Follicular Phase Lecture Notes Flashcards
How do the ovaries develop?
Primordial germ cells (PGCs) migrate to the developing gonads and proliferate. Gonadal somatic cells differentiate into ovarian stroma, granulosa, and theca cells. Germ cells differentiate and enter meiosis, forming oocytes, which, surrounded by a layer of granulosa cells, form primordial follicles.
After recruitment for growth, primordial follicles develop to the secondary follicle stage, containing multiple layers of granulosa cells surrounded by theca cells. In sexually mature females, follicles develop into the preovulatory stage and oocytes resume meiosis, arresting after completion of the first meiotic division before ovulation.
What is folliculogenesis?
Developmental process in which an activated primordial follicle develops to a preovulatory size through the growth and differentiation of the oocyte and its surrounding granulosa cells
What is a follicle?
The functional unit of the ovary; supports the development of competent, mature oocytes
How are ovarian follicles classified?
- Number of granulosa cells surrounding the oocyte
- morphology of the granulosa cells
- diameter
- presence or absence of antrum
What is a primary follicle?
In prophase in the first meiotic division, the oocyte is closely surrounded by a single layer of squamous follicle cells. In growth stages, the oocyte is surrounded by a single layer of cuboidal follicle cells
What is a secondary follicle?
A multilayered mass of granulosa cells surround the oocyte
What is a tertiary follicle?
This actively growing follicle has many dividing granulosa cells around it, and a fluid-filled antrum, which arises by the coalescence of small fluid-filled cavities among the granulosa cells.
What is a mature (Graafian) follicle?
Also called the preovulatory follicle; contains the mature (primary to secondary stage) oocyte. Extends through the full thickness of the ovarian cortex and causes a bulge on the surface of the ovary. The mitotic activity of the granulosa cells decreases, and the antrum increases in size.
What are the three phases of follicular development?
Gonadotropin-independent phase, gonadotropin-responsive phase, and gonadotropin- dependent phase
What happens during the gonadotropin-independent phase?
Also called primordial follicle activation. Begins with the transformation of the flattened granulosa cells of the primordial follicle into a single layer of cuboidal granulosa (follicular) cells to become the primary follicle. The underlying mechanism is unknown, and both granulosa cells and the oocyte particiapte in this process. Follicle growth through the primordial, primary, and secondary stages, which is entirely independent of FSH and LH.
What happens during the gonadotropin-responsive phase?
Follicle transition from the preantral stage to the early antral stage, which, although primarily controlled by intraovarian regulators, can be stimulated by FSH. Acquisition of FSH dependence is crucial in determining follicular fate beyond the preantral stage.
What happens during the gonadotropin-dependent phase?
Follicle growth and maturation beyond the early antral stage, which includes follicle recruitment, selection, and ovulation, and is entirely dependent on FSH and LH.
What are the different types of follicular dynamics?
- Recruitment: the process by which the follicle departs from the resting pool to initiate growth.
- Selection: the process by which the maturing follicular cohort is reduced to a number appropriate for the species-specific ovulatory quota.
- Dominance: the status of the follicle destined to ovulate, and its role in regulating the size of the ovulatory quota.
- Atresia: the degeneration and reabsorption of the ovarian follicles
What is the selection of a single dominant follicle dependent on?
1) acquisition of LH dependence
2) greater capacity for estradiol production
3) activation of the IGF system
4) an antiapoptotic follicular microenvironment
What is ovarian aging?
The physiological aging process characterized by gradual decline in quantity and quality of oocyte or follicular pool
