Anus

The anus is a canal at the end of the digestive tract through which feces is expelled. It is about five inches long and is an extension of the rectum. It is only open during the expulsion of feces, because it is usually kept closed by sphincter muscles, which can be relaxed at will.

Bulbospongiosus Muscle

In males, the bulbospongiosus muscles are united and surround the base of the penis. They assist in emptying the urethra. In females, these muscles are separated in the middle by the vagina and act to constrict the vaginal opening. They can also retard the flow of blood into veins, which help to maintain an erection in the penis of the male and the clitoris of the female.

Erectile Tissue

The body, or shaft, of the penis is composed of three columns of erectile tissue. These include a pair of "corpora cavernosa" near the back and a single "corpus spongiosum" below. These columns are enclosed by skin, a thin layer of subcutaneous tissue, and a layer of connective tissue. In addition, each column is surrounded by a tough capsule of white fibrous connective tissue. The corpus spongiosum, through which the urethra extends, is enlarged at the end to form a sensitive, cone-shaped "glans penis," which covers the ends of the corpora cavernosa and bears the urethral opening. Inside the glans penis, the corpus spongiosum is dilated and forms the "navicular fossa."

Ejactulatory Duct

The ejaculatory duct is one of either of the paired ducts in males that is the junction of the duct from the seminal vesicle with the vas deferens, pass through the prostate, and open into or close to the prostatic utricle.

Prostate Gland

The prostate gland is a solid, chestnut-shaped organ surrounding the first part of the urethra (tube which carries the urine and semen) in the male. It produces secretions which form a part of the semen. The prostate gland lies just under the bladder and in front of the rectum. It consists of two main zones: the inner zone, which produces secretions to keep the lining of the male urethra moist, and the outer zone, which produces seminal fluids to facilitate the passage of semen into the female. The "urethra" is a two-stemmed duct leading from the bladder and from the prostate gland into the penis. The word, "aphrodisiac," is derived from Aphrodite, the Greek goddess of love and sexual pleasure. The ancient Greeks thought honey would produce an increase in sexual powers and they believed the same of the hair from a wolf's tail and ground snake bones. The French used an "aphrodisia" which they called the "love apple" - actually a tomato. Today, the hope lies in oysters. Sadly, the fallacy that a ground rhinoceros horn will help in this plight has put this animal on the endangered species list. Actually, aphrodisiacs are in the mind and operate only by the power of suggestion - if at all.

Pubic Symphysis

The pubic symphysis is a cartilage-like articulation between the pubic bones. It is a slightly movable joint that contains three ligaments: the superior pubic, the arcuate pubic and the interpubic disk.

Rectum

The rectum is a short, muscular tube that forms the lowest portion of the large intestine and connects it to the anus. Feces collects here until pressure on the rectal walls cause nerve impulses to pass to the brain, which then sends messages to the voluntary muscles in the anus to relax, permitting expulsion.

Sacrum

The sacrum is a large triangular bone at the base of the lower spine. Its broad upper part joins the lowest lumbar vertebrae and its narrow lower part joins the coccyx or "tail bone". The sides are connected to the iliums (the largest bones forming the pelvis). The sacrum is a strong bone and rarely fractures. The five vertebrae that make up the sacrum are separated in early life, but gradually become fused together between the eighteenth and thirtieth years. The spinous processes of these fused bones are represented by a ridge of tubercles. The sacrum is wedged between the coxal bones of the pelvis and is united to them by fibrocartilage at the sacroiliac joints. The weight of the body is transmitted to the legs through the pelvic girdle at these joints.

Septum

A septum is a thin dividing wall within or between parts of the body. The nasal septum is a sheet of cartilage and bone that separates the nostrils. The scrotal septum is a thin wall of tissues separating the two pouches of the scrotum, which hangs below the penis and holds the testes.

Vesicle

A vesicle is a small skin blister, usually filled with clear fluid, that forms where there has been some skin damage. "Vesicle" also refers to any small saclike pouch in the body; for example, the seminal vesicles are small sacs in which seminal fluid is stored.

