Anatomy

Question 1

What is the normal width of the small bowel, large bowel and cecum?

Answer 1

Small bowel - 3cm

Large bowel - 6cm

Cecum - 9cm

Question 2

What are the three most common causes of small bowel obstruction?

Answer 2

1. Adhesions
2. Hernia
3. Tumour

Question 3

What are the two most common causes of large bowel obstruction?

Answer 3

1. Tumour
2. Diverticulitis

Question 4

Where do bowel cancer mets tend to appear?

Answer 4

Liver

Question 5

Where is the lymphatic drainage of the large bowel and proximal 2/3 of the rectum?

Answer 5

Inferior mesenteric lymph nodes

Question 6

Where is the lymphatic drainage of the distal 1/3 of the rectum?

Answer 6

Either the same as the rest of the rectum or to the internal iliac and superficial inguinal lymph nodes

Question 7

Where is the lymphatic drainage of the small bowel?

Answer 7

Superior mesenteric lymph nodes and cisterna chyli

Question 8

What are the two anal sphincters?

Answer 8

Internal and External

Question 9

What are the characteristics of the internal anal sphincter:

• Control
• Type of nerve innervation and nerve
• Position
• Function

Answer 9

• Involuntary autonomic (S4)
• Sympathetic
• Upper 2/3 of canal
• It maintains the resting control by being kept shut and preventing incontience

Question 10

What are the characteristics of the external anal sphincter:

• Control
• Type of nerve innervation and nerve
• Position (layers and continuation of..?)
• Function

Answer 10

• Voluntary (striated)
• Pudendal S2-S4 keeps it closed, we relax it
• Three layers - Subcutaneous, superfical, deep (continuation with puborectalis)

Question 11

What is the arterial blood supply to the anus?

Answer 11

Superior Rectal artery via the IMA

Middle rectal artery via the internal iliac

Inferior rectal artery via the internal iliac and inferior pudendal

Question 12

What is the venous drainage of the anus?

Answer 12

Superior rectal vein to IMV (Portal)

Middle rectal vain to internal iliac vein (systemic)

Inferior rectal vein to the internal iliac (systemic)

Question 13

What is Alcocks canal?

Answer 13

A anatomical area where the pudendal nerve, internal pudendal artery and internal pudendal vein travel through

Question 14

What is the key nerve in the pelvis and what does it do?

Answer 14

Pudendal (S2-S4)

• Sensation to external genitalia
• Maintains anal tone via external ana sphincter
• Controls external urethral sphincter

Question 15

What system does the SRV drain to?

Answer 15

Portal

Question 16

What system does the MRV and IRV drain to?

Answer 16

Systemic

Question 17

What does the pectinate line distinguise

Answer 17

Portal and systemic blood supplies

Endoderm and ectoderm (below)