1

2 Lecture 13 Outline (Ch. 48) I.Animal Nutrition Overview II.Essential Parts of Animal Diet III. Food Intake IV.Digestive Compartments V.Adaptations VI.Obesity

3 Overview: The Need to Feed Food is taken in, taken apart, and taken up in the process of animal nutrition In general, animals fall into three categories: –Herbivores eat mainly autotrophs (plants, algae) –Carnivores eat other animals –Omnivores regularly consume animals as well as plants or algal matter

4 Chemical energy, which is converted into ATP and powers processes in the body Organic carbon and organic nitrogen Essential nutrients must be obtained from dietary sources Essential Parts of Diet –Essential amino acids –Essential fatty acids –Vitamins –Minerals

5 Meat, eggs, cheese - provide all nine essential amino acids ( “complete” proteins) Individuals eating only plant proteins need specific plant combinations for all essential amino acids Essential Parts of Diet Beans and other legumes Corn (maize) and other grains Lysine Essential amino acids for adults Tryptophan Isoleucine Leucine Phenylalanine Threonine Valine Methionine

6 Animals can synthesize most fatty acids they need The essential fatty acids are certain unsaturated fatty acids that must be obtained from the diet Essential Parts of Diet Vitamins: organic molecules needed in small amounts 13 essential vitamins for humans Fat-soluble & water-soluble B-complex Biotin Vitamin C (ascorbic acid) Vitamin A Vitamin D Vitamin E Vitamin K

7 Minerals Minerals: inorganic nutrients, small amounts needed Calcium Phosphorus Potassium Sulfur Chlorine Sodium Magnesium Iron A diet missing a certain essential part or not enough calories overall leads to malnourishment or undernourishment

8 Ingestion: the act of eating Suspension feeders - many aquatic animals, which sift small food particles from the water Substrate feeders are animals that live in or on their food source Fluid feeders suck nutrient-rich fluid from a living host Bulk feeders eat relatively large pieces of food Food Intake

9 Humpback whale, a suspension feeder Baleen Leaf miner caterpillar, substrate feeder Caterpillar Feces Mosquito, a fluid feeder Rock python, a bulk feeder

10 Digestion is the process of breaking food down into molecules small enough to absorb –In chemical digestion, the process of enzymatic hydrolysis splits bonds in molecules with the addition of water Absorption is uptake of nutrients by body cells Elimination is the passage of undigested material out of the digestive compartment Food Intake

11 IngestionDigestion Absorption Elimination Undigested material Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Small molecules Mechanical digestion Food Pieces of food Food Intake

12 Digestive Compartments Most animals process food in specialized compartments Reduces risk animal digesting its own cells/ tissues Gastrovascular cavity Food Epidermis Mouth Tentacles Gastrodermis

13 More complex animals: digestive tube with two openings (mouth, anus) Tube called a complete digestive tract or an alimentary canal Can have specialized regions, carry out digestion and absorption stepwise Digestive Compartments Esophagus Mouth Pharynx CropGizzard Typhlosole Intestine Lumen of intestine Anus (b) Grasshopper Foregut (c) Bird (a) Earthworm MidgutHindgut Esophagus Rectum Anus Mouth Crop Gastric cecae Esophagus Mouth Crop Anus Stomach Gizzard Intestine

14 Cecum Anus Ascending portion of large intestine Gall- bladder Small intestine Large intestine Small intestine Rectum Pancreas Liver Salivary glands Tongue Oral cavity Pharynx Esophagus Sphincter Stomach Sphincter Duodenum of small intestine Appendix Liver Pancreas Small intestine Large intestine Rectum Stomach Gall- bladder A schematic diagram of the human digestive system Esophagus Salivary glands Mouth Digestive Compartments Mammalian alimentary canal and accessory glands that secrete digestive juices through ducts

15 Larynx Trachea Epiglottis up Pharynx Tongue Glottis Esophagus Esophageal sphincter contracted Food To stomach To lungs Epiglottis down Esophageal sphincter relaxed Glottis up and closed Epiglottis up Esophageal sphincter contracted Sphincter relaxed Relaxed muscles Contracted muscles Relaxed muscles Stomach Glottis down and open Oral Cavity, Pharynx, Esophagus Food shaped into a bolus, lubricated by saliva, digestion begins with amylase. Pharynx, a junction that opens to both the esophagus and the trachea (windpipe) The esophagus conducts food from the pharynx down to the stomach by peristalsis Epiglottis blocks entry to the trachea, and larynx.

