The office of a Sphincter Muscle, of which we have several, as that of the bladder and anus, is to keep closed the aperture they surround. The sphincter ani closes the rectum, and pulls down the bulb of the urethra, by which it assists in ejecting the urine and semen.
The Levator Muscles lift up the part they are connected with. The levator ani muscles form the funnel appearance of the rectum, and help to draw it up after the fæces or stools are evacuated. They also assist in sustaining the contents of the pelvis, and help to eject the semen and urine, and contents of the rectum, and, perhaps, by pressing upon the veins, contribute to the erection of the penis.
| 1. Coccyx. 2. Semen. 3. Covering of the Thigh. 4. Great Sacro Sciatic Ligament. a. Bulb of the Urethra. b. Corpus Spongiosum. c. Crura of the Penis, being the conclusion of— d. Corpora Cavernosa Penis. e. Sphincter of the Anus. f. Levatores Ani, covered by a fascia or prolongation of the triangular ligament of the Urethra. g. Great Gluteal Muscles. h, h. Triangular Ligament of the Urethra. The artery of the bulb is seen on the left as it runs between the Crus Penis and bulb of the Urethra. View larger image |
1. Coccyx.
2. Semen.
3. Covering of the Thigh.
4. Great Sacro Sciatic Ligament.
a. Bulb of the Urethra.
b. Corpus Spongiosum.