Jejunum Flashcards

Explore the jejunum's location, intestinal folds, mesenteric anatomy, arterial supply, nutrient absorption, and clinical significance.

Card 1 of 30Question

What is the jejunum?

The middle division of the small intestine, extending from the duodenojejunal flexure toward the ileum.

In This Section

1. What is the jejunum?

The middle division of the small intestine, extending from the duodenojejunal flexure toward the ileum.

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

The proximal two-fifths.

3. Where are jejunal loops most commonly located?

In the left upper and central regions of the abdominal cavity.

4. Which anatomical landmark marks the beginning of the jejunum?

The duodenojejunal flexure.

5. Which fibromuscular structure supports the duodenojejunal flexure?

The suspensory muscle of the duodenum, also called the ligament of Treitz.

6. Is there a sharply defined anatomical boundary between the jejunum and ileum?

No. The jejunum gradually transitions into the ileum.

7. How is the jejunum classified in relation to the peritoneum?

It is intraperitoneal and suspended from the posterior abdominal wall by the mesentery.

8. What structures pass through the jejunal mesentery?

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

9. How does the jejunal wall typically compare with the ileal wall?

It is thicker, with a generally wider lumen and more prominent mucosal folds.

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

Mucosa, submucosa, muscularis externa, and serosa.

11. What are the plicae circulares of the jejunum?

Prominent circular folds of mucosa and submucosa that increase absorptive surface area.

12. How do jejunal circular folds compare with those of the ileum?

They are generally taller, larger, and more numerous.

13. What are intestinal villi?

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

14. Which epithelial cells perform most nutrient absorption in the jejunum?

Enterocytes bearing apical brush-border microvilli.

15. Which intestinal glands open between the jejunal villi?

The intestinal glands, also called crypts of Lieberkuhn.

16. Which specialized cells at the base of jejunal intestinal crypts produce antimicrobial substances?

Paneth cells.

17. What is the principal digestive function of the jejunum?

Absorption of most digested nutrients, including carbohydrates, amino acids, and lipids.

18. Which important mineral is predominantly absorbed in the duodenum and proximal jejunum?

Iron.

19. Where are dietary long-chain lipids packaged into chylomicrons transported after absorption?

Into the central lacteals of intestinal villi.

20. Which major artery provides the principal arterial supply to the jejunum?

The superior mesenteric artery through its jejunal branches.

21. How are the arterial arcades of the jejunum typically arranged?

They form relatively few tiers, usually one or two, within the mesentery.

22. How do the jejunal vasa recta compare with those of the ileum?

They are generally longer and less numerous.

23. What is a characteristic feature of fat distribution in the jejunal mesentery?

Mesenteric fat is relatively sparse near the intestinal wall, producing translucent mesenteric windows.

24. Through which major vein does venous blood from the jejunum drain?

The superior mesenteric vein through its jejunal tributaries.

25. Which lymph nodes receive lymphatic drainage from the jejunum?

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

26. Which autonomic plexus distributes sympathetic innervation to the jejunum?

The superior mesenteric plexus.

27. Which nerve provides parasympathetic innervation to the jejunum?

The vagus nerve (cranial nerve X).

28. Which enteric nerve plexus primarily coordinates jejunal smooth muscle motility?

The myenteric (Auerbach) plexus between the circular and longitudinal muscle layers.

29. Why can extensive jejunal resection cause malabsorption?

It reduces the intestinal surface area available for nutrient and fluid absorption.

30. Which anatomical features help surgeons distinguish the jejunum from the ileum?

Thicker walls, prominent circular folds, fewer arterial arcades, longer vasa recta, and less mesenteric fat near the bowel.