* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Animal Nutrition Nutritional Requirements • • • • Nutritional diet fulfills 3 needs: 1Fuel – energy for work. 2Raw materials – for biosynthesis. 3Essential nutrients – body can’t make. • Flow of energy in/out – budget. http://www.victoriapacking.com/images/nutrition/nutritionwheel.gif • ATP comes from oxidation of organic molecules. • Take in more calories than needed – rest for biosynthesis. • Liver stores excess as glycogen; above and beyond stores, stores as fat. http://www.cincinnatichildrens.org/NR/rdonlyres/32143992-B411-43F4-8B25-AB3A460A3478/0/LiverFINALweb.jpg • Regulation of blood glucose: glucose levels rise – pancreas secretes insulin – stimulates liver to store excess – decreases levels. • Glucose drops – pancreas secretes glucagon – breakdown of glycogen – increases levels. • Fewer calories than needed – fuel taken out of storage (liver 1st, muscles 2nd) • Most people have enough stores to last weeks. • Undernourishment – uses muscles for energy, eventually brain. • Even if survives, permanent damage occurs. http://devdata.worldbank.org/mdg/images/goal1%20fig7-disadvantage.gif • Overnourishment – excessive food intake – results in obesity. • Advantage during hunting/gathering days. • Human body has set weight – sets limits on weight loss/gain. http://faculty.washington.edu/kepeter/119/images/cholesterol_obesity_rates.jpg • Leptin (hormone) – produced by adipose cells – decreases hunger (when levels high). • Decrease causes increase in appetite. • Obesity beneficial in some species (travel long distances) • Animal’s diet must supply materials for biosynthesis. • Also supply essential nutrients (i.e. vitamin C) http://um-jmh.org/images/healthlibrary/fruit.gif • Missing nutrients – malnourished. • More common than undernourishment. • 20 amino acids needed to make proteins – eight are essential (needed from diet). • Protein deficiency most common malnourishment – causes mental retardation in children. • Animal proteins – complete (have all essential amino acids) • Plant proteins – incomplete. • Combination in plants fulfill all essentials. • Can’t be stored – need to be eaten daily. • Animals adapt to needs – penguins use muscle proteins for energy for molting. • Essential fatty acids needed as well. • Vitamins – organic molecules needed in small quantities. • 13 essential vitamins. • Minerals – inorganic nutrients needed in small amounts. • Excess of sodium (salt) dangerous – high blood pressure; excess iron – liver damage. Food Types • 3 categories of eating habits – 1herbivores (plant eaters), 2carnivores (meat eaters), 3omnivores (both) • Most animals opportunistic – will eat outside category if needed. • 4 ways to ingest food. http://www.qrg.northwestern.edu/projects/marssim/simhtml/pics-for-sim/cowface.jpg • 1Suspenion-feeders – sift small particles from water (baleen whales) • 2Deposit-feeders – eat through sediment; extract decaying organic material (earthworms) • 3Substrate-feeders – live on food source (maggots) • 4Fluid-feeders – suck fluids from host (mosquitoes, leeches) • Most animals bulk-feeders – eat large pieces of food. • Use fangs, teeth, claws, etc. to eat food. Overview of food processing • 1Ingestion - food taken into system. (Eating) • Polymers broken down into monomers so body can digest them. • 2Digestion - breaking food down into molecules small enough for body to absorb. http://iei.ul.ie/iei/images/graphics/Animals/Horses/Anatomy/digestion.jpg • Digestion reverses process that cell uses to link together monomers to form macromolecules. • Mechanical digestion - physical breaking down of food; chemical digestion - act of enzymes on broken down food. • 3Absorption - animal’s cells take up small molecules (i.e. amino acids, simple sugars) from digestive compartment. • 4Elimination - undigested material passes out of digestive compartment. http://www.slp-slimming.co.uk/images/digestion2.jpg • To avoid digesting own self, most digestion compartmentalized. • In cell - food vacuoles - hydrolytic enzymes break down food without digesting cell’s own cytoplasm (intracellular digestion). http://cache.eb.com/eb/image?id=8038 • Protists - take in food by phagocytosis or pinocytosis. • Food digested in food vacuole, than fuses with lysosomes to break food down further. • Vacuole fuses with anal pore that eliminates it from body. • Extracellular digestion - food broken down outside cell. • Cnidaria have digestive sacs with single openings (gastrovascular cavities). • Food taken in, eliminated through same opening. Fig. 41.11 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Organisms have complete digestive tracts (alimentary canals) with mouth, digestive tube, anus specialized to carry out digestion. • Food ingested through mouth, pharynx passes through esophagus to crop, gizzard, or stomach, depending on species. http://khoomei.com/pics/pharynx.jpg • Crop (or stomach) - food storage. • Gizzard - breaks down food. • Allows organisms to ingest additional food before earlier meals completely digested. Fig. 41.