Lecture #18 Date ______  Chapter 41 ~ Animal Nutrition **** DO NOT rely on notes to teach you. These are provided to summarize the key points that YOU HAVE READ ABOUT

You Must Know  The major components of the alimentary canal (oral cavity, pharynx, esophagus, stomach, small intestines) and their contributions to animal nutrition  The major digestive glands (salivary gland, pancreas, liver, gallbladder) and their contributions to animal nutrition  The general scheme of chemical digestion of carbohydrates, fats, proteins and nucleic acids

Essential Nutrients  About half of the 20 amino acids are essential and must be obtained from food  There are essential fatty acids that animals cannot make and must ingest  Vitamins, like B vitamins and vitamin E are organic vitamins required in the diet of small amounts  Minerals (calcium and phosphorus) are simple inorganic nutrients that are required in small amounts.

Main Stages of Food Processing 4 stages of food processing 1) Ingestion – the act of taking in food 2) Digestion – the breakdown of food into small molecules capable of being absorbed by cells of body (macromolecules are digested by hydrolysis) 3) Absorption – body’s cells take up small molecules (like amino acids and simple sugars) from digestive tract 4) Elimination – the passing of undigested material from digestive tract

Main stages of food processing (cont.)  Intracellular digestion – food breakdown occurs in cell enclosed by protective membrane (sponges digest food this way)  Extracellular Digestion – food breakdown occurs outside of cells - Carried out by most animals - Allows for animal to devour large amounts of food  in many animals, digestion takes place in gastrovascular cavity (single opening where food enters and waste exits  more complex animals have complete digestive tract (alimentarry canals) which are one-way tubes that begin at mounth and end at anus

Main stages of food processing (cont.)  in many animals, digestion takes place in gastrovascular cavity (single opening where food enters and waste exits  more complex animals have complete digestive tract (alimentarry canals) which are one-way tubes that begin at mounth and end at anus

Mammalian digestion  Peristalsis: the movement of food through the digestive system (rhythmic waves of contraction of smooth muscle  Sphincters: muscular ring valve that regulate passage of material between digestive compartments

Mammalian digestion  When food is in the oral cavity (mouth), a nervous reaction causes saliva to be secreted and lubricate food to facilitate swallowing  it starts chemical digestion because saliva contains the enzyme amylase, which hydrolyzes starch and glycogen into smaller sugars  during chewing, food is shaped into a ball called a bolus  during swallowing the bolus enters the pharynx (a junction that opens to the esophagus and trachea)  During swallowing the epiglottis, a cartilage flap covers the trachea delivering food down the esophagus

Mammalian digestion  the esophagus moves food from pharynx down to stomach through peristalsis  The stomach functions to store food and secreting digestive fluids (gastric juices) 2 components of gastric juices  Hydrochloric acid (HCl) – pH of 2 that breaks down extracellular matrix of meat and plants and kills most bacteria from food  Pepsin – enzyme that hydrolyzes proteins into smaller polypeptides ***pepsinogen – inactive form that prevents cells from digesting themselves  Mucus – produced by stomach lining provides more protection

Mammalian digestion  The result of digestion in stomach is a substance called acid chyme  Acid chyme is moved from stomach to small intestine through the pyloric sphincter  First section of the small intestine is the duodenum  Duodenum – major site of chemical digestion. Here the acid chyme mixes with secretions from liver and pancreas  Pancreas releases bicarbonate fluid which is a buffer against acid contents from the stomach  The liver makes bile which is stored in the gall bladder and it breaks down fats to small fat droplets to be digested

Mammalian digestion Chemical digestion in the duodenum can be summarized by: I.Carbohydrates: breakdown of starch and glycogen begin with salivary amylase in the mouth. It continues with amylase from the pancreas to break it down to monosaccharides II.Proteins: pepsin breaks down proteins the stomach. In the duodenum trypsin and chymotrypsin continue to break down polypeptide chains. Dipeptidase, carboxypeptidase and aminopeptidase break it down to amino acids III.Nucleic acids: the breakdown of nucleic acids starts with the hydrolysis of DNA and RNA into their nucleotides. The nucleotides are then broken down into their phosphate, sugar, and bases. Most enzymes responsible for all of this enter the duodenum from the pancreas IV.Fats: digestion of fats start in the small intestine. Bile coats fats and the enzyme lipase hydrolyzes it into fat droplets

Mammalian digestion,  Small intestines have an epithelial lining with folds folds called villi which has projections called microvilli (increases surface area for absorption of stuff)  Villi have blood capillaries and lymph vessels - blood capillaries absorb monomers and drain into the hepatic portal vessel that lead to the liver which regulates the nutrient distrubution to the body - lacteal is the lymph vessel that absorb fatty acids

Mammalian digestion Hormones Regulate Everything  Gastrin is produced by stomach and increases production of gastric juices  Enterogastrone is produced by duodenum in the presence of fats and slows peristalsis to have more time to digest fats  Secretin and Cholecystokinin – are secreted by wall of duodenum and increase flow of gastric juice from pancreas and gall bladder

Mammalian Digestion  The large intestine (AKA colon), is connected to the small intestine by a sphincter. The point of connection is the cecum, a small pouch with an extension called the appendix  The main functions of the colon are water recovery and to compact waste  The colon has a bunch of harmless bacteria, including Escherichia coli (E. coli) ***presence of E. coli means waste contamination (sometimes in food…YUCK!)  The end of the colon is the rectum where feces is eliminated.

Evolutionary adaptations  Mammal’s dentition (teeth) is usually telling of it’s diet  Herbivores generally have longer alimentary canals than carnivores to reflect the longer time to digest vegetation