Sigmoid Colon Flashcards

Explore the sigmoid colon's pelvic course, mesenteric attachments, blood supply, autonomic innervation, and clinical anatomy.

Card 1 of 28Question

What is the sigmoid colon?

The S-shaped segment of the large intestine connecting the descending colon to the rectum.

In This Section

1. What is the sigmoid colon?

The S-shaped segment of the large intestine connecting the descending colon to the rectum.

2. Where does the sigmoid colon typically begin?

At the pelvic brim near the left iliac fossa, where the descending colon becomes continuous with it.

3. At approximately which vertebral level does the sigmoid colon become the rectum?

At the third sacral vertebral level (S3).

4. What is the approximate length of the adult sigmoid colon?

Approximately 40 cm, although its length varies considerably.

5. In which anatomical cavity is most of the sigmoid colon usually located?

The pelvic cavity, although its mobile loops may extend into the abdomen.

6. How is the sigmoid colon classified in relation to the peritoneum?

It is intraperitoneal and suspended by the sigmoid mesocolon.

7. What is the sigmoid mesocolon?

A double layer of peritoneum attaching the sigmoid colon to the posterior pelvic wall.

8. What is the typical shape of the root of the sigmoid mesocolon?

An inverted V-shaped attachment to the posterior pelvic wall.

9. Which major blood vessel lies near the apex of the sigmoid mesocolon root?

The left common iliac artery near its bifurcation.

10. Which retroperitoneal structure passes close to the apex of the sigmoid mesocolon root?

The left ureter.

11. Which peritoneal recess may be found beneath the sigmoid mesocolon?

The intersigmoid recess.

12. What are the three characteristic external features of the sigmoid colon?

Taeniae coli, haustra, and epiploic appendages.

13. What happens to the taeniae coli at the rectosigmoid junction?

They spread out to form a continuous outer longitudinal muscle layer in the rectum.

14. Which embryological division of the gastrointestinal tract gives rise to the sigmoid colon?

The hindgut.

15. Which major artery supplies the sigmoid colon?

The inferior mesenteric artery.

16. Which branches of the inferior mesenteric artery primarily supply the sigmoid colon?

The sigmoid arteries, usually two to four branches.

17. Which arterial arcade provides collateral circulation along the sigmoid colon?

The marginal artery of the colon, formed by anastomoses between adjacent colic arteries.

18. Which artery supplies the distal sigmoid colon and continues into the rectum?

The superior rectal artery, the terminal continuation of the inferior mesenteric artery.

19. Through which vein does blood from the sigmoid colon primarily drain?

The inferior mesenteric vein through its sigmoid tributaries.

20. Which lymph nodes receive lymphatic drainage from the sigmoid colon?

Epicolic and paracolic nodes, followed by sigmoid and inferior mesenteric lymph nodes.

21. Which autonomic plexus provides sympathetic innervation to the sigmoid colon?

The inferior mesenteric plexus.

22. Which nerves provide parasympathetic innervation to the sigmoid colon?

The pelvic splanchnic nerves arising from spinal segments S2 to S4.

23. What is the primary physiological function of the sigmoid colon?

Temporary storage and propulsion of feces toward the rectum, with continued water and electrolyte absorption.

24. What is the characteristic histological appearance of the sigmoid colonic mucosa?

Straight intestinal crypts containing numerous goblet cells, without intestinal villi.

25. What is sigmoid volvulus?

Twisting of the sigmoid colon around its mesenteric axis, potentially causing bowel obstruction and ischemia.

26. Which anatomical features predispose the sigmoid colon to volvulus?

An elongated, mobile sigmoid loop with a relatively narrow mesenteric attachment.

27. Why is diverticular disease particularly common in the sigmoid colon?

Its relatively narrow lumen and high intraluminal pressures favor mucosal herniation through weak points in the muscular wall.

28. Why must the left ureter be identified during sigmoid colectomy?

It lies close to the sigmoid mesocolon and may be injured during mobilization or division of mesenteric vessels.