DIGESTIVE SYSTEM.pdf

DIGESTIVE SYSTEM INTRODUCTION The food substances are broken into smaller particles and converted into the absorbable materials by the process called digestion. A normal adult consumes about 1kg solid diet and about 1-2 liters of liquid diet in one day. All these are subject...

DIGESTIVE SYSTEM INTRODUCTION The food substances are broken into smaller particles and converted into the absorbable materials by the process called digestion. A normal adult consumes about 1kg solid diet and about 1-2 liters of liquid diet in one day. All these are subjected to digestive process before being absorbed into blood and distributed to the tissues of the body.  Functions of digestive system Ingestion of food substances Breaking the food substances into small particles Transport of the small particles to different areas of the digestive tract Secretion of necessary enzymes and other substances for digestion Digestion of food particles Absorption of nutrients Removal of waste products from the body  Physiology of digestive system can be divided into 4 divisions Secretion Digestion Movement Absorption  FUNCTIONAL ANATOMY GASTRO INTESTINAL SYSTEM Digestive system is made up of Gastro intestinal tract / alimentary canal Accessory organs GI tract Is a tubular structure extending from the mouth up to anus with a length of 30 feet Parts of GI Tract Accessory organs Mouth Teeth Pharynx Tongue Esophagus Salivary glands Stomach Exocrine part of Small intestine pancreas Large intestine Liver Gall bladder  Wall of GIT Formed by 4 layers Mucus layer Submucus layer Muscular layer Serous or fibrous layer Mucus layer Inner most layer of wall of digestive tract Known as gastrointestinal mucosa or mucus membrane It faces cavity of stomach Submucus layer Present from esophagus onwards. Absent in mouth & pharynx Blood vessels, lymphatic vessels & nerve plexus are present. Muscular layer Lips, cheeks and wall of pharynx have skeletal muscle fiber Esophagus has both skeletal & smooth muscle fibers Wall of stomach & intestine is formed by smooth muscle fibers Auerbach’s nerve plexes present in between smooth muscle fibers of intestine Smooth muscle fibers at anal canal constitute internal anal sphincter The external anal sphincter is formed by skeletal muscle fibers Serous or fibrous layer The outer most layer of the wall of GIT Fibrous layer covers pharynx & esophagus Serous layer covers stomach, small intestine, large intestine  Nerve supply to GIT Intrinsic nerve supply Extrinsic nerve supply Intrinsic nerve supply Present within GIT Two types Auerbach’s plexus – regulate the movements of GIT Meissner’s plexus - regulate secretory functions of GIT - Constriction of blood vessels of GIT Extrinsic nerve supply Sympathetic & parasympathetic divisions of autonomic nervous system innervate the GIT Sympathetic nerve fibers - Inhibit the movements of GIT -Decreases the secretions of GIT Parasympathetic nerve fibers – Increase the motility of GIT - Increases the secretions of GIT Mouth Functions Ingestion of food material, chewing and mixing the food with saliva Appreciation of taste through taste buds Transfer of food to esophagus by swallowing Saliva - Digestive juice , secreted by salivary glands Salivary glands Three pairs of major glands are Parotid glands Submaxillary glands/ submandibular glands Sublingual glands Saliva Volume – 1000-1500 ml/day, approximately 1ml/min Slightly acidic with pH 6.35-6.85 Functions 1. The mucin of saliva moistens, lubricate the bolus of food & facilitates the swallowing 2. Saliva by its solvent action dissolves the solid food, which in turn stimulates the taste buds 3. The enzyme lysozyme of saliva kills bacteria like Staphylococcus, Streptococcus & Brucella 4. Saliva has two digestive enzymes Salivary amylase Lingual lipase Salivary amylase – a carbohydrate splitting enzyme It acts on cooked / boiled starch to convert into maltose Though starch digestion starts in mouth, major part occurs in the stomach because food stays only for a short time in mouth. The optimum pH necessary for activation is 6 Salivary amylase cannot act on cellulose Lingual lipase – a fat splitting enzyme It converts triglycerides into fatty acids & 1,2 – diaglycerol  The enzyme maltase is present only traces in human saliva, it coverts maltose into glucose Regulation of salivary secretion Saliva is secreted continuously but the activity varies depending upon the activity. During mastication of food the secretion increases & decreases during sleep.  