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What makes up the pelvic outlet?

1. Pubic symphysis.
2. Ischiopubic ramus.
3. Ischial tuberosity.
4. ST ligament.
5. Coccyx.

It is a diamond shape.


What is the pelvic outlet divided into?

Urogenital (superior) and anal (inferior) triangles.


Where is the perineal body situated?

It is right in the midline between the urogenital triangle and the anal triangle.


What is the perineal body composed of?

Fibrous connective tissue.


What is attached to the perineal body?

1. Levator ani.
2. Bulbospongiosus.
3. External anal sphincter.
4. Perineal muscles.


Describe the pelvic floor?

It is the muscle: Levator Ani. It is a diaphragm, separating the pelvic cavity from the outside world.


What is the levator ani divided into?

3 major divisions:
1. Ischiococcygeus.
2. Iliococcygeus.
3. Pubococcygeus - can subdivide into more bits.
One continuous sheet of muscle.


What is the levator ani innervated by?

Pudendal nerve (S2-4) but majority is innervated by nerve to levator ani.


What are the pubococcygeus divisions?

1. Levator prostatae.
2. Pubovaginalis.
3. Puborectalis.


Describe the puborectalis subdivision?

It loops around the back of the rectus and creates an angle in the rectum. This helps to maintain faecal contents. When you defaecate this muscle relaxes.


Describe the iliococcygeus muscle?

It attaches to fascia of obturator internus. it prevents prolapse of pelvic viscera.


What nerve innervates the iliococcygeus muscle?

The pudendal nerve (S2-S4) and nerve to levator ani (S3-4).


Describe the external anal sphincter?

It is skeletal muscle, therefore it is under conscious control. It attaches anteriorly to the perineal body to the anococcygeal ligament. It closes the anus (rectal control aided buy the puborectalis).


What nerve innervates the external anal sphincter?

The pudendal nerve (S2-4) - inferior rectal branch.


Describe the internal anal sphincter?

It is smooth muscle - under ANS control (involuntary control). It is deep to the external anal sphincter and is separated by connective tissue.


Describe the ischioanal fossa?

It is the region either side of the anal canal. Medially to it is the anal sphincter. Laterally to it is the obturator internus and superiorly to it is the levator ani muscle. The floor of it is superficial fascia. It is all filled in with fat - clinically significant.


Describe surface anatomy?

The landmarks (all palpable):
1. Ischial Tuberosity - laterally.
2. Coccyx - posteriorly.
3. Perineal body - in midline between anus and vagina/scrotum.
Pudendal vessels enter at the lateral apex - need to be aware of the lateral apex.


Describe the anal canal?

This is where the rectum pierces the pelvic floor. there are anal columns - contain a terminal radicle of the superior rectal vessels. Below the line there is the transition of epithelium: endoderm (mesothelium) into skin.


What is the arterial supply and the lymphatic drainage to the anal canal?

1. Superior rectal artery (inferior mesenteric) - pre-aortic nodes at L3 (inferior mesenteric) drain the lymphatics. This artery comes right down to the anal columns.
2. Middle rectal artery (internal iliac) - internal iliac nodes.
3. Inferior rectal artery (internal pudendal) supplies the lower part of the rectum and the anal canal - internal iliac nodes.

At the anal canal inferior to the pectinate line - superficial inguinal nodes.


Describe venous drainage of the rectum/anal canal?

The superior rectal vein will drain back up to the inferior mesenteric vein (back to portal). There are inferior rectal veins as well - portal-systemic anatomosis.


Describe the urogenital triangle (perineal membrane)?

Region between the pubic symphysis to the ischial tuberosities on each side.


Describe the urogenital diaphragm?

There are layers of this diaphragm:
1. Superior layer of fascia (deep, blends with perineal body and membrane).
2. Sphincter urethrae and deep transverse perineal muscles.
3. Inferior layer of fascia (superficia, the perineal membrane).


Describe the male variation of the deep perineal pouch?

1. 'Membranous' urethra.
2. Bulbourethral glands.
3. Neurovascular stuff - e.g. dorsal nerve of penis.


Describe the female variation of the deep perineal pouch?

1. Vagina.
2. Compressor urethrae muscle.
3. Dorsal nerve of the clitoris.

N.B. Bartholin's glands in the superficial pouch.


Describe the superficial perineal pouch?

Anything between the perineal membrane and the skin is the superficial pouch. This includes the pudendal vessels, erectile tissues, perineal muscles and bartholin's glands (in females.


Describe the fascia and communication in the superficial pouch?

The scrapa's fascia of the abdomen is continuous with the darts fascia of the penis/scrotum which is continuous with the collets fascia of the perineum.


Describe the internal pudendal artery?

It supplies inferior rectum and perineal structures.


What are the internal pudendal artery branches?

1. Inferior rectal.
2. Perineal.
3. Dorsal artery of Penis.

1. Inferior rectal.
2. Perineal.
3. Dorsal artery of clitoris.


Describe the pudendal nerve?

It comes from S2-4.


What does the pudendal nerve supply?

It supplies the perineal muscles, external urethral sphincter, skin of genitalia and perineum as well as erectile muscles (ischiocavernosus and bulbiospongiosus).