11Lecture 28, 29 November 2005Feeding and Digestion (Chapter 4)MetabolismVertebrate PhysiologyECOL 437 (aka MCB 437, VetSci 437)University of ArizonaFall 2005instr: Kevin Boninet.a.: Kristen Potter21. Feeding and Digestion2. MetabolismText:Chapter 4(skim 5-7, read 8+9)-Exams (end of class from Kristen)-Seminar Write-Ups (29 Nov) (talk on 02 Dec; -%15)-Term Paper (01 Dec)-Oral Presentations last week of class (PPT files to KEB one day before)(most on 07 Dec, four on 06 Dec in lecture)23437 2005 Ex300.511.522.53034384246505458626670747882869094score (out of 100)# students19n33.5min92max68.5median67.13mean4Pough et al. 200435Pough et al. 20046Pough et al. 200447Feeding, Digestion, Absorption, NUTRTITIONCHONCaPProteinsLipidsCarbohydratesHill et al. 2004, Fig 4-18ProteinsDi, tri, polypeptides20-22 standard amino acids16% N by weightEssential amino acidsDeamination59Hill et al. 200410Hill et al. 2004, Fig 4-2b611LipidsFatty Acids (FAs)Triacylglycerides (glycerol + 3 FAs)Energy StorageEssential FAs12Hill et al. 2004713+=Hill et al. 2004, Fig 4-314CarbohydratesMono, di, polysaccharidesChitinCellulose(2 most abundant organic compounds on earth)Glycogenstore Glu for CNS in vertebratesLactose815CarbohydratesHill et al. 2004, Fig 4-416Vitamins and MineralsVit A (retinol, retinal; rhodopsin)Water Soluble:B Vitamins, Vitamin CLipid Soluble:Vits A, D, E, KMetalloproteins (e.g., hemoglobin)917VitaminsHill et al. 2004, Fig 4-518VitaminsHill et al. 20041019Nutritional Requirements…(Essential?) 20-Food quality-Body Size-Temperature (ectotherms)Digestive SystemsTransit time (time to digest), cost, and anatomy variable:(Eckert 15-11) (Eckert 15-12)1121(Eckert 15-16)22Generalized Digestive System(Eckert15-13)123412 (incl. stomach)34Salivary glands (mucin) to lubricateTongue for chemoreception1223Foregut-Conducting, Storage, Digestion-Esophagus and StomachCrop in some for storage/regurgitationStomach- begins digestion (e.g., pepsin)- food storage- mechanical mixing (muscular walls)- Monogastric (1 chamber, carnivores and omnivores)- Digastric (> 1 chamber)e.g., Some birds use to grind with pebbles and sand24ForegutMonogastric Stomach- strong muscular sac/tube- sphincters at both ends- mucus from goblet cells of gastric pit- HCl from parietal cellsof gastric gland- pepsinogen from chiefcells of gastric gland(Eckert 15-17)1122331325ForegutDigastric Stomach-herbivores-anaerobic fermentationby symbiotic bacteriaand protozoans(Eckert 15-18)-regurgitation1234-digestiveenzymes( Carbohydrates -> sugars and gases )sugars, amino acids, short FAs into bloodDomestic cattle,1L/min gas!(methane and CO2)26Midgut-Chemical digestion and Absorption (~ small intestine)-from stomach through pyloric sphincter into duodenum-alkaline 1-Duodenum (mucus + secretions from liver, pancreas)Bile duct from liver-Bile breaks up fats and neutralizes acidsPancreatic Juice-proteases, lipases, carbohydrases, antacid2-Jejunum (digestion and absorption)3-Ileum (mostly absorption)-Internal symbionts help digest, provide nutrition, vitamins-Gas exchange in some air-breathing fishes(Eckert 15-31)1427MidgutAnatomy:-longitudinal smooth muscle-circular smooth muscle-epithelium-submucosa(connective tissue)-mucosa(mucous membrane)(Eckert 15-19)Epithelial cells sloughed rapidly(2x1010cells/day),lining replaced every few days28Midgut-Intestinal Epithelium, SURFACE AREA-aids absorption of digested nutrients-epithelium arrangement:-circular folds-villi with blood vessels-central lacteal (lymph system)-microvilli (2x105per mm2)(Eckert 15-19)(Eckert 15-20)1529Midgut-Intestinal Epithelium, SURFACE AREA-intestinal chyme-surface of microvilli:-covered with glycocalyx-mucus and water mixed in-absorption through epithelialcells-microvilli with actin, interacts with myosin for movement(Eckert 15-20)30(Eckert 15-20)Villi with microvilli(brush border)1631Hindgut-Water and Ion absorption; Defecation-reabsorb water and ions at end of small intestine (ilieum) and from large intestine/colon-feces into cloaca/rectum for excretion-cloaca can also be site of urine modification (e.g., birds)-bacterial digestion in hindgut fermenters(especially in cecum)-coprophagy/cecotrophy(e.g., rabbits)32Hindgut-Water and Ion absorption; defecationhorserabbithindgut fermenters(Eckert 15-22)1733Gut PlasticityAlter gut size, activity (reversible)-Sustained increased metabolism can increase birdgut length by 1/5-Mammals increase GI tract mass 3-4x post-hibernation34Gut PlasticityAlter gut size, activity (reversible)-Some infrequently-feeding snakes: - intestine 2x larger within 2 days- microvilli length and area up 400%- glucose transport rate up as much as 22x- other transporters also up-regulated (e.g., a.a. absorption)(Eckert 15-23)1835MotilityContraction of gut and movement of contents:1. Propulsion, expulsion2. Mixing and grinding (enzymes, mechanical digestion)3. Stirring so brush border/epithelial lining gets nutrientsPeristalsis-longitudinal muscle-circular muscle(Eckert 15-24)Move food along...36(Eckert 15-25)Regurgitation, Vomiting?KneadingMovement1937MotilityControl of smooth muscle contractionIntrinsic-pacemaker activity (basic electric rhythm = BER)-stretch-chemical signals from chymeExtrinsic-GI peptide hormones-autonomic NS(Myenteric and submucosal plexus)Sympathetic and Parasympathetic innervation38Intrinsic-pacemaker activity (basic electric rhythm = BER)-cations and Ca2+(Eckert 15-26)2039ExtrinsicMyenteric and submucosal plexus(Eckert 15-27)Parasympathetic (~ACh)-increased motility-increased secretionSympathetic (~norepi)-decreased motility-decreased secretionOther neurotransmitters also40(Eckert15-31)(proenzymes)Los Secretions2141Los SecretionsDigestive Enzymes hydrolyze larger molecules:e.g., Sugars (glycosidic bonds) into monosaccharidesProteases (protein peptide bonds -> amino acids)-endopeptidases-exopeptidases~specialized (e.g., Trypsin cleaves arg. or lys.)Pepsin(from pepsinogen in acid, ~pH=2 envir.)42Los SecretionsCarbohydrasesa. Amylases-salivary glands, pancreas, stomachb. Glycosidases-absorptive cells, glycocalyx, disaccharides (midgut)Cellulase-symbiotic microorgansims(Eckert 15-33)2243Los SecretionsLipases1. Break up insoluble fats using bile salts etc.2. Formation of micelles (small lipid spheres)3. Lipases cleave lipids into fatty acids plusmono- or diglycerides44Los Secretions (triggers)SalivaryWater, electrolytes, mucin, amylase, antimicrobialsDecreased salivation in response to sympathetic NSGastricHCl (hydrochloric acid) from parietal