Skin

Skin is the outside covering of body tissue, which protects inner cells and organs from the outside environment. The skin is the largest organ of the body, and its cells are continuously replaced as they are lost to normal wear and tear. The skin totals between twelve and twenty square feet in area and accounts for 12%% of body weight. It is composed of three integrated layers: the epidermis, the dermis and the subcutis. The thickness of the epidermis and the dermis varies over different parts of the body. It is thickest on the palms of the hands and feet, where friction is needed for gripping, and it is thinnest on the eyelids, which must be light and flexible. The epidermis also grows into fingernails, toenails and hair. The dermis, or true skin, is thick, sturdy, rich in nerves and blood vessels and in sweat glands. It shields and repairs injured tissue. This layer consists mostly of collagen, which originates from cells called fibroblasts and is one of the strongest proteins found in nature. It gives skin durability and resilence. The subcutis, joined to the bottom of the dermis, is the deepest layer of the skin. It contains "lipocytes," which produce lipids for the subcutaneous tissue to make a fatty layer which cushions muscles, bones and inner organs against shocks, and acts as an insulator and source of energy during lean times. The skin registers sensation constantly and supports a teeming, unseen population of tiny organisms. Not only does the skin harden from use, but it molds into varied shapes, and it responds to the most delicate touch, becoming an organ of communication - sometimes more eloquent than words. So tough and durable is the skin that when a 2,000-year-old Egyptian mummy was fingerprinted, the ridges were perfectly preserved.

Small Intestine

If the small intestine were not looped back and forth upon itself, it could not fit into the abdominal space it occupies. It is held in place by tissues which are attached to the abdominal wall and measures eighteen to twenty-three feet in the average adult, which makes it about four times longer than the person is tall. It is a three-part tube of about one and one-half to two inches in diameter and is divided into three sections: (1) the duodenum, a receiving area for chemicals and partially digested food from the stomach; (2) the jejunum, where most of the nutrients are absorbed into the blood and (3) the ileum, where the remaining nutrients are absorbed before moving into the large intestine. The intestines process about 2.5 gallons of food, liquids and bodily waste every day. In order for enough nutrients to be absorbed into the body, it must come in contact with large numbers of intestinal cells which are folded like gathered skirts. Each of these cells contain thousands of tiny finger-like projections called "villi," and each villus contains microscopic "microvilli". In one square inch of small intestine, there are about 20,000 villi and ten billion microvilli. Each villus brings in fresh, oxygenated blood and sends out nutrient-enriched blood. The villi sway constantly to stir up liquefied food and remove the nutrients which can be absorbed and then passed through the membranes of the villi into the blood and lymph vessels. The fatty nutrients go to the lymph vessels, and glucose and amino acids go to the blood and on to the liver. The muscles which encircle this tube constrict about seven to twelve times a minute to move the food back and forth, to churn it, knead it, and to mix it with gastric juices. The small intestine also makes waves which move the food forward, but these are usually weak and infrequent to allow the food to stay in one place until the nutrients can be absorbed. If a toxic substance enters the small intestine, these movements may be strong and rapid to expel the poisons quickly.

Sphincter Muscles

A "sphincter" is a ring of muscle around a natural opening or passage that acts like a valve, regulating inflow and outflow. The outlet from the stomach into the duodenum is the "pyloric" sphincter and controls the stomach's outflow. The "anal" sphincter alters rectal outflow and is partly voluntary, allowing a decision on when to empty the bowel.

Suspensory Ligament

The suspensory ligament is the ligament that helps give support to the scrotum.

Urethra

The urethra is a tube that conveys urine from the urinary bladder to the outside of the body. Its wall is lined with mucous membranes and contains a relatively thick layer of smooth muscle tissue. It also contains numerous mucous glands, called "urethral glands," that secrete mucus into the urethral canal. In females the urethra is about 4 cm long. It passes forward from the bladder, descends below the symphysis pubis, and empties into the labia minor. Its opening is located above the vaginal opening and about 2.5 cm below the clitoris. In males, the urethra, which functions both as a urinary canal and a passageway for cells and secretions from various reproductive organs, can be divided into three sections: the prostatic urethra, the membranous urethra, and the penile urethr

Urinary Bladder

The bladder is a hollow muscular organ that acts as a reservoir for urine. The adult bladder can hold a pint or more of fluid. It lies behind the pubic bone and is protected by the pelvis. The bladder walls are made up of muscle and an inner lining. At the back are two ureters which carry the urine from the kidneys. The bladder collects and stores urine until it can be expelled from the body.

Urogenital Diaphragm

The outlet of the pelvis is spanned by two muscular sheets - a deeper "pelvic diaphragm" and a more superficial "urogenital diaphragm." The pelvic diaphragm forms the floor of the pelvic cavity, and the urogenital diaphragm fills the space within the pubic arch. The muscles of the male and female urogenital diaphragm include the following: (1) "superficial transversus perinei," a small bundle of muscle fibers that pass along the back border of the urogenital diaphragm and assists other muscles in supporting the pelvic tissues; (2) the "bulbospongiosus" muscles, which are united and surround the base of the penis; (3) the "ischiocavernosus muscle," a tendinous structure that extends down to the margin of the pubic arch and assists the function of #2; and (4) the "sphincter urethrae" are muscles that arch around the urethra and unite with those on the other side. Together they act as a sphincter that closes the urethra by compression and opens it by relaxation to control the flow of urine.