1. Nutrition
Autotrophs
plants, some protists & bacteria
producers

2. Nutrition Heterotrophs animals, fungi, some protists & bacteria
consumers

3. Animal Nutrition Most obtain food by ingestion
take in their food whole or piece by piece

4. Animal Nutrition Classify based on what they eat:
Herbivores (primary consumers)
eat autotrophs
Carnivores (secondary or higher consumers)
eat heterotrophs
Omnivores
eat both

5. Stages of Food Processing
Ingestion
eating
Digestion
breaking down food into small molecules
mechanical and chemical (enzymatic hydrolysis)
Absorption
body takes in small molecules
Elimination
undigested material exits the body

6. Digestion Must take place in specialized compartments
to avoid damage to body cells

7. Food vacuoles
food enters by endocytosis & then vacuole merges with lysosome
Some protists
Sponges
only animal with only intracellular digestion

8. Figure 41.10 Intracellular digestion in Paramecium

10. Gastrovascular Cavities
single opening
serve to both digest & transport nutrients
extracellular digestion, then intracellular
Platyhelminthes (planaria) & Cnidarians (hydra)

11. What is the advantage of extracellular digestion?
Eat larger food

12. Extracellular digestion in a gastrovascular cavity

13. Alimentary canals or Complete Digestive Tracts
two openings: mouth & anus
food passes in one direction
Found in all other animals

14. What is the advantage of one-way movement of food?
Allows for specialization of different regions of the digestive tract

15. Figure 41.12 Alimentary canals

16. Types of Digestive Systems
Nematode
Earthworm
Mouth
Pharynx
Intestine
Anus
Crop
Gizzard
Salamander
Esophagus
Liver
Pancreas
Stomach
Cloaca
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17. Mammalian Digestive System
Four-layered wall surrounds the lumen
Mucosa (epithelial tissue)
Submuscosa (connective tissue)
Muscularis (muscle)
Serosa (connective tissue)

19. Salivary gland Oral cavity Pharynx Salivary glands Esophagus Liver
Gallbladder
Pharynx
Cecum
Appendix
Anus
Rectum
Small intestine
Pancreas
Stomach
Colon
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20. Human Digestive System
Mouth
teeth mechanically break down food
Similar in function to the gizzard of birds and worms
saliva is secreted from salivary glands
mucous protects mouth
antibacterial agents
buffer to neutralize acidity
salivary amylase – hydrolyzes glucose polymers

21. Human Digestive System
Pharynx (throat)
swallowing
Esophagus
peristalsis

22. Swallowing 1. As food moves to 2. During swallowing, the larynx rises
Pharynx
Soft palate
Hard palate
Tongue
Epiglottis
Larynx
Trachea
Esophagus
Air
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1. As food moves to
the back of the
mouth, the soft
palate seals off
the nasal cavity.
2. During swallowing, the larynx rises
and is sealed off by the epiglottis.
This forces the bolus into the
esophagus and prevents entry into
the trachea. As the bolus moves
into the esophagus the larynx relaxes.

23. Peristalic movement Esophagus Relaxation Contraction Food Bolus
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24. Human Digestive System
Stomach
stores food (as does the crop in other organisms)
lining secretes gastric juice
Pepsinogen (inactive) becomes pepsin (active) in low pH
smooth muscles churn the food
Acid chyme

25. The Stomach Gastric pit Muscularis Pyloric sphincter Longitudinal
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Gastric pit
Muscularis
Pyloric
sphincter
Longitudinal
Circular
Oblique
Serosa
Submucosa
Mucosa
Gastric glands
Chief
cell
Parietal
Mucous
Esophagus
Stomach
Duodenum

26. Human Digestive System
Small Intestine
Longest part of the canal (6 m in humans)
Duodenum (first 25 cm) – most digestion takes place
Jejunum and ileum – mainly absorption
Very large surface area (300 m2) – folds, villi & microvilli
Similar to mycelium in fungi & roots in plants

27. The Small Intestine Small intestine Villus Epithelial cell Capillary
Villi
Villus
Mucosa
Serosa
Submucosa
Muscularis
Epithelial
cell
Capillary
Lacteal
Vein
Artery
Lymphatic
duct

28. Pancreatic islet (of Langerhans)
From liver
Gallbladder
Pancreatic
duct
Pancreas
Common
bile duct
Duodenum
 cell
 cell
Pancreatic islet
(of Langerhans)
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29. Human Digestive System
Accessory Glands:
Pancreas
digestive enzymes
Lipase-lipids; pancreatic amylase-starch; trypsin - proteins
Bicarbonate- buffer

30. Human Digestive System
Accessory Glands:
Liver
produces bile salts which are stored in the gallbladder until needed
aid in the digestion of fats by emulsification
Gallbladder

31. Human Digestive System
Large Intestine or Colon
main function is concentration & storage of wastes
absorption of water, sodium, vitamin K
Feces are moved along by peristalsis and exit the body through the anus

32. Hormonal Control of Digestion
Gastrin
released by the stomach
feeds back to cause the secretion of gastric juices
Low pH inhibits its production – negative feedback

33. Stomach Liver Pancreas Gallbladder Duodenum ( + ) Proteins pH Enzymes
Bicarbonate
Pepsin
HCl
Parietal cells
Gastrin
Bile
Acinar
cells
Liver
Chief cells
Secretin
CCK
( – )
GIP
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34. Hormonal Control of Digestion
Enterogastrones
Released by duodenum of small intestine
inhibit peristalsis & secretions in the stomach
Secretin
Stimulated by low pH
causes pancreas to release bicarbonate
CCK (cholecystokinin)
Stimulated by high fat content
Stimulates gall bladder to release bile
GIP (gastric inhibitory peptide)
Inhibits emptying of the stomach

35. Stomach Liver Pancreas Gallbladder Duodenum ( + ) Proteins pH Enzymes
Bicarbonate
Pepsin
HCl
Parietal cells
Gastrin
Bile
Acinar
cells
Liver
Chief cells
Secretin
CCK
( – )
GIP
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36. Evolutionary Adaptations to Diet
Teeth
pointed in carnivores, flat in herbivores

37. Mouth and Teeth Horse Lion Human Herbivore Carnivore Omnivore Molars
Premolars
Incisors
Canines
Horse
Lion
Human
Herbivore
Carnivore
Omnivore
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38. Evolutionary Adaptations to Diet
Length of gut
longer in herbivores than carnivores
Cecum
houses bacteria that aid in digestion

39. Nonruminant Herbivore
Stomach
Anus
Spiral
loop
Esophagus
Rumen
Reticulum
Omasum
Abomasum
Cecum
Insectivore
Short intestine, no cecum
Carnivore
Short intestine and
colon, small cecum
Ruminant Herbivore
Four-chambered stomach with large rumen;
long small and large intestine
Small
intestine
Large
Nonruminant Herbivore
Simple stomach, large cecum
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40. Evolutionary Adaptations to Diet
Ruminant Stomach- cows, deer

41. Rumen Small intestine Esophagus Reticulum Abomasum Omasum
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42. Evolutionary Adaptations to Diet
Coprophagy – rodents, rabbits