Sexual Anatomy

1. Sexual Anatomy Female-External Female-Internal Male-External Male-Internal

2. Male Internal Sex Organs • Increased knowledge of the structure and function of your reproductive organs can: • Improve sexual health • Increase sexual pleasure • Increase responsibility in sexual behavior • Female and male sexual organs develop from similar tissue before birth. • Genitals: External sexual organs

3. Male Internal Sex Organs • The primary function of the internal sexual organs of the human male is the production of semen. • Defined: Fluid containing sperm and secretions from the testicles, prostate, and seminal vesicles that is expelled from the penis during ejaculation. • Also known as Ejaculate • Contains Sperm: Male reproductive cell • Only one is needed to fertilize an egg • 1% of semen

4. Male Internal Sex Organs • Seminal Fluid: Fluid from the prostate and other sex glands that helps transport semen out of a man’s body during ejaculation. • Teaspoon of semen contains between 200 and 500 million sperm • 99% of semen is composed: • Ascorbic and Citric Acids, Enzymes, Fructose, Water, Substances • Amount of semen ejaculated by a male is a teaspoonful • Volume is influenced by • Amount of time since the last ejaculation • Duration of arousal prior to ejaculation • Age (men tend to produce less ejaculate as they age)

5. Seminiferous Tubules • Defined: Thin coiled tubes located in the testicles in which sperm are produced. • Located within the testes • Inside approximately 250 cone-shaped lobes of the interior of each testicle • Placed end to end they would span the length of two football fields • Thin, densely coiled sperm-bearing tubes • Site of Spermatogenesis: • Sperm production

6. Seminiferous Tubules • Leydig’s Cells: (Interstitial Cells) Produce Androgens • Close proximity to blood vessels allows direct secretion of androgens into the bloodstream • Androgens: Hormones that promote the development of male genitals and secondary sex characteristics. • Testosterone is the most important androgen

7. Epididymis • Defined: Tightly coiled thin walled tube where sperm maturation is completed. • C-Shaped • Attached to the back and top surface of each testis • Sperm may be stored for a period of several weeks. • During this time sperm cells continue to mature but are completely inactive

8. Vas Deferens • Defined: Tubes that convey sperm from the testes to the ejaculatory duct of the penis. • Eventually the sperm stored in the epididymis move into the vas deferens: • Carries sperm up into the body cavity, where at the base of the bladder they form the ejaculatory ducts • The two ejaculatory ducts run through the prostate gland and connect to the urethra. • Common duct that carries urine from the bladder to the opening of the penis where it is expelled from the body.

9. Seminal Vesicles • Defined: Two small glands that lie behind the bladder and secrete fluid that combines with sperm in the ejaculatory ducts. • Excretory ducts of the seminal vesicles join the vas deferens to form the ejaculatory ducts. • Seminal vesicles contribute to the production of seminal fluid, the viscous fluid ejaculated through the penis • Secretion of the seminal vesicles is high in fructose (form of sugar) • Sugar serves as a nutrient for the sperm, which require energy to make it to their destination • Once enriched by the secretions of the seminal vesicles, the sperm begin to propel themselves by the whiplike action of their tails

10. Prostate Gland • Defined: Gland which lies just below the bladder and surrounds the urethra, that produces about 30% of the seminal fluid released during ejaculation. • The other 70% is produced by the seminal vesicles • Composed of muscle as well as glandular tissue

11. Prostate gland • Both the ejaculatory ducts and the urethra pass through this gland, located at the base of the bladder and normally about the size and shape of a walnut. • During arousal the muscular tissue of the prostate gland squeezes shut and the urethral duct to the bladder • Thus preventing urine from mixing with the semen and disturbing the chemical balance required by sperm. • If the prostate gland becomes enlarged, as it often does as men age, the swelling can close off the ejaculatory ducts and urethra, making urination difficult and painful.

12. Cowper’s Glands • Defined: (bulbourethral glands) Glands located beneath the prostate that produce a clear, colorless liquid before ejaculation that neutralizes acid to prevent damage to the sperm. • Two small structures about the size of a pea located one on each side of the urethra just below the prostate gland • When a man is sexually aroused these glands may produce a fluid secretion called pre-ejaculate • Tiny ducts carry this secretion from the Cowper’s glands to the urethra. • It neutralizes the acidity of the urethra and also may help to lubricate the urethra and thus increase the flow of seminal fluid

13. Cowper’s Glands • Some men notice the secretion of the Cowper’s Glands as soon as they get an erection • Others rarely or never produce these droplets • For many men this secretion appears just prior to ejaculation • While this fluid is not semen, it may contain healthy sperm if the man has not urinated since the last ejaculation • This is one reason why the withdrawal method of birth control is not highly effective (withdrawal of the penis from the vagina prior to ejaculation)