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Digestive
System
Chapter 41
What you need to know!



The major compartments of the alimentary
canal – oral cavity, pharynx, esophagus,
stomach, small intestines, and large intestines
– and their contributions to animal nutrition.
The major digestive glands – salivary glands,
pancreas, liver, and gallbladder – and their
contributions to animal nutrition.
The general scheme of chemical digestion of
carbohydrates, fats, proteins, and nucleic
acids.
Diet
Essential nutrients are required for survival and
include minerals and organic molecules (the
animal cannot make itself)
1. 10/20 amino acids are essential amino acids
2. Essential fatty acids (linoleic acid is used in
our cell membranes)
3. Vitamins like B and E are organic and
required in small amounts
4. Minerals like Ca and P are inorganic
nutrients required in small amounts
Food Processing
1.
2.
Ingestion: eating
Digestion: breakdown food
a)
b)
c)
3.
4.
Intracellular: broken down within the cell &
protected by a membrane
Extracellular: broken down outside the cells
Gastrovascular cavity: ingestion and
elimination from the same hole (protostomes)
with digestion in an inner cavity
Absorption: cells absorb required molecules
Elimination: excrement
Mammalian Digestion
Path of Food
1.
2.
3.
Mouth, Saliva (lubricate and amylase), &
Chewing make a bolus 
Pharynx (epiglottis prevents bolus from
entering trachea) and esophagus
(peristalsis) deliver 
Stomach stores and digests with gastric
juice (HCl & Pepsin) transforms bolus to
acid chyme 
Path of Food
4.
Small intestine where most chemical
digestion occurs (pancreas and liver
digestive enzymes) 

5.
6.
Villi increase surface area of SI where
capillaries absorb monomers and smaller
molecules
Large intestine or colon absorbs water
and compacts waste 
Rectum stores and eliminates waste
Digestive Hormones
 Gastrin
- stomach increases gastric juices
 Enterogastrone – small intestine slows
peristalsis allowing for increased digestion
 Secretin and cholecystokinin (CCK) –
small intestine increases flow of digestive
fluids from the pancreas & gall bladder
(liver)