Vagina

Question 1

Vagina Function

Answer 1

One long passage connecting upper reproductive tract to vulva
Functions:
- Female copulatory organ
- Expulsion of urine (micturition)  lower part of vagina
- Birth canal

Question 2

Vagina Regions

Answer 2

There are 3 distinct regions of vagina (from distal):
- Vestibule (contains urethral opening)
- Cranial vagina
Have unique cellular composition because arise from different regions in embryo

Question 3

Vestibule

Answer 3

In most species, vestibule is well developed = urethral opening is ‘hidden’
- Important in artificial insemination (don’t want to put semen in urethra)
Vestibular glands secrete mucous in receptive females (lubrication)
Species differences:
- Sub urethral diverticulum (cow, sow)  dead ended pouch below urethra
- Urethral tubercle (bitch)  protrusion of urethra in vestibule

Question 4

Cranial vagina

Answer 4

Runs from vestibule to cervix
In cow, ewe, mare & bitch, cervix protrudes into cranial vagina, forming pockets – fornix vagina

Increased blood flow (red colouring) under E2 in cranial vagina of receptive females

Question 5

Species Differences

Answer 5

Vestibule & vagina equal lengths in cow, ewe, mare.

Vestibule is SHORTER than cranial vagina in sow, bitch, queen. Thus rethral opening still close to external vulva.

Question 6

Tissue types in vagina

Answer 6

Vagina has poorly organised/defined muscle layer, but a well developed & highly adapted mucosal epithelium
- This is stratified squamous epithelium, with no glands
Like skin, vagina mucosa can thicken by incr. no. of cell layers (i.e. increasing differentiation/maturity – basal to superficial)

Question 7

Vaginal epithelium constantly changes

Answer 7

Under influence of hormone E2 (fluctuates cyclically), the vaginal epithelium thickens.

Thickening protects vagina from mechanical damage & pathogenic invasion during mating

Fully developed vaginal epithelium contains 4 cell types:
1. Basal
2. Parabasal
3. Intermediate
4. Superficial (cornified)
Remember: just 1 cell transiting through all types.

Question 8

Vaginal Epithelium cell changes

Answer 8

Basal = small, round, high ratio of nucleus:cytoplasm
Parabasal = slightly bigger, equal ratio of nucleus:cytoplasm
Intermediate = nucleus similar to parabasal but more abundant cytoplasm
Superficial = dead thus nuclei shrinking or absent (anuclear), cornified due to keratin, vacuoles present

Question 9

Clinical Application – vagina cytology

Answer 9

• Cell populations change in response to rising/falling estrogen in female cycle
• Female receptivity can be assessed using vaginal cytology – smear from cranial vagina (specifically what stage of cycle female is in by seeing what cells)