Animal Nutrition

Page
7

Hormonal control of digestion

Secretin and CCK

Stomach

Gallbladder

Liver

+

Duodenum

of small intestine

Bile

Gastrin

Secretin

Pancreas

CCK

CCK

Key

Stimulation Inhibition

+

–

+

+

+

–

Slide 49

Pancreatic Secretions

The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum.

Its solution is alkaline and neutralizes the acidic chyme.

Slide 50

Bile Production by the Liver

In the small intestine, bile aids in digestion and absorption of fats. Bile emulsifies fat. This is physical NOT chemical digestion. Fat emulsification increases the surface area for chemical digestion of fats by lipases.

Bile is made in the liver and stored in the gallbladder.

Slide 51

Secretions of the Small Intestine

The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes.

Enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine.

Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water.

Slide 52

Absorption in the Small Intestine - Villi

The small intestine has villi and microvilli that increase the surface area for absorption. Villi and microvilli are exposed to the intestinal lumen = space / cavity.

The enormous microvillar surface area greatly increases the rate of nutrient absorption.

Slide 53

Structure of the small intestine

Muscle layers

Microvilli (brush border) at apical (lumenal) surface

Vein carrying blood to hepatic portal vein

Villi

Intestinal wall

Key

Nutrient absorption

Large circular folds

Blood capillaries

Epithelial cells

Villi

Lymph vessel

Basal surface

Lacteal

Epithelial cells

Lumen

Slide 54

Small Intestine

Muscle layers

Vein carrying blood to hepatic portal vein

Villi

Intestinal wall

Key

Nutrient absorption

Large circular folds

Slide 55

Small Intestine

Microvilli (brush border) at apical (lumenal) surface

Key

Nutrient absorption

Blood capillaries

Epithelial cells

Villi

Lymph vessel

Basal surface

Lacteal

Epithelial cells