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Digestive System. Dr. Manodeep Chakraborty. Digestion Digestive system Functions of Digestive system Ingestion Propulsion Digestion Absorption Secretion Elimination Regulation of water balance Regulation of electrolyte balance Excretion. Organs of digestive system
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Digestive System Dr. Manodeep Chakraborty
Digestion • Digestive system • Functions of Digestive system • Ingestion • Propulsion • Digestion • Absorption • Secretion • Elimination • Regulation of water balance • Regulation of electrolyte balance • Excretion
Organs of digestive system # Alimentary tract or GIT • Mouth • Pharynx • Oesophagus • Stomach • Small intestine • Large intestine • Rectum & anal canal # Accessary glands/organs • Salivary glands • Pancreas • Liver & biliary tract • Gall bladder
Alimentary tract (GIT) • Histology • Adventitia or serosa • Parietal • Visceral • Muscle layer • Submucosa • Mucosa lining • Mucous membrane • Lamina propria • Musculari’s mucosa
Nerve Supply • Parasympathetic • One pair of cranial, vagus, sacral nerves • Sympathetic • Spinal cord & lumbar region
Mouth • Vestibule • Palate • Uvula • Palatine tonsil
Tongue • three varieties of papillae • Vallate papillae • Fungiform papillae • Filiform • Blood supply : Lingual branch of external carotid artery • Nerve supply : Hypoglossal nerves (12) Lingual branch of mandibular nerves Facial & glossopharangeal nerves (7 & 9) Functions : Speech, Taste
Teeth • Incisions • Canine • Premolars • Molars • Structure of teeth • Bloods supply : Maxillary arteries & internal jugular vein • Nerve supply : Trigeminal nerve (5) Maxillar & mandibular nerves
Salivary glands • Types • Parotid • Submandibular • Sublingual • Structure of salivary glands • Composition of Saliva • water, minerals, salivary amylase, mucus, lysozyme, immunoglobulins, blood clotting factors • Secretion of saliva • Functions of saliva • Digestion, lubrication, cleaning, nonspecific defense, taste
Pharynx • Lining membrane (stratified squamous) • Middle layer : Fibrous tissue • Outer layer : Involuntary muscle
Cricopharyngeal • Oesophagus
Stomach • Organs associated with the stomach • Structure of stomach • Walls of stomach • Four layer as that of alimentary canal • Muscle layer • Congitudinal fibre • Circular fibre • Oblique fibre • Mucosa • Blood supply
Chyme • Gastric juice • Function • Secretion of gastric juice • Cephalic phase • Gastric phase • Intestinal phase
Functions of the stomach • Temporary storage • Chemical digestion • Mechanical digestion • Absorption • Defense • Preparation of iron for absorption • Production & secretion of intrinsic factor • Regulation of the passage of gastric contents into the duodenum • Secretion of the hormone gastrin
Small intestine • Duodenum • Jejunum • Ileum • Structure of small intestine • Peritoneum • Mucosa
Intestinal juice (15oo ml) • Composition • water, mucus, mineral salts, enzymes, hormones Enzymes : Dipeptidase, Tripeptidase, Oligopeptidase, Aminopeptidase, Carboxypeptidase Carbohydrate digesting enzyme : Sucrase, maltase, iosomaltase, lactase Lipid digesting enzymes : Intestinal lipase, Cholesterol esterase, lecithinase Hormones : Enterogastrin, secretin, cholecystokinin • Functions • Peristalsis • Secretion of intestinal juice • Completion of chemical digestion of carbohydrates • Protection against infection • Secretion of cholecystokinin • Absorption of nutrients • Chemical digestion in the small intestine
Pancreatic juice (1-2litres) • Composition • Enzymes Proteolytic enzymes • Trypsinogen • Chymotrypsinogen • Procarboxy peptidase • Collagenase • Elastase • Nuclease – DNAase RNAase
Functions of pancreatic juice • Digestion of protein (Trypsinogen & Chymotrypsinogen) • Digestion of carbohydrate (Amylase) • Digestion of fats (Lipase)
Bile (500 – 1000 ml) • Composition Bile acid : Cholic acid, Chenodeoxycholic acid Bile pigments : Bilirubin, Biliverdin, Urobilinogen, Stercobilin Cholesterol, Fatty acids, Phospholipids
Functions of bile • Absorption of nutrients • Diffusion • Active transport
Large intestine • Cecum • Colon • Ascending • Transverse • Descending • Sigmoid • Rectum • Anal canal
Functions of the colon • Absorption, mass movement, microbial activity, defaecation • Composition of faeces
Pancreas • Exocrine • Endocrine
Liver • Portal tissue
Functions • Carbohydrate metabolism • Fat metabolism • Protein metabolism • Production of heat • Secretion of bile • Storage of glucagon
Gall bladder • Functions of the gall bladder • Reservior for bile • Concentration of the bile by upto 10-15 fold • Release of stored bile
Absorption of digested food • Mechanism of absorptions are • Diffusion • Faciliated diffusion • Active transport • Vesicle mediated transport
Metabolism • Catabolism • Anabolism • Metabolic rate • Basal metabolic rate • Central metabolic pathways • Glycolysis • Citric acid cycle • Oxidative phosphorylation
Metabolism of carbohydrate • Metabolism of protein • Metabolism of fat
Diseases of mouth • Acute ginivitis • Rare acute condition with severe ulceration of gums occurs that affect the lips mouth, throat, palatine tonsil • Caused by Borrelia vincerti, Fusiform bacillus • Diseases of salivary glands • Mumps • Acute inflammatory condition of salivary glands especially the parotid • Caused by mumps virus
Calculus formation • Crystallization of mineral salts in saliva • Partially or completely block the ducts leading to swelling of the glands, a predisposition to infection and atrophy • Diseases of oesophagus • Oesophagitis • Swallowing of caustic material, acquire fungal infection by immuno compromised people, viral infections e.g. Herpes simplex • Sever injury, healing causes fibrosis, risk of development of oesophageal structure as the fibrous tissue shrinks
Reflux oesophagitis • Indigestion or heat burn due to regurgitation of acidic gastric juice into oesophagus • Irritation, Inflammation, Pain, Ulceration, Haemorrhage • Reflux of gastric content is associated with increase in intraabdominal pressure e.g. in pregnancy, constipation & obesity • High acidic content of gastric juice • Low levels of secretion of hormone gastrin
Achalasia • Peristalsis of the lower oesophagus is impaired • Lower oesophageal sphincter fails to relax during swallowing causing dysphagia • Regurgitationn of gastric content and aspiration pneumonia
Gastritis • Either an excess of acid in the stomach or insufficient mucus to protect the surface epithlium • Causes for gastrtis • Prolonged use of NSAIDS • Excessive alcohol consumption • Food poisoning • Ingestion of corrosive poisons, acid & alkalies • Regurgitation of the bile into the stomach • Helicobacter pylori
Peptic ulcer disease • It is a circumscribed ulceration of mucus membrane penetrating through the muscularis mucosa & occurring in areas bathed by acid and pepsin in the stomach & duodenum. • Gastric ulcer • Duodenal ulcer • Complications : Haemorrhage, Perforation, Gastric outflow obstruction, Development of malignant tumour