mammalian nutrition ocr mammalian physiology and behaviour a2 revision

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”