Overview
The vagina is a distensible fibromuscular tube of the female reproductive tract, which extends posterosuperiorly from the external vaginal orifice to the cervix. It has several roles within the female reproductive system:
- Sexual intercourse – receives the penis and ejaculate, assisting in its transport to the uterus.
- Childbirth – expands to provide a channel for delivery of a newborn from the uterus.
- Menstruation – serves as a canal for menstrual fluid and tissue to leave the body.
Structure
- The anterior and posterior walls are normally collapsed, thus creating a H-shaped cross section.
- At the superior end, the vagina surrounds the cervix, creating two domes (anterior and posterior) termed fornices.
- The posterior fornix acts as a natural reservoir for semen after intravaginal ejaculation
Layers
The vagina is composed of four histological layers (internal to external):
- Stratified squamous epithelium – this layer provides protection and is lubricated by cervical mucus (the vagina itself does not contain any glands).
- Elastic lamina propria – a dense connective tissue layer which projects papillae into the overlying epithelium. The larger veins are located here.
- Fibromuscular layer – comprising two layers of smooth muscle; an inner circular and an outer longitudinal layer.
- Adventitia – a fibrous layer, which provides additional strength to the vagina whilst also binding it to surrounding structures.
Arterial Supply
- Uterine and vaginal arteries – both visceral branches arising from the anterior division of the internal iliac artery
Venous Drainage
- Venous return is by the vaginal venous plexus, which drains into the internal iliac veins via the uterine vein.
Lymphatic Drainage
Lymphatic drainage is divided into three sections:
- Superior – drains to external iliac nodes
- Middle – drains to internal iliac nodes
- Inferior – drains to superficial inguinal lymph nodes.
Innervation
Innervation is predominantly from the autonomic nervous system.
- Parasympathetic and sympathetic nerves arise from the uterovaginal nerve plexus (from the inferior hypogastric plexus).
- Only the inferior 1/5 of the vagina receives somatic innervation via the deep perineal nerve – branch of the pudendal nerve (lumbar plexus)
Relations
- Anterior – bladder and urethra.
- Posterior – rectouterine pouch, rectum and anal canal.
- Lateral – ureters and levator ani muscle.
Development
- Upper two-thirds of the vagina, cervix and uterus: all derived from the paired Mullerian / paramesonephric ducts.
- Lower one-third of the vagina: derived from the bilateral sinovaginal bulbs which arise from the urogenital sinus
Anatomical Variants
- Vaginal septum – formed if there in complete joining of the Mullerian duct with the sinovaginal bulb at the Mullerian tubercle during formation of the vaginal lumen
- Vaginal agenesis – typically part of Mayer-Rokitansky-Kuster-Hauser syndrome (46, XX karyotype)