Menstrual Cycle

Menstrual Cycle

• Interaction between the endocrine and reproductive systems.

• From the Latin “mensis” meaning “month”

Defn:

• Controls (1) the development and release of an egg for fertilization and (2) the preparation of the uterus to receive a fertilized egg.

Four stages

1. Follicle phase (~Day 5 - Day 13)

• Pituitary hormones FSH and LH travel to the ovaries where they cause a follicle to develop.

• As follicle develops it produces increased amounts of estrogen. This prepares the endometrium.

2. Ovulation (~Day 14)

• Shortest phase.

• 3 - 4 days

• Sudden rush of FSH and LH causes the follicle to rupture and release the ovum.

3. Luteal Phase (~Day 15-28)

• CL continues to produce estrogen and begins to produce progesterone.

• Progesterone increases the blood supply to the endometrium and fully prepares it.– If fertilization takes place - zygote

divides several times and implants in the endometrium.

– CL continues to function for several weeks.

4. Menstruation (~Day 1 - 4)

• If no fertilization…

– egg does not implant– CL begins to disintegrate– levels of progesterone an estrogen

fall

• lining of uterus detaches along with blood and unfertilized ovum is discharged.

Menstrual Hormones

Menstrual Hormones

Hormone Source Effect

FSH Pituitary Maturation offollicles

LH Pituitary Ovulation

Estrogen FollicleCorpus luteum

Thickens theendometrium

Progesterone Corpus luteum Maintainsendometrium