16 Digestion in the Stomach The stomach stores food and secretes gastric juice, which converts a meal to acid chyme Gastric juice - hydrochloric acid (parietal cells) and the enzyme pepsin (chief cells) Mucus protects the stomach lining from gastric juice Interior surface of stomach Esophagus Chief cells Small intestine Epithelium Stomach Sphincter Parietal cell Chief cell Folds of epithelial tissue Pepsin Sphincter Pepsinogen HCl H+H+ Cl – Parietal cells Mucus cells Gastric gland µm

17 Digestion in the Small Intestine The small intestine: longest section of alimentary canal Major organ of digestion and absorption First is the duodenum - acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself. pancreas proteases trypsin & chymotrypsin amylase & lipase neutralizes the acidic chyme liver/gallbladder bile aids digestion and absorption of fats small intestine lining of duodenum (brush border) produces several digestive enzymes jejunum and ileum mainly absorb water & nutrients

18 Digestion in the Small Intestine

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

20 Absorption in the Small Intestine small intestine has huge surface area, from villi and microvilli exposed to the intestinal lumen enormous microvillar surface greatly increases rate of nutrient absorption Muscle layers Microvilli (brush border) at apical (lumenal) surface Vein carrying blood to hepatic portal vein Villi Intestinal wall Key Nutrient absorption Large circular folds Blood capillaries Epithelial cells Villi Lymph vessel Basal surface Lacteal Epithelial cells Lumen

21 Absorption in the Small Intestine

22 Absorption in the Large Intestine The colon of the large intestine is connected to the small intestine The cecum aids in fermentation of plant material, connects where the small and large intestines meet Human cecum has extension (appendix), plays a minor role in immunity Feces stored in rectum until eliminated

23 The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins Two sphincters between the rectum and anus control bowel movements –Smooth muscle sphincter (involuntary) –Striated muscle sphincter (voluntary) Absorption in the Large Intestine

24 Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation Cecum Small intestine HerbivoreCarnivore Colon (large intestine) Stomach Small intestine Adaptations

25 Mutualistic Adaptations Many herbivores have symbiotic microorganisms that digest cellulose The most elaborate adaptations in ruminants Esophagus Omasum Abomasum Intestine Rumen Reticulum

26 Energy Sources and Stores Animals store excess calories as glycogen in the liver and muscles Energy secondarily stored as adipose, or fat, cells When fewer calories are taken in than are expended, fuel is taken from storage and oxidized 100 µm Fat cells Obesity is due to excessive intake of food energy, excess stored as fat Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes

27 Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level rises after eating. Stimulus: Blood glucose level drops below set point. Energy Sources and Stores

28 Leptin PYY Insulin Ghrelin Energy Sources and Stores The complexity of weight control in humans is evident from studies of the hormone leptin Mice that inherit a defect in the gene for leptin become very obese

29 Obese mouse with mutant ob gene (left) next to wild-type sibling mouse.

30 Obesity and Evolution The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival A species of birds called petrels become obese as chicks; in order to consume enough protein from high-fat food, chicks need to consume more calories than they burn

31 A plump petrel

Lecture 13 Summary 1. Essential Nutrients (Ch. 48) -Amino acids, fatty acids, vitamins, minerals 2. Types of Food Intake and Digestive Tracts (Ch. 48) -Suspension, substrate, fluid, bulk feeders -Gastrovascular, simple, complex digestive cavities 3. Digestive Tract and Enzymes/Secretions (Ch. 48) - Mouth - Stomach - Auxiliary Organs - Small Intestine - Large Intestine 4. Adaptations and Control (Ch. 48) -Diet and digestive tract -Mutualisms -Obesity and Energy Stores