Vagina and Vestibule - Anatomy & Physiology

()Map REPRODUCTIVE SYSTEM (Map) FEMALE REPRODUCTIVE TRACT

Introduction

The vagina constitutes the part of the female reproductive tract between the cervix and the vulva. With the vestibule and vulva, it is the copulatory organ and the birth canal. The hymen is the poorly developed, vestigial, mucosal folds at the junction of the vagina and vestibule.

Anatomical Boundaries

Vagina

• Extends from the external ostium of the Uterus to the entrance of the Urethra.
• Long and thin walled.
• Located in the median position within the pelvic cavity.
• Located between the rectum dorsally and bladder ventrally.
• Mostly retroperitoneal, but the cranial parts are covered by peritoneum.

Vaginal Fornix

• Protruding cervix restricts the lumen of the cranial vagina to a ring-like space known as the fornix.
• This is a cranioventral recess in the mare and bitch.
• The recess is caudoventral in the cow and ewe.

Vestibule

• Extends from the external urethral opening to the external vulva, so combines urinary and reproductive functions.
• Shorter than the vagina.
• Lies mostly behind the ischial arch, sloping ventrally to its opening at the vulva.
• The wall contains vestibular glands.
  • Secretions from these glands keeps the mucosa of the vestibule moist and facilitates coitus and parturition.
  • At oestrus, the odour of these secretions sexually stimulates the male.

Vestibular Bulbs

• Present in the mare and bitch
• Dark patches on the vestibular walls mark the position of vestibular bulbs.
• Vestibular bulbs are a concentration of veins forming erectile tissue, this is the female homologue of the bulb of the penis.
• During the dog's 'tie', the bulbs are erect and press against the penis, caudal to the enlarged bulb of the glans.

Vestibule

Vestibular Glands

• Cow, queen and sometimes the ewe have major vestibular glands ('glands of Bartholin').
  • In the cow and Ewe, a large glandular mass is present on each side of the vestibule. This drains via a single duct.
• Bitch, ewe, mare and some have only minor vestibular glands.
  • Vestibular glands are small in the bitch, but numerous. Duct openings are arranged in a linear series.