Small Intestine Flashcards

Explore the small intestine's three divisions, wall structure, mesenteric attachments, vascular supply, innervation, and absorptive functions.

Card 1 of 30Question

What are the three anatomical divisions of the small intestine?

The duodenum, jejunum, and ileum.

In This Section

1. What are the three anatomical divisions of the small intestine?

The duodenum, jejunum, and ileum.

2. Where does the small intestine begin and end?

It extends from the pylorus of the stomach to the ileocecal junction.

3. What is the approximate length of the small intestine in a living adult?

Approximately 3 to 5 meters, with considerable individual variation.

4. What is the approximate length of the duodenum?

About 25 cm.

5. What are the four anatomical parts of the duodenum?

Superior, descending, horizontal, and ascending parts.

6. Which part of the duodenum receives the major duodenal papilla?

The descending second part of the duodenum.

7. Which structures usually join to form the hepatopancreatic ampulla?

The common bile duct and main pancreatic duct.

8. What marks the transition between the duodenum and jejunum?

The duodenojejunal flexure, supported by the suspensory muscle of the duodenum.

9. How does the duodenum differ from the jejunum and ileum in its peritoneal relationship?

Most of the duodenum is secondarily retroperitoneal, whereas the jejunum and ileum are intraperitoneal.

10. What proportion of the mobile small intestine is approximately formed by the jejunum?

The proximal two-fifths of the jejunum and ileum combined.

11. Which abdominal region typically contains most jejunal loops?

The left upper and central abdomen.

12. Where are ileal loops most commonly located?

The right lower abdomen and pelvis.

13. Which gross anatomical features distinguish the jejunum from the ileum?

The jejunum has a thicker wall, larger circular folds, fewer arterial arcades, and longer vasa recta.

14. What are the four principal layers of the small intestinal wall?

Mucosa, submucosa, muscularis externa, and serosa or adventitia.

15. Which three structural adaptations increase the absorptive surface area of the small intestine?

Circular folds, intestinal villi, and microvilli.

16. What are the plicae circulares?

Permanent circular folds of mucosa and submucosa that increase intestinal surface area.

17. What are intestinal villi?

Finger-like projections of the mucosa containing blood capillaries and central lymphatic lacteals.

18. Which epithelial cells are primarily responsible for nutrient absorption in the small intestine?

Enterocytes with apical brush-border microvilli.

19. Which glands are characteristic of the duodenal submucosa?

Brunner's glands, which secrete alkaline mucus.

20. Which organized lymphoid structures are especially prominent in the ileum?

Peyer's patches, aggregates of lymphoid follicles involved in intestinal immune surveillance.

21. Which part of the small intestine is the principal site for vitamin B12 and bile salt absorption?

The terminal ileum.

22. What is the mesentery of the jejunum and ileum?

A double layer of peritoneum suspending the intestine from the posterior abdominal wall and carrying its neurovascular structures.

23. Where does the root of the small intestinal mesentery extend?

Obliquely from the duodenojejunal flexure to the ileocecal region.

24. Which arteries supply the duodenum?

The superior and inferior pancreaticoduodenal arteries, arising from the gastroduodenal and superior mesenteric arteries.

25. Which artery provides the principal blood supply to the jejunum and ileum?

The superior mesenteric artery through its jejunal and ileal branches.

26. How do the arterial arcades of the jejunum and ileum typically differ?

The jejunum has fewer arterial arcades and longer vasa recta; the ileum has more arcades and shorter vasa recta.

27. Through which major vein does most blood from the small intestine drain?

The superior mesenteric vein, which contributes to the hepatic portal vein.

28. Which lymph nodes receive lymph from the jejunum and ileum?

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

29. Which nerves provide parasympathetic innervation to the small intestine?

The vagus nerve (cranial nerve X).

30. Which autonomic plexuses distribute sympathetic fibers to the small intestine?

The celiac and superior mesenteric plexuses.