Cervix of Animals

The cervix of animals is a thick walled, tubular sphincter muscle between the vagina and uterus with a constricted lumen.

Cervix of animals serves as a point of orientation during the clinical examinations of the genital organs in bovine.

The canal of the cervix opens into the anterior vagina through the external os or os externum and into the uterus through the os uterinum or internal os. The cervical canal is characterized by various prominences.

In ruminants these prominences are in the form of transverse or spirally interlocking ridges known as annular rings. They are prominent in cows and in ewe where they fit into each other to close the cervix securely.

In cow the number of annular rings is 3-5 in number. In sow, the rings are in a corkscrew arrangement that is adapted to the spiral twisting of the tip of the boar‘s penis.

In mare there are numerous small longitudinal folds of muscous membrane present and these folds in the canal project into the vagina preventing contamination.

At the external and internal os are finger like projections called plica palmate. The portion of the cervix that projects into the vagina are called portio vaginalis.

The junction of the cervix and vagina is a blind pouch called Fornix. Absent in sows and prominent in mares.

Histology of Cervix

Histologically the cervix consists of serosa, muscularis and mucosa. The mucosa is lined by tall columnar epithelial cells in between the goblet cells.

During estrus a thin stringy mucus is secreted while during pregnancy a thick tenacious mucus is secreted. The cervical wall is made up of fibroblastic collageneous tissue and muscular tissue. The collagen is responsible for the high tensile strength of the cervix.

In bovines at the time of natural service the penis touches the external os and the semen is spread over the os.

In mares due to the dilated and less cartilaginous cervix, the semen is deposited directly into the uterus.

Function of the Cervix

• Cervix prevents entry of pathogens into the uterus.
• Facilitates sperm transport.
• Acts as a sperm reservoir.
• Plays a vital role in selection of viable sperms and prevents transport of nonviable and defective sperms.
• Relaxes at the time of estrus and at the time of parturition to allow expulsion of the fetus.
• Increasing quantities of mucus is secreted at estrus and at pregnancy. At pregnancy the mucus to form the cervical plug of scal.