Histology of the Reproductive System: Ovary and Uterus

Practical Activity No. 1: Histology in General Medicine - Reproductive System

Overview and Materials

This practical activity focuses on the histology of the reproductive system for third-year medical students. It involves examining various tissues using Hematoxylin and Eosin (HE) stain. The slides included in this practical activity are:

  1. Ovary – the mature follicle (de Graaf follicle)
  2. Ovary – the corpus luteum
  3. Uterus – the follicular (proliferative) phase of the endometrium
  4. Uterus – the luteal (secretory) phase of the endometrium

Note: This material is for internal use only; any unauthorized copying or distribution is prohibited.

Structure of the Ovary

The ovary exhibits a distinct morphology that can be summarized in the following layers:

  • Surface Epithelium: A simple cuboidal or squamous epithelium covering the surface of the ovary.
  • Tunica Albuginea: A dense connective tissue layer located just below the epithelium, which is devoid of blood vessels.
  • Cortex: Located peripherally beneath the tunica albuginea, the cortex is rich in ovarian follicles in various stages of development, including primordial follicles, primary follicles, secondary follicles, mature follicles, corpus luteum, corpus albicans, and atretic follicles.
  • Medulla: Positioned deeper within the ovary, consisting of loose connective tissue containing blood vessels and nerves.
  • Hilum: The entry and exit point for blood vessels, lymphatics, and nerves. The hilum contains cells similar to Leydig cells found in the testicles.
Detailed Histology of the Ovary
1. Mature Follicle (De Graaf Follicle)

At high magnification, the mature follicle (tertiary follicle) displays the following characteristics:

  • Antrum Follicularum: A single large cavity filled with follicular fluid.
  • Membrana Granulosa: Surrounds the antrum, comprised of 2-3 cell layers of granulosa cells that push towards the periphery.
  • Basement Membrane: Separates the granulosa from the theca interna cells.
  • Oocyte Location: Positioned eccentrically within the follicle, surrounded by cumulus oophorus (discus proligerus), which contains the corona radiata formed by elongated granulosa cells arranged radially around the oocyte.

Figures to Note:

  • Antrum Follicularum: Central cavity containing fluid.
  • Membrana Granulosa: Layer of granulosa cells.
  • Cumulus Oophorus & Corona Radiata: Protective layer surrounding the oocyte.
2. Corpus Luteum

The corpus luteum develops following ovulation and has distinguishing features:

  • Histology: Composed of rounded or polygonal lutein cells arranged in anastomosing strands interspersed with capillaries.

  • Types of Lutein Cells:
      - Theca Lutein Cells: Smaller cells located at the periphery, associated with blood vessels.
      - Follicular Lutein Cells: Larger and occupy most of the corpus luteum, displaying abundant eosinophilic cytoplasm.

  • High Magnification Features: Follicular lutein cells display a vacuolar eosinophilic cytoplasm and are characterized by a larger, rounded, hypochromatic nucleus. Theca lutein cells have a darker cytoplasm and a smaller nucleus.

Histology of the Uterus

The uterine wall comprises three distinct layers, each with specific structural and functional features:

  • Perimetrium (Outer Layer): Composed of part peritoneal serosa (covering the fundus and posterior body) and adventitia (in other areas).
  • Myometrium (Muscular Layer): The thickest layer containing bundles of smooth muscle fibers arranged in multiple orientations, with a rich arterial and venous supply.
  • Endometrium (Mucosal Layer): Composed of surface epithelium and lamina propria that includes:
      - Surface Epithelium: Columnar epithelial lining with ciliated and secretory cells.
      - Endometrial Glands: Simple tubular glands lined by columnar epithelium, rich in cells.
Phases of the Endometrium
1. Follicular (Proliferative) Phase
  • Occurs in the first 14 days of the menstrual cycle, during which:
      - The endometrium thickens to a size of 2-3 mm.
      - Endometrial glands become straight and wavy with a narrow and empty lumen; the stroma appears dense and cellular.
      - Spiral arteries can be seen, which do not reach the endometrial surface at this stage.
2. Luteal (Secretory) Phase
  • Takes place post-ovulation; the endometrium reaches a thickness of 5-6 mm.
      - Endometrial glands grow coiled with larger, irregular lumens that may contain eosinophilic secretions.
      - Secretory cells demonstrate vacuoles that shift from subnuclear to supranuclear as secretion accumulates.
      - Stromal cells differentiate into decidual cells, which are rich in glycogen, and the spiral arteries extensively coil to reach the epithelial surface.
Conclusion

The observations made in this histological analysis of the reproductive system provide critical insights into the structure and function of the ovaries and uterus during different phases of the menstrual cycle. For further information and detailed histological images, it is recommended to refer to the website: www.histologyguide.com.