Stimulation of sympathetic nerve fibers causes less secretion of saliva which is thick & rich in mucus.  Stimulation of parasympathetic nerve fibers causes profuse & watery saliva.  Functions of stomach 1.Storage function The food is stored in the stomach for 3-4 hours and emptied into the intestine slowly. The maximum capacity of stomach is up to 1.5 liters. The slow emptying of stomach provides enough time for the intestine for proper digestion & absorption of food substances. 2.Mechanical function The peristaltic movements of stomach mix the bolus with gastric juice and covert it into the semisolid material known as chyme. 3.Digestive function-Mainly protein digestion 4. Protective function – HCL destroys many bacteria in food 5. Hemopoietic function Intrinsic factor of Castle present in gastric juice is necessary for absorption of vitamin B12, which is called as extrinsic factor – important maturation factor during erythropoiesis. 6. Excretory function – Toxins, alkaloids& metals are excreted through gastric juice.  Gastric juice Is the mixture of secretions from different glands of the stomach Properties of gastric juice Volume : 1200 – 1500 ml/day Highly acidic with pH of 0.9 – 1.2 (due to HCL) Composition A. Gastric enzymes B. Gastric mucus C. Intrinsic factors D. HCL A. Gastric enzymes Pepsin – major protein splitting enzyme. The precursor of pepsin is pepsinogen, which is secreted by chief cell. Gastric lipase – a weak lipid splitting Other gastric enzymes are gelatinase & urase. B. Gastric mucus A glycoprotein, which is like a flexible gel covering the gastric mucus membrane. C. Intrinsic factor Secreted by parietal cells, necessary for absorption of extrinsic factor. D. HCL - secreted by parietal cells  Functions of gastric juice 1. Digestive function Gastric juice mainly act on proteins a.Pepsin – a proteolytic enzyme The products of protein digestion are proteases, peptones and polypeptides Pepsin causes curdling & digestion of milk. b.Gastric lipase- a weak lipolytic enzyme Inactive at pH below 2.5, becomes active when pH is between 4 and 5 The products of lipid digestion are fatty acids and glycerol. c. Gelatinase – acts on gelatin. d. Urase – acts on urea and produces ammonia 2. Hemopoietic function The intrinsic factor necessary for the absorption of the extrinsic factor from gastrointestinal tract to blood. 3.Protective function Mucus responsible for protection of wall of stomach 4.Function of HCL Activates pepsinogen into pepsin Has bacteriolytic action Causes acidity of chyme. When the acid chyme leaves stomach enters intestine causes release of hormones – secretin and cholecytokinin. These hormones, in turn stimulate the release of other digestive juices into intestine. Provides acid medium for action of enzymes. Phases of gastric secretion Secretion of gastric juice occurs when the food is taken in the mouth. Neural & hormonal mechanisms are involved in gastric secretion, which occurs in 4 phases 1. Cephalic phase 2. Gastric phase 3. Intestinal phase 4. Inter digestive phase 1.Cephalic phase While taking food, the secretion of gastric juice starts even before food enters the stomach. The impulses are sent from head so this phase called cephalic phase. The gastric juice secreted in this phase is called appetite juice. This occurs as conditioned & unconditioned reflex. In both, pepsinogen & hydrochloric acid are secreted. Unconditioned reflex This causes gastric secretion when food is placed in the mouth. Afferent impulses arise from taste buds reaches to appetite centre in amygdala & hypothalamus. From here efferent impulses pass through vagus nerve to wall of the stomach Conditioned reflex In this, the sight, smell, hearing or thought of food causes gastric secretion. The impulses arising from cerebral cortex reach stomach via vagus. 2.Gastric phase When the food enters the stomach, secretion of gastric juice increases which is rich in pepsinogen & HCL. Mechanism involved are I. Local myenteric reflex – nervous mechanism II. Vagovagal reflex – nervous mechanism III. Gastrin – hormonal mechanism  Local myenteric reflex When food enters the stomach, the food particles stimulate the local nerve plexus in the wall of stomach. Vagovagal reflex Presence of food in stomach stimulates the sensory endings. Impulses pass to the brainstem via sensory fibers of vagus. The efferent impulses pass through the motor fibers. As both afferent & efferent impulses through vagus, this is called vagovagal reflex. Gastrin Is one of the gastrointestinal hormones. Gastrin is released when food enters stomach. 