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M01.10.20 Epididymis
The epididymis is a crucial component of the male reproductive system, serving as a site for sperm maturation, storage, and transport. Its histological structure supports these functions through specialized cellular arrangements and distinct regions.
Gross Overview
The epididymis consists of three parts:
- Head (Caput): Receives sperm from the efferent ductules of the testis.
- Body (Corpus): Involved in sperm maturation.
- Tail (Cauda): Stores sperm until ejaculation.
Histological Features
1. Epithelial Lining
The lining of the epididymal duct is composed of pseudostratified columnar epithelium with two primary cell types:
- Principal Cells:
- Tall columnar cells with long stereocilia.
- Function: Absorption of excess fluid, secretion of glycoproteins, and maintenance of the luminal environment for sperm maturation.
- Basal Cells:
- Small, round cells located at the base of the epithelium.
- Function: Act as stem cells for the epithelial lining.
2. Basement Membrane
- The epithelial layer is supported by a prominent basement membrane that separates it from the underlying connective tissue.
Epididymis Normal epididymis, medium power microscopic
3. Lamina Propria
- A layer of loose connective tissue beneath the basement membrane containing fibroblasts, blood vessels, and immune cells.
4. Smooth Muscle Layers
The epididymal duct is surrounded by layers of smooth muscle, which vary in thickness depending on the region:
- Head and Body: Thin layer of smooth muscle for slow peristaltic contractions aiding sperm movement.
- Tail: Thickened smooth muscle layers to propel sperm during ejaculation under the influence of sympathetic stimulation.
Epididymis Normal appendix epididymis, low power microscopic
Key Histological Functions
| Feature | Function |
|---|---|
| Pseudostratified Epithelium | Facilitates sperm maturation and absorption. |
| Stereocilia | Increases surface area for absorption. |
| Smooth Muscle Layers | Assists in sperm transport. |
Points to Remember
- The stereocilia in the epididymis are non-motile and should not be confused with cilia.
- The tail of the epididymis stores mature sperm and has the thickest smooth muscle layer for ejaculation.
- Principal cells are involved in secreting factors essential for sperm maturation.
Bibliography
- Gartner LP, Hiatt JL. Color Atlas and Text of Histology.
- Ross MH, Pawlina W. Histology: A Text and Atlas.