Ileum Flashcards

Examine the ileum's anatomy, mesenteric attachments, intestinal wall, vascular supply, lymphoid tissue, and absorptive functions.

Card 1 of 30Question

What is the ileum?

The distal portion of the small intestine, extending from the jejunum to the ileocecal junction.

In This Section

1. What is the ileum?

The distal portion of the small intestine, extending from the jejunum to the ileocecal junction.

2. What approximate proportion of the jejunum and ileum combined is formed by the ileum?

The distal three-fifths.

3. Where are ileal loops most commonly located?

In the right lower abdomen and pelvic cavity.

4. Which structure marks the distal termination of the ileum?

The ileocecal junction, where the terminal ileum opens into the cecum.

5. Is there a distinct external anatomical boundary between the jejunum and ileum?

No. The transition is gradual, without a sharply defined anatomical boundary.

6. How is the ileum classified in relation to the peritoneum?

It is intraperitoneal and suspended by the mesentery of the small intestine.

7. What structures are carried within the ileal mesentery?

Blood vessels, lymphatic vessels, lymph nodes, autonomic nerves, and connective tissue.

8. How does the wall of the ileum generally compare with that of the jejunum?

The ileal wall is thinner and usually has a narrower lumen.

9. How do the circular folds of the ileum compare with those of the jejunum?

They are smaller and less numerous, becoming sparse or absent near the terminal ileum.

10. What are the four principal histological layers of the ileal wall?

Mucosa, submucosa, muscularis externa, and serosa.

11. Which mucosal projections increase the absorptive surface area of the ileum?

Intestinal villi covered by epithelial cells bearing microvilli.

12. Which organized lymphoid structures are particularly prominent in the ileum?

Peyer's patches, also called aggregated lymphoid nodules.

13. Where are Peyer's patches typically concentrated within the ileal wall?

In the mucosa and submucosa, especially along the antimesenteric border.

14. What is the principal function of Peyer's patches?

Immune surveillance and initiation of mucosal immune responses to intestinal antigens.

15. Which specialized epithelial cells transport luminal antigens to immune tissue over Peyer's patches?

Microfold cells, also called M cells.

16. Which vitamin is absorbed in the terminal ileum through an intrinsic factor-dependent mechanism?

Vitamin B12, also called cobalamin.

17. Which digestive substances are actively reabsorbed in the terminal ileum for enterohepatic circulation?

Bile salts.

18. Which major artery provides the principal arterial supply to the ileum?

The superior mesenteric artery through its ileal branches.

19. Which artery commonly contributes to the blood supply of the terminal ileum?

The ileocolic artery through its ileal branch.

20. How are the arterial arcades of the ileum typically arranged?

They form multiple interconnected tiers, generally more numerous than those of the jejunum.

21. How do the ileal vasa recta compare with those of the jejunum?

They are generally shorter and more numerous.

22. How does mesenteric fat distribution differ between the ileum and jejunum?

Ileal mesenteric fat commonly extends closer to the intestinal wall, leaving fewer translucent windows.

23. Through which major vein does venous blood from the ileum drain?

The superior mesenteric vein through ileal and ileocolic tributaries.

24. Which lymph nodes receive lymphatic drainage from the ileum?

Juxta-intestinal and intermediate mesenteric nodes, followed by superior mesenteric lymph nodes.

25. Which autonomic plexus distributes sympathetic innervation to the ileum?

The superior mesenteric plexus.

26. Which nerve provides parasympathetic innervation to the ileum?

The vagus nerve (cranial nerve X).

27. What is Meckel's diverticulum?

A congenital true diverticulum of the ileum caused by persistence of the proximal vitelline duct.

28. On which border of the ileum is Meckel's diverticulum usually located?

The antimesenteric border, typically near the ileocecal junction.

29. Which inflammatory bowel disease commonly affects the terminal ileum?

Crohn's disease, which can produce transmural inflammation, strictures, and fistulas.

30. Why can extensive terminal ileal resection cause vitamin B12 deficiency?

It removes the principal site of intrinsic factor-bound vitamin B12 absorption.