Biology Workbook For Dummies
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Knowledge of the organ systems involved in human sexual reproduction helps you learn about the reproduction process. The following figure illustrates the male reproductive system:

  • The egg-shaped male gonads, called testes, rest in a sac called the scrotum. Sperm don’t develop normally at the human body’s core temperature, so keeping them cooler outside the body allows normal development.

  • The staff-like penis consists of erectile tissue (shaded in the figure) that surrounds a narrow tube called the urethra (part of the excretory system). During sexual intercourse, the erectile tissue fills with blood, allowing the penis to stiffen so that it can enter the female’s vagina.

    The head of the penis, called the glans, contains many nerve endings and is very sensitive to stimulation. At birth, a flap of skin called the prepuce (or foreskin) covers the glans. In some cultures, the foreskin is surgically removed by circumcision.

    [Credit:     From LifeART®, Super Anatomy 1, © 2002, Lippincott Willi
    Credit: From LifeART®, Super Anatomy 1, © 2002, Lippincott Williams & Wilkins

Sperm production, called spermatogenesis, begins in each testis. The sperm mature as they follow this path out of the male reproductive system:

  1. Sperm move into the epididymus, a coiled tube that rests on the testis.

    The epididymus stores the sperm as they continue to develop.

  2. During ejaculation, when sperm-containing fluid leaves the penis, muscular contractions push sperm from the epididymus into a tube called the vas deferens.

  3. The sperm travel through the vas deferens up into the abdomen and around the bladder until they reach a gland called the seminal vesicle.

    During ejaculation, the seminal vesicle secretes a thick solution that provides the sperm with fructose to use as a source of energy as they swim through the female reproductive system.

  4. The vas deferens and seminal vesicle join to form a short duct called the ejaculatory duct.

    The ejaculatory duct passes through the prostate gland, which secretes a thin fluid that provides nutrients to the sperm.

  5. The ejaculatory ducts from both sides of the male reproductive system join and empty into the urethra, which carries the sperm out of the body during sexual intercourse.

    Mucus from the bulbourethral gland, which joins the urethra just after the ejaculatory duct, also empties into the urethra. Semen, the fluid released during ejaculation, consists of sperm plus the fluids from the three glands in the male reproductive system.

When the pleasurable feelings of orgasm occur in a male, a sphincter muscle closes off the bladder to prevent urine from entering the urethra. Shutting out urine allows the urethra to be used solely for ejaculation at that time.

For questions 1 – 9, use the terms that follow to label the structures of the male reproductive system in the figure.

a. Testes

b. Vas deferens

c. Prepuce (foreskin)

d. Seminal vesicle

e. Epididymis

f. Urethra

g. Prostate gland

h. Bulbourethral gland

i. Glans penis

For question 10, put the terms that follow in order to show the path of sperm from the testes out of the male reproductive system.

a. Ejaculatory duct

b. Testes

c. Vas deferens

d. Urethra

e. Epididymis

The following are the answers to the practice questions:

  1. d. Seminal vesicle

  2. h. Bulbourethral gland

  3. b. Vas deferens

  4. e. Epididymis

  5. a. Testes

  6. g. Prostate gland

  7. f. Urethra

  8. i. Glans penis

  9. c. Prepuce (foreskin)

  10. The answer is b. Testes e. Epididymis c. Vas deferens a. Ejaculatory duct d. Urethra.

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