. Author manuscript; available in PMC: 2018 Dec 1.

Published in final edited form as: Drug Deliv Transl Res. 2017 Dec;7(6):775–795. doi: 10.1007/s13346-017-0385-4

Table 3.

Anatomical and physiological comparison of vagina and anorectum

	Vagina	Anorectum
Length	6–8 cm	Anal canal – 2.5–4 cm Rectum – 10–15 cm
Surface Area	65.73 to 107.07 cm²	Rectum – 200–400 cm²
Fluid volume	0.5–0.75 mL	1–3 mL
Epithelial Tissue Type	Vagina and ectocervix – Multilayer squamous epithelium Endocervix – Simple columnar epithelium (single layer)	Anus – Squamous epithelium Rectum and upper zone in anus – Simple columnar epithelium (single layer)
Pressure	0 mm of Hg	Resting: 40–70mm of Hg During squeeze: 100–200 mm of Hg
pH	4–4.5	7–8
Buffer capacity	High	Low
Relative HIV target cells(e.g. CD4+ T cells)	Low	High