Lecture 14

Question 1

What makes up the pelvic outlet?

Answer 1

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

It is a diamond shape.

Question 2

What is the pelvic outlet divided into?

Answer 2

Urogenital (superior) and anal (inferior) triangles.

Question 3

Where is the perineal body situated?

Answer 3

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

Question 4

What is the perineal body composed of?

Answer 4

Fibrous connective tissue.

Question 5

What is attached to the perineal body?

Answer 5

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

Question 6

Describe the pelvic floor?

Answer 6

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

Question 7

What is the levator ani divided into?

Answer 7

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

Question 8

What is the levator ani innervated by?

Answer 8

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

Question 9

What are the pubococcygeus divisions?

Answer 9

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

Question 10

Describe the puborectalis subdivision?

Answer 10

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.

Question 11

Describe the iliococcygeus muscle?

Answer 11

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

Question 12

What nerve innervates the iliococcygeus muscle?

Answer 12

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

Question 13

Describe the external anal sphincter?

Answer 13

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).

Question 14

What nerve innervates the external anal sphincter?

Answer 14

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

Question 15

Describe the internal anal sphincter?

Answer 15

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

Question 16

Describe the ischioanal fossa?

Answer 16

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.

Question 17

Describe surface anatomy?

Answer 17

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.

Question 18

Describe the anal canal?

Answer 18

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.

Question 19

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

Answer 19

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.

Question 20

Describe venous drainage of the rectum/anal canal?

Answer 20

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.

Question 21

Describe the urogenital triangle (perineal membrane)?

Answer 21

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

Question 22

Describe the urogenital diaphragm?

Answer 22

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).

Question 23

Describe the male variation of the deep perineal pouch?

Answer 23

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

Question 24

Describe the female variation of the deep perineal pouch?

Answer 24

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

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

Question 25

Describe the superficial perineal pouch?

Answer 25

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.

Question 26

Describe the fascia and communication in the superficial pouch?

Answer 26

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.

Question 27

Describe the internal pudendal artery?

Answer 27

It supplies inferior rectum and perineal structures.

Question 28

What are the internal pudendal artery branches?

Answer 28

Male: 1. Inferior rectal. 2. Perineal. 3. Dorsal artery of Penis. Female: 1. Inferior rectal. 2. Perineal. 3. Dorsal artery of clitoris.

Question 29

Describe the pudendal nerve?

Answer 29

It comes from S2-4.

Question 30

What does the pudendal nerve supply?

Answer 30

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

Question 31

What are the branches of the pudendal nerve?

Answer 31

1. Inferior rectal. 2. Perineal. 3. Dorsal nerve of clitoris/penis.

Question 32

Describe the parasympathetic supply for sex (nervous system)?

Answer 32

It comes from S2-4 from the inferior hypogastric plexus. It passes through the deep perineal much to the erectile tissues to vasodilator the arteries and to cause an erection of the penis/clitoris.

Question 33

Describe the sympathetic supply for sex (nervous system)?

Answer 33

It comes from the inferior hypogastric plexus. It causes ejaculation, and contraction of the internal urethral sphincter; it closes off the urethra and prevents back flow.

Question 34

Describe the pudendal nerve supply for sex (nervous system)?

Answer 34

It comes from S2-4. It gives sensory to the penis/clitoris and causes contraction of the ischiocavernosus and bulbospongiosus muscles (cyclical contraction in orgasm).

Question 35

Describe the dermatomes?

Answer 35

If you damage the S2-4 dermatomes you can get saddle anaesthesia. This is caused by compression of the caudal equina.

Question 36

Describe pudendal nerve damage?

Answer 36

It can occur in cyclists. If you damage the pudendal nerve you will lose a lot of function in the other branches i.e. erectile dysfunction or continence.

Question 37

Describe episiotomy?

Answer 37

Surgical incision in the perineum to facilitate childbirth.

Question 38

When will you do an episiotomy?

Answer 38

1. Risk to the mother or third or fourth degree tearing. 2. Fetal distress. 3. Shoulder dystocia - shoulders get caught underneath the pubic symphysis, so you need to put your hand into the birth canal. 4. Instrumental delivery. 5. Rigid perineal muscles.

Question 39

What is the episiotomy rate in NZ?

Answer 39

15% of total vaginal deliveries and is increasing.

Question 40

What are the types of episiotomy?

Answer 40

1. Medio-latera - can run risk of faecal incontinence. | 2. Midline - can risk to cause fourth degree tear near anal canal.