Chapter 41 Animal Nutrition

Overview: The Need to Feed Herbivores eat mainly autotrophs (plants and algae) Carnivores eat other animals Omnivores regularly consume animals as well as plants or algal matter

There are four classes of essential nutrients: Essential amino acids Essential fatty acids Vitamins Minerals

Animals require 20 amino acids and can synthesize about half Essential Amino Acids Animals require 20 amino acids and can synthesize about half Essential amino acids- must be obtained from food in preassembled form “Complete” proteins- provides all the essential amino acids (meat, eggs, and cheese) Most plant proteins are incomplete in amino acid makeup

Essential amino acids for adults Methionine Beans and other legumes Valine Threonine Phenylalanine Leucine Corn (maize) and other grains Isoleucine Tryptophan Lysine

Animals can synthesize most of the fatty acids they need Essential Fatty Acids Animals can synthesize most of the fatty acids they need The essential fatty acids are certain unsaturated fatty acids

Vitamins are organic molecules required in the diet in small amounts 13 essential vitamins Two categories: fat-soluble and water-soluble

Minerals Minerals are simple inorganic nutrients, usually required in small amounts

Dietary Deficiencies Undernourishment- diet with less chemical energy than the body requires Malnourishment- absence from the diet of one or more essential nutrients

An undernourished individual will Undernourishment An undernourished individual will Use up stored fat and carbohydrates Break down its own proteins Lose muscle mass Suffer protein deficiency of the brain Die or suffer irreversible damage

Malnourishment Malnourishment can cause deformities, disease, and death

The main stages of food processing are ingestion, digestion, absorption, and elimination Ingestion is the act of eating

Suspension Feeders Many aquatic animals are suspension feeders, which sift small food particles from the water

Substrate Feeders Leaf miner caterpillar, a substrate feeder Substrate feeders are animals that live in or on their food source Caterpillar Feces

Fluid feeders suck nutrient-rich fluid from a living host Mosquito, a fluid feeder

Bulk feeders eat relatively large pieces of food Rock python, a bulk feeder

Absorption is uptake of nutrients by body cells Digestion is the process of breaking food down into molecules small enough to absorb 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

Nutrient molecules enter body cells Mechanical digestion Small molecules Pieces of food Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Mechanical digestion Food Undigested material 1 Ingestion 2 Digestion 3 Absorption 4 Elimination

Digestive Compartments Intracellular Digestion- food is engulfed by endocytosis and digested within food vacuoles Extracellular Digestion- food particles are broken down outside of cells

Tentacles Food Gastrovascular cavity Mouth Epidermis Gastrodermis

Crop Gizzard Esophagus Intestine Pharynx Gastrovascular cavity- functions in both digestion and distribution of nutrients Complete digestive tract (alimentary canal)- digestive tube with two openings, a mouth and an anus Anus Mouth Typhlosole Lumen of intestine (a) Earthworm Foregut Midgut Hindgut Esophagus Rectum Anus Crop Mouth Gastric cecae (b) Grasshopper Stomach Gizzard Intestine Mouth Esophagus Crop Anus (c) Bird

Crop Gizzard Esophagus Intestine Pharynx Anus Mouth Typhlosole Lumen of intestine (a) Earthworm

Foregut Midgut Hindgut Esophagus Rectum Anus Crop Mouth Gastric cecae (b) Grasshopper

Stomach Gizzard Intestine Mouth Esophagus Crop Anus (c) Bird

Organs of the mammalian digestive system Peristalsis- rhythmic contractions of muscles to push along food Sphincters regulate the movement of material between compartments

Salivary glands Mouth Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

Duodenum of small intestine Tongue Sphincter Oral cavity Salivary glands Pharynx Esophagus Sphincter Liver Stomach Ascending portion of large intestine Gall- bladder Duodenum of small intestine Pancreas Small intestine Small intestine Large intestine Rectum Anus Appendix Cecum

The Oral Cavity, Pharynx, and Esophagus Salivary glands Mouth Oral cavity- mechanical digestion takes place Salivary glands deliver saliva to lubricate food Amylase- initiates breakdown of glucose polymers Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

The Oral Cavity, Pharynx, and Esophagus Salivary glands Mouth The tongue shapes food into a bolus and provides help with swallowing Pharynx (throat)- opens to both the esophagus and the trachea (windpipe) Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