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Mammalian Digestive System • Consists of alimentary canal, various accessory glands that secrete digestive juices into canal through ducts. • Peristalsis, rhythmic waves of contraction by smooth muscles in walls of canal, push food along. http://www.biotech.um.edu.mt/home_pages/chris/GIT/GITimages/Peristalsis.jpg • Sphincters, muscular ring-like valves, regulate passage of material between specialized chambers of canal. • Accessory glands - salivary glands, pancreas, liver, gallbladder. Fig. 41.13 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Physical, chemical digestion of food begins in mouth. • Presence of food in oral cavity triggers nervous reflex - causes salivary glands to deliver saliva through ducts to oral cavity. • Salivation may occur in anticipation -learned associations between eating, time of day, cooking odors, etc. http://www.plwc.org/oncology_content/content_images/glands_credit_small.jpg • Saliva contains mucin - helps food slide down esophagus easier. • Chemical digestion of carbohydrates main source of chemical energy, begins in oral cavity - done by salivary amylase. • Food made into ball - bolus. http://hopkins-gi.nts.jhu.edu/images/shared/disease/database/shared_2973_SW-08.jpg • Pharynx (throat) - junction that opens to esophagus and trachea (windpipe). • Swallow - top of windpipe moves up - opening, glottis, blocked by cartilaginous flap, (epiglottis) helps to prevent us from choking. • Not swallowing - esophageal sphincter muscles contracted epiglottis up, glottis open, allowing airflow to lungs. • When food bolus reaches pharynx, larynx moves upward and epiglottis tips over glottis, closing off trachea. http://www.biology.eku.edu/RITCHISO/epiglottis.gif • Esophageal sphincter relaxes, bolus enters esophagus. • Larynx moves downward, trachea opened, peristalsis moves bolus down esophagus to stomach. Fig. 41.14 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Esophagus conducts food from pharynx down to stomach by peristalsis. • Stomach located in upper abdominal cavity, below diaphragm. • Stomach secretes digestive fluid (gastric juice), mixes secretion with food by churning action of smooth muscles in stomach wall. http://www.medicinenet.com/images/illustrations/stomach.jpg • Gastric juice secreted by epithelium lining numerous deep pits in stomach wall. • Contains hydrochloric acid (acidic enough to dissolve iron nails) and pepsin, enzyme that begins hydrolysis of proteins. http://courseweb.edteched.uottawa.ca/Medicine-histology/English/Gastrointestinal/Sm_Images/fig10stompits.gif • Pepsin secreted in inactive form, pepsinogen, by specialized chief cells in gastric pits. • Parietal cells, also in pits, secrete hydrochloric acid - converts pepsinogen to active pepsin only when both reach lumen of stomach, minimizing self-digestion. • Stomach’s 2nd line of defense against self-digestion is coating of mucus, secreted by epithelial cells, protects stomach lining. • Ulcers occur when stomach lining eaten through. http://www.medicinenet.com/images/illustrations/peptic_ulcer.jpg • Stomach churns food, produces chyme. • Sometimes chyme backs up into esophagus (heartburn). • Pyloric sphincter (at opening of small intestine) prevents material from moving into small intestine too quickly. http://trc.ucdavis.edu/biosci10v/bis10v/week10/chyme.gif • Small intestine longest section of alimentary canal. • Most absorption takes place here. • Duodenum - chyme from stomach mixes with digestive juices from pancreas, liver, gall bladder, gland cells of intestinal wall. • Liver performs wide variety of important functions in body, including production of bile. • Bile stored in gall bladder until ready to use. • Bile used to breakdown fats. • Each enzyme has specific role in digestion. • Starch, glycogen continue to be broken down in small intestine. • Pancreatic amylase aids in process. • Digestion of proteins in small intestine completes process begun by pepsin. • Done by several enzymes. http://www.medicinenet.com/images/illustrations/pancreas.jpg • Trypsin, chymotrypsin attack peptide bonds adjacent to specific amino acids, breaking larger polypeptides into shorter chains. • Dipeptidases, attached to intestinal lining, split smaller chains. • Carboxypeptidase, aminopeptidase split off 1 amino acid from carboxyl or amino end of peptide, respectively. • Nucleic acids digested in small intestines by an enzyme (nuclease). • All fat in meal reaches small intestine undigested. • Emulsification allows fat droplets to be coated by bile so they can pass through system. • Lipase - enzyme that breaks fats down. http://drbonesshow.com/images-e1/emulsification1.jpg • Most digestion occurs in duodenum. • Other 2 sections of small intestine, jejunum and ileum, function mainly in absorption of nutrients and water. • Nutrients in lumen must pass lining of digestive tract. http://www.uen.org/utahlink/tours/admin/tour/13125/13125smintestineapple.jpg • Surface area of small increased by microvilli - appendages off of villi. • Help increase amount of absorption. Fig. 41.19 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Transport of nutrients across epithelial cells can be passive. • Active mechanisms of digestion, including peristalsis, enzyme secretion, active transport, may require animal to expend amount of energy = 3% - 30% of chemical energy contained in meal. http://biology.kenyon.edu/HHMI/Biol113/intestine.gif • Hormones released by wall of stomach and duodenum ensure digestive secretions present only when needed. • Can be released when we see or smell food. http://www.mydr.com.au/content/images/categories/gastro/stomach_normal.gif • Certain substances in food stimulate stomach wall to release hormone gastrin into circulatory system. • As recirculates, gastrin stimulates further secretion of gastric juice. • If pH of stomach contents become too low, acid will inhibit release of gastrin. http://classes.kumc.edu/som/radanatomy/images/4904-002.jpg • Other hormones, (enterogastrones), are secreted by walls of duodenum. • Cholecystokinin (CCK), secreted in response to presence of amino acids or fatty acids, causes gallbladder to contract, release bile into small intestine; triggers release of pancreatic enzymes. http://www.le.ac.uk/pa/teach/va/imagesR/f1c.jpg • Large intestine (colon) connected to small intestine where sphincter controls movement of materials. • Small cecum (1st part of colon) of humans has appendix - makes minor contribution to body defense. http://basicjuice.blogs.com/basicjuice/images/appendix-thumb.jpg • Major function of colon - to recover water that has entered alimentary canal as solvent to digestive juices. • Digestive wastes, feces, become more solid as move along colon by peristalsis. http://www.medicinenet.com/images/ILLUSTRATIONS/colon_cancer.jpg • In large intestine - rich flora of mostly harmless bacteria. • Feces contain masses of bacteria and undigested materials including cellulose. • Terminal portion of colon - rectum, feces stored until eliminated. • 2 sphincters, 1 involuntary, 1 voluntary, control movement of feces out of rectum. http://www.owensboro.kctcs.edu/gcaplan/anat2/notes/Image475.gif Evolutionary Adaptations • Vertebrate digestive systems alike, have some differences based on diets. • Dentition (animal’s assortment of teeth) example of structural variation reflecting diet. • Nonmammalian vertebrates - less specialized dentition (exceptions) • Snakes - ability to swallow food whole. • Unhinge jaw to get entire organism in. • Large, expandable stomachs common in carnivores - may go for long time between meals; must eat as much as they can when they catch prey. http://members.tripod.com/mistergecko0/0d5912e0.jpg • Length of vertebrate digestive system correlated with diet. • More plants, longer tract seems to be to allow more time for digestion and reabsorption. • Most energy in plants comes from cell walls. • Cellulose cannot be digested by many organisms. • Symbiotic microbes can digest it. Location of symbiotic microbes in herbivores’ digestive tracts varies depending on species. http://www.nature.com/news/2001/010118/images/cellulose_200.jpg • Most elaborate adaptations for herbivorous diet have evolved in ruminants (deer, cattle, sheep). • When cow first chews and swallows mouthful of grass, boluses enter rumen and reticulum. http://www.redmills.ie/images/ruminants.jpg • Symbiotic bacteria, protists digest cellulose-rich meal, secreting fatty acids. Cow regurgitates, rechews cud, which further breaks down cellulose fibers. Cow reswallows cud, water removed. • Cud, with many microorganisms digested by cow’s enzymes.