Essentials of Anatomy and Physiology

469

Progesterone

Estrogen

FSH

LH

Endometrial changesduring the menstrual cycle

Ovariancycle

Hormone levels (relative scale)

Functional
layer

Basilar

layer

Primary

follicle

Secondary

follicles

Graafian

follicle

Corpus

luteum

Corpus

albicans

Ovulation

0 5 10 15 20 25 28

Days

Menstrual

flow

Figure 20–9. The menstrual cycle. The levels of the important hormones are shown rel-

ative to one another throughout the cycle. Changes in the ovarian follicle are depicted. The

relative thickness of the endometrium is also shown.

QUESTION:Which hormone triggers ovulation? What else does this hormone do to the

follicle?