Learning Male Body Parts
Learning Male Body Parts
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In this
section the main sexual and reproductive organs, genitals, of
the male are illustrated and described. If you are a male, it should be easy to relate it
to your own body. If you are a female you will learn that men's and women's bodies are
more alike than different. It's just that the differences are what we notice first, and
they play an important role in other areas of our lives. The first table lists a few of
the organs that develop from the same tissue in a fetus, whether male or female. The sex
of a fetus cannot be seen with a sonogram until sometime after the 6th week when hormones
begin to be released. These hormones, or their absence, cause the development of the same
genital tissue in males and females. Some men are most concerned about the size of their penis, but that is not what's covered here. The size of the man's penis is not even on the list of what women say makes a man a good lover. So, don't compare the size and shape as part of the lesson here. That varies as much as the differences in ears, eyes and other body parts. |
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Homologous Sex Organs
(formed from the same fetal tissue)
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Male Glans of the penis Foreskin of the penis Shaft of the penis Scrotal sac Testes |
Female Clitoris Hood of the clitoris Labia Minora Labia Majora Ovaries |
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| As you learn more about these genital body parts return and check out these illustrations. As you can see the genital tissue is the same before it begins to change. The change depends on a testosterone product released in male fetuses called dihydrotesterone, DHT. The change is completed at week twelve. Without DHT, the genitals of the fetus will develop into female structures. |
Scrotum and Penis
| The scrotum is a pouch of skin that hangs behind the penis and contains the testes. The pouch hangs loosely away from the body in warm weather. It must maintain a temperature 3 or 4 degrees lower than the body in order for the testes to produce sperm. (See below for cold.) |  |
The penis is the male sexual organ which passes both urine and sperm. It extends into the pelvic cavity and attaches to the pubic bone. It does not contain bone or muscles, except for those muscles on the tip of the penis which are needed to eject urine and sperm. |
| The outer layer of the scrotum is darker than the other body tissue and is covered with a sparse amount of hair at adolescence. The inner layer is composed of smooth muscle fibers called tunica dartos, which help draw the pouch closer to the body when the testes are exposed to cold. |  |
Inside the scrotum, the testes are suspended by the spermatic cord (see below) which contains blood vessels and nerves as well as the cremasteric muscle fibers which also help draw the testicles closer to the body. The testes may also be drawn closer to the body during sexual stimulation. |
Inside the Testes
| The Vas deferens is the sperm carrying tube that travels upward inside the spermatic cord until it reaches the urethra. A vasectomy is the removal of a small section of each vas deferens to stop the passage of sperm. The epididymis is a c-shaped structure at the back of the testes where sperm are matured and stored. |  |
The seminiferous tubules are thin, highly coiled structures where millions of sperm are continuously produced. Men continue to produce sperm well into old age. The interstitial cells are located between the tubules and are the major source of male hormones, androgens, which are directly secreted into the bloodstream. |
Cancer of the testicles is rare, but it is the most common form of cancer in young males. Males need to examine their testes every month. Check web site http://www.vix.com/menmag/testican.htm for the information needed.
Inside the Penis
| The head of the penis is called the glans; the rim is the corona. It is full of nerve endings. Inside the penis is the urethra through which passes urine. The penis is full of structures that fill with more blood from arteries than the veins can carry away during sexual excitement and during sleep. (The penis has several erections during sleep.) |  |
The smallest such structure is called the spongy body (corpus spongiosum). The spongy body expands to form the glans. The two larger ones are the cavernous bodies (corpora cavernosa) which lie side by side and connect to the pubic bone with the inner most tips called the crura. The part of the penis between the glans and the body is the shaft. There is no muscle in the shaft. |
| The penis is covered with loose, hairless skin. This cross-sectional view of the inside of the penis shows the urethra and the internal chambers that are necessary for an erection to occur the urethra. The urethra is used for urinating and for expelling semen. |  |
The three chambers of tissue, the cavernous bodies and the spongy body, produce an erection when the arteries carry more blood to this tissue than the veins can carry away, causing engorgement. Sexual arousal is one cause of an erection. |
Circumcision
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Circumcision is the surgical removal of the foreskin of the penis. It is practiced for religious or hygienic reasons. Many studies have been done, with very mixed results, on whether circumcision is a good idea. Smegma, a waxy substance, may accumulate under the foreskin, so it needs to be pulled back and washed every day. |
Cross-section: Male Reproductive and Sexual Organs
| The seminal vesicles are two small glands that secrete the majority (70%) of the fluid in semen. The fluid is alkaline and rich in fructose which nourishes sperm so they can swim with their tail. The ejaculatory ducts are two short ducts that run through the prostate gland and open into the urethra. The prostate gland is located at the base of the bladder. It contributes about 30% of the seminal fluid (200+ million sperm, part of the ejaculation, a very small percentage) |  |
It's thin alkaline secretions flow into the urethra and join the semen and seminal fluid before ejaculation. The vas deferens are the two sperm carrying tubes that travel from the testes to the urethra. The male sterilization procedure, a vasectomy, is removing a section from each vas deference so sperm is not ejaculated. The Cowper's glands are pea-sized and alongside the base of the urethra. They secrete a drop of alkaline fluid sometime after arousal and can contain sperm. |
| There are two stages to an ejaculation, when semen is expelled from the body - the emission phase and the expulsion phase. During the emission phase, the first stage of a male orgasm, the seminal fluid is gathered in the urethral bulb, inside the prostate gland. This portion of the urethra expands like a balloon. Before the sperm can swim it is pushed upward to join the other fluids by cilia, hair-like filaments that line the walls of the vas deference. Two muscles, urethral sphincters, one where the urethra exits the bladder and one at the base of the prostate, trap the semen. In the second stage, the expulsion phase, the semen is expelled out of the penis by strong contractions of muscles surrounding the urethral bulb and at the root of the penis. (The root of the penis is the portion that extends internally into the pelvic cavity.) Expulsion takes three to ten seconds. |
Need to review these terms? Go to the flashcards.
