Digestive system

 Activities during digestion of food : 1. Ingestion : - Taking food inside alimentary tract ( Oral Cavity 2. Propulsion - Movement of food in alimentary tract . 3. Digestion - Mechanical breakdown of food by mastication and chemical digestion by enzymatic action . 4. Absorption : - Transfer of digested form of food from alimentary canal blood and lymphatic capillaries . 5. Elimination - Excretion of undigested food as faeces by process of defecation . DIGESTIVE SYSTEM ORGANS Digestive system is made up of gastrointestinal tract or alimentary canal and accessory organs . Primary digestive organs are 1. Mouth 2. Pharynx 3. Esophagus 4. Stomach 5. Small intestine 6. Large Intestine - Accessory digestive organs are 1. Exocrine part of pancreas . 2. Liver 3. Gall Bladder 4. Salivary glands .

Wall of Gastrointestinal Tract : - In general , wall of GI tract is formed by four layers which are from inside out are - ( i ) Mucus layer ( GI mucosa / mucus membrane ) formed by epithelial tissue . ( ii ) SUB mucus Layers : - Consist of collagen fibers , elastic fiber and connective tissue . ( iii ) Muscular Layer : - Formed by circular and longitudinal smooth muscles . ( iv ) Serous or Fibrous Layer : - Outer most layer of GI Tract , Formed by Connective tissue . MOUTH ( Oral Cavity / Buccal Cavity ) It is formed by ( i ) Cheeks ( ii ) Lips ( iii ) Palate ( iv ) Teeth ( Mastication of food ) ( v ) Tongue : - Sense organs for taste or gustatory sensation are the taste buds . Sensory area of taste on tongue : Tip of tongue : - has salt and sweet receptor posterior part of tongue has bitter receptor Lateral part of tongue : - has sour receptor . ( vi ) Salivary gland - The saliva is secreted by three pair of major salivary glands these are ( a ) Parotid glands : - Largest gland Secretion from these glands are emptied into the oral cavity by stensen duct . ( b ) Sub maxillary glands ( Submandibular Glands ) : Saliva from these glands is emptied into the oral cavity by Wharton duct . ( c ) Sublingual Glands ( Smallest Glands ) : These glands is emptied into the oral cavity by duct of Rivinus or Bartholin duct . Saliva Volume 1000 to 1500 / Day PH 6.35 to 6.85 ( slightly acidic ) Composition of Saliva Solid 0.5 % 99.5 % Water Enzymes in Saliva : ( i ) Salivary Amylase ( Ptyalin ) = ( Amylolytic Enzyme ) It act on cooked or boiled starch and convert into dextrin and maltose . ( ii ) Maltase - Present in traces in human saliva and it converts maltose into glucose

Ser point > When food mixed with saliva , it is known as bolus Swallowing centre ( DEGLUTITION ) is situated in medulla oblongata . REFLEX REGLUTITION OF SALIVARY SECRETION Salivary reflexes are of two types - ( i ) Unconditioned Reflex : - it is inborn reflex that is present since birth . It does not need any previous experience . The reflex induce salivary secretion when any substances is placed in mouth . Conditioned Reflex : It is one that is Acquired by experience , and it need previous experience , The salivary secretion is induced by the sight smell , hearing and thought of food . Stomach > The Stomach is a Sac like muscular structure forming the widest and most Cardial distensible part of the digestive system . > It is connected above the lower end of oesophogus and below the duodenon . notch Esophagus Fundus > It act as a reservior of food and help in digestion of protein . > It is about 10 inch long and capacity of stomach is 1.5 to 2 litre . Duodenum Pyloric antrum > The empty stomach is J in shaped ( Vertical ) . > When it partially distended ( after taking food ) it becomes piriform in shape . ▸ Stomach lie obliquely in the upper and left quadrant of abdomen . ▸ Stomach has four parts - cardiac region fundus region , body or corpus ( largest ) and pyloric region ( pyloric Antrum and pyloric canal ) > The stomach has two orifics ( opening ) cardiac orifice and pyloric orifice Stomach has two curvanture = lesser curvature ( cancave ) and greater curvanture ( convex ) Stomach has two Sphincter : Cardiac Sphincter : - at lower end of oesophagus Pyloric Sphincter : at lower end of pyloric canal . Stomach has two peritoneal fold - lesser omentum and greater omentum . 65 | Page ALME Pylorus QIN Cardia Angolas nesure duit

