The vagina is a distensible muscular tube that is approximately 9cm long. It has several important roles in the female:
- 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.
It extends upwards and backwards from the vestibule of the external genitalia to the cervix (lower part of the uterus).
In this article, we will look at the anatomy of the vagina – its structure, innervation, vascular and lymphatic supply.
The vagina is closely related to many of the organs in the pelvic region:
- Anterior to the vagina is the bladder and urethra.
- Posterior to the vagina is the rectum and anus.
- Laterally located are the ureters and uterine arteries.
Clinical Relevance: Vaginal (Obstetric) Fistulae
A vaginal fistula is an open communication between the vagina and one of the adjacent pelvic organs.
It typically occurs as a result of prolonged labour, where a Caesarean section is not available. It is seen as a disease of poverty. As the fetus slowly progresses down the vaginal wall, it exerts pressure which limits the blood supply and results in necrosis.
There are three main types of vaginal fistulae:
- Vesicovaginal – between the vagina and the bladder. Urine enters the vagina constantly.
- Urethrovaginal – between the vagina and the urethra. Urine only enters the vagina during urination.
- Rectovaginal – between the vagina and the rectum. Faecal matter can enter the vagina.
The vagina is composed of 4 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).
- Oestrogen stimulates the epithelial cells to secrete glycogen. The glycogen is digested by the natural flora of the vagina to produce lactic acid, and maintain a low vaginal pH of ~4.5. This prevents infection by other organisms.
- Elastic lamina propria – a dense connective tissue layer which projects papillae into the overlying epithelium. The larger veins are located here.
- Together, the lamina propria and epithelium comprise the vaginal mucosa.
- 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.
Clinical Relevance: Vaginal Candidiasis
Vaginal candidiasis refers to a yeast infection of the vagina. The most common organism is Candida albicans – responsible for approximately 90% of infections. It typically occurs when the natural bacterial flora of the vagina is disrupted – e.g. patients on antibiotic therapy.
Common clinical features of vaginal candidiasis include itching, soreness and a white ‘cheesy’ discharge. It is usually treated with topical, intravaginal or oral antifungals.
Vascular Supply and Lymphatics
Arterial supply to the vagina is via the uterine and vaginal arteries; both branches of the internal iliac artery.
Venous return is by the vaginal venous plexus, which drains into the internal iliac veins via the uterine vein.
Lymphatic drainage is via the iliac and superficial inguinal lymph nodes.
The parasympathetic and sympathetic nerves supplying the vagina are derived from the uterovaginal nerve plexus. The uterovaginal plexus lies in the base of the broad ligament, either side of the supravaginal part of the cervix.
The inferior fibres from the uterovaginal plexus supply the superior part of the vagina. These are derived from the inferior hypogastric plexus and the pelvic splanchnic nerves.
The inferior part of the vagina is innervated by a branch of the pudendal nerve called the deep perineal nerve.