. The continuity of the plasma membrane is restored by the fusion of the broken edges of the membrane, and the cell is able to accumulate the secretory product anew. This mechanism is used by apocrine sweat glands, the mammary glands and the prostate.
	Holocrine secretion designates the breakdown and discharge of the entire secretory cell. It is only seen in the sebaceous glands of the skin.

Ancient anatomy

Galen

Modern anatomy

History of anatomy

From Wikipedia, the free encyclopedia

Students essays

Secretory Mechanisms

Atlas of Human Anatomy in Cross Section

The Skull Practical