The uterine wall consists of three layers: the endometrium, myometrium, and perimetrium. The endometrium undergoes cyclic changes during the menstrual cycle in response to hormones from the ovaries. It has two layers - a functional layer that is shed during menstruation and a basal layer that remains. The menstrual cycle involves the maturation and release of an egg, and hormonal changes produced by the ovaries cause the endometrium to cycle between phases of proliferation and secretion. If fertilization does not occur, the corpus luteum degenerates and menstruation begins as the endometrium enters an ischemic phase and is shed.

1. UTERINE
CYCLE

3. The uterine wall
• Endometrium
• Myometrium
• Perimetrium

5. Endometrium
• Undergoes hormone modulated cyclic
changes during different phases of the
menstrual cycle

6. Layers of the endometrium
• Functional layer
• Basal layer

7. • The menstrual cycle is the period during which
-- the oocyte matures
--the oocyte is ovulated
--the oocyte enters the uterine tube

8. • The hormones produced by the ovarian
follicles and corpus luteum (estrogen and
progesterone) produce cyclic changes in the
endometrium

10. • The endometrium is a “mirror” of the ovarian
cycle

11. • The average menstrual cycle is 28 days (23-35
days) with day 1 of the cycle designated as the
day on which menstrual flow begins

13. Phases of menstrual cycle
1. Menstrual phase
2. Proliferative phase
3. Luteal phase
4. Ischemic phase
5. Pregnancy phase

14. Menstrual phase
• The functional layer of the uterine wall is
sloughed off and discarded with the menstrual
flow which lasts 4-5 days
• Blood + endometrial tissue
• Eroded endometrium is thin

15. Proliferative phase
• Follicular phase, estrogenic: lasts about 9
days
• Coincides with the growth of ovarian follicles
and is controlled by estrogen secreted by
these follicles
• 2 to 3 fold increase in the thickness of the
endometrium

16. Cont:
• Phases of repair and proliferation
• Surface epithelium reforms and covers the
endometrium
• The gland increase in number and length
• The spiral arteries elongate

17. Luteal phase
• Secretory: lasts 13 days
• Coincides with the formation, functioning and
growth of corpus luteum
• Glands become wide, tortuous and saccular
• Endometrium thickens because of the
influence of progesterone and estrogen

19. If fertilization does not occur
• Corpus luteum degenerates
• Decreased estrogen and progesterone
• Secretory endometrium enters an ischemic
phase
• Menstruation occurs

20. Ischemic phase
• Occurs when oocyte is not fertilized
• Spiral arteries constrict, giving the
endometrium a pale appearance
• Loss of 20-80 ml of blood
• Menstruation lasts 3-5 days