Folliculogenesis, Oogenesis, and Ovulation

Vocabulary flashcards covering the biological processes of oogenesis, folliculogenesis, the structures involved in ovulation, and the formation of the corpus luteum.

Folliculogenesis

The development of ovarian follicles that are eligible for ovulation.

Oogenesis

The development of a primary egg cell into a mature ovum that is competent for fertilisation.

Ovulation

The release of the ova from the ovary.

Ovary Cortex

The gametogenic region of the ovary.

Ovary Medulla

The supportive region of the ovary.

Oogonia

Diploid ($2N$) cells that undergo mitosis to produce primary oocytes during prenatal oogenesis.

Nuclear Arrest

The state when the primary oocyte ($2N$) begins meiosis Prophase I and is held by meiotic inhibitors until after puberty.

Secondary Oocyte

A haploid ($1N$) cell produced post-puberty during each cycle when meiosis I resumes following the preovulatory LH surge.

Polar Body

A small cell produced during meiosis I and meiosis II alongside the oocyte/ovum; meiosis I results in one, and meiosis II results in another (or three if the first divides).

Primordial Follicle

An immature follicle consisting of a primary oocyte surrounded by flattened granulosa cells.

Primary Follicle

A follicle characterized by cuboidal granulosa cells surrounding the oocyte.

Secondary Follicle

A follicle with two or more layers of granulosa cells, a small number of theca cells, and the initial formation of the zona pellucida.

Tertiary Follicle

Also known as an antral follicle; it contains an antrum (cavity) filled with follicular fluid and has distinct theca interna and theca externa layers.

Preovulatory Follicle

Also known as a Graafian follicle; it is the mature stage of follicular development containing a cumulus oophorus.

Preantral Phase

The phase of folliculogenesis including primordial, primary, and secondary follicles; it is not dependent on gonadotropic hormones.

Antral Phase

The phase of folliculogenesis including tertiary and preovulatory follicles; it is dependent on gonadotropic hormones.

Atresia

The process involving the death and disappearance of over $90\%$ of follicles that do not reach dominance for ovulation.

Theca interna cells

Cells that possess LH receptors and use cholesterol to produce androstenedione.

Granulosa cells

Cells that possess FSH receptors and use androstenedione to produce oestradiol.

Corpus Haemorrhagicum

A structure formed approximately the first $3$ days post-ovulation where follicle walls collapse, blood vessels rupture, and a small blood clot forms in the cavity.

Luteinisation

The process where theca interna and granulosa cells mix and transform to form active luteal tissue that produces progesterone.

Corpus Albicans

A light yellow to white scar tissue remnant of the corpus luteum following luteolysis; it contains no glandular tissue.

LH preovulatory surge

The hormonal signal that triggers a complex set of events—including increased blood flow, ovarian contractions, and connective tissue destruction—leading to ovulation.