1. Anatomy of the Small Intestine
CH 23
Anatomy of the
Small Intestine
James F. Thompson, Ph.D.

2. Small Intestine Site of final digestion, and absorption of meals
Anatomy - divided into 3 segments
duodenum
shortest
25 cm long, from pylorus of stomach
jejunum - ~2.5 m long
ileum
~3.6 m long
joins large intestine at ileocecal sphincter

3. General Histology of GI Tract
Same histological organization from inside to outside and from end to end

4. Small Intestine: Anatomy
Highly adapted for digestion and absorption
Long and highly convoluted to maximize surface area
Same 4 tissue layers but slightly modified
Plicae circulares (circular folds), villi and microvilli increase surface area for efficient absorption

5. Plicae Circulares (pill camera)

6. Small Intestine: Anatomy
Absorbed lipids routed through
lacteals to lymphatic circulation to systemic circulation to adipose tissues

7. Lymphatic Vessels Carrying Chyle
lymphatics in the
mesentery over the
small intestine

8. Duodenal Histology

9. Small Intestine: Mucosa
villi (fingers) ~ mm
 surface area
microvilli (brush border)
lamina propria
arteriole
venule
capillary network
lacteal

10. End CH 23 Anatomy of the Small Intestine