Henry Gray (18211865). Anatomy of the Human Body. 1918.
10. Surface Markings of the Perineum
A line drawn transversely across in front of the ischial tuberosities divides the perineum into a posterior or rectal, and an anterior or urogenital, triangle. This line passes through the central point of the perineum, which is situated about 2.5 cm. in front of the center of the anal aperture or, in the male, midway between the anus and the reflection of the skin on to the scrotum.
Rectum and Anal Canal.A finger inserted through the anal orifice is grasped by the Sphincter ani externus, passes into the region of the Sphincter ani internus, and higher up encounters the resistance of the Puborectalis; beyond this it may reach the lowest of the transverse rectal folds. In front, the urethral bulb and membranous part of the urethra are first identified, and then about 4 cm. above the anal orifice the prostate is felt; beyond this the vesiculæ seminales, if enlarged, and the fundus of the bladder, when distended, can be recognized. On either side is the ischiorectal fossa. Behind are the anococcygeal body, the pelvic surfaces of the coccyx and lower end of the sacrum, and the sacrospinous ligaments (Fig. 1228).
Male Urogenital Organs.The corpora cavernosa penis can be followed backward to the crura which are attached to the sides of the pubic arch. The glans penis, covered by the prepuce, and the external urethral orifice can be examined, and the course of the urethra traced along the under surface of the penis to the bulb which is situated immediately in front of the central point of the perineum. Through the wall of the scrotum on either side the testis can be palpated; it lies toward the back of the scrotum, and along its posterior border the epididymis can be felt; passing upward along the medial side of the epididymis is the spermatic cord, which can be traced upward to the subcutaneous inguinal ring.
By means of a sound the general topography of the urethra and bladder can be investigated; with the urethroscope the interior of the urethra can be illuminated and viewed directly; with the cystoscope the interior of the bladder is in a similar manner illuminated for visual examination. In the bladder the main points to which attention is directed are the trigone, the torus uretericus, the plicæ uretericæ, and the openings of the ureters and urethra (see Fig. 1240).
Female Urogenital Organs.In the pudendal cleft(Fig. 1229) between the labia minora are the openings of the vagina and urethra. In the virgin the vaginal opening is partly closed by the hymenafter coitus the remains of the hymen are represented by the carunculæ hymenales. Between the hymen and the frenulum of the labia is the fossa navicularis, while in the groove between the hymen and the labium minus, on either side, the small opening of the greater vestibular (Bartholins) gland can be seen. These glands when enlarged can be felt on either side of the posterior part of the vaginal orifice. By inserting a finger into the vagina the following structures can be examined through its wall (Fig. 1230). Behind, from below upward, are the anal canal, the rectum, and the rectouterine excavation. Projecting into the roof of the vagina is the vaginal portion of the cervix uteri with the external uterine orifice; in front of and behind the cervix the anterior and posterior vaginal fornices respectively can be examined. With the finger in the vagina and the other hand on the abdominal wall the whole of the cervix and body of the uterus, the uterine tubes, and the ovaries can be palpated. If a speculum be introduced into the vagina, the walls of the passage, the vaginal portion of the cervix, and the external uterine orifice can all be exposed for visual examination.
The external urethral orifice lies in front of the vaginal opening; the angular gap in which it is situated between the two converging labia minora is termed the vestibule. The urethral canal in the female is very dilatable and can be explored with the finger. About 2.5 cm. in front of the external orifice of the urethra are the glans and prepuce of the clitoris, and still farther forward is the mons pubis.