Vaginal anatomy

Wall structure and fornices

The vaginal wall is highly elastic and consists of three layers:

• Mucous membrane. Lined with stratified squamous epithelium. Its surface features prominent longitudinal and transverse folds (rugae vaginales). Important histological feature: the vaginal mucosa completely lacks glands and hair follicles.
• Muscular layer. Formed by bundles of smooth myocytes densely interwoven with elastic fibers, allowing the organ to stretch significantly.
• Adventitia. The outer connective tissue layer that fixes the organ to surrounding tissues.

In its upper part, the vagina surrounds the cervix, which protrudes into its lumen. The space between the vaginal walls and the cervix forms the vaginal fornices (fornices vaginae). Anatomically, the anterior, lateral, and posterior fornices are distinguished. Of these, the posterior fornix is the deepest.

Topography and syntopy

The vagina is located in the pelvic cavity and has close topographic relationships with adjacent organs:

1. Anteriorly, the upper part of the organ is adjacent to the urinary bladder, and the lower part to the urethra.
2. Posteriorly, the vagina borders the rectum. In the middle pelvic compartment, these organs are reliably separated by the rectovaginal septum (septum rectovaginale).
3. Laterally, the organ is surrounded by the deep transverse perineal muscle and the medial bundles of the levator ani muscle (m. levator ani).

In relation to the peritoneum, the vagina is located subperitoneally (extraperitoneally). The only exception is the posterior fornix: the peritoneum descends onto it from the posterior surface of the supravaginal part of the cervix and covers it for 2 cm. In this zone, the vagina directly borders the rectouterine pouch (Pouch of Douglas).

Blood supply, lymph drainage, and innervation

The vascular and nerve network of the vagina is closely connected with the blood supply of the uterus and pelvic floor:

• Arteries. Nutrition is provided by vaginal branches arising from the uterine artery (a. uterina) and the internal pudendal artery (a. pudenda interna).
• Veins. Blood outflow occurs into the dense vaginal venous plexus (plexus venosus vaginalis). It forms extensive anastomoses with the venous plexuses of the uterus, rectum, and urinary bladder.
• Lymphatic drainage. Lymph is directed to the iliac lymph nodes. The lymphatic bed of the vagina is integrated with drainage pathways from the uterus and urinary bladder.
• Innervation. Has a dual nature. The upper sections receive autonomic fibers from the intramural ganglia of the uterovaginal plexus (nn. vaginales). The lower part of the organ is innervated by somatic branches of the pudendal nerve (n. pudendus).

Clinical significance

The anatomical structure of the vagina determines several critically important aspects in obstetrics and gynecology:

• Diagnostic puncture. Since the posterior fornix is covered by the peritoneum and is the lowest point of the rectouterine pouch, it is used for culdocentesis when fluid or blood accumulation in the pelvic cavity is suspected.
• Risk of fistula formation. Due to the tight apposition of the anterior wall to the bladder and the posterior wall to the rectum, severe birth trauma can lead to the formation of pathological communications: vesicovaginal or rectovaginal fistulas.

Class and exam questions

What else to study on this topic

• Histological structure of the mucous membrane and sources of vaginal secretion formation.
• Topography and boundaries of the rectouterine pouch (Pouch of Douglas).
• Mechanism and causes of vesicovaginal and rectovaginal fistula formation.
• Anastomoses of the vaginal venous plexus with other pelvic venous plexuses.
• The role of the levator ani muscle in pelvic organ fixation.

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