Ovary

cortex of the ovary?

• Outer layer, immediately under the tunica albuginea.

• Contains and matures follicles (primordial, primary, secondary, and antral), forms the corpus luteum, and produces sex steroids.

• Dense connective tissue stroma embedded with thousands of follicles, providing a structural framework.

• The site of ovulation and folliculogenesis

• site of all the follicles and developing oocytes

medulla of ovary

• Location: Inner, central portion.

• Function: Supports the cortex by providing a rich blood supply, lymphatic vessels, and nerve supply.

• Composition: Loose connective tissue, large coiled arteries (helicrine arteries), veins, and nerves.

• Key Feature: High vascularity, essential for supporting the metabolic needs of the active corte

How are primordial follicles characterised

single layer of flattened surrounding follicular cells

What happens to primordial follicles

• present in ovary from birth

• each month, a selection develop into primary follicles

• 1 of these primary follicles develop into a secondary follicle and the rest undergo follicular atresia

Antrum of secondary follicles

a fluid-filled cavity that forms within the granulosa cell layer during the late stage of a secondary follicle’s development

Follicular theca cells

• located outside BM, surrounding granulosa cells

• synthesise androgens which are passed to granulosa cells

• differentiate and appear later, during the transition to secondary follicles.

• become small luteal cells in the corpus luteum producing progesterone

Follicular granulosa cells

• directly surround the oocyte.

• Granulosa cells convert androgens into oestrogens using the enzyme aromatase.

• appear early (primary follicles).

• become large luteal cells in corpus luteum, producing progesterone

Theca interna cells

• closest to antrum

• contain lots of little blood vessels

• contain endocrine cells

Theca externa cells

• external wall of follicle

• fibrous, connective tissue layer

What contributes to the release if the oocyte?

Each month, 1 secondary follicle is selected, it becomes very large and eventually the pressure building in the antrum contributes to releasing the oocyte

Follicular atresia

• the natural, hormonally controlled degenerative process where ovarian follicles stop developing and are resorbed, ensuring only the highest quality oocytes are ovulated

• can happen at any stage of life

• granulosa cells start to die off first so they cannot support the developing oocytes and the follicle will die

• necessary to maintain a healthy reproductive system

• can cause infertility or early ovarian failure if it happens too quickly

The corpus luteum

a temporary, yellow endocrine structure formed in the ovary after ovulation. It is crucial for early pregnancy, producing progesterone to prepare the uterine lining and maintain gestation. If fertilization does not occur, it typically regresses within two weeks, causing menstruation