HUMAN BIOLOGY

RepRoductive systems 327

corpus luteum degenerates, and the endometrial lining is shed
through menstruation.
Estrogen, progesterone, FSH, and LH control the maturation
and release of eggs, as well as changes in the endometrium.
They are part of feedback loops involving the hypothalamus,
anterior pituitary, and ovaries.

Section 16.3 Testes are a male’s primary
reproductive organs. The male reproductive
system also includes accessory ducts and
glands.
Sperm develop mostly in the seminiferous
tubules and mature in the epididymis. The
seminal vesicles, bulbourethral glands, and prostate gland
produce fluids that mix with sperm, forming semen.
A vas deferens leading from each testis transports sperm
outward when a male ejaculates.

Section 16.4 Testosterone, LH, and FSH control

the formation of sperm. They are part of feedback

loops among the hypothalamus, anterior pituitary, and

testes. In the seminiferous tubules, Sertoli cells nourish

sperm. Leydig cells in tissue between the tubules secrete

testosterone.

A mature sperm cell has a head, midpiece, and tail.

The acrosome capping the head contains enzymes that

help a sperm penetrate an egg.

In both males and females, gonadotropin-releasing

hormone (GnRH) from the hypothala mus stimulates the

anterior pituitary to release LH and FSH.

Sections 16.5, 16.6 Sexual inter-

course (coitus) is the usual way an egg

(a secondary oocyte) and sperm meet for

fertilization. It typically involves a sequence

of physiological changes in both partners

and may culminate in orgasm. Fertilization

produces a zygote, a cell with chromosomes

from both the mother and father.

Sections 16.7, 16.8 Physical,

chemi cal, surgical, and behavioral strategies

are available for controlling unwanted

pregnancies and helping infertile couples.

Efforts to control fertility raise important

ethical questions.

Sections 16.9–16.11 Sexually

transmitted diseases (STDs) are passed by

sexual activity. Bacteria cause chlamyd-

ia, gonorrhea, and syphilis. Viral STDs

include AIDS, genital herpes, genital warts

(HPV), and viral hepatitis. Untreated STDs

can seriously harm health. Abstinence or

being in an infection-free monogamous

relationship is the only sure way of not

being exposed to an STD.

Section 16.12 Major reproductive

cancers in females include cancers of the

breast, ovaries, cervix, and uterus. In males

major reproductive cancers are cancers of the

testes and prostate.

Review QueStionS

1. Distinguish between:
   a. seminiferous tubule and vas deferens
   b. sperm and semen
   c. Leydig cells and Sertoli cells
   d. primary oocyte and secondary oocyte
   e. follicle and corpus luteum
   f. the three phases of the menstrual cycle


2. Which hormones influence the development of sperm?


3. Which hormones influence the menstrual and ovarian cycles?


4. List four events that are triggered by the surge of LH at the
   midpoint of the menstrual cycle.


5. What changes occur in the endometrium during the
   ovarian cycle?


6. Label the parts of the female reproductive system and list
   their functions.

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© Cengage Learning

7. Label the parts of the male reproductive system and state
   their functions.


8. Which oocyte stage is ovulated? What happens to it if it
   encounters a sperm cell there? What happens if it does not
   meet up with sperm?

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