Vagina

Structure/Morphology

The vagina is a fibromuscular elastic tube that extends from its opening in the vulvar region superiorly to the external os, which marks the junction between the cervix and the vagina. Here is a recess, the fornix, and it is divided into four parts (anterior, posterior, and two lateral fornices).

The anterior vaginal wall is approximately 7.5 cm long, while the posterior wall is approximately 9 cm long (Standring, 2016). The width of the vagina increases as it ascends. The inner surfaces of the anterior and posterior vaginal walls are in contact with each other, forming a transverse slit.

The external opening of the vagina is called the introitus and is in close proximity to the hymen (or hymenal caruncles), a mucosal membrane that sits within the vaginal orifice.

The walls of the vagina consist of:

—an inner mucosa;

—a muscular layer;

—an outer adventitial layer.

Anatomical Relations

The bladder sits anterior to the vagina and its anterior vaginal wall aids in the stability of the base of the bladder and the proximal urethra. The vagina is separated from the bladder by the peritoneal fold, thus forming the vesicouterine pouch.

The rectum is posterior to the vagina and the posterior vaginal wall aids in stabilizing the rectum. The upper portion of the vagina is separated from the rectum by the rectouterine pouch (Pouch of Douglas); the middle portion of the vagina is separated from the rectum by rectovaginal fascia (or Denonvilliers’ fascia) and the lower portion of the vagina is separated from the anal canal by the perineal body.

The upper portion of the vagina is supported by several ligaments such as the transverse cervical, uterosacral, and pubocervical ligaments, and the levator ani muscle. Specifically, the pubovaginalis portion of the levator ani muscle supports the mid-region of the vagina by forming a muscular sling. The lower vagina receives support from the muscle fibers of the bulbospongiosus muscle.

Function

The vagina has several functions, including production of acidic mucosa for protection, an organ for receptive sexual intercourse, and serving as the channel for childbirth.

Arterial Supply

The vaginal arteries are branches of the anterior division of the internal iliac arteries. Additional branches arising from the uterine, middle rectal, and internal pudendal arteries may also supply the vagina.

Venous Drainage

The vaginal venous plexus surrounds the walls of the vagina. The upper portion of the plexus is drained into the uterine vein or uterine venous plexus, which returns blood to the internal iliac veins. The lower portion of the vaginal venous plexus is drained into the internal pudendal veins via the vaginal veins.

Innervation

The distal vagina is supplied by the pudendal nerve (S2, S3, S4). The proximal vagina is innervated by the uterovaginal plexus, which contains autonomic and visceral afferent neurons. The parasympathetic innervation to the plexus arrives via pelvic splanchnic nerves (S2, S3, S4) and sympathetic innervation arrives via lumbar and sacral splanchnic nerves (Standring, 2016).

Lymphatic Drainage

The paravaginal lymph nodes surround the vagina. The most superior nodes of this group accompany the uterine artery and their efferent’s drain to the interior and external iliac nodes. Intermediate nodes accompany the vaginal artery and drain to the internal iliac nodes. The lowest nodes drain lymph from the vulva and perineal skin, which passes to the superficial inguinal lymph nodes (Földi et al., 2012).

List of Clinical Correlates

—Vaginal fistula

References

Földi, M., Földi, E., Strößenreuther, R. and Kubik, S. (2012) Földi's Textbook of Lymphology: for Physicians and Lymphedema Therapists. Elsevier Health Sciences.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.