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Smali Inlestine Structure: II

GASTROINTESTINAL PHYSIOLOGY

Icjunum (high power)

Two jejunal villi <x100>; (left in contraction, right relaxed>

Three-dimensional magnification of jejunal wali

Lamina Lymph Crypt of Lieberkuhn Muscularis

Submucosa Circular muscle Longitudinal muscle Serosa

lejunum (Iow power)

lleum (Iow power)

Epithelium

Villus

Lamina propria Crypt of Licberkuhn Muscularis mucosae Aggregaled lymph nodule Submucosa Circular muscle Longitudinal muscle

Figurę 7.17 Small Intestine Microscopic Structure

“■*« lejunum and ileum have a large surface area for secretion and jrsorption. The surface area is inueased by presence of circular -•o-? valves or nngs of Kerckring), villi, and microvilli. Because the ■s—«a£l intestine provides a large surface interface between the exter-j and internal environments, it represents a first-łine defense _jmst forcign antigens. Accordmgly, large collections of lymphoid tissue are found in the lamina propria and submucosa. In generał, the following changes occur from the proximal jejunum to the terminal ileum; the number and lenglh of the villi decrease, the number of mucous cells increases, and there is an inc/ease in the amount of lymphoid tissue.

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