3.Intestinal phase When chyme enters the intestine , immediately gastrin is secreted by intestinal mucosa & transported to stomach by blood. Gastrin acts on glands of the stomach & causes the secretion of gastric juice. Later there is complete stoppage of secretion of gastric juice due to hormones like enterogastrone, gastric inhibitory peptide(GIP), vasoactive intestinal polypeptide(VIP) secreted in small intestine 4.Interdigestive phase Secretion of some amount of gastric juice in between meals due to hormones like gastrin.  Applied physiology 1.Gastritis Inflammation of gastric mucus membrane Types a. Acute gastritis – inflammation of superficial layers of mucus membrane and infiltration with leukocytes, mostly neutrophils. Causes NSAIDs – non steroidal anti inflammatory drugs. Alcohol Poisoning Increased peptic activity. b. Chronic gastritis – inflammation of deeper layers of mucus membrane and infiltration with more lymphocytes. Causes Helicobacter pylori infection. Excess of alcohol intake, long term use of NSAID. Auto immune disease. Symptoms Abdominal upset or pain felt as diffused burning sensation. Often referred to epigastric region. Nausea, vomiting, anorexia, indigestion, discomfort or feeling of fullness in the epigastric region. Belching – process to relieve swallowed air that is accumulated in stomach. 2.Gastric atrophy Is the condition in which muscles of stomach shrink and become weak. The glands of the stomach also shrink resulting in the deficiency of gastric juice. Cause – Chronic gastritis Symptoms Generally no noticeable symptom. May lead achlorhydria and pernicious anemia. Chances of gastric cancer. 3.Peptic ulcer An ulcer in the wall of stomach or duodenum caused by digestive action of gastric juice Peptic ulcer in stomach known as gastric ulcer and in duodenum known as duodenal ulcer Causes Increased peptic activity due to excessive secretion of pepsin in gastric juice Hyperacidity of gastric juice Constant stress Long term usage of NSAIDs Helicobacter pylori infection Features Severe burning pain at epigastric region In gastric ulcer- pain occurs while eating or drinking In duodenal ulcer – pain felt 1 or 2 hours after food intake or during night. Nausea, vomiting & heartburn Anorexia & loss of weight seen in gastric ulcer  SMALL INTESTINE Small intestine is the part of GI tract extending between the pyloric sphincter of stomach and ileocecal valve, which opens into large intestine Length is about 300 cm Consists of three portions Proximal part – duodenum Middle part – jejunum Distal part – ileum Intestinal villi Mucus membrane of small intestine is covered by minute projections called villi The villi are lined by columnar cells, which are called enterocytes Each enterocyte gives rise to many projections called microvilli Within each villus, there is a central channel called lacteal which opens into lymphatic vessels Intestinal glands Argentaffin cells secrete the intrinsic factor Goblet cells secrete mucus Paneth cells secrete enzymes Brunner’s gland secrete mucus & traces of enzymes Succus entericus Secretion from small intestine is called succus entericus Volume – 1800 ml/day pH – 8.3 Functions of succus entericus 1.Digestive function The enzymes of succus entericus act on partially digested food and convert them into final digestive products Proteolytic enzymes are peptidases such as aminopeptidase, dipeptidase and tripeptidase, they convert peptides into amino acids Amylolytic enzymes are lactase, sucrase, maltase, dextrinase and trehalase.  Lactase, sucrase and maltase convert the disaccharides into two molecules of monosaccharides Dextrinase converts dextrin, maltose and maltrose into glucose The enzyme trehalase converts trehalose into glucose ( Trehalose is the carbohydrate present in mushrooms and yeast ) Lipolytic enzyme intestinal lipase acts on triglycerides and converts them into fatty acids 2.Protective function The mucus present in the succus entericus protects the intestinal wall from acid chyme thus prevents the intestinal ulcer 3.Activator function The enterokinase present in intestinal juice activates trypsinogen into trypsin. Trypsin in turn activates other enzymes 4.Hemopoietic function The intrinsic factor of Castle, which present in the intestine, plays important role in erythropoiesis Functions of