1. WARM-UP (Ch. 40) What is the principle of countercurrent exchange?
(Review) What are the 4 classes of macromolecules?
(Ch. 41) You eat a piece of candy. List the structures it passes through as it travels through your alimentary canal.
Where does most of the digestion of the candy in #3 happen?

2. Chapter 41: Animal Nutrition

3. What you need to know:
Major compartments of alimentary canal (organs) – and their contributions to animal nutrition.
Digestive glands: salivary, pancreas, liver, gall bladder – and their contributions to animal nutrition.
Digestion of carbs, proteins, fats, nucleic acids.

4. Essential Nutrients: required by cells, obtained through food
Four classes of essential nutrients:
Essential amino acids (8)
Essential fatty acids
Vitamins (13) - fat-soluble, water-soluble
Minerals

5. Table 41.1 Vitamin Requirements of Humans

6. Table 4.2 Mineral Requirements of Humans

7. Dietary Deficiencies
Undernourished: diet is deficient in calories, not enough energy
Malnourishment: missing 1+ essential nutrients
Herbivore licks exposed salts and minerals lacking in plants.

8. The main stages of food processing:
Ingestion: eating
Digestion: breakdown of food into small molecules
Mechanical (chewing, grinding)
Chemical (enzymes)
Absorption: cells take up nutrients
Elimination: pass undigested materials from digestive system

11. Digestive Compartments
Most animals process food in specialized compartments
Intracellular: digestion of food inside cells by food vacuoles
Ex. phagocytosis, pinocytosis, sponges
Extracellular: food broken down outside of cells
Gastrovascular cavity (simple) or alimentary canal (complex)

12. Intracellular Digestion: Sponges

13. Extracellular Digestion
Compartments are outside of the animal’s body
Gastrovascular cavity: simple animals; single- opening, two-way digestion (food in, waste out)
Digestion in a hydra

14. Alimentary canal: more complex, one-way tubes with mouth and anus

15. Specialized organs for digestion in Humans
Digestive system = alimentary canal + glands
Glands = salivary glands, pancreas, liver, and gallbladder
Q: Can you name the organs of the human alimentary canal in order?

17. Peristalsis: push food through rhythmic contractions of muscles in the wall of the canal
Sphincters: valves regulate the movement of material between compartments
Digestion of Macromolecules:
Mouth = carbs
Stomach = proteins
Small Intestine = carbs, proteins, fats, nucleic acids

18. Digestion in the Mouth Oral cavity: mechanical, chemical digestion
Salivary glands: saliva lubricates food
Teeth chew food into smaller particles
Salivary amylase: breakdown glucose polymers
Saliva contains mucus, a viscous mixture of water, salts, cells, and glycoproteins
Pharynx: back of throat
Epiglottis: flap of cartilage, covers trachea when swallowing
Esophagus: food tube (pharynx  stomach)

20. Digestion in the Stomach
The stomach stores food and secretes gastric juice, which converts a meal to acid chyme
HCl: pH 2, kills bacteria & denatures proteins
Pepsin: enzyme (protease) that hydrolyze proteins into smaller peptides
Pepsinogen (inactive)  pepsin (active) by HCl
Mucus: protects lining of stomach
Gastric ulcers: lesions in the lining, caused mainly by bacterium Heliobacter pylori

22. Digestion in the Small Intestine
SI = major organ of digestion and absorption
Duodenum: first section, digestive juices, major chemical digestion
Digestive juices:
Pancreas: bicarbonate (basic), trypsin & chymotrypsin (proteases); lipase (fats); amylase (carbs); nuclease (DNA, RNA)
Bile: made in liver, stored in gall bladder
Emulsify fats (make smaller droplets)

24. Hormones that coordinate digestion:
Gastrin: produced by stomach, production of gastric juices
Entrogastrin: produced by SI (duodenum), peristalsis to allow time for fat digestion
Secretin & CCK (cholesystokinin): secreted by SI (duodenum), flow of digestive juices from pancreas & gall bladder

25. Absorption in the Small Intestine
Villi and microvilli increase surface area

26. Villi  capillaries  hepatic portal vein  liver  heart
Liver: distribute nutrients, detox, glucose storage (glycogen)

27. Absorption in the Large Intestine
LI = colon
Function = compact waste, reabsorb water
Cecum: pouch where SI & LI meet, ferment plant material
Appendix = extension of cecum, role in immunity
Rectum: end of LI, feces stored until elimination

28. Evolutionary adaptations of vertebrate digestive systems correlate with diet
Dentition: teeth correlate with diet
Herbivores: longer alimentary canal, longer cecum

29. Mutualistic Adaptations
Many herbivores have fermentation chambers, where mutualistic microorganisms digest cellulose (ruminants)

30. Homeostatic Mechanisms
Vertebrates store excess calories as glycogen in the liver and muscle cells, and as fat in adipose tissue
Overnourishment can lead to obesity
Leptin: hormone, suppresses appetite

31. Glucose Homeostasis