In the male, this area is divided into two lateral triangles by the median antero-posterior prominence of the bulb of the penis (corpus spongiosum). The two crura of the penis (corpora cavernosa) diverge as they pass backwards towards the tuberosity of the ischium, and the main pubic vessels lie under cover of these erectile organs. The triangle is completed behind by the transversus perinei muscle. All the above-mentioned erectile structures and muscles lie superficial to the triangular ligament.

In the female, this area is practically cut into two lateral triangles by the orifice of the vagina, each side of which lies the bulb of the vestibule, an organ of erectile tissue, corresponding developmentally to the male corpus spongiosum. More superficially, the two labia majora converge towards the mons veneris in front, whilst, on the mesial aspect of the labia majora, the labia minora converge towards the clitoris, between which body and the vaginal margin a smooth triangular space exists, the vestibule. At the junction of the vagina and the vestibule the urethra opens.

Vaginal Examination

Passing along the posterior vaginal wall the finger enters the superior fornix, the upper part of which is in direct relation with the peritoneal cavity (Douglas's pouch). Along the anterior wall the smaller anterior fornix is first encountered, this cul-de-sac not being directly related to the peritoneal cavity, and immediately above this the os uteri may be examined. Bi-manually, much information can usually be gained with regard to the size and position of the uterus, the condition of the uterine appendages, the contents of Douglas's pouch, etc.