Henry Gray (18251861). Anatomy of the Human Body. 1918.
The Inferior Hemorrhoidal Artery (a. hæmorrhoidalis inferior) arises from the internal pudendal as it passes above the ischial tuberosity. Piercing the wall of Alcocks canal it divides into two or three branches which cross the ischiorectal fossa, and are distributed to the muscles and integument of the anal region, and send offshoots around the lower edge of the Glutæus maximus to the skin of the buttock. They anastomose with the corresponding vessels of the opposite side, with the superior and middle hemorrhoidal, and with the perineal artery.
The Perineal Artery (a. perinei; superficial perineal artery) arises from the internal pudendal, in front of the preceding branches, and turns upward, crossing either over or under the Transversus perinæi superficialis, and runs forward, parallel to the pubic arch, in the interspace between the Bulbocavernosus and Ischiocavernosus, both of which it supplies, and finally divides into several posterior scrotal branches which are distributed to the skin and dartos tunic of the scrotum. As it crosses the Transversus perinæi superficialis it gives off the transverse perineal artery which runs transversely on the cutaneous surface of the muscle, and anastomoses with the corresponding vessel of the opposite side and with the perineal and inferior hemorrhoidal arteries. It supplies the Transversus perinæi superficialis and the structures between the anus and the urethral bulb.
The Artery of the Urethral Bulb (a. bulbi urethræ) is a short vessel of large caliber which arises from the internal pudendal between the two layers of fascia of the urogenital diaphragm; it passes medialward, pierces the inferior fascia of the urogenital diaphragm, and gives off branches which ramify in the bulb of the urethra and in the posterior part of the corpus cavernosum urethræ. It gives off a small branch to the bulbo-urethral gland.
The Urethral Artery (a. urethralis) arises a short distance in front of the artery of the urethral bulb. It runs forward and medialward, pierces the inferior fascia of the urogenital diaphragm and enters the corpus cavernosum urethræ, in which it is continued forward to the glans penis.