Download Chapter 41: Animal Nutrition Outline

Chapter 41 : Animal Nutrition
 Ingestion – the act of eating, first stage in food processing
o Takes place in the oral cavity, or mouth
o Does not take very long
 Digestion –the breakdown of food into molecules small enough for the body to absorb, second stage of food
processing
o Oral Cavity
 Mechanical Digestion – with different sized teeth, food is broken down in order to have an increased surface area,
to make absorption quicker, and to make swallowing easier
 Chemical Digestion – saliva has 2 functions
Lubricates the food to make swallowing easier
Contains amylase, which hydrolyzes starch and glycogen into smaller polysaccharides and disaccharides
 The product of the mechanical and chemical digestion is called a bolus, and it moves from the oral cavity down
through the pharynx to the esophagus which ends at the stomach
o Stomach
 Has accordion like folds in order to stretch
 Mechanical Digestion
Contractions and relaxations of the stomach muscles act as a grinding motion to further breakdown food
 Chemical Digestion
Gastric juice (pH of 2) makes cells separate by destroying their extracellular matrix
Gastric Juices contain pepsin, which starts as pepsinogen but mixes with hydrochloric acid to create pepsin
Pepsin breaks the polypeptide bonds of amino acids breaking them into small polysaccharides and disaccharides
 The product of the mechanical and chemical digestion is called chyme, and is a mix of solids and liquids
o Small Intestine
 Chemical Digestion
In the duodenum (first 25 cm) the chime mixes with enzymes and juices from the pancreas, the liver, the
gallbladder, and the gland cells of the intestinal wall
 The pancreas emits an alkaline juice to neutralize the chime since the small intestine cannot handle the acidity
 The pancreas also emits protease to breakdown proteins
 The liver emits bile, which is stored in the gallbladder. The bile has salt in it the helps digest many fats
 The intestinal wall secretes several enzymes that aid in breaking down different types of food.
 Mechanical Digestion
The chime, bile, and enzyme mixture is passed along by peristalsis until it reaches the jejumen, the second part
of the small intestine.
 The food is now completely digested and it is time for absorption
 Absorption – the uptake of small nutrient molecules by an organism’s body, third stage of food processing
o Small Intestine
 Has a surface area of 300 m2
 Has 3 layers of folds
Large circular folds
Villi on each of the large fold
Microvilli on each villi
 Each villi has a set of capillaries and a vessel from the lymphatic system, the lacteal
 The nutrients are absorbed across the unicellular layer of the intestinal epithelium to the capillaries or the lacteal
Passive Transport – move down their concentration gradients of the lumen to the epithelium to the capillaries
Chylomicrons – fats are mixed with cholesterol and proteins to form chylomicrons which are transported across
the epithelium and into lacteals
 Capillaries drain to hepatic portal vein to the liver for further release nutrients into the bloodstream
o Large Intestine
 The large intestine reabsorbs water that has been added to the mixture by the digestive juices
 Elimination
o Large Intestine – prepares waste materials
o Rectum – stores until anus can expel them