small intestine 1.Mechanical function Thorough mixing of chyme with digestive juices like succus entericus, pancreatic juice and bile 2.Secretory function Secretes succus entericus, enterokinase and the gastrointestinal hormones 3.Hormonal function The gastrointestinal hormones secreted by small intestine are secretin, enterogastrone and CCK-PZ (Cholecystokinin – pancreozymin) These hormones regulate the secretory activities of small intestine and pancreas These hormones controls the movements of gastrointestinal tract 4.Digestive function The digestion of various food substances completed in small intestine These functions are carried out by the enzymes of succus entericus 5.Activator function The enterokinase secreted by small intestine activates trypsinogen into trypsin. Trypsin, in turn activates other hormones 6.Hemopoietic function The intrinsic factor present in small intestine is necessary for absorption of vitamin B12 from gastrointestinal tract into blood 7.Hydrolytic function Succus entericus of small intestine provides water which helps in all hydrolytic processes of enzymatic reactions involved in digestion of various foodstuffs 8. Absorptive functions The digested products of foodstuffs, proteins, carbohydrates, fats and other nutritive substances like vitamins, minerals and water are absorbed mostly in small intestine From the lumen of intestine, these substances pass through lacteal of villi, cross the mucosa and enter the blood directly or through lymphatics Regulation of secretion of succus entericus Nervous regulation Stimulation of parasympathetic nerves causes vasodilatation and increases the secretion of succus entericus Stimulation of sympathetic nerves causes vasoconstriction and decreases the secretion of succus entericus Hormonal regulation When the chyme enters the small intestine, the intestinal mucosa secretes enterocrinin, secretin and cholecytokinin. These hormones promote the secretion of succus entericus by stimulating the intestinal glands  Applied physiology Malabsorption syndrome The conditions in which the failure of digestion and absorption occurs in small intestine Causes Crohn’s disease – inflammatory bowel disease Tropical sprue – malabsorption affecting residents/ visitors to tropical areas Stetorrhea- malabsorption of fat by deficiency of pancreatic lipase Celiac disease- caused by gluten, the protein present in wheat, oats, rye, barley and other grains, it damages mucosa and does atrophy of villi in small intestine  Large intestine It extends from ileocecal valve up to anus Also known as colon It consists of 7 parts 1. Cecum with appendix 2. Ascending colon 3. Transverse colon 4. Descending colon 5. Sigmoid colon 6. Rectum 7. Anal canal  Functions It absorbs water, electrolytes, glucose, alcohol and some drugs like anesthetic agents, sedatives and steroids The unwanted substances form feces, which is excreted out Excretion of heavy metals like mercury, lead, bismuth and arsenic through feces  Secretes mucin which does lubrication of the mucosa and bowel contents Alkaline nature of large intestinal juice neutralizes acids formed by bacterial action The bacterial flora of large intestine synthesizes folic acid, vitB12 and vitK  Applied physiology Constipation Failure of voiding of feces which produces discomfort is known as constipation Diarrhea Frequent and profuse discharge of loose or fluid contents from intestine is called diarrhea Appendicitis The inflammation of appendix Ulcerative colitis Is an inflammatory bowel disease, also known as colitis/ proctitis  PANCREAS Is a dual organ The endocrine function involves production of the hormones – Insulin & Glucogon. The exocrine function involves the secretion of digestive juice – pancreatic juice. Nerve supply Splanchnic nerve – sympathetic Vagus nerve - parasympathetic Properterties of pancreatic juice Volume – 500 – 800 ml/ day Alkaline with pH – 8 - 8.3 Enzymes of pancreatic juice Proteolytic enzymes Trypsin Chymotrypsin Carboxypeptidase A Carboxypeptidase B Nuclease Elastase Collagenase  Lipolytic enzymes Pancreatic lipase Cholesterol ester hydrolase Phospholipase A Phospholipase B Amylolytic enzyme Pancreatic enzyme  FUNCTIONS OF PANCREATIC JUICE 1.Digestion of proteins Trypsin Most powerful protein splitting enzyme It is an endopeptidase because it breaks the interior bonds of protein molecules Curdles the milk Accelerates blood clotting Activates other enzymes of pancreatic juice.  