THE VAGINA

DEFINITION: The vagina is a muscular, dilatable canal which extends from the vulva (external urethral meatus) upwards and backwards to the cervix.

SITUATION: It lies between the bladder anteriorly and the rectum posteriorly.

LENGTH:

• Anterior wall: 7.5 cm
• Posterior wall: 9 cm (longer because the cervix projects into the upper part of the anterior wall)

SHAPE: It is H-shaped in transverse section due to the lateral walls being in contact.

DIRECTION: It passes upwards and backwards at an angle of 60–70 degrees to the horizontal.

STRUCTURE The vagina consists of three layers:

1. Inner mucous membrane:
   
   • Non-keratinized stratified squamous epithelium.
   • Thrown into folds known as rugae which allow for distension during childbirth.
   • Contains no glands but is kept moist by:
     
     • Cervical secretion
     • Fluid from the vaginal walls
     • Discharge from the vestibular glands
2. Middle muscular layer:
   
   • Composed of smooth muscle fibres arranged in:
     
     • Outer longitudinal
     • Inner circular layers
   • Weak muscle, poorly developed.
3. Outer fibrous layer:
   
   • Dense connective tissue which blends with the pelvic fascia and supports the vagina.

RELATIONS

ANTERIORLY:

• Upper ⅓: Base of the bladder
• Lower ⅔: Urethra (embedded in the anterior vaginal wall)

POSTERIORLY:

• Upper ⅓: Pouch of Douglas (peritoneal cavity)
• Middle ⅓: Rectum
• Lower ⅓: Perineal body

LATERALLY:

• Upper part: Ureters (pass medially to enter the bladder)
• Middle part: Pelvic fascia and levator ani muscles
• Lower part: Bulbospongiosus muscles and vestibular bulbs

VAULTS OF THE VAGINA The upper part of the vagina surrounds the cervix forming four fornices:

• Anterior fornix: Shallow
• Posterior fornix: Deepest (related to the pouch of Douglas)
• Two lateral fornices

BLOOD SUPPLY

ARTERIAL SUPPLY:

• Upper part: Cervical branch of the uterine artery
• Middle part: Vaginal artery (branch of internal iliac or uterine artery)
• Lower part: Pudendal branches of the internal pudendal artery

VENOUS DRAINAGE: Forms a plexus around the vagina → drains into internal iliac veins.

NERVE SUPPLY

• Upper part: Sympathetic and parasympathetic from pelvic plexus
• Lower part: Pudendal nerve (somatic)

LYMPHATIC DRAINAGE

• Upper ⅓: Internal iliac nodes
• Middle ⅓: Internal iliac nodes
• Lower ⅓: Superficial inguinal nodes

FUNCTIONS OF THE VAGINA

1. Organ of copulation – receives the penis during intercourse.
2. Birth canal – distensible passage for the fetus during delivery.
3. Exit for menstrual flow.
4. Supports the uterus, bladder, and rectum (via pelvic floor).

APPLIED ANATOMY

VAGINAL EXAMINATION (V.E.)

• Done to assess:
  
  • Cervical dilatation, effacement, position
  • Station of the presenting part
  • Pelvic capacity
  • Membrane status

VAULTS IN CLINICAL PRACTICE

• Posterior fornix: Used for:
  
  • Culdocentesis (to detect blood in pouch of Douglas)
  • Insertion of vaginal pessaries
• Lateral fornices: Uterine arteries and ureters lie close → risk during hysterectomy.

VAGINAL DISCHARGE

• Normal: White, mucoid, non-offensive (due to cervical mucus + desquamated cells).
• Abnormal: Indicates infection (e.g., candidiasis, trichomoniasis, bacterial vaginosis).

PROLAPSE

Weakening of supports → descent of vaginal walls:

• Anterior wall: Cystocele
• Posterior wall: Rectocele
• Upper vagina: Uterine prolapse

VAGINAL FISTULAE

Abnormal communications due to obstructed labor or injury:

1. Vesico-vaginal fistula (VVF): Urine leaks into vagina → continuous incontinence.
2. Recto-vaginal fistula: Faeces/flatus pass through vagina.

VAGINAL INFECTIONS

• Candida albicans: Cottage cheese discharge, itching.
• Trichomonas vaginalis: Frothy green discharge, offensive.
• Gonorrhoea: May ascend → PID.

VAGINAL pH

• Normally acidic (3.8–4.5) due to glycogen → lactic acid by Döderlein’s bacilli.
• Maintains normal flora, prevents infection.
• pH rises in:
  
  • Menopause (↓ estrogen)
  • Postpartum
  • Antibiotic use

VAGINAL SUPPORTS

1. Upper third:
   
   • Pubocervical ligaments
   • Transverse cervical (cardinal) ligaments
   • Uterosacral ligaments
2. Middle third: Pelvic fascia
3. Lower third: Perineal body and levator ani

CHANGES DURING PREGNANCY

1. Increased vascularity → bluish (Chadwick’s sign).
2. Softening (Goodell’s sign).
3. Increased secretion → physiological discharge.
4. Lengthening of anterior wall.

CHANGES DURING LABOR

• First stage: Vagina forms lower part of birth canal.
• Second stage: Distends fully to allow passage of fetus.
• Risk of tears: Especially at fourchette and posterior wall.

VAGINAL EXAMINATION TECHNIQUE

1. Empty bladder.
2. Dorsal position, knees flexed and apart.
3. Aseptic technique (gloves, antiseptic).
4. Two fingers inserted gently.
5. Assess:
   
   • Tone, capacity, rugae
   • Cervix (dilatation, effacement)
   • Presenting part (station, position)
   • Membranes

CONGENITAL ANOMALIES

1. Imperforate hymen → cryptomenorrhea.
2. Vaginal septum → transverse or longitudinal.
3. Vaginal atresia → absence of vagina (Mayer-Rokitansky syndrome).

SUMMARY TABLE: VAGINA