Chapter Summary

Internal Affairs (113.0K)

Introduction to the Male Reproductive System

1. The common purpose of the male and female reproductive systems is to produce offspring.
2. The functions of the male reproductive system are to produce spermatozoa, secrete androgens, and transfer spermatozoa to the reproductive system of the female.
3. Features of the male reproductive system include the primary sex organs (the testes), secondary sex organs (those that are essential for reproduction), and secondary sex characteristics (sexual attractants, expressed after puberty).

Perineum and Scrotum

1. The saclike scrotum, located in the urogenital portion of the perineum, supports and protects the testes and regulates their position relative to the pelvic region of the body.
2. Each testis is contained within its own scrotal compartment and is separated from the other by the scrotal septum.

Testes

1. The testes are partitioned into wedge-shaped lobules; the lobules are composed of seminiferous tubules, which produce sperm cells, and of interstitial tissue, which produces androgens.
2. Spermatogenesis occurs by meiotic division of the cells that line the seminiferous tubules.
1. At the end of the first meiotic division, two secondary spermatocytes have been produced.
2. At the end of the second meiotic division, four haploid spermatids have been produced.

3. The conversion of spermatids to spermatozoa is called spermiogenesis.
4. A sperm consists of a head and a flagellum and matures in the epididymides prior to ejaculation.
1. The acrosome of the head contains digestive enzymes for penetrating an ovum.
2. The flagellum provides undulating movement of about 3 mm per hour.

Spermatic Ducts, Accessory Reproductive Glands, and the Urethra

1. The epididymides and the ductus deferentia are the components of the spermatic ducts.
1. The highly coiled epididymides are the tubular structures on the testes where spermatozoa mature and are stored.
2. The ductus deferentia convey spermatozoa from the epididymides to the ejaculatory ducts during emission. Each ductus deferens forms a component of the spermatic cord.

2. The seminal vesicles and prostate provide additives to the spermatozoa in the formation of semen.
1. The seminal vesicles are located posterior to the base of the urinary bladder; they secrete about 60% of the additive fluid of semen.
2. The prostate surrounds the urethra just below the urinary bladder; it secretes about 40% of the additive fluid of semen.
3. Spermatozoa constitute less than 1% of the volume of an ejaculate.
4. The small bulbourethral glands secrete fluid that serves as a lubricant for the erect penis in preparation for coitus.

3. The male urethra, which serves both the urinary and reproductive systems, is divided into prostatic, membranous, and spongy portions.

Penis

1. The penis is specialized to become erect for insertion into the vagina during coitus.
2. The body of the penis consists of three columns of erectile tissue, the spongy urethra, and associated vessels and nerves.
3. The root of the penis is attached to the pubic arch and urogenital diaphragm.
4. The glans penis is the terminal end, which is covered with the prepuce in an uncircumcised male.

Mechanisms of Erection, Emission, and Ejaculation

1. Erection of the penis occurs as the erectile tissue becomes engorged with blood. Emission is the movement of the spermatozoa from the epididymides to the ejaculatory ducts, and ejaculation is the forceful expulsion of semen from the ejaculatory ducts and urethra of the penis.
2. Parasympathetic stimuli to arteries in the penis cause the erectile tissue to engorge with blood as arteriole flow increases and venous drainage decreases.
3. Ejaculation is the result of sympathetic reflexes in the smooth muscles of the male reproductive organs.