Chymotrypsin An endopeptidase Hydrolyses the proteins into polypeptides Digestion of milk – digests casein faster than trypsin. The combination of both enzymes causes more rapid digestion of milk Carboxypeptidases Breaks terminal bond of protein molecules hence called exopeptidases Act on polypeptides and other proteins to convert into amino acids. Nucleases - responsible for digestion of nucleic acids Elastase - digests elastic fibers Collagenase – digests collagen 2.Digestion of lipids Pancreatic lipase A powerful lipolytic enzyme It converts triglycerides into monoglycerides and fatty acids 3.Digestion of carbohydrates Pancreatic amylase Only amylolytic enzyme present in pancreatic juice Converts starch into maltose 4.Neutralizing action of pancreatic juice Pancreatic juice is highly alkaline, hence neutralizes acidity of chyme in intestine. This is an important function, because the acid chyme can destroy the intestinal mucus membrane. Thus the pancreatic juice protects the intestine from destructive action of acid chyme. Mechanism of pancreatic secretion Secretion of pancreatic enzymes Synthesized in ribosomes attached to the endoplasmic reticulum of acinar cells of pancreas The amino acids, raw materials to the synthesis of pancreatic enzymes derived from blood Synthesized enzymes packed into different zymogen granules by Golgi apparatus and stored in cytoplasm.  When stimulated, the acinar cells (functional unit of the exocrine pancreas)release the zymogen granules into the pancreatic duct From the granules the enzymes are liberated into intestine where these enzymes are activated Secretion of bicarbonate ions From cells of pancreatic ducts Regulation of pancreatic secretion Occurs in three stages Cephalic phase Gastric phase Intestinal phase Cephalic phase by vagus nerve Unconditioned reflex – when food is taken inside the mouth there is secretion of pancreatic juice Conditioned reflex – sight, smell and thought of the food causes secretion of pancreatic juice Gastric phase When food enters to the stomach, a gastrointestinal hormone, gastrin secreted into stomach. The gastrin is transported by blood, while reaching to pancreas stimulate pancreatic juice The pancreatic juice secreted during gastric phase contains more enzyme Intestinal phase When chyme from stomach enters the intestine more pancreatice juice is secreted due to release of two hormones namely, Secretin & Cholecytokinin a. Secretin Produced in S cells of mucus membrane in duodenum & jejunum Acts on cells of pancreatic ductules causing secretion of large amount of watery juice with high concentration of bicarbonate ion. b. Cholecystokinin Secreted by I cells in mucosa of duodenum and jejunum Stimulant for the release is chyme Action Causes secretion of pancreatic juice with more amount of enzymes Causes contraction of gall bladder Accelerates the activity of secretin to produce more alkaline juice Increases the secretion of enterokinase Inhibits the gastric motility Increases the motility of intestine  Applied physiology 1.Pancreatitis Inflammation of pancreatic acini Causes Acute pancreatitis is due to heavy alcohol/ gallstones Chronic pancreatitis is due to long time exposure to low alcohol/ chronic obstruction of biliary ducts. It may be hereditory / idiopathic Features Pain in upper abdomen Fever, nausea, vomiting Tender& swollen abdomen Weight loss occurs in chronic pancreatitis 2.Steatorrhea Is a condition in which fecal matter is foul smelling and frothy with large quantity of undigested fat Causes Lack of pancreatic lipase Liver disease affecting secretion of bile Celiac disease Cystic fibrosis – pancreatic duct is blocked by mucus  LIVER Is both secretory & excretory organ Largest gland in body Weighs about 1.5 kg Located in the upper right side of abdominal cavity immediately beneath diaphragm Liver is made up of liver cells called hepatocytes and a system of blood vessels Biliary system Also known as extrahepatic biliary apparatus Is formed by gall bladder and the ducts called extra hepatic bile ducts The bile secreted in the hepatic cells is poured into a thin canaliculus called bile canaliculus  Few canaliculi unite to form small ducts, which finally form right & left hepatic ducts The hepatic ducts join to form common hepatic duct, this joins cystic duct from gallbladder to form common bile duct The common bile duct unites with pancreatic duct forming the common hepatopancreatic duct or ampulla of Vater opens into the duodenum Blood