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Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter 14<br />

Gastrointestinal Function<br />

William E. Hornbuckle<br />

Department <strong>of</strong> <strong>Clinical</strong> Sciences<br />

New York State College <strong>of</strong> Veterinary Medicine<br />

Cornell University<br />

Ithaca, New York<br />

Kenneth W. Simpson<br />

Department <strong>of</strong> <strong>Clinical</strong> Sciences<br />

New York State College <strong>of</strong> Veterinary Medicine<br />

Cornell University<br />

Ithaca, New York<br />

Bud C. Tennant<br />

Department <strong>of</strong> <strong>Clinical</strong> Sciences<br />

New York State College <strong>of</strong> Veterinary Medicine<br />

Cornell University<br />

Ithaca, New York<br />

I. INTRODUCTION<br />

II. SALIVARY SECRETIONS<br />

A. Mechanisms <strong>of</strong> Secretion<br />

B. Composition <strong>of</strong> Saliva<br />

C. Functions <strong>of</strong> Saliva<br />

III. GASTRIC SECRETIONS<br />

A. Composition <strong>of</strong> Gastric Secretions<br />

B. Control <strong>of</strong> Gastric Se cretion<br />

IV. BILIARY SECRETIONS<br />

A. Composition <strong>of</strong> Bile<br />

B. Properties <strong>of</strong> Bile<br />

C. Synthesis <strong>of</strong> Bile Acids<br />

D. Enterohepatic Circulation <strong>of</strong> Bile Acids<br />

V. EXOCRINE PANCREATIC SECRETIONS<br />

A. Composition <strong>of</strong> Pancreatic Juice<br />

B. Control <strong>of</strong> Pancreatic Secretions<br />

VI. OTHER GASTROINTESTINAL HORMONES<br />

A. Motilin<br />

B. Somatostatin<br />

C. Enteroglucagon<br />

VII. DIGESTION AND ABSORPTION<br />

A. Water and Electrolytes<br />

B. Carbohydrate Digestion and Absorption<br />

C. Proteins<br />

D. Lipids<br />

E. Cobalamin<br />

VIII. DISTURBANCES OF GASTROINTESTINAL<br />

FUNCTION<br />

A. Vomition<br />

B. Gastric Dilatation-Volvulus<br />

C. Ischemia-Reperfusion Injury<br />

D. Acute Diarrheas<br />

E. Malabsorption<br />

F. Tests <strong>of</strong> Malabsorption<br />

G. Bacterial Overgrowth<br />

H. Helicobacteria<br />

I. Intestinal Permeability<br />

J. Protein-Losing Enteropathy<br />

K. Ulcerative Colitis<br />

L. Equine Hyperammonemia<br />

M. Clostridial-Associated Diseases in Horses and Cows<br />

IX. DISTURBANCES OF RUMEN FUNCTION<br />

A. Acute Rumen Indigestion (Rumen Overload, Lactic<br />

Acidosis)<br />

B. Acute Rumen Tympany (Bloat)<br />

C. Urea Poisoning<br />

REFERENCES<br />

I . INTRODUCTION<br />

The digestive system is composed <strong>of</strong> the gastrointestinal<br />

(GI) tract or the alimentary canal, salivary glands, the<br />

liver, and the exocrine pancreas. The principal functions <strong>of</strong><br />

the gastrointestinal tract are to digest and absorb ingested<br />

nutrients and to excrete waste products <strong>of</strong> digestion. Most<br />

nutrients are ingested in a form that is either too complex<br />

for absorption or insoluble and therefore indigestible or<br />

incapable <strong>of</strong> being digested. Within the GI tract, much <strong>of</strong><br />

these substances are solubilized and further degraded enzymatically<br />

to simple molecules, sufficiently small in size<br />

and in a form that permits absorption across the mucosal<br />

epithelium. This chapter describes the normal biochemical<br />

processes <strong>of</strong> intestinal secretion, digestion, and absorption.<br />

Once these issues have been put in perspective, the chapter<br />

explores the pathogenesis <strong>of</strong> the important gastrointestinal<br />

diseases <strong>of</strong> domestic animals and the biochemical basis for<br />

their diagnosis and treatment.<br />

II . SALIVARY SECRETIONS<br />

A . Mechanisms <strong>of</strong> Secretion<br />

Saliva is produced by three major pairs <strong>of</strong> salivary glands<br />

and by small glands distributed throughout the buccal<br />

mucosa and submucosa. Two types <strong>of</strong> secretory cells are<br />

found in the acinar portions <strong>of</strong> the salivary glands: (1) the<br />

mucous cells, which contain droplets <strong>of</strong> mucus, and (2) the<br />

serous cells, which contain multiple secretory granules.<br />

<strong>Clinical</strong> <strong>Biochemistry</strong> <strong>of</strong> <strong>Domestic</strong> <strong>Animals</strong>, 6th <strong>Edition</strong> 413<br />

Copyright © 2008, Elsevier Inc.<br />

All rights reserved.

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