1. Chapter 41 – Animal Nutrition

2. Food Types / Feeding Mechanisms
Opportunistic
Herbivore: eat autotrophs
Carnivore: eat other animals
Omnivore: both
Feeding Adaptations
Suspension-feeders: sift food from water (baleen whale)
Substrate-feeders: live in or on their food (leaf miner) (earthworm: deposit-feeder)
Fluid-feeders: suck fluids from a host (mosquito)
Bulk-feeders: eat large pieces of food (most animals)

3. Homeostasis & Energy Budget
“Budget” – flow of energy into and out of an animal’s body
Regulated through homeostatic mechanisms, ex. Glucose
Blood glucose rises, pancreas secretes insulin, enhances transport of glucose into body cells and stimulates liver and muscle to store glucose as glycogen
Blood glucose falls, pancreas secretes glucagon, promotes breakdown of glycogen in liver and release into the blood stream

4. Caloric Imbalance
Undernourishment – stores of fat and glycogen used up, body breaks down proteins for fuel, caloric deficiency
Overnourishment – body hoards fat instead of using it for fuel
Malnourishment – essential nutrient deficiency
Obesity – a global problem, lead to a variety of health problems
Science currently conducting research to discover homeostatic mechanisms for food intake

5. Appetite Regulation
Most appetite regulatory hormones are proteins, dozens of genes have been identified that code for these hormones
Leptin – produced by adipose tissue, suppresses appetite as fat increases
PYY – small intestine, after meals, suppresses appetite
Insulin – pancreas, rise in sugar levels after a meal, suppresses appetite
Ghrelin – stomach wall, triggers feelings of hunger as mealtime approaches, as diet/lose weight, ghrelin levels increase
Many of these are feedback mechanisms that prevent people from becoming overweight or obese

6. Nutritional Requirements
Essential nutrients: materials that must be obtained in preassembled form
Essential amino acids: the 8 amino acids that must be obtained in the diet
Essential fatty acids: unsaturated fatty acids
Vitamins: organic coenzymes
Minerals: inorganic cofactors

7. Essential Vitamins

9. Food Processing 1-Ingestion: act of eating
2-Digestion: process of food break down
enzymatic hydrolysis
intracellular: breakdown within cells (sponges)
extracellular: breakdown outside cells (most animals)
alimentary canals (digestive tract)
3- Absorption: cells take up small molecules
4- Elimination: removal of undigested material

10. The Alimentary Canal
Primitive inverts have gastrovascular cavity – a digetive sac with a single opening, functions in digestion and distribution of nutrients (cnidarians and flatworms)
All others have an alimentary canal – a digestive tube extending between two openings, a mouth and an anus

11. Mammalian digestion, I
Peristalsis: rhythmic waves of contraction by smooth muscle
Sphincters: ring-like valves that regulate passage of material
Accessory glands: salivary glands; pancreas; liver; gall bladder

12. Mammalian digestion, II
Oral cavity: salivary amylase (hydrolyzes starch), bolus (ball of chewed food
Pharynx (the throat): epiglottis - a cartilaginous flap that moves up to cover the trachea (windpipe) during swallowing
Esophagus: conducts food from the pharynx down to the stomach by peristalsis

13. Mammalian digestion, II cont.
Stomach – stores food and performs preliminary steps of digestion
Churning and enzymes convert food to nutrient broth called acid chyme
Secretion of enzymes – controlled by nerve impulses and hormone gastrin
3 types of secretory cells:
Mucous cells, secrete mucin (thin mucous layer protects stomach lining) and gastrin (stimulates further secretion of gastric juice)
Chief cells, secrete pepsinogen (inactive precursor of pepsin, becomes active when mixed with acid)
Parietal cells, secrete HCl
gastric juice (HCl and pepsin)
HC I- acidity (pH 1-4) kills bacteria, starts conversion of pepsinogen to pepsin
pepsin – begins to split peptide bonds of large polypeptide chains

14. Mammalian digestion, III
Small intestine – more than 6 meters in length in humans; where most enzymatic hydrolysis and absorption of nutrients occurs
3 sections:
duodenum – 25 cm, acid chyme mixes with digestive juices from the pancreas, liver, gall bladder, and intestinal wall
pancreas – protease for protein digestion and bicarbonate to buffer the acid chyme
liver – bile for fat emulsification (stored in the gall bladder)
brush border – epithelial lining of duodenum, secretion of several different digestive enzymes
jejunum - begin the absorption of amino acids, sugars, fatty acids and glycerol
Ileum – significant absorption due to large number of villi

15. Mammalian digestion, IV
Villi (large circular folds) contain microvilli – increase surface area to increase nutrient absorption; each villus contains microscopic blood vessels (capillaries) and a lacteal (a small lymphatic vessel)
Nutrients are absorbed across the intestinal epithelium and across the epithelium of the capillaries or lacteal
Hepatic portal vein – carries nutrient rich blood away from villi directly to the liver (can interconvert various organic molecules)

16. Mammalian digestion, V Hormonal Action:
gastrin – stomach, gastric juice production
secretin – small intestine, stimulates pancreas to release buffer (sodium bicarbonate)
cholecystokinin (CCK) – small intestine, triggers release of bile from gall bladder and enzymes from the pancreas
enterogastrone – small intestine, assists in fat hydrolysis by stopping peristalsis when fat rich acid chyme reaches the duodenum

17. Mammalian digestion, III cont.

18. Mammalian digestion, VI
Large intestine (colon) – site of water absorption
Cecum
Appendix
Feces
Rectum/anus

19. Evolutionary adaptations
Dentition: an animal’s assortment of teeth
Digestive system length
Symbiosis
Ruminants