supply Liver receives blood from two sources – Hepatic artery & Portal vein Hepatic artery Arises directly from aorta and supplies pure arterial blood to liver Portal vein Formed by superior mesenteric vein and splenic vein Portal vein brings deoxygenated blood from stomach, intestine, spleen and pancreas. It contains monosaccharides, amino acids & hormones of stomach, intestine and pancreas The flow of blood from intestine to liver through portal vein is known as enterohepatic circulation  Blood from hepatic artery & portal vein gets mixed up in hepatic sinusoids, which supplies oxygen & nutrients to hepatic cells Hepatic vein Substance produced by liver cells, waste products, carbon dioxide are discharged into sinusoids The sinusoids drain into hepatic vein through central veins. Right & left hepatic veins open into inferior vena cava  BILE Bile is golden yellow or greenish fluid. It is poured into digestive tract along with pancreatic juice through the common opening called ampulla of Vater After formation, the bile enters the gall bladder where it is stored While it is stored, large amount of water & electrolytes are absorbed & get concentrated Properties Volume – 800 – 1200 ml/ day Alkaline , pH – 8 – 8.6 Composition Water -97.6%, solids – 2.4%, contains both organic & inorganic substances Organic substances are bile salts, bile pigments, lecithin and fatty acids Inorganic substances are sodium, potassium, chloride and bicarbonate Functions of bile salts 1.Emulsification of fats The bile salts reduce the surface tension of lipids by detergent action, now lipids become water soluble. This action of bile salt on lipid substances is called emulsification of lipids, which occurs in the presence of lecithin of bile. Due to emulsification, the fat globules are broken into minute particles The emulsification is essential for the digestion of lipids by various enzymes of gastrointestinal tract 2.Absorption of fat When bile salts combine with lipids micelles are formed which is water soluble hence easily absorbed. This action of bile salts is called hydrotropic effect 3.Choliretic action Bile salts stimulate the secretion of bile from liver 4.Cholagogue action Cholagogue is an agent which increases the release of bile from gallbladder into intestine. Bile salts stimulates secretion of hormone CCK –PZ, which causes contraction of gallbladder and release of bile 5.Laxative action Bile salts stimulates peristaltic movements of intestine 6.Prevention of gallstone formation Bile salt prevent the formation of gallstone by keeping the cholesterol and lecithin in solution. In the absence of bile salts, cholesterol precipitates along with lecithin to form gallstone Bile pigments Bilirubin and biliverdin are two bile pigments These pigments are formed during the breakdown of hemoglobin, which is released from destroyed RBCs in the reticuloendothelial cells Normal bilirubin content in serum is 0.5 –1.5 mg%  Functions of bile 1.Digestive function – emulsification of fat 2.Absorptive function – absorption of fat 3.Excretory function Bile pigments are major excretory product The other substances excreted are  Heavy metals like copper and iron  Toxins  Bacteria like Typhoid  Cholesterol  Lecithin  Alkaline phosphatase 4.Laxative function 5.Antiseptic function Bile is a natural detergent, inhibits growth of certain bacteria in the lumen of intestine 6.Maintainance of pH in gastrointestinal tract As bile is highly alkaline, neutralizes acid chyme entering intestine from stomach 7.Lubrication function The mucin in bile acts as a lubricant for the chyme in intestine Regulation of bile secretion Bile is continuously secreted, secretion increases three hours after meals The secretion of bile from the liver and the release from the gallbladder are influenced by some chemical agents, which are categorized into choleretic, cholagogue and hydrocholeretic agents Choleretics Substances which increase the secretion of bile from liver They are Acetylcholine secreted by vagal nerve endings, secretin, CCK-PZ, acid chyme in intestine and bile salts  Cholagogues Which increase the release of bile from gallbladder into intestine They are calcium, fatty acids, amino acids and inorganic acids, they stimulate cholecytokinin, which in turn causes contraction of gallbladder and flow of bile into intestine Hydrocholeretics Which causes secretion of bile from liver with more amount of solids Ex. Hydrochloric acid FUNCTIONS OF LIVER 1.Metabolism