[1] The external urethral orifice is placed about 25–30 millimetres (1–1.2 in)[2] behind the clitoris and immediately in front of that of the vagina; it usually assumes the form of a short, sagittal cleft with slightly raised margins.

The vaginal orifice is a median slit below and behind the opening of the urethra; its size varies inversely with that of the hymen.

The sides of the vestibule are visible as Hart's line on the inside of the inner lips; Hart's line is the outer edge of the area and marks the change from vulvar skin to the smoother transitional skin of the vulva.

Except for great apes (including humans) and some rodents, the vestibule in most female placentals (urogenital sinus) is a tubular and internal structure.

[5] This article incorporates text in the public domain from page 1264 of the 20th edition of Gray's Anatomy (1918)