CorpusHuman Anatomy
ReproductiveOrgan

Vagina

Vagina (colpos)

Also known as: vaginal canal, fornix, birth canal

A distensible fibromuscular tube ≈7–9 cm long extending upward and backward from the vestibule to the cervix; it receives the penis, conveys menstrual flow and forms the lower birth canal.

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Overview

LengthAnterior wall ≈7.5 cm; posterior wall ≈9 cm
pH≈3.8–4.5

The vagina's anterior and posterior walls normally lie in contact (H-shaped in cross-section). The anterior wall (≈7.5 cm) is shorter than the posterior wall (≈9 cm) because the cervix enters the upper anterior wall. The recess around the cervix forms the fornices — anterior, two lateral and the deepest, posterior fornix, which is separated from the rectouterine pouch only by the vaginal wall and peritoneum. At its lower end the vagina passes through the urogenital hiatus of the pelvic floor and opens into the vestibule; the hymen partially closes the orifice in the young.

The wall has a mucosa of non-keratinised stratified squamous epithelium (thick and glycogen-rich under estrogen) with transverse folds (rugae) and no glands — lubrication comes from transudation across the wall, cervical mucus and the vestibular glands; a lamina propria rich in elastic fibres and thin-walled veins; a muscularis of smooth muscle; and an outer adventitia. Lactobacilli ferment glycogen from shed epithelial cells to lactic acid, keeping the pH at ≈3.8–4.5, which inhibits pathogens.

Location

Pelvis and perineum, between the bladder and urethra in front and the rectum and anal canal behind; axis directed upward and backward.

Parts & subdivisions

  1. Fornices
    Anterior, posterior (deepest; related to the pouch of Douglas) and lateral (near the ureters and uterine arteries).
  2. Vaginal orifice and hymen
    Opens into the vestibule; hymenal remnants after rupture form carunculae.
  3. Rugae
    Transverse mucosal folds allowing distension.

Anatomy

Innervation

Upper ≈three-quarters: visceral (uterovaginal plexus) — sensitive mainly to stretch. Lower ≈quarter: somatic (deep perineal nerve, branch of the pudendal nerve) — sensitive to touch and pain.

Arterial supply

Vaginal artery (internal iliac or uterine), vaginal branches of the uterine artery, middle rectal and internal pudendal arteries; longitudinal anastomoses form the azygos arteries of the vagina.

Venous drainage

Vaginal venous plexus → internal iliac veins (communicating with vesical, uterine and rectal plexuses).

Lymphatic drainage

Upper third → internal and external iliac nodes; middle third → internal iliac nodes; lower part (below the hymen) → superficial inguinal nodes.

Relations

Anterior: bladder base and urethra (urethra fused to the lower anterior wall). Posterior: rectouterine pouch (upper), rectum (middle, via the rectovaginal septum), perineal body and anal canal (lower). Lateral: ureters near the lateral fornices; levator ani; vestibular bulbs and greater vestibular glands at the orifice.

Histology

Non-keratinised stratified squamous epithelium (glycogen-rich), no glands; elastic lamina propria; inner circular and outer longitudinal smooth muscle; adventitia.

Development

Upper part from the uterovaginal primordium (paramesonephric ducts); lower part from the sinovaginal bulbs of the urogenital sinus; the hymen marks their junction with the vestibule.

Function

  • Receives the penis and semen during intercourse.
  • Outflow tract for menstrual blood and cervical secretions.
  • Lower part of the birth canal.

Clinical significance

Vaginal discharge

Bacterial vaginosis (loss of lactobacilli, Gardnerella; thin grey fishy discharge, pH >4.5, clue cells), candidiasis (thick white discharge, itching, normal pH), trichomoniasis (frothy yellow-green discharge, strawberry cervix) and cervicitis.

Pelvic organ prolapse

Weakness of vaginal supports allows the bladder (cystocele), rectum (rectocele), small bowel (enterocele) or uterus/vault to bulge into the vagina.

Outflow and developmental anomalies

Imperforate hymen causes haematocolpos with cyclical pain and primary amenorrhoea; vaginal agenesis occurs in MRKH syndrome. Obstructed labour can cause vesicovaginal or rectovaginal fistula.

Compiled from standard anatomy and physiology references — see the Reproductive System sources. For education only; not medical advice.