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?

Chapter 41: Animal Nutrition

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.

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

Table 41.1 Vitamin Requirements of Humans

Table 4.2 Mineral Requirements of Humans

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.

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

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)

Intracellular Digestion: Sponges

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

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

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?

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

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)

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

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)

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

Absorption in the Small Intestine Villi and microvilli increase surface area

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

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

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

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

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

Glucose Homeostasis