Answers to Review Questions - Chapter 48
1. Trace the passage of sperm from the seminiferous tubule through the male
reproductive system until it leaves the male body during ejaculation.
From the seminiferous tubule, sperm travel to the epididymis, the vas deferens, the
ejaculatory duct, and the urethra, which transports sperm until it leaves the body during
ejaculation.
2. What are the actions of testosterone? What effects do luteinizing hormone (LH)
and follicle-stimulating hormone (FSH) have on the male reproductive system?
Before birth, testosterone stimulates the development of the primary sex characteristics
and the descent of the testes into the scrotum. At puberty, testosterone stimulates the
development of the secondary sex characteristics. In the adult, testosterone maintains
the secondary sex characteristics and stimulates spermatogenesis. At puberty, the
hypothalamus begins to secrete GnRH, which in turn stimulates the anterior pituitary to
secrete FSH and LH. FSH stimulates Seroli cells to secrete androgen-binding protein to
facilitate spermatogenesis, and LH stimulates interstitial cells to secrete testosterone.
FSH, LH, and testosterone all stimulate testosterone secretion and spermatogenesis.
3. Explain the physiological basis for erection of the penis.
When the male is sexually stimulated, parasympathetic neurons dilate the arteries in the
penis. Blood fills the blood vessels of the erectile tissue, and this compresses the veins
that conduct blood away from the penis, slowing the outflow of blood. Because more
blood enters the penis than can leave, the erectile tissue becomes engorged with blood,
and the penis increases in length, diameter, and firmness.
4. How is oogenesis different from spermatogenesis? Why are so many sperm
produced in the male and so few ova produced in the female?
In oogenesis, each primary oocyte generates one ovum. In spermatogenesis, each
primary spermatocyte generates four sperm. So many sperm are produced because they
may die as a result of unfavorable pH or phagocytosis in the female reproductive tract.
5. What is the function of the corpus luteum? What is the fate of the corpus luteum
when the ovum is not fertilized?
The corpus luteum functions as a temporary endocrine glad that secretes estrogen and
progesterone. If the ovum is not fertilized, the corpus luteum degenerates.
6. What are the specific actions of FSH and LH in the female? Of estrogen? Of
progesterone?
FSH stimulates development of follicles and the secretion of estrogen. LH stimulates
ovulation and the development of the corpus luteum. Estrogens stimulate growth of the
sex organs at puberty and development of secondary sex characteristics. Estrogens also
stimulate the monthly preparation of the endometrium. Progesterone stimulates the
completion of the preparation of the endometrium for pregnancy.
7. What is the function of human chorionic gonadotropin (hCG)?
The function of hCG is to signal the corpus luteum to continue to function.
8. What are the actions of estrogen and progesterone in maintaining pregnancy?
Estrogens stimulate the development of the uterine wall. Progesterone inhibits uterine
contractions so that the fetus is not expelled too soon.
9. What are the three types of hormonal contraception? How do hormonal
contraceptives prevent pregnancy?
Hormonal contraception includes oral contraceptives, contraceptive patches, and
injectable contraceptives. Hormonal contraceptives prevent ovulation, so pregnancy
cannot occur.
10. What is the most common STD in the United States? What percentage of
sexually active young people will acquire an STD?
The most common STD in the United States is chlamydia. One in three sexually active
young people will acquire a sexually-transmitted disease by age 24.