mammalian nutrition ocr mammalian physiology and behaviour a2 revision

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  • Mammalian NutritionOCR Mammalian Physiology and BehaviourA2 Revision

  • Mammalian NutritionHeterotrophic nutritionMechanical and chemical digestionEnzymes sites of production and actionMicroscope analysis of stomach, ileum and colon.Structure and function of stomachStructure and function of pancreasIleum and colon in absorptionNervous and hormonal control of digestionSpecialisations of herbivores and carnivores.

  • Balanced DietMacronutrients fats, proteins and carbohydratesEssential amino acidsEssential fatty acids linolenic acid and linoleic acidMicronutrients vitamins and mineralsWaterFibre

    Heterotroph or Autotroph

  • Heterotrophic NutritionThere are four main stages involved in the processing of food in the gut of a mammal.

    Ingestion Food is taken into the mouth and mechanically broken down and crushed by the teeth.

    Digestion Large insoluble molecules are broken down into smaller soluble molecules by the action of digestive enzymes.Hydrolysis reactions.

    AbsorptionProducts of digestion are absorbed through the gut wall.

    EgestionElimination of undigested food, dead cells and bacteria as faeces.

  • The Digestive SystemThe digestive system is made up of the alimentary canal and digestive organs.


  • The digestive system

  • Enzymes and DigestionCarbohydrate digestionSaliva contains amylase which hydrolyses some starch to maltose.Pancreatic juice contains amylaseIn small intestineMaltase hydrolyse maltose to glucoseSucrase hydrolyse sucrose to glucose and fructoseLactase hydrolyse lactose to glucose and galactose

  • Enzymes and DigestionProtein DigestionEndopeptidases and exopeptidasesStomach pepsin (pepsinogen)Duodenum trypsin (trypsinogen), chymotrypsinCarboxypeptidaseIleumpeptidase

  • Enzymes and DigestionLipid digestionStomach lipaseDuodenum and ileum lipase (pancreatic juice)bile emulsification

  • Mouth and OesophagusMasticationSaliva mucus and amylaseBolusPeristalsis

  • StomachCardiac and Pyloric sphinctersDigestion in stomachGastric pitsOxyntic (parietal) cells hydrochloric acidChief cells pepsinogenGoblet cells alkaline mucusAbsorption in stomachSmall lipid soluble molecules e.g. aspirin, alcohol

  • MICROSCOPIC FEATURES OF BOVINE STOMACH. Epithelium, Muscularis mucosa, submucosa, muscularis externa and Serosa.This region of the stomach consists gastric glands which contain parietal and chief cells

  • Gastric Gland

  • Liver and pancreasLiverBile secreted into gall bladder

    Pancreas (exocrine function)Secrete pancreatic juiceTrypsinogen, chymotrypsinogen and enterokinase, carboxypeptidaseLipaseAmylaseHydrogencarbonate ions

  • Small Intestine - StructureDuodenumPancreatic duct and bile duct open hereIleumVillimicrovilli (brushborder)Large surface areaBlood capillariesLactealsCrypts of LieberkuhnGoblet and paneth cells

  • Structure of the Small Intestine

  • Small Intestine - digestionDesigned so that the products of digestion are concentrated next to the cells that will absorb them.

    Proteins (trypsin, chymotrypsin, carboxypeptidase)LipidsStarch (amylase)

    Plasma membrane of epithelial cells contain enzymes (exopeptidases and carbohydrases)

  • Small Intestine - AbsorptionFinal products of digestion are absorbed across the plasma membrane of epithelial cells in the villi. Blood capillaries Amino acids - active transportMonosaccharides - cotransport glucose with sodium ions LactealsFatty acids and glycerol are lipid soluble (micelles)Form chylomicron Water osmosis (wpg) Inorganic ions facilitated diffusion or active transport) Vitamins (a, d and e) fat soluble, diffusion

  • Large IntestineColon, caecum, appendix, rectumColumnar epithelium with microvilli and goblet cellsFunction to absorb inorganic ions and waterIndigestible material, mucus and cells pass into rectum and then out through anus.

  • structure of the colon

  • Control of DigestionCoordinated by both nervous and endocrine working togetherBuccal cavitySecretion of saliva autonomic response along vagus nerveConditioned reflexStomachSecretion of gastric juice conditioned reflexGastrin releasedPancreasPancreatic juiceCholecystokinin (causes gall bladder to contract)Small intestineSecretin

  • Digestion in CarnivoresConcentrated food sources

    AdaptationsSharp incisorsLong pointed caninesWell developed jaw musclesShort alimentary canalCarnassial teeth

  • Digestion in HerbivoresFood surrounded by cellulose cell walls

    AdaptationsDiastemaMolars with ridges and cuspsIncisors and horny padContinual teeth growthRumen, reticulum, omasum, abomasumChewing the cud

    Revision presentation for Mammalian Physiology and behaviour.Recap on main points of specification, and on what pupils should still be able to recall from KS3 and KS4Next slide to summarise the topic before going into detail on each one.Summary of the main OCR specification, each one will now be looked at in more detail.

