1. Essential amino acids from a vegetarian diet
8 Essential amino acids for adults
Methionine
Beans and other legumes
Valine
Threonine
Phenylalanine
Leucine
Corn (maize) and other grains
Figure 41.2 Essential amino acids from a vegetarian diet
Isoleucine
Tryptophan
Lysine

4. Humpback whale, a suspension feeder
Baleen
Figure 41.6 Four main feeding mechanisms of animals
Humpback whale, a suspension feeder

5. Substrate feeders are animals that live in or on their food source.
Leaf miner caterpillar, a substrate feeder
Figure 41.6 Four main feeding mechanisms of animals
Caterpillar Feces

6. Fluid feeders suck nutrient-rich fluid from a living host.
Figure 41.6 Four main feeding mechanisms of animals
Mosquito, a fluid feeder

7. Bulk feeders eat relatively large pieces of food.
Figure 41.6 Four main feeding mechanisms of animals
Rock python, a bulk feeder

8. The four stages of food processing
Small molecules
Pieces of food
Chemical
digestion (enzymatic
hydrolysis)
Nutrient molecules enter body cells
Mechanical digestion
Food
Undigested material
Figure 41.7 The four stages of food processing 1
Ingestion 2
Digestion
Mechanical & Chemical 3
Absorption 4
Elimination

9. Digestion in a hydra Gastrovascular cavity Tentacles Food Mouth
Figure 41.8 Digestion in a hydra
Epidermis
Gastrodermis

10. Variation in alimentary canals
Crop
Gizzard
Esophagus
Intestine
Pharynx
Anus
Mouth
Typhlosole
Lumen of intestine
(a) Earthworm
Foregut
Midgut
Hindgut
Esophagus
Rectum
Anus
Crop
Mouth
Gastric cecae
Figure 41.9 Variation in alimentary canals
(b) Grasshopper
Stomach
Gizzard
Intestine
Mouth
Esophagus
Crop
Anus
(c) Bird

11. human digestive system
Tongue
Sphincter
Salivary glands
Oral cavity
Salivary glands
Pharynx
Mouth
Esophagus
Esophagus
pyloric
sphincter
Liver
Stomach
Gall- bladder
Ascending portion of large intestine
Stomach
Gall- bladder
Duodenum of small intestine
Pancreas
Small intestine
Liver
Small intestine
Small intestine
Figure The human digestive system
Pancreas
Large intestine
Large intestine
Rectum
Rectum
Anus
Anus
Appendix
A schematic diagram of the human digestive system
Cecum

12. From mouth to stomach: the swallowing reflex and peristalsis
Food
Epiglottis up
Tongue
Pharynx
Esophageal sphincter contracted
Epiglottis down
Glottis
Glottis down and open
Esophageal sphincter contracted
Larynx
Trachea
Esophagus
Esophageal sphincter relaxed
Glottis up and closed
Relaxed muscles
To lungs
To stomach
Contracted muscles
Relaxed muscles
Sphincter relaxed
Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis
Stomach

13. The stomach and its secretions
Esophagus
Sphincter
Stomach
Sphincter
5 µm
Small intestine
Folds of epithelial tissue
Interior surface of stomach
Epithelium 3
Pepsinogen
and HCl are secreted. 1
Pepsinogen
Pepsin 2
Gastric gland
HCl 2
HCl converts pepsinogen to
pepsin. 1
Figure The stomach and its secretions
Mucus cells H+
Cl– 3. 3
Pepsin activates more pepsinogen.
Chief cells
Chief cell
Parietal cells
Parietal cell

14. Enzymatic hydrolysis in the human digestive system
Carbohydrate digestion
Protein digestion
Nucleic acid digestion
Fat digestion
Oral cavity, pharynx, esophagus
Polysaccharides
Disaccharides
(starch, glycogen)
(sucrose, lactose)
Salivary amylase
Smaller polysaccharides, maltose
Proteins
Stomach
Pepsin
Small polypeptides
Lumen of small
intestine
Polysaccharides
Polypeptides
DNA, RNA
Fat globules
Pancreatic amylases
Pancreatic trypsin and chymotrypsin
Pancreatic nucleases
Bile salts
Maltose and other disaccharides
Fat droplets
Nucleotides
Smaller polypeptides
Pancreatic lipase
Pancreatic carboxypeptidase
Figure Enzymatic hydrolysis in the human digestive system
Glycerol, fatty acids, monoglycerides
Amino acids
Epithelium of small intestine (brush border)
Small peptides
Nucleotidases
Nucleosides
Disaccharidases
Dipeptidases, carboxypeptidase, and aminopeptidase
Nucleosidases and phosphatases
Monosaccharides
Amino acids
Nitrogenous bases, sugars, phosphates

15. Hormonal control of digestion
Liver
Gallbladder
Bile
Stomach
Secretin and CCK –
Gastrin +
CCK +
Pancreas
Hormonal control of digestion
Figure Hormonal control of digestion
Duodenum
of small intestine
Secretin +
Key
CCK +
Stimulation Inhibition + –

16. Structure of the small intestine
Microvilli (brush border) at apical (lumenal) surface
Vein carrying blood to hepatic portal vein
Lumen
Blood capillaries
Epithelial cells
Basal surface
Muscle layers
Large circular folds
Epithelial cells
Villi
Lacteal
Figure The structure of the small intestine
Key
Lymph vessel
Nutrient absorption
Villi
Intestinal wall

17. Digital image of a human colon
Figure Digital image of a human colon

18. Dentition and diet Incisors Molars Canines Premolars (a) Carnivore
(b) Herbivore
Figure Dentition and diet
(c) Omnivore

19. Alimentary canals of a carnivore (coyote) and herbivore (koala)
Small intestine
Stomach
Small intestine
Cecum
Figure The alimentary canals of a carnivore (coyote) and herbivore (koala)
Colon (large intestine)
Carnivore
Herbivore

20. Ruminant digestion Rumen Reticulum Intestine Esophagus Abomasum Omasum1
Rumen 2
Reticulum
Intestine
Esophagus
Figure Ruminant digestion 4
Abomasum 3
Omasum

21. Homeostatic regulation of cellular fuel
Stimulus: Blood glucose level rises after eating.
Homeostasis: 90 mg glucose/
100 mL blood
Stimulus: Blood glucose level drops below set point.
Figure Homeostatic regulation of cellular fuel
Homeostatic regulation of cellular fuel

22. appetite-regulating hormones
Ghrelin
Figure A few of the appetite-regulating hormones
Insulin
Leptin
PYY

23. A plump petrel chick
Figure A plump petrel

24. Fat cells from the abdomen of a human
Figure Fat cells from the abdomen of a human

25. Review Bloodstream Veins to heart Lymphatic system Hepatic portal vein
Liver
Lipids
Absorbed food (except lipids)
Absorbed water
Mouth
Stomach
Esophagus
Small intestine
Anus
Secretions from the gastric glands of the stomach
Large intestine
Rectum
Secretions from the pancreas and the liver

26. You should now be able to:
Name the three nutritional needs that must be met by an animal’s diet.
Describe the four classes of essential nutrients.
Distinguish among undernourishment, overnourishment, and malnourishment.
Describe the four main stages of food processing.
Distinguish between a complete digestive tract and a gastrovascular cavity.

27. Follow a meal through the mammalian digestive system:
List important enzymes and describe their roles
Compare where and how the major types of macromolecules are digested and absorbed
Relate variations in dentition with different diets.
Explain where and in what form energy-rich molecules may be stored in the human body.