Lecture 14: Oogenesis

What part of the ovary has the oocytes

Cortex

During development, what surrounds the PGCs/oocytes

Regressing primitive sex cords

Define oogenesis

The formation, development, and maturation of the female gametes

When does oocyte mitosis occur in female development

Prenatally

Alternate name for the oocyte plasma membrane

Oolema

Name of the wall around the oocyte plasma membrane

Zona Pellucida

What is the zona pellucida made of

Glycoproteins

Describe the specifics of the composition of zone pellucida

Made of 3 glycoproteins:


1. ZP 1 & 2 are structural
2. ZP 3 is a receptor binding glycoprotein

What exists between the zona pellucida and plasma membrane

Perivitelline space

What are the cells outside the zona pellucida

Follicular cells

What type of ova is undergoing mitosis

Oogonia

What type of ova is undergoing meiosis

Oocyte

At what stage does meiosis get arrested prenatally

Prophase 1

After meiosis 1, what is formed

A secondary oocyte, with the first polar body

Describe the polar bodies

It is a vesicle with the other half of the DNA from meiosis that doesn’t become a daughter oocyte. The first polar body has 2n chromosomes, the second polar body has 1n chromosomes. They cannot push through the zona pellucida, and reside in the perivitelline space.

After meiosis 2, what is formed

An ootid, with the second polar body (1n). The first polar body (2n) is still retained in the perivitelline space.

When does the extra 3n in the polar bodies get released

During implantation, when the zona pellucida degrades

What causes oogenesis to be arrested during prophase 1

High oocyte cAMP levels

Describe the mechanism behind meiotic arrest

Follicular cells are producing a lot of cAMP. At this point, the gap junctions are open, so the cAMP moves into the cytosol of the oocyte. The cAMP inactivates Maturation Promoting Factor, which prevents meiosis from occurring.

Describe the mechanism that restarts meiosis

In an LH surge during estrus, the LH bind to the follicular cells and closes the gap junctions. The cAMP can no longer move into the oocyte, and Maturation Promoting Factor stays active, and meiosis can happen