Essentials of Anatomy and Physiology

Anterior pituitary

Anterior pituitary

Ovary (follicle)

Placenta during pregnancy

Ovary (corpus luteum)

Placenta during pregnancy

Ovary (corpus luteum)

Ovary (corpus luteum)

Placenta during pregnancy

• Initiates development of ovarian follicles


• Stimulates secretion of estrogen by follicle cells


• Causes ovulation


• Converts the ruptured ovarian follicle into the corpus luteum


• Stimulates secretion of progesterone by the corpus luteum


• Promotes maturation of ovarian follicles


• Promotes growth of blood vessels in the endometrium


• Initiates development of the secondary sex characteristics:
  —growth of the uterus and other reproductive organs
  —growth of the mammary ducts and fat deposition in the breasts
  —broadening of the pelvic bone
  —subcutaneous fat deposition in hips and thighs


• Promotes further growth of blood vessels in the endometrium and
  storage of nutrients


• Inhibits contractions of the myometrium


• Inhibits secretion of FSH


• Inhibits contractions of the myometrium to facilitate implantation


• Promotes stretching of ligaments of the pubic symphysis

AGING AND THE

REPRODUCTIVE SYSTEMS

For women there is a definite end to reproductive
capability; this is called the menopause and usually
occurs between the ages of 45 and 55. Estrogen secre-
tion decreases; ovulation and menstrual cycles become
irregular and finally cease. The decrease in estrogen
has other effects as well. Loss of bone matrix may lead
to osteoporosis and fractures; an increase in blood
cholesterol makes women more likely to develop
coronary artery disease; drying of the vaginal mucosa
increases susceptibility to vaginal infections. Estrogen
replacement therapy may delay some of these conse-
quences of menopause, but there are risks involved,
and women should be fully informed of them before
starting such therapy. The likelihood of breast cancer
also increases with age, and women over age 50 should
consider having a mammogram to serve as a baseline,
then one at least every other year.
For most men, testosterone secretion continues

throughout life, as does sperm production, though

both diminish with advancing age. Perhaps the most

common reproductive problem for older men is pro-

static hypertrophy, enlargement of the prostate gland.

As the urethra is compressed by the growing prostate

gland, urination becomes difficult, and residual urine

in the bladder increases the chance of urinary tract

infection. Prostate hypertrophy is usually benign, but

cancer of the prostate is one of the more common can-

cers in elderly men.

SUMMARY

The production of male or female gametes is a process

that is regulated by hormones. When fertilization of

an ovum by a sperm cell takes place, the zygote, or fer-

tilized egg, has the potential to become a new human

being. The development of the zygote to embryo-

fetus to newborn infant is also dependent on hor-

mones and is the subject of our next chapter.

470 The Reproductive Systems

Table 20–3 HORMONES OF FEMALE REPRODUCTION

Hormone Secreted by Functions

FSH

LH

Estrogen*

Progesterone

Inhibin

Relaxin

*Estrogen has effects on organs such as bones and blood vessels in both men and women. Estrogen is produced in fat tissue in

the breasts and hips. In men, testosterone is converted to estrogen in the brain.