The Oral Cavity, Pharynx, and Esophagus Salivary glands Mouth Esophagus conducts food from the pharynx down to the stomach by peristalsis Swallowing causes the epiglottis to block entry to the trachea Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

Food Epiglottis up Tongue Epiglottis up Pharynx Esophageal sphincter contracted Epiglottis down Glottis Glottis down and open Esophageal sphincter contracted Larynx Trachea Esophagus Esophageal sphincter relaxed Glottis up and closed Relaxed muscles To lungs To stomach Contracted muscles Relaxed muscles Sphincter relaxed Stomach

Digestion in the Stomach- Chemical Digestion in the Stomach Gastric juice is made up of hydrochloric acid and the enzyme pepsin Parietal cells secrete hydrogen and chloride ions separately Chief cells secrete inactive pepsinogen, it is activated to pepsin when mixed with HCl Mucus protects the stomach lining from gastric juice

Esophagus Sphincter Stomach Sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface of stomach

Interior surface of stomach Epithelium 3 1 Pepsinogen Pepsin Pepsinogen and HCl are secreted. 2 HCl Gastric gland 2 HCl converts pepsinogen to pepsin. 1 3 Pepsin activates more pepsinogen. Mucus cells H+ Cl– Chief cells Chief cell Parietal cells Parietal cell

Stomach Dynamics Coordinated contraction and relaxation of stomach muscle churn the stomach’s contents Sphincters prevent chyme from entering the esophagus and regulate its entry into the small intestine Esophagus Sphincter Stomach Sphincter 5 µm Small intestine Folds of epithelial tissue Interior surface of stomach

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

Digestion in the Small Intestine Salivary glands Mouth Major organ of digestion and absorption Duodenum (first part of small intestine)- acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

Liver Gallbladder Bile Stomach Secretin and CCK – Gastrin + CCK + Pancreas Duodenum of small intestine Secretin + Key CCK + Stimulation Inhibition + –

Pancreatic Secretions Salivary glands Mouth The pancreas produces proteases trypsin and chymotrypsin, protein-digesting enzymes that are activated after entering the duodenum Its solution neutralizes the acidic chyme Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

Bile Production by the Liver Salivary glands Mouth Aids in digestion and absorption of fats Bile is made in the liver and stored in the gallbladder Esophagus Gall- bladder Stomach Small intestine Liver Pancreas Large intestine Rectum Anus A schematic diagram of the human digestive system

Secretions of the Small Intestine The epithelial lining of the duodenum produces several digestive enzymes Most digestion occurs in the duodenum; the jejunum and ileum function mainly in absorption of nutrients and water

Absorption in the Small Intestine The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen The enormous microvillar surface greatly increases the rate of nutrient absorption

Vein carrying blood to hepatic portal vein Muscle layers Large circular folds Villi Key Nutrient absorption Intestinal wall

Microvilli (brush border) at apical (lumenal) surface Blood capillaries Epithelial cells Basal surface Epithelial cells Lacteal Lymph vessel Villi Key Nutrient absorption

Absorption in the Large Intestine Colon of the large intestine is connected to the small intestine Cecum aids in the fermentation of plant material and connects where the small and large intestines meet Appendix- an extension off the cecum, which plays a very minor role in immunity The colon recover waters that has entered the alimentary canal and houses E. coli strains, some of which produce vitamins

Small intestine Large intestine Anus Ascending portion of large intestine Small intestine Small intestine Large intestine Rectum Anus Appendix Cecum

All snakes can unhinge their jaws to swallow prey whole Dental Adaptations Incisors The teeth of poisonous snakes are modified as fangs for injecting venom All snakes can unhinge their jaws to swallow prey whole Molars Canines Premolars (a) Carnivore (b) Herbivore (c) Omnivore

Stomach and Intestinal Adaptations Herbivores have longer alimentary canals than carnivores, they need more time to digest vegetation Small intestine Stomach Small intestine Cecum Colon (large intestine) Carnivore Herbivore

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

1 Rumen 2 Reticulum Intestine Esophagus 4 Abomasum 3 Omasum

Energy Sources and Stores Animals store excess calories primarily as glycogen in the liver and muscles Energy is secondarily stored as adipose, or fat, cells

Overnourishment and Obesity Overnourishment causes obesity, which results from excessive intake of food energy with the excess stored as fat Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival

Ghrelin Insulin Leptin PYY

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