Vagina

The vagina is a midline fibromuscular tubular structureorgan positioned in the female perineum extending superiorly from the vulva, to the cervix and uterus in the pelvis. 

Gross anatomy

The vagina is 8-10 cm in length, extending posterosuperior from the vestibule through the urogenital diaphragm to the uterus. The vagina forms a 90° angle with the uterus. 

The vagina can be divided into the following parts:

• vestibule: between labia minora, incompletely covered by the hymen
• vault: upper end of the vagina
• fornices (anterior, posterior, lateral): recesses formed as the vagina surrounds the cervix

The anterior and posterior vaginal walls are usually closely applied to each other, diverging at the vaginal vault and fornices. 

The vagina is supported by various structures:

• levator ani
• transverse cervical ligament
• pubocervical ligament
• uterosacral ligament
• perineal membrane and perineal body

After menopause, the vagina shortens in length and the fornices almost completely disappear. 

Relations

• anteriorly: cervix, bladder, urethra
• posteriorly: pouch of Douglas, Denonvillier's fascia, perineal body
• laterally: levator ani, pelvic fascia, ureters ³

BloodArterial supply

• arterial supply: vaginal, uterine, internal pudendal and middle rectal arteries (branches of internal iliac arteries)

Venous drainage

• venous supply: vaginal venous plexus draining into internal iliac veins

Lymphatic drainage

• upper three-quarters: internal and external iliac nodes
• lower quarter: superficial inguinal nodes

Innervation

• upper vagina: parasympathetic fibres from pelvic splanchnic nerves (S2-S4)
• lower 2-3 cm vagina: pudendal nerve

Histology

Three layers:

1. Mucosamucosa (non-keratinised stratified squamous epithelium): is hormonally sensitive, and lubricated from the Cervical and Bartholin's glands
2. Muscularismuscularis: connective tissue and smooth muscle (outer longitudinal and inner circular)
3. Adventitiaadventitia: endopelvic fascia that connects the vagina to surrounding pelvic structures to maintain support

Embryology

Embryological derivation of the vagina is from two parts, which is important for derivingunderstanding the origin of congenital anomalies:

• 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

Radiographic features

Ultrasound

During transabdominal (TA) scanning the distended bladder, which acts as an acoustic window, does not affect vaginal position. The vagina can, therefore, be used as an effective landmark, even if the uterus does not occupy its familiar position in the pelvis. The vagina is best seen with a midsagittal TA approach, with a partially filled-filled bladder. The vagina is hypoechoic and the mucosa is echogenic. The echogenicity of the mucosa diminishes in menopause, with the loss of oestrogen stimulation.

Related pathology

• vaginal cancer
• colovaginal fistula
• vesicovaginal fistula
• vaginal atresia
• vaginal stenosis
• congenital uterovaginal anomalies