Lecture 15: Folliculogenesis

Describe the function of the ovary

Production of follicles, oocytes, corpus lutea, hormones, and proteins

What forms the primordial follicles

Oogonia wrapped with the regressing primitive sex cords

Where does folliculogenesis occur

In the cortex of the ovary

Why do females have a finite number of oocytes

Because mitosis of oogonia stops, and meiosis starts, during prenatal development

Describe a primordial follicle

An oocyte surrounded by a single layer of squamous somatic cells, called follicular cells, contains a primary oocyte

Describe a primary follicle

An oocyte surrounded by a single cuboidal layer of follicular cells, contains a primary oocyte

Describe a secondary follicle

Has 2+ layers of cuboidal (ish) granulosa cells (were follicular cells) that are surrounded by many layers of theca cells. The zona pellucida forms around the oocyte, within the granulosa cells

Describe an antral follicle

Large layers of granulosa and theca cells, development of fluid filled antrum that grows until maturity. The larger the follicle, the larger the antrum

What is the name of the granulosa cells directly around the oocyte in antral follicles

Cumulus cells

Describe the 2 cell 2 gonadotropin model in folliculogenesis

* LH binds to theca cells → triggers cAMP → activates protein kinase → converts cholesterol to testosterone
* FSH binds to granulosa cells → triggers cAMP, activates protein kinase → activates aromatase → converts testosterone (from theca cells) to estradiol
* The E2 causes a number of effects in the body, specifically brain and repro tract
* the larger the antral follicle, the more E2 produced

Which follicular cell is analogous to Leydig cells

Theca cells

Which follicular cell is analogous to Sertoli cells

Granulosa cells

What follicles are undergoing gonadotropin-independent growth

Primordial, primary, and secondary

What follicles are undergoing gonadotropin-dependent growth

Antral

Define monotocous

Matures one follicle at a time, has one ovulation per cycle, has one offspring

Define polytocous

Matures many follicles at a time, has many ovulations per cycle, has many offspring

List the phases of antral follicular development

1. recruitment (small)
2. selection (medium)
3. dominance (large)
4. ovulatory follicle

What is it called when the antral follicle doesn’t make it to the next stage of development and dies off

Atresia

What phases of antral development are FSH dependent

Recruitment and part of selection

What phases of antral development are LH dependent

Part of selection and dominance

Describe the positive feedback in antral follicular development

Small follicle produces E2 → causes hypothalamus to release GnRH → causes AP to release FSH → triggers more growth → more E2 production from granulosa cells → hypothalamus → GnRH → FSH → more E2

What triggers/coincides with the switch from FSH to LH dependency

The granulosa cells start producing inhibin in the selection phase → AP → decreases FSH production