Cycles

Ovarian + Uterine cycles

A

• FSH is high but begins declining

• LH is stable

• An antral follicle with a primary oocyte is developing into a mature follicle

• Estrogen begins to increase as follicles develop, progesterone remains low

• The functional layer of the endometrium sheds

B

• FSH declines, then starts increasing towards a peak

• LH begins to increase

• A mature follicle containing a secondary oocyte forms

• Estrogen increases and peaks to its highest level

• Progesterone remains low

• The endometrium starts to build in thickness

C&D

• LH peaks to its highest level

• FSH also has a small peak

• The secondary oocyte is released from a mature follicle

• Estrogen declines sharply

• Progesterone is still at its stable low level

E

• FSH and LH have dropped to their lowest levels

• A corpus luteum forms from the remaining follicular cells of the mature follicle

• If the oocyte remains unfertilized, the corpus luteum starts regressing

• Progesterone increases, peaking to its highest level, then starts declining

• Estrogen increases to its second highest level, then declines

• The endometrium continues building to its thickest level with concentrated capillary growth

E

• FSH and LH start increasing to a low and steady level

• The corpus luteum regresses to a corpus albicans, which is the remaining scar tissue from the mature follicle

• Estrogen and progesterone return to their lowest levels

• The functional layer of the endometrium sheds

Ovarian cycle phases

1. Follicular phase

2. Ovulation

3. Luteal phase

Uterine cycle phases

1. Menstrual phase

2. Proliferative phase

3. Secretory phase