Oogenesis and Folliculogenesis Lecture Notes

Vocabulary flashcards covering the stages of oogenesis, follicular development, and the physiological transitions from embryo to fertilization.

Oogenesis

A pathway from embryo to folliculogenesis and readiness for fertilization.

Primordial Germ Cells (PGCs)

The embryonic precursors of oocytes and spermatozoa that arise from embryonic tissues and migrate to the future gonad.

Oogonia

Diploid ($2n$) stem cells having self-renewing capacity that develop from the germinal epithelium and divide by mitosis.

Primary Oocyte

A large diploid ($2n; 4c$) cell formed from oogonia that undergoes Meiosis I and arrests at the diplotene stage of prophase I until puberty.

Secondary Oocyte

A haploid ($1n; 2c$) cell produced by Meiosis I that arrests at the metaphase stage of Meiosis II and is normally the cell ovulated in domestic species.

First Polar Body

A small haploid cell produced during the first meiotic division that later divides to form two more polar bodies.

Second Polar Body

A small cell formed following the completion of Meiosis II after fertilization occurs.

Ovum

A large, non-motile, and spherical haploid ($1n; 1c$) cell formed after the secondary oocyte is fertilized by a spermatozoon.

Primordial Follicle

The resting, nongrowing population of follicles formed during fetal life, consisting of a primary oocyte enclosed in a single layer of pregranulosa cells.

Primary Follicle

A follicle where the oocyte is surrounded by a single layer of cuboidal granulosa cells and the formation of the zona pellucida (ZP) begins.

Secondary Follicle

A follicle featuring several layers of granulosa cells, theca layers, and an independent blood supply of $1$ or $2$ arterioles.

Theca Interna

A layer of the follicle that differentiates into epithelioid cells containing organelles required for steroid secretion.

Theca Externa

A layer of the follicle where stromal cells retain their spindle-shaped morphology.

Graafian Follicle

Also known as an antral follicle, it contains a fluid-filled cavity at its maximal size with the oocyte located eccentrically within the antrum.

Cumulus Oophorus

The specific granulosa cells that immediately surround the oocyte within an antral follicle.

Mural Granulosa Cells

Granulosa cells located closest to the basement membrane which are more steroidogenically active than those in the cumulus oophorus.

Zona Pellucida (ZP)

A structure surrounding the oocyte across which extensive gap junctions allow communication between granulosa cells and the oocyte.

LH Surge

The endocrine trigger for the final preovulatory transition that releases meiotic arrest and allows the completion of Meiosis I.

Atresia

One of two processes (along with entry into the growth phase) through which the population of primordial follicles is progressively depleted.

Germinal Epithelium

The tissue overlying the ovary where the oogonium develops as a diploid stem cell.

Corpus Luteum

An ovarian structure formed after ovulation occurs from the remains of the ruptured follicle.

Corpus Albicans

The regressed or degenerated form of the corpus luteum.