    Balanced diet whats eaten and why?

    Heterotroph = need to eat food containing organic molecules

    Autotroph = obtain energy from sunlight, and use this energy to build organic molecules from inorganic ones (e.g. carbohydrates)

    Four main stages ingestion, digestion, absorption and egestion.1. SerosaOuter coat of fibrous connective tissue2. Muscularis mucosaOuter longitudinal muscleInner circular muscle3. Submucosa Connective tissue high proportion of collagen and elastin4. MucosaInner layers of glandular tissue, connective tissue and a thin layer of muscleGlands of epitheliumColumnar epithelium of stomachGoblet cells of small intestineGlands of connective tissue of mucosaOesophageal glandsGastric glandsGlands at the base of the villi (crypts of Lieberkuhn)Glands in submucosaBrunners glands of duodenumGlands outside gutSalivary glands, liver and pancreasLumenSite of digestion of foodMesenteryAttaches gut to dorsal body wallCarries blood, lymph vessels and nerve supply3 fundamental processes of the digestive systemsecretion enzymes, mucus and ions into the lumen, hormones into the bloodAbsorptionTransport water, ions and nutrients from lumen to the bloodMotilityContractions of smooth muscle in the wall that crush mix and propel contents

    Chemical digestionhydrolysis reactions

    Mechanical digestionMasticationChurning movements of the stomachAll digestive enzymes are hydrolasesProteases = proteinsCarbohydrases = carbohydratesLipases = lipids

    MouthStarch maltose (amylase)DuodenumStarch maltose (amylase)IleumMaltose glucose (maltase)Sucrose glucose and fructose (sucrase)Lactose glucose and galactose (lactase)

    Endopeptidase within protein moleculesExopeptidase end amino acids in the chain

    Proteins stomach, duodenum and ileum stomach Pepsin (endopeptidase) polypeptides into shorter lengthspepsinogen (hydrochloric acid)DuodenumTrypsin, chymotrypsin polypeptides into shorter lengthstrypsinogen and chymotrypsinogen (enterokinase)Carboxypeptidase (exopeptidase) into single amino acidIleumpeptidase (exopeptidase) single amino acidsStomach Lipase = triglycerides fatty acids and glycerol

    Duodenum and ileumLipase (pancreatic juice) = trigly. FA and GlyBile salts = emulsification increase surface area for lipase action

    Mastication increases surface area3 pairs salivary glands saliva dissolves soluble components of food receptors in taste budsMucus helps form bolus ease of swallowingAmylase begins starch breakdownPeristalsis pushes food towards the stomachSac with sphincters at each end to control entry and exit of food to and from stomach.Cardiac sphincter (entry), Pyloric sphincterContracts keeps food in stomachRelaxes allows chyme to pass into small intestine

    Digestion in stomachgastric juice mostly water, with HCLOxyntic (parietal) cells secrete HCL, deep invaginations, numerous mitochondriaPH1 or less kills bacteria found in foodChief cells secrete pepsinogenGoblet cells alkaline mucus, containing hydrogencarbonate ions (protects stomach wall)

    Absorption in stomachNone major nutrients absorbed through wallsSmall lipid soluble molecules pass easily, e.g. aspirin and alcoholStructure of the stomach wall.


    LiverSecretes bile, stored in gall bladder, along bile duct into duodenumBile contains salts derived from cholesterol, help emulsify fatsBile contains hydrogencarbonate ions neutralise the acidic mixture

    PancreasExocrine function secrete pancreatic juice into the pancreatic ductEnzymes in pancreatic juice trypsin, chymotrypsin, enterokinase, carboxypeptidase, lipase, amylase, hydrogencarbonate ions

    Structure of pancreas and histology (central concepts)- endocrine and exocrine functionsAbout 5 m long3 different regions duodenum, jejunum, ileumMucosa layer folded into Villi about 1mm tallEpithelium cells have microvilli forming brushborderGives a LSAContain network of capillaries and lymphatic capillariesAbsorption and transport of digested foodSmooth muscle in each villi contract and relax to make the villi sway.Crypts of Lieberkuhn, which are glands between the villiContain goblet cells and paneth cells (may destroy pathogens by phagocytosis)Undifferentiated cells divide rapidly to produce new cells to replace the old/damaged ones on surfaces of the villiCells work way to top of villi and shed into lumenDigestion in small intestineProteins peptides amino acids trypsin, chymotrypsin, carboxypeptidaseLipids FA and glycerolStarch maltose (amylase)Epithelial cells of villi (majority of digestion)Enzymes become absor


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