Oogenesis begins in the female embryo with primordial germ cells differentiating into oogonia that divide to form millions of germ cells. During gestation most oogonia die off while the remaining enter the first meiotic division to become primary oocytes that remain in the ovaries in a non-dividing state. At puberty, a drop in estrogen signals the release of hormones that stimulate around 20 primary oocytes to mature through meiosis I to become secondary oocytes with one being ovulated from its follicle while the others are reabsorbed. If the ovulated oocyte is fertilized, the empty follicle forms the corpus luteum which produces hormones to support pregnancy.

1. OOGENESIS
Production of Ova
What is Oogenesis
 The formation, development, and maturation of an ovum.
Oogenesis begins in the female embryo
 Primoridal germ cells differentiate into oogoina (stem cells)
 At 2 – 7 months of gestation, ~ 1000 oogonia divide to form ~ 7 million germ cells
 From 7 – 9 months, most oogonia die
 the remaining enter the first meiotic division
 primary oocyte
 The primary oocytes remain resting within small follicles until puberty
Ovary
Process of Ovulation
 Started by drop in estrogen
 Signals hypothalamus to release GnRH
 GnRH goes to pituitary, and it relases FSH
 Increase in FSH stimulates about ~20 oocytes to mature
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2.  Meiosis I to form secondary oocyte
 One oocyte (in most cases) matures and is expelled. The others are reabsorbed
before ovulation occurs
Follicle
 Estrogen and progesterone are secreted by some of the cells in the follicle
 Cytoplasm and nutrients
 Ovulation occurs when follicle and ovarian surface open
Corpus leuteum
 The empty follicle becomes the corpus leuteum
 If pregnancy does not occur, it is reabsorbed
 If pregnancy does occur, it produces hormones that help maintain pregnancy
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