MR areer point Arterial Supply : - Stomach is supplied by gastric artery which is a branch of celiac trunk that arises from abdominal aorta . Venous Drainage : - The vein of the stomach ( gastric vein ) drain deoxygenated blood into the portal vein . Glands of Stomach ( Gastric Gland ) Gastric glands are classified into three types , on the basis of their location in the stomach . ( A ) Fundic glands / main gastric glands / oxyntic glands : - Situated in body and fundus of stomach.the cell of fundic gland are : ( i ) Chief cells or pepsinogen cells : - they secrete pepsinog rennin , lipase ( ii ) Parietal cells or oxyntic cells : - they secrete HCL and intrinsic factor . ( iii ) Mucus neck cell : - they secrete mucin ( B ) Pyloric Glands - They are present in pylorus . Cells of pyloric glands are ( i ) G - Cells - They secrete gastrin hormone . It stimulate gastric glands for the secretion of gastric juice . It also stimulate pancrease for the secretion of pancreatic juice . ( ii ) Mucus Cell : - They secrete mucin . ( C ) Cardic gland - They are present in cardiac region . They mainly secret mucin . Gastric Juice It is the mixture of secretion from different gastric glands . Properties of gastric juice - Volume = 1200-1500ml / day PH = Highly Acidic ( 0.9-1.2 ) due to presence of HCL Composition : -99.5 % Water + 0.5 % Solid Enzymes in Gastric Juice : ( i ) Pepsinogen : It is converted into pepsin by HCL . It is a proteolytic enzyme . It convert protein into proteases , peptones and polypeptides . It also digest the milk protein ( casein ) . ( ii ) Gastric Lipase : - It is a weak lipolytic enzyme . ( iii ) Rennin : It is milk curdling enzyme , not present in human being . MED OFFE ( 1 bc ( (

Function of Stomach and Gastric Juice ( 1 ) Mechanical Function : ( a ) Storage Function : - Maximum capacity up to 2 litre . ( b ) Formation of chyme - Peristaltic movements of stomach mix the bolus with gastric juice and convert it into known as chyme . ( 2 ) Hemopoietic Function : - Intrinsic factor is require for the absorption of Vit - B12 which is a maturation factor for RBC . ( 3 ) Excretory Function : - Many substances like toxins , alkaloids and metals are excreted through gastric juice . ( 4 ) Digestive function : - Mainly protein digestion by pepsin . ( 5 ) Protective Function : - By HCL : - ( i ) Bacteriolytic action ( ii ) activate pepsinogen By Mucus :-( i ) Protect the stomach wall from irritation or mechanical injury ( ii ) Prevent the digestive action of pepsin on the wall of stomach . ( iii ) Protect the gastric mucosa from HCL of gastric juice .

MTR career ppoint Pancrease Pancrease is a dual organ having two function , namely endocrine function production of hormones and exocrine function is concerned with the secretion of digestive juice called pancreatic juice . Pancrease is made up to acini or acinar cell . pancreatic juice is put down by Pancreatic duct or wirsung duct . Wirsung duct joins common bile duct to form ampulla of vater , which open into the duodenum . Pancreatic Juice : Volume 500-800 ml / day PH- Highly Alkaline ( 8 to 8.3 ) due to bicarbonate Composition -99.5 % Water + 0.5 Solid Enzymes in pancreatic Juices : ( A ) Proteolytic Enzymes : - ( i ) Trysinogen : ➤ It convert into the active trypsin by entero kinase , secreted by duodenum . > This enzyme also has auto catalytic action . > It is a powerful proteolytic enzyme . It convert protein into proteoses and polypeptides . ▸ It also convert caseinogens in the milk into cascin . It also activate the other enzymes of pancreatie juice . ( ii ) chymotrypsinogen -It is activated into chymotrypsin by trypsin . The function is same just like trypsin ( iii ) Nucleases - Digest DNA and RNA ( iv ) Elastase : - Digest elastic fibers ( v ) Collagenase - Digest Collegen fibers . ( B ) Lipolytic Enzymes : ( i ) Pancreatic lipase - it is a powerful lipolytic enzyme . It digests triglycerides into manoglycerides and fatty acid . ( ii ) Phospholipase A and B These enzymes are activated by trypsin . They digest phospholipids . ( C ) Amylolytic Enzyme ( i ) Pancreatic Amylase : It convert starch into dextrin and maltose . Function of Pancreatic Juice ( 1 ) Digestive Function : - Pancreatic juice play an important role in digestion of protein and lipid , it also has mild digestive action on carbohydrates by the proteolytic , lipolytic and amylolytic enzymes .. ( 2 ) Neutralizing action of pancreatic juice - the alkaline pancreatic juice neutralizes the acidity of chyme in the intestine , Neutralizing action is an important function of pancreatic juice because it protects the intestine from the destructive action of acid in the chyme . 68 | Page SmR CAPELLY INTO TR weer point REGUL CEPHALIA Conditione Sight , s thought heanng at Unconditio Presence in mo GASTRIC Bolus im Gastric INTESTI Chyme Li and It pr ( S 69 | Pag

