The menstrual cycle occurs in four stages and is controlled by hormones from the pituitary gland and ovaries. In the first follicle stage, follicle stimulating hormone causes a follicle to form and produce estrogen. In the second ovulation stage, the estrogen surge causes luteinizing hormone to be released from the pituitary, rupturing the follicle and releasing an egg. In the third corpus luteum stage, the ruptured follicle forms the corpus luteum which produces progesterone. If no pregnancy occurs, the corpus luteum decomposes in the fourth menstruation stage, dropping hormone levels and causing the uterine lining to shed and be released.

1. Menstruation
 IF fertilization does NOT take place
 Menstrual cycle – a series of changes controlled by
hormones that help prepare the female uterus for a
possible pregnancy
 The cycle is controlled by hormones of the
pituitary gland and ovaries
 The menstrual cycle occurs in 4 stages

2. Ova maturing in a Follicle

3. stage 1 - Follicle stage
 Ovarian hormones (estrogen and
progesterone) are in low concentrations
 The pituitary produces FSH which causes a
follicle (egg cell capsule) to form
 As the follicle grows it makes increased
amounts of estrogen
 Estrogen has negative feedback on the pituitary to
stop FSH
 Estrogen causes the uterine lining (endometrium)
to grow thicker

4. Stage 2 - Ovulation
 Increased estrogen
from the follicle
stimulates the pituitary
gland to produce LH
 The LH surge causes
the follicle to rupture
and the egg cell is sent
to the oviduct

5. Stage 3 – Corpus Luteum
 The ruptured follicle
heals inside the ovary
forming the corpus
luteum
 Yellow body
 The corpus luteum
produces progesterone
 Estrogen and
progesterone maintains
the added growth of the
uterine lining

6.  An embryo in the uterus will secrete a
chemical called HCG
 HCG prevents the corpus luteum from
decomposing which maintains progesterone
levels
 The endometrium is not shed
 HCG is the chemical that is detected by
pregnancy tests

7. Stage 4 - Menstruation
 If an embryo is not present approximately 2
weeks after ovulation the corpus luteum
decomposes
 Estrogen and progesterone levels decrease
 The endometrium (uterine lining) is shed and
moves out through the vagina

8. Menstrual cycle