MHS 224 Ovary and Oviduct

Ovary

The corpus luteum of the ovary develops from the collapsed follicle after ovulation under the influence of luteinizing hormone (LH) from the pituitary.

• Capsule - covers the outer surface.
  • Germinal Epithelium - the surface is covered by a simple cuboidal epithelium.
  • Tunica Albuginea - layer of dense irregular connective tissue that supports the epithelium.
• Cortex - outer region that is the site of oocyte development.
  • Ovarian Follicles - oocytes surrounded by one or more layers of cells.
    • Primordial Follicles - oocytes arrested in development located in the outer cortex.
      • Primary Oocyte - large (25 to 30 µm), round to oval cells with a vesicular nucleus.
      • Zona Pellucida - layer of glycoproteins between the oocyte and granulosa cells. It is visible a thin, eosinophilic band in many follicles.
      • Follicular Cells - single layer of flattened cells that surround each oocyte.
    • Primary Follicles - primary oocytes surrounded by one or more layers of cuboidal-shaped granulosa cells (which develop from follicular cells).
      • Unilaminar - primary oocytes surrounded by a single layer of granulosa cells.
      • Multilaminar - primary oocytes surrounded by multiple layers of granulosa cells.

• Corpus Luteum - a temporary endocrine organ that can grow to be 1 to 5 cm in diameter.
  • Its thick wall is composed of two types of cells:
    • Granulosa Lutein Cells - centrally located cells derived from granulosa cells. They form the majority of the corpus luteum.
      • Large cells (~30 µm diameter) with eosinophilic cytoplasm.
      • Secrete progesterone and convert androgens formed by theca lutein cells into estrogen.
    • Theca Lutein Cells - more peripherally located cells derived from theca interna cells.
      • Smaller cells (~15 µm diameter) more deeply stained than granulosa lutein cells.
      • Secrete androgens, progesterone and some estrogen.
  • Central Cavity - the blood and fibrin-containing clot has almost completely digested by macrophages at its periphery.
• Atretic Follicles (#1,#2) - follicles that fail to reach maturity and ovulation degrade by atresia. The disintegration of the granulosa stratum by apoptosis is an early event.
• Medulla - inner region of fibroelastic connective tissue with many large, tortuous blood vessels, lymph vessels and nerve fibers.
  • Does not contain ovarian follicles.