SUMMARY OF THE ORGANIZATION OF THE PERINEUM

1.1 The pubic symphysis

1.2 The inferior pubic rami

1.3 The ischial rami

1.4 The ischial tuberosities

1.5 Sacrotuberous ligaments

1.6 The coccyx.

The line joining the two ischial tuberosites divides the perineum into two triangular parts.

2.1 The anal triangle, posterior to this line, containing the anus.

2.2 The urogenital region, anterior to this line, and containing scrotum, and the root of the penis ( or the vulva in the female ).

The Pelvic Diaphragm

Components

•  Laveta ani

•  Coccygeus muscles, together with their investing fasciae; both superiorly and inferiorly.

The lavetor ari muscles and their fascia form the larger and more important part of the pelvic diaphragm.

These muscles originate from;

•  The pelvic surface of the body of the pubis

•  Tendinous arch, formed by a thickening of the parietal pelvic fascia over the obturator internus muscle.

•  Ischial spine.

They insert onto;

•  Central perineal tendon

•  The wall of the anal canal

•  Anococcygeal ligament

•  Coccyx.

Parts of Lavetor Ani

•  Pubococcygeus, is the main par. It arises from the pubis, and inserts into the coccyx, and the anococcygeal ligament. The anococcygeal ligament, is the median fibrous intersection of the pubococcygeus muscles from the two sides. It is located between the anal canal and the tip of the coccyx. The pubococcygens encircles the urethra, vagina, and anus and merges into the central perineal tendon.

•  The puborectalis, is the part that loops around the anorectal junction, and arises from the pubis.

•  Lavetor prostatae, are the anterior fibres that run inferior to the prostate. In the females, these fibres constitute the pubo vaginali muscle.

1. Constitute the pelvic floor for the containment/support of pelvic viscera - resisting inferior thrust during e.g. coughing, deep expiration etc.

2. They raise the pelvic floor, assisting the anterior abdominal wall muscles in compressing the viscera, e.g. in coughing, deep expiration, vomiting, urinating.

3. Support of the prostate and the vagina providing sphincteric action of the latter, and urethra.

4. The puborectalis holds the anorectal junction anteriorly, increasing the angle between the rectum, and anal canal. This prevents passage of feces from the rectum, into the anal canal when defecation is not desired, or is inconvenient.

5. The gutter arrangement, facilitates the rotation of the baby's head during parturition, in accordance with the pelvic diameters.

6. Supports the fetal head while cervix is dilating during parturition.

•  The coccygeus muscle, is continuous with the iliococcygeus muscle; and forms the posterior and smaller part of the pelvic diaphragm.

•  It rises from the pelvic surface of the ischial spine.

•  It inserts on the lateral margins of the 5 th sacral vertebra and coccyx.

•  The fibres support the coccyx, and pull it anteriorly, after it has been pressed posteriorly during child-birth.

•  The anus

•  The urethra

•  The vagina (in females)