Descending and sigmoid colon (Dave's notes)

Question 1

What is the length of and what are the boundaries of the descending colon

Answer 1

• 30cm from splenic flexure to pelvic brim.
• Plastered to the posterior abdominal wall. 20% have a mesentary.

Question 2

Describe the relations of the descending colon

Answer 2

Lies on the lumbar and then iliac fascia

Question 3

Where are the teniae coli located on the descending colon?

Answer 3

As they do for the ascending colon; anterior, posteriomedial and posterolateral

Question 4

How does the descending colon move during development?

Answer 4

It hinges to the left; vessels lie immediately below the peritoneum

Question 5

What is the blood supply of the descending colon?

Answer 5

The left colic, which arises from the IMA

Question 6

Describe the length and boundaries of the sigmoid colon

Answer 6

Up to 45cm long from pelvic brim to commencement of the rectum at S3, starts with the commencement of mesentery

Question 7

How do the teniae differ in the sigmoid relative to the descending colon?

Answer 7

Sacculations persist but the teniae are much wider

Question 8

Why is diverticulosis most common in this part of the bowel?

Answer 8

Appendages epiploicae are most common here

Question 9

Describe the shape of the sigmoid mesentary

Answer 9

The mesentary is hinged but did not completely fuse so forms an A-shaped base with the limbs diverging. Fans out from a 10cm base to a 40cm border. Vessels lie in this mesentary

Question 10

What landmark marks the apex of the sigmoid’s mesentary?

Answer 10

The bifurcation of the common iliac artery over the SI joint

Question 11

To what is the lateral limb of the sigmoid mesentary attached?

Answer 11

mid point of inguinal ligament.

(descends along pelvic brim, over external iliac vessels and terminates at the mid point)

Question 12

To what landmark does the medial limb of the sigmoid mesentary extend?

Answer 12

The medial limb of the sigmoid mesentary extends to the midline at S3

( superior rectal found in the base of medial limb)

Question 13

What is the blood supply of the sigmoid colon?

Answer 13

Sigmoid arteries from the IMA

Question 14

Describe the venous drainage and lymphatic drainage of the sigmoid colon

Answer 14

Veins and lymph follow the arterial supply

Question 15

What is the nerve supply of the sigmoid colon?

Answer 15

Sympathetic and parasympathetic. Pain fibres give periumbilical pain from the midgut and hypogastric from the hindgut????

Question 16

Describe the parasympathetic supply to the descending colon and sigmoid colon

Answer 16

Parasympathetic supply to the splenic flexure is via vagi, and beyond this is from the pelvic splanchnic nerves

Question 17

Describe the sympathetic supply to the sigmoid colon

Answer 17

The sympathetic supply to the sigmoid colon is from spinal cord segments T10-12.