Cervix – the cervix is a thick walled, firm tubular structure approx. 6 cm in length and 3-4 cm in diameter. It is made up of longitudinal folds of endometrium. The cervical canal is straight with a cranial, internal uterine orifice and a caudal, external orifice which projects into the vagina. The intravaginal part of the cervix is known as the fornix. Except at estrus and parturition, the cervical canal is closed providing a physical barrier to the uterus.
Vagina - The vagina is a long thin walled fibromuscular distensible tube which projects cranially from the perineum into the peritoneal part of the pelvic cavity to the cervix. It is about 15 – 20 cm long and 10-12 cm in diameter. Dorsally it is related to the rectum and ventrally to the bladder & urethra. Its lumen is usually collapsed dorsoventrally. During breeding & foaling, the vagina is capable of considerable stretch due to large amounts of elastic tissue within its muscular walls. The vaginal mucus membrane is covered with stratified squamous epithelium arranged in longitudinal folds. It contains an inner circular & outer longitudinal muscle layer. It is surrounded by an outer adventitia. A transverse fold of mucosa cranial to the opening of the urethra represents the remains of the hymen which is more prominent in horses than other domestic species. The vagina contains the urethral orifice where the urethra enters. The vestibule continues the vagina caudally and hangs with the vulva over the icshiatic arch. The vestibule is where urine exits out of the body. The lining of the vestibule contains many mucus glands.
Vulva - The vulva is made up of 2 labia and a clitoris . The labial skin is usually pigmented although it may be speckled. This is the end of the reproductive tract. It is a slit like opening 12-15 cm long. The labia contain many sebaceous & sweat glands and the vulva is also lined with a mucus membrane continuous with the vestibule.
The clitoris is the female penis made up of a root, body & glans. It is well developed in mares. It lies with the clitoral fossa of the ventral vulva.
The relationship of the vulva to the pelvic skeleton varies considerably although there is an ideal conformation for reproductive success. The vulva should be vertical and directly below the anus; it should not deviate laterally. The lips of the vulva should be level with or slightly below the icshiatic arch and form a seal. This ideal conformation becomes altered with every manipulation of foaling the mare experiences.
Constrictor muscles act on the vulva, labia and clitoris to aid in expelling the last drops of urine and ‘winking’ during a mare’s estrus cycle.
389
Made with FlippingBook Publishing Software