Liver > Liver is the largest gland of the body and wedge shaped . It is both secretary and excretory organ . It weight about 1.5kg in man . > It is located in the upper and right quadrant of the abdominal cavity . It produce bile which help in digestion . > The liver is divided into two lobes mainly right lobe ( Larger ) and Left Lobe ( Smaller ) Coronary Ligament Right Lobe Loft GMR

er point Blood Supply to Liver : Liver receives blood from two sources namely - blood to liver . ( 1 ) Hepatic Artery : - Arises directly from abdominal aorta and supply oxygenated ( ii ) Portal Vein - It brings deoxygenated blood from stomach , intestine spleen and The deoxygenated blood is carried from the liver by pancrease to liver through portal vein . it is known as enterohepatic circulation . Hepatic Vein : - The substances syn , thesized by hepatic colls , the waste products and carbon dioxide are discharged into sinusoids . The sinusoids drain them into the central vein of the lobule . The central vein from many lobules unite to form bigger vein which ultimately form hepatic vein ( right & left ) Which open into inferior vena cava . Nerve Supply - The liver receives its nerve supply from the hepatic plexus which contains both sympathetic and parasympathetic ( Vegal ) Fibers . Gall Bladder - Gall Bladder is a small sac like structure and reservoir of bile situated in the fossa on the inferior surface of right lobe of the liver . The gall bladder is 7 to 10cm long , 3cm broad and about 30 to 50 ml in capacity . Functions of gall bladder : 1. Storage of Bile - 30 to 50ml 2. Concentration of bile : - the mucosa of gall bladder rapidly reabsorbs water so the concentration of bile increase up to 5 to 10 time , Cholecysto kinin and secretion are responsible for the contraction of gall bladder . Properties , composition and function of bile : ➤ Volume = 800 to 1200 ml / day > PH = 8 to 8.6 , alkaline ( Bicarbonate is responsible for it ) ➤ Organic substances of bile - Bile pigment , Bile salt , cholesterol , Lecithein and fatty acid ( i ) Bile Pigment : - Bile pigment ( Bilirubin and Biliverdin ) are the excretory product of bile which are formed during breakdown of hemoglobin . These are responsible for the golden yellow color of bile . ( ii ) Bile Salt - The two major bile salt are present in bile . These are Na / K taurocholate and Na / K glycochoalate The digestive function of bile is mostly performed by bile salt Function of Bile Salt : ( a ) Emulsification of lipid - Bile salt reduces the surface tension of lipid and make them water soluble . this action of bile salt is called emulsification . ( b ) Absorptive Function : - Bile salt combine with lipid to form micelles . These are water soluble and easily absorb by intestine ( c ) Laxative Acton : - Bile Salt Increase Movement of GIT . 71 | Page Gme Carter point DOG HAST

