Animal DigestionAnimal DigestionAnimal DigestionAnimal Digestion

Prepared by: Steve Guzman

Animals ingest their food in a variety of ways

Figure 1: Suspension

feeder; tube worm

filtering food through

its tentacle

Figure 2: Substrate feeder;

caterpillarcaterpillar

Figure 3: Fluid feeder; mosquito

Figure 4: Bulk feeder; grey heron

Chemical digestionChemical digestionChemical digestionChemical digestion: the breakdown of large organic molecules to their components

Figure 5: Chemical digestion:

the breakdown of large

organic molecules of their

components

Overview: Food processing occurs in four stages

Diagram 1: The four main stages of food

processing

Digestion occurs in specialized compartments

Diagram 2: Digestion in the gastrovascular

cavity of a hydra

Digestion occurs in specialized compartments (cont.)

Figure 6: Three

examples of

alimentary canals

The human digestive system consists of an alimentary canal and accessory glands

Diagram 3: The human

digestive system

Digestion begins in the oral cavity

Figure 7: The human

oral activity

After swallowing, peristalsis moves food through the esophagus to the stomach

Diagram 4: The human swallowing reflex

After swallowing, peristalsis moves food through the esophagus to the stomach (cont.)

Figure 8: Peristalsis

moving a food bolus

down the esophagus

The Stomach

Diagram 5: The stomach

and its production of

gastric juice

Digestive ailments include acid reflux and gastric ulcers

Figure 9: Ulcer-causing

bacteria, Helicobacter pylori

Sources of Digestive Enzymes and Bile

Figure 10: The small intestine and

related digestive organs

Digestion in the Small Intestine

Table 1

Absorption in the Small Intestine

Diagram 6: Structure of the small intestine

One of the liver’s many functions is processing nutrient-laden blood from the intestines

Figure 11: The hepatic

portal system

The large intestine reclaims water and compacts the feces

Figure 12: The relationship

of the small and large

intestine

Evolutionary adaptation of vertebrate digestive systems often relate to diet

Figure 13: The alimentary canal

in a carnivore (coyote) and an

herbivore (koala)herbivore (koala)

Chemical energy powers the body

Table 2

An animal’s diet must supply essential nutrients

Figure 15: Obesity; a form of

malnourishment

Figure 14: Anorexia;

a form of

undernourishment

Vegetarians must be sure to obtain all eight essential amino acids

Figure 16: Essential

amino acids from a

vegetarian diet

A healthy diet includes 13 vitamins and many essential minerals

Figure 17: Vitamin B12: a

coenzyme in nucleic acid

metabolism; maturation of red

blood cells

Figure 18: Calcium: Functions in

bone and tooth formation, blood

clotting, nerve and muscle function

What do food labels tell us?

Figure 19: Whole wheat bread labels

The human health problem of obesity may reflect our evolutionary past

Figure 21: A mouse with a defect in a gene for leptin, an

appetite-suppressing hormone (left); a normal mouse

right (right)

Figure 20: Fat cells

from the abdomen

of a human