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Ch. 41 Need to Feed Animal nutrition • Food being taken in, taken apart, and taken up Herbivores • Dine mainly on plants Carnivores • Dine mainly on other animals Omnivores • Regularly dine on animals, plants, and algae Opportunistic Feeders • Eat outside normal diet when usual Essential Nutrients Materials that an animal’s cells require but cannot synthesize Essential Amino Acids • Must be obtained from food (8) Essential Fatty Acids • Most are synthesized Vitamins • Organic molecules that have diverse functions and are required in the diet in very small amounts • Water soluble vs. fat soluble Minerals • Inorganic nutrients required in small amounts • cofactors Essential Nutrients Essential Nutrients Dietary Deficiencies Diet that lacks one or more essential nutrients or consistently supplies less chemical energy than the body requires Malnourished • Failure to obtain adequate nutrition Undernutrition • A diet that fails to provide adequate sources of chemical energy Overnourished • obesity Assessing Nutritional Needs Ingestion, Digestion, Absorption, Elimination 1. Ingestion – act of eating/feeding 2. Digestion – Food is broken down into molecules small enough for the body to absorb – Mechanical and chemical 3. Absorption – uptake of small molecules from digestion 4. Elimination – undigested material passes out of the digestive compartment Four Main Feeding Mechanisms of Animals Suspension feeders and filter feeders • Eat small organisms or food particles suspended in the water – clams, oysters • Use a filtering structure to strain food from water – Baleen whale Substrate feeders • live on or in their food source • leaf miners Feeding Adaptations Deposit feeders • substrate feeder that ingests partially decayed organic matter • Earthworms Fluid feeders • suck nutrient rich fluids from a living host • aphids, hummingbirds, bees, leeches, mosquitoes Bulk feeders • eat relatively large pieces of food • adaptations to kill prey or tear off vegetation Digestive Compartments Intracellular Digestion • Hydrolysis of food inside vacuoles • Begins with phagocytosis or pinocytosis Food vacuoles • organelle that digests its food without hydrolytic enzymes mixing with the cell’s cytoplasm • Fuse with lysosomes • Sponges Digestive Compartments Extracellular digestion • Digestion occurs within compartments that are continuous, with the outside of the body Gastrovascular cavity • digestive sac with a single opening; functions in both digestion and nutrient absorption • More complex animals have alimentary canals Digestive Compartments Alimentary canal (complete digestive tract) • digestive tube running between two openings: mouth and anus • organized into compartments for digestion and absorption (increases efficiency) • unidirectional passage of food Mammalian Digestion Organs Specialized for Sequential Food Processing Alimentary Canal and Accessory Organs Peristalsis • Alternating waves of contraction and relaxation in the smooth muscles lining the canal Sphincters • junctions b/w specialized compartments that act like ringlike valves Oral Cavity, Pharynx, Esophagus Oral Cavity • Beginning of physical and chemical digestion – chewing – secretions from salivary glands Saliva contains… – mucin, buffers, antibacterial agents, amylase Bolus – chewed food that enters the pharynx Oral Cavity, Pharynx, Esophagus Pharynx • intersection for both digestive and respiratory systems • epiglottis blocks trachea during swallowing Esophagus • conducts bolus from pharynx to stomach via peristalsis Digestion in the Stomach Food storage • elastic wall with rugae to hold up to 2L of food Churning • contraction of stomach muscles • mixed about every 20 minutes; takes 2-6 hours to pass to the small intestine • Begins digestion of protein • bolus chyme • passes to small intestine through pyloric sphincter Digestion in the Stomach Secretion • controlled by the hormone, gastrin • mucous cells (secrete mucin & gastrin) • chief cells (release pepsinogen or zymogen) • parietal cells (secrete HCl & intrinsic factor) • HCl + pepsinogen pepsin (a protease – a protein digesting enzyme) Digestion in the Small Intestine • Cholecystokinin • Major organ of digestion and absorption • Pancreas, liver, gall bladder, and small intestine all contribute to what occurs here • Products released into duodenum – 1st part of the small intestine • Jejunum and ileum – Villi and microvilli Pancreatic Secretions Exocrine gland Secretes hydrolytic enzymes Produces bicarbonate solution to neutralize stomach acid Bile Production and Secretions by Liver Bile • Mixture of substances made in the liver that act as emulsifiers of fat • Stored and concentrated in the gall bladder Epithelial lining • Source of many digestive enzymes Absorption in the Small Intestine Villi • Fingerlike, epithelial projections • Microvilli – epithelial projections on each villus cell Hepatic portal vein • Blood vessel that leads to directly to the liver • Liver regulates distribution of nutrients and allows toxins to be removed Absorption in the Small Intestine Chylomicrons • Water soluble fat globules made of triglycerides coated in phospholipids, cholesterol and proteins Lacteal • Vessel at the end of each villus • Part of lymphatic system Absorption in the Large Intestine Cecum, colon, rectum Appendix is an extension of the cecum • lymphoid tissue Water reabsorption Feces moved along by peristalsis • Becomes increasingly solid Intestinal bacteria • Methane, hydrogen sulfide, vitamin K, biotin, folic acid Two sphincters (one voluntary and one involuntary) control the exiting of the feces Digestive System Digestive System Dental Adaptations •carnivores: pointed canines & incisors •herbivores: broad, ridged surfaces •omnivores: unspecialized •snakes: fangs Stomach and Intestinal Adaptations Length of tract and diet –herbivores and omnivores have a longer tract b/c cell walls are more difficult to digest Mutualistic Adaptations Symbiotic bacteria and protozoa • Produce cellulase • Horses: in large cecum • Rabbits and some rodents: in cecum and colon – Corophagy (”dung eating”) • Ruminants – Deer sheep cattle Regulation of Digestion 1. Gastrin 2. Cholecystokinin and secretin Glucose Homeostasis 1. High blood glucose – insulin 2. Low blood glucose – glucagon Regulation of Appetite and Consumption Ghrelin • Triggers feelings of hunger Insulin • Suppresses appetite Leptin • Suppresses appetite PYY • Appetite suppressant; counters ghrelin