Veterinary Andrology and Reproductive Techniques

EPIDIDYMIS

• The epididymis is a single, torturous, coiled tubule closely attached to the testis by fibrous tissue.
• It has smooth muscle coat that moves the sperm along its path by peristaltic wave towards vas deferens.
• The epididymis has three distinct parts
• Head (caput) - flat, U-shaped and covers nearly one third of the proximal end of the testis
• Body (corpus) - corpus epididymis is comparatively narrow part, running toward distal end of the testis along its posterior border
• Tail (cauda) - is enlarged end of the epididymis at the distal pole of the testis and is continuous with the vas deferens.

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The length of the epididymal tube in different animals is as follows.

• Bull - 30 m
• Ram - 50 m
• Boar - 50 m
• Horse - 20 m

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Histologically two prominent layers of muscle is present in epididymis

• circular muscle fibers layer
• pseudostratified columnar cells
• Based on histology, the epididymis can be divided in three segments
  • Proximal segment has ciliated cells (having kinocilia) beating out-words.
  • Middle segment of the epididymis, the lumen is wide and the cilia are not so straight.
  • Terminal segment of the epididymis the cilia are short, the lumen is very wide and is packed with spermatozoa.
• This classification doesnot have any relation with anatomical classification.

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Functions of the epididymis

• Various functions of the epididymis are as follows
• Absorption
• Secretion
• Maturation
• Transporatation and
• Storage
• Absorption
• The epithelial cells of the epididymis is involved in absorption of excessive fluid released by the testis.
• The fluid released by testes is several times more than the volume of the semen ejaculate.
• Ram’s testes produce about 60 ml fluid daily but while collecting only one ml of semen is obtained.
• The tail of the epididymis is actively involved in this absorption. Thus in the cauda epididymis the spermatozoa suspension is highly concentrated.
• Secretion:
• The epididymal cells secretions maintain the viability of the spermatozoa during storage by providing sufficient nutrients.
• Maturation
• The final maturation changes of the spermatozoa occur during its storage in the epididymis.
• There is migration of the cytoplasmic droplet from the neck of the spermatozoa (proximal protoplasmic droplet) to the distal end of the middle piece (distal protoplasmic droplet) in bull.
• This change is associated with cytochemical changes in the spermatozoa leading to its increased capacity for motility and fertilizing ability.
• Transportation
• The transportation of the spermatozoa from rete testis to the efferent tubules is mainly due to the presence of testicular fluid.
• The further transport of the spermatozoa is due to action of the ciliated epithelium and the action of peristaltic waves of the muscle fibers in the duct.
• The average duration of the epididymal journey of the spermatozoa in different species is
  • Bull - 10 days
  • Ram - 13-15 days
  • Boar - 9-12 days
  • Stallion - 8-11 days
• Storage
• The epididymis is the store house for spermatozoon.
• The two epididymides can accommodate up to 3-4 days production of spermatozoa.
• The cauda epididymis stores nearly 50% of the extragonadal sperms.
• However, sperms in the epididymis remain in quiescent in metabolic activity.

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