MR Career point MR spreer point Parts o Small in ( 1 ) P ( 2 ) N ( 3 ) D ( d ) Prevention of Gall Stone Formation - Bile salt keep the cholesterol and lecithin in solution . In the absence of bile salt , cholesterol precipitate and form gall stone . ( e ) Secretion of bile : - Bile salt stimulate the liver ( cholerectic action ) and gall bladder ( cholagogue action ) for the secretion of bile . Function of Liver : 1. Digestive Function : - Mainly by Bile Salt . 2. Metabolic Function : - Maximum Metabolism of carbohydrates , protein and Fat . Maximum heat is produced in liver . 3. Storage Function : - Glycogen Amino acid , Iron , Folic acid and Vit A , D , E , K and Vit - B12 4. Synthetic Function : -Glucose ( by Gluconeogenesis ) , Plasma Protein and Clotting Factors , Steroids , heparin 5. Excretory Function : - It Excrete cholesterol , bile pigment , heavy metals toxins and bacteria . 6. Defensive and Detoxification : -Defensive by Kupffer Cells , Detoxification - Total destruction of toxic substance and convert them into non toxic materials . Small Intestine Small intestine and Surrounding Organs It extending between the pyloric sphincter of stomach and ileocecal valve , which open onto large intestine , it has less diameter than large intestine but it is longer than large intestine . Its length is about 6 meter . duode Maximum digestion and absorption of food product takes places in small intestine . farge testine mesentery rerum Intestinal Villi and glands of small intestine : Mucus membrane of small intestine is converted by minute projection called villi . Villi are lined by columnar cells , which are called enterocytes . Each enterocyte gives rise to hair- like projection called Microvilli . > Villi and Microvilli increase the surface area of mueus membrane . This facilitates the absorptive function of intestine .. > The first part of duodenum contain some mucus glands , which are called brunner glands , they secretes mucus and traces of enzymes . 72 | Page Ge FRO Succus Secretio Volume Compe Bicarb Enzyn ( 1 ) ( 11 ) Funct ( 1 ) of S = ( i 73

TR areer point . Parts of Small intestine Small intestine consist of three portions ( 1 ) Proximal part known as duodenum ( about 30cm ) ( 2 ) Middle part known as jejunum ( 150-200 cm ) ( 3 ) Distal part known as ileum ( 400-500 cm ) Succus Entericus : Secretion from small intestine is called succus entericus . Volume = 1800ml / day , pH = 8.3 ( Alkaline ) Composition = 99.5 ( water ) + 0.5 solids Bicarbonate concentration is high succes entericus Enzymes in succus entericus - ( i ) ( iii ) Proteolytic Enzymes : - eg . Peptidase it convert into amino acid . Intestinal Lipase - it convert triglycerides into fatty acid . Amylolylic Enzyme : - eg . Sucrase , maltase , lactase and dextrinase . They convert sucrose , maltose and lactose into glucose , fructose and gala dose . Function of Small intestine : ( 1 ) Digestive Function : - By Succus entericus ( ii ) Mechanical Function : - Movement of small intestine help in through mixing of chyme with digestive juices like- pancreatic juice , bile and succus entericus Sucess entericus pancreatic juice and bile . ( in ) Secretary function : - it secrete enzyme - enterokinase Hormones - Secretion , cholecystokinn . CMR C INT

MR areer point Large Intestine Ascending Colon Cecum It is about 1.5 meter in length It extends from ileocecal value up to Anus . Part of Large intestine ( i ) cecum ( 5-7 cm ) , ( ii ) Appendix ( 8cm ) , ( iii ) Ascending colon ( 12 20cm ) , ( iv ) Transverse colon ( 45cm ) , ( v ) Descending colon ( 22-30cm ) ( vi ) Sigmoid Colon Appendix Rectum ( 40 cm ) ( vii ) Rectum ( 12 cm ) ( viii ) Anal Canal ( 4cm ) Villi and Microvilli are absent in large intestine Secretion of Large Intestine : Large intestinal juice is watery fluid with PH of 8 It Contain 99.5 % water and 0.5 % of solids . Digestive enzymes are absent and concentration of bicarbonate is high in large intestine . Function of large Intestine - ( 1 ) Neutralization of Acids : Strong acid formed by bacterial action in large intestine are neutralized by alkaline nature of large intestinal juice . Absorptive function : - eg . Water , electrolyte alcohol , organic substances like glucose , drugs like anesthetic agents sedatives and ( 11 ) steroids ( ii ) Excretory function : Large intestine excretes heavy metals like mercury , lead , bismuth and arsenic . ( iv ) Formation of feces Transverse Colon , Small Bowel Anus TR PEEP P Descending Colon Sigmoid Colon DIS IL IF C F