1. Uterine (Menstrual) Cycle
Stages of the menstrual cycle
Menstrual phase
Proliferative stage
Secretory stage

2. Menstrual Cycle: Phase 1 Menstrual phase
Days 1–5
Outer layer of the endometrium is sloughed
Bleeding occurs for 3–5 days (female’s “period”)
Low levels of estrogen and progesterone

3. Menstrual Cycle: Phase 2 Proliferative stage
Days 6–14 (AKA: The follicular phase)
FSH is stimulating the follicle to mature
As the follicle matures it is releasing estrogen
Estrogen is causing the endometrium to thicken
Ovulation occurs at the end of this stage (Day 14)
A surge in LH causes ovulation

4. Menstrual Cycle: Phase 3 Secretory stage
Days 15–28 (AKA: The luteal phase)
Corpus luteum develops
Corpus luteum releases progesterone
Levels of progesterone increase the blood supply to the endometrium (thickening the lining)

5. Secretory stage (continued)
If fertilization does occur
Embryo produces a hormone (HCG) that stops the corpus luteum from disappearing
If fertilization does NOT occur
Corpus luteum degenerates

6. Ovarian Cycle
Figure 16.12c

7. Uterine (Menstrual) Cycle
Figure 16.12d