Page 411 - Anatomy and Physiology of Farm Animals, 8th Edition

396 / Anatomy and Physiology of Farm Animals

• Describe the role of the stomach in the processes of physical and chemical break-
down of foodstuffs are termed mechanical
production and movement of chyme.
VetBooks.ir • Compare and contrast digestive physiol- and chemical digestion, respectively. In
ogy in the ruminant versus the horse. Be
addition to monosaccharides, amino acids,
sure to include the importance of micro- and fatty acids, the gastrointestinal tract
bial digestion and the physiologic impor- must absorb other essential minor nutri-
tance of major anatomical differences. ents (e.g., salts, vitamins), so that they are
available to the cells of the body.
The gastrointestinal tract is essentially a
or normal metabolism, cells of an animal’s long, tube of smooth muscle extending
Fbody need the three major classes of from mouth to anus. The tube has two dis-
nutrients (carbohydrates, proteins, and tinct layers of smooth muscle in its wall
lipids) delivered to them via the blood in (circular and longitudinal layers) and is
their simplest forms (monosaccharides, lined with epithelia that function as selec-
amino acids, and fatty acids). Animals con- tive barriers between the lumen and the
sume foodstuffs that contain these nutrients body fluids. The anatomic and functional
in more complex chemical and physical characteristics of the mucosa and its
forms. It is the function of the gastrointes- epithelia vary greatly among segments of
tinal tract to reduce the consumed food- the intestine (Fig. 21‐1). Indigestible sub-
stuffs to simpler molecules and to transfer stances or items (such as a coin) can pass
them to the blood so that they can be through the tract without being altered
delivered to the cells for metabolism. The and without affecting the animal if they are

a d

e
e f
f
g g
b h h c
i i
j j
l k
Figure 21-1. Cross‐sections through various segments of the digestive tract. a and b, esophagus with
stratified squamous epithelium; c, small intestine with columnar epithelium and submucosal glands and
aggregated lymphatic nodules in some segments; d, large intestine; e, tunica mucosa: epithelium; f, lamina
propria; g, lamina muscularis; h, tela submucosa; i, tunica muscularis: circular layer; j, longitudinal layer;
k,, tunica serosa; l, tunica adventitia. Source: Dellmann and Eurell, 1998. Reproduced with permission of
John Wiley & Sons, Inc.