function Metabolism of carbohydrates, proteins, lipids, vitamins and many hormones is carried out in liver 2.Storage function Substances like glycogen, amino acids, iron, folic acid & vitamin A,B12,D are stored in liver 3.Synthetic function Produce glucose by gluconeogenesis Synthesizes plasma proteins Synthesizes other proteins such as clotting factors, complement factors, steroids, hormone binding proteins, somatomedin &heparin 4.Secretion of bile 5.Excretory function Liver excretes cholesterol, bile pigments, heavy metals, toxins, bacteria and virus 6.Heat production Liver is the organ where maximum heat is produced due to metabolic actions 7.Hemopoietic function In fetus the blood cells are produced in liver It stores vitamin B12 & iron Liver produces thrombopoetin that promotes production of thrombocytes 8.Hemolytic function The senile red blood cells after the lifespan of 120 days are destroyed by reticulo endothelial cells of liver 9.Inactivation of hormones and drugs Liver catabolizes hormones such as growth hormone, parathormone, cartisol, insulin, glucagon and estrogen It inactivates fat soluble drugs, converts them into water soluble substances which are excreted through bile or urine 10.Defensive function The foreign bodies like bacteria or antigens are swallowed and digested by reticuloendothelial cells of liver by means of phagocytosis Reticuloendothelial cells activate immune system of the body 11.Detoxification function Liver cells involved in removal of toxic property of various harmful substances by two ways By total destruction of substances by means of metabolic degradation By converting toxic substances into non toxic materials by means of conjugation with glucuronic acid or sulphates  GALL BLADDER The bile secreted from liver is stored in gallbladder. The capacity of gallbladder is approximately 50 ml FUNCTIONS 1.Storage of bile Bile is continuously secreted from liver enters the gallbladder through cystic duct and stored, whenever required bile is released into intestine from gallbladder 2.Concentration of bile Mucosa of gallbladder rapidly reabsorbs water and electrolytes but bile salts, bile pigments, cholesterol and lecithin are not reabsorbed, so the concentration of these substances in bile is increased 5-10 times 3.Alteration of pH of bile While being stored in gallbladder, the pH of bile is reduced from 8-8.6 to 7-7.6 and becomes less alkaline 4.Secretion of mucin Gallbladder secretes mucin which acts as a lubricant in intestine for the chyme  Applied physiology Jaundice Yellowish pigmentation of skin & mucus membrane Due to increased bilirubin level in blood Normal serum bilirubin level – 0.5 to 1.5 mg% Types -3 Hemolytic jaundice/ pre hepatic Hepatocellular jaundice/ hepatic Obstructive jaundice/ post hepatic / extra hepatic Hemolytic jaundice Due to excessive destruction of RBCs the bilirubin level in the blood get increase, the liver cells cannot excrete that much bilirubin rapidly, thus accumulation of bilirubin occurs in blood resulting in jaundice The free / unconjugated bilirubin level is high in the blood Hepatocellular Due to damage of liver cells by toxic substances or by infection Here bilirubin is conjugated but can not be excreted, hence it returns to blood Obstructive jaundice Due to the obstruction of bile flow at any level of the biliary system The bile can not be poured into small intestine, bile salts & bile pigments enter the circulation Conjugated bilirubin level is more in blood Cirrhosis of liver The inflammation and damage of parenchyma of liver is known as cirrhosis of liver Causes Infection Retention of bile in liver due to obstruction of ducts of biliary system Enlargement of liver due to intoxication Infiltration of fat in hepatic cells Features Fever, nausea and vomiting Jaundice Muscular weakness and wasting Drowsiness Coma in advanced stages Hepatitis Inflammation of liver May be acute or chronic Causes Virus, bacteria Poisons Auto immune diseases Drug abuse Alcohol Therapeutic drugs Inheritance from mother during parturition Viral hepatitis is of 5 types- hepatitis A, B, C, D & E Features Fever Nausea Vomiting Diarrhoea Loss of appetite Headache Weakness Cholelithiasis Is the formation of gall stone Normally, cholesterol present in the bile combines with bile salts and lecithin, which make the cholesterol soluble in water Under some abnormal conditions, this water soluble cholesterol precipitates resulting in the formation of gallstone