What is the anatomy of the vagina?

Anatomy of the Vagina

The vagina is a fibromuscular tubular structure extending from the vulvar vestibule externally to the uterine cervix internally, with distinct anatomical layers and specialized epithelium that changes from the introitus to the upper vagina.

Anatomical Boundaries and Structure

• Location: The vagina is a median fibromuscular structure extending from the vulva inferiorly to the uterine cervix superiorly 1
• Length: Typically measures 7-9 cm along the anterior wall and 8-10 cm along the posterior wall
• Orientation: Angles posteriorly from the introitus toward the sacrum at approximately 45 degrees

Vaginal Introitus (Entrance)

• Marks the external opening of the vagina
• Equivalent to Level III of the vagina 2
• Components include:
  • Anterior vestibule (6 anatomical layers)
  • Posterior vestibule (3 anatomical layers)
  • Perineum (inverse trapezoid shape) 2
• Bordered laterally by Hart's line, which marks the transition from nonkeratinizing epithelium to keratinized epithelium of the labia minora 2

Epithelial Lining

• Type: Non-keratinized stratified squamous epithelium
• Characteristics: Lacks glands but is moistened by transudation from blood vessels and secretions from the upper genital tract
• Transition: At the ectocervix, there is a squamocolumnar junction (ectropion) which is a normal developmental finding in adolescents 3

Anatomical Divisions

Upper Vagina

• Connects to the cervix, forming vaginal fornices (anterior, posterior, and lateral recesses)
• Posterior fornix is deeper than the anterior fornix
• Supported by cardinal and uterosacral ligaments

Middle Vagina

• Supported laterally by levator ani muscles and endopelvic fascia
• Forms the vaginal canal proper

Lower Vagina (Introitus)

• Surrounded by the bulbocavernosus muscles
• Contains the hymenal remnants
• Transitions to the vulvar vestibule

Supporting Structures

• Muscular Support: Primarily from the levator ani muscle complex
• Fascial Support: Endopelvic fascia connects the vagina to the pelvic sidewalls
• Adjacent Structures:
  • Anteriorly: Urethra and bladder
  • Posteriorly: Rectum and anal canal
  • Laterally: Levator ani muscles and pelvic fascia

Vascular, Lymphatic, and Nerve Supply

• Arterial Supply: Branches from the internal iliac artery, including vaginal, uterine, and internal pudendal arteries
• Venous Drainage: Vaginal venous plexus draining into internal iliac veins
• Lymphatic Drainage:
  • Upper vagina: To internal iliac and sacral nodes
  • Lower vagina: To superficial inguinal nodes 3
• Innervation:
  • Autonomic innervation from pelvic splanchnic nerves (parasympathetic) and hypogastric plexus (sympathetic)
  • Sensory innervation from pudendal nerve (S2-S4)

Clinical Significance

• The vagina undergoes significant changes during the reproductive cycle, pregnancy, and menopause
• The ectropion (squamocolumnar junction visible on the exocervix) is normal in adolescents and can cause increased vaginal discharge 3
• Vaginal epithelium responds to hormonal influences, becoming thicker and more glycogenated under estrogen stimulation
• Proper examination requires understanding of normal anatomy to identify pathological conditions 3

Specialized Structures

• Bartholin's Glands: Located at the vaginal introitus, providing lubrication
• Skene's Glands: Located near the urethral meatus
• Vaginal Rugae: Transverse folds that increase surface area and provide elasticity

Understanding vaginal anatomy is essential for proper clinical assessment, diagnosis of pathological conditions, and surgical interventions such as perineorrhaphy, which can achieve significant anatomical benefits including increased perineal length and reduced genital hiatus 2.