Mammalian Nutrition
OCR Mammalian Physiology and Behaviour
A2 Revision
Mammalian Nutrition
Heterotrophic 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 Diet
o Macronutrients – fats, proteins and carbohydrateso Essential amino acidso Essential fatty acids – linolenic acid and linoleic acido Micronutrients – vitamins and mineralso Watero Fibre
Heterotroph or Autotroph
Heterotrophic Nutrition
There are four main stages involved in the processing of food in the gut of a mammal.
Ingestion o Food is taken into the mouth and mechanically broken
down and crushed by the teeth.
Digestion o Large insoluble molecules are broken down into smaller
soluble molecules by the action of digestive enzymes.o Hydrolysis reactions.
Absorptiono Products of digestion are absorbed through the gut wall.
Egestiono Elimination of undigested food, dead cells and bacteria
as faeces.
The Digestive System
The digestive system is made up of the alimentary canal and digestive organs.
Serosa
submucosa
Muscularis mucosa
Longitudinal muscles
Circular muscles
mesentery
lumen
Glands outside the gut
Glands in submucosa
Glands of connective tissue of mucosa
Glands of epithelium
mucosa
The digestive system
Enzymes and DigestionCarbohydrate digestion
Saliva contains amylase which hydrolyses some starch to maltose.
Pancreatic juice contains amylase
In small intestineo Maltase hydrolyse maltose to glucoseo Sucrase hydrolyse sucrose to glucose and fructoseo Lactase hydrolyse lactose to glucose and galactose
Enzymes and DigestionProtein Digestion
Endopeptidases and exopeptidasesStomach pepsin (pepsinogen)Duodenum trypsin (trypsinogen), chymotrypsin
CarboxypeptidaseIleum peptidase
Enzymes and DigestionLipid digestion
Stomach lipaseDuodenum and ileum lipase (pancreatic juice)
bile emulsification
Mouth and Oesophagus
MasticationSaliva – mucus and amylaseBolusPeristalsis
StomachCardiac and Pyloric sphinctersDigestion in stomacho Gastric pits
• Oxyntic (parietal) cells – hydrochloric acid• Chief cells – pepsinogen• Goblet cells – alkaline mucus
Absorption in stomacho Small 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 pancreas
Livero Bile secreted into gall bladder
Pancreas (exocrine function)o Secrete pancreatic juice
• Trypsinogen, chymotrypsinogen and enterokinase, carboxypeptidase
• Lipase• Amylase• Hydrogencarbonate ions
Small Intestine - Structure
Duodenumo Pancreatic duct and bile duct open here
Ileumo Villi
• microvilli (brushborder)• Large surface area• Blood capillaries• Lacteals
o Crypts of Lieberkuhn• Goblet and paneth cells
Structure of the Small Intestine
Small Intestine - digestion
Designed so that the products of digestion are concentrated next to the cells that will absorb them.
Proteins (trypsin, chymotrypsin, carboxypeptidase)
Lipids
Starch (amylase)
Plasma membrane of epithelial cells contain enzymes (exopeptidases and carbohydrases)
Small Intestine - Absorption
Final products of digestion are absorbed across the plasma membrane of epithelial cells in the villi.
Blood capillaries o Amino acids - active transporto Monosaccharides - cotransport – glucose with
sodium ions
Lactealso Fatty acids and glycerol are lipid soluble (micelles)o Form chylomicron
Water – osmosis (wpg)
Inorganic ions – facilitated diffusion or active transport)
Vitamins (a, d and e) – fat soluble, diffusion
Large Intestine
Colon, caecum, appendix, rectum
Columnar epithelium with microvilli and goblet cells
Function to absorb inorganic ions and water
Indigestible material, mucus and cells pass into rectum and then out through anus.
structure of the colon
Control of Digestion
Coordinated by both nervous and endocrine working together
Buccal cavityo Secretion of saliva – autonomic response along
vagus nerveo Conditioned reflex
Stomacho Secretion of gastric juice – conditioned reflexo Gastrin released
Pancreaso Pancreatic juiceo Cholecystokinin (causes gall bladder to contract)
Small intestineo Secretin
Digestion in Carnivores
Concentrated food sources
Adaptationso Sharp incisorso Long pointed canineso Well developed jaw muscleso Short alimentary canalo Carnassial teeth
Digestion in Herbivores
Food surrounded by cellulose cell walls
Adaptationso Diastemao Molars with ridges and cuspso Incisors and horny pado Continual teeth growtho Rumen, reticulum, omasum, abomasumo “Chewing the cud”
