Oogenesis and the Ovarian Cycle

What happens hormonally at the end of the ovarian cycle?

Corpus luteum degenerates and hormone levels drop sharply --> FSH and LH no longer blocked --> cycle begins again

What are the two phases of the ovarian cycle

Follicular Phase days 1-14 and luteal phase days 15-28

What happens to the corpus luteum if pregnancy occurs?

It continues to produce hormones until the placenta takes over

How do hormones starts the ovarian cycle?

On day 1 FSH is released which triggers the release of FSH and LH --> stimulates the growth of many follicles and estrogen release from the ovaries --> estrogen inhibits release of FSH and LH

How does oocyte mature during the fetal period?

Oogonia multiply by mitosis --> primary oocyte develops in primordial follicle --> primary oocyte stalls in prophase 1 until puberty

Oogonia

Ovarian Stem cells

How do the primary oocytes mature after puberty?

Primary oocyte activated --> matures to secondary oocyte --> arrests in Metaphase II and is ovulated --> penetrated by sperm and completes meiosis II --> ovum

What occurs during the follicular phase?

Primordial Follicle --> Primary Follicle --> secondary follicle --> late secondary follicle forms with accumulation of fluid --> antrum forms and isolates oocyte with corona radiata --> follicle begins to bulge from the ovary (vesicular follicle)

What happens to the corpus luteum if no pregnancy occurs?

degenerates into a corpus albicans and hormone production ceases

What is happening midcycle hormonally?

high estrogen levels cause a surge of LH at day 14 --> Ovulation --> ruptured follicle transformed into corpus luteum --> CL produces inhibin, progesterone, and estrogen

Ovarian Cycle

monthly series of events associated with maturation of an egg that is 28 days

What occurs during the luteal phase?

ruptured follicle collapses and forms corpus luteum which secrets estrogens progesterones

Oogenesis

the formation of female gametes, begins in the fetal period

What occurs during Ovulation?

the ovary wall ruptures and expels the oocyte with its corona radiata