Digestive System Part 2 PDF, Dr. Hana Abusaida, 2024

ORGANS ASSOCIATED WITH THE DIGESTIVE TRACT Lecture 1  Salivary glands  Pancreas Dr. Hana Abusaida Department of Histology Faculty of Medicine, Tripoli University 2024  Learning Objectives B...

ORGANS ASSOCIATED WITH THE DIGESTIVE TRACT Lecture 1  Salivary glands  Pancreas Dr. Hana Abusaida Department of Histology Faculty of Medicine, Tripoli University 2024  Learning Objectives By the end of these lectures, the student should be able to: Describe the histological structure of the three types of salivary glands, liver, pancreas and gall bladder. Applying some medical applications related with the subject. Dr.Hana Abusaida, Histology Department, Tripoli University  Organs Associated With the Digestive Tract Include: salivary glands, pancreas, liver, and gallbladder I- Salivary Glands Exocrine glands in the mouth. Salivary glands divided into two groups: 1. Major glands. Produce 90% of saliva. Large, capsulated Produce 0.75 to 1.50 L of saliva daily. Three types of large salivary glands: 1) Parotid 2) Submandibular gland. 3) Sublingual gland. * 3 types of secretions for salivary glands: Serous, seromucous, or mucous. Dr.Hana Abusaida, Histology Department, Tripoli University  Salivary Glands 2- Minor glands Small, non capsulated. Secrete 10% of saliva. Secretions mainly mucous except for Von Ebner glands. Present in mucosa and submucosa of oral cavity: a) Von Ebner glands: circumvallate and folliate papillae of the tongue. b) Glands of Blandin-Nuhn: on ventral tongue c) Palatine glands: in the palates. d) Weber glands: on sides of tongue. Dr.Hana Abusaida, Histology Department, Tripoli University  Functions of Salivary glands: Produce Saliva Saliva comprises: 98% water, plus electrolytes, mucus, glycoproteins, enzymes (such as amylase and lipase), antimicrobial agents such as IgA , peroxidase, lactoferrin and lysozyme. 1. Protection a) Lubricant, moisturizes the inside mouth to creates smoother speech. b) formation of salivary pellicle ( protein film for teeth protection). 2. Digestion a) Converts starch into maltose with salivary amylase. b) Helps chewing and swallowing. 3. Antimicrobial a) Lysozyme, peroxidase and lactoferrin fight against pathogenic microorganisms. 4. Tissue repair a) Saliva accelerates blood coagulation, so bleeding time of oral tissues shorter than other tissues. b) Clot less solid than normal. Dr.Hana Abusaida, Histology Department, Tripoli University  MEDICAL APPLICATION Dry mouth or xerostomia Insufficient secretions of saliva, leading to dry mouth or xerostomia, Caused by various factors such as:  Side effect of certain diseases and infections.  Dehydration.  The normal side effect of drugs. Sialorrhea or excessive saliva production, Associated with:  Inflammation of oral cavity (Sialadenitis).  Viral infection. Dr.Hana Abusaida, Histology Department, Tripoli University Structure of major Salivary glands: 1- A stroma (capsule of connective tissue). 2- A parenchyma consists of lobules, 3- Lobules separated by septa (C.T.). 4- Lobules composed of acini (secretory unit) + ducts (duct system). 5- Secretory unit composed of cells. 6- Ducts composed of cells connected to acini. Dr.Hana Abusaida, Histology Department, Tripoli University  Structure of major Salivary glands: Two major kinds of secretory unit cells 1- Serous cells Watery secretions. pyramidal in shape, with broad base and a narrow apical surface. Round nucleus at the basal third of the cell. Well-stained RER. Basophilic cytoplasm. Junctional complexes. Cells forming an acinus (rounded secretory unit) with a very small lumen. Apical zymogen granules. produce digestive enzymes and other proteins. Ex, Parotid gland & Pancrease. Dr.Hana Abusaida, Histology Department, Tripoli University  Two major kinds of secretory unit cells 2- Mucous cells Mucus-secreting cells. More columnar in shape. With flat, basal nuclei. Apical granules with hydrophilic mucins (cause poor cell staining). Wider lumen. Organized as cylindrical tubules rather than acini. Produce mucins, function for lubrication and protection. Dr.Hana Abusaida, Histology Department, Tripoli University Dr.Hana Abusaida, Histology Department, Tripoli University  Submandibular gland ( Mixed gland ) Dr.Hana Abusaida, Histology Department, Tripoli University  Myoepithelial cells Found inside the basal lamina of the secretory units. Well developed and branched Sometimes called basket cells). Spindle-shaped, lie parallel to the duct's length. Their contraction accelerates secretion of the product. Dr.Hana Abusaida, Histology Department, Tripoli University  Intralobular duct system of salivary glands Secretory acini and tubules empty into: 1- Intercalated ducts The smallest branches with small diameter. Lined by small cuboidal epithlial cells. Nucleus in the center. Some times secretory granules, few microvilli Myoepithelial cells are present 2- Striated ducts lined by columnar cells. Are cells specialized for ion transport pink striations in the basal half of the columnar cells. The striations produced by mitochondria in the folds of the cell membrane. Dr.Hana Abusaida, Histology Department, Tripoli University  Intralobular duct system 3- Excretory Duct Increasing size and thicker C.T. Unusual, combining various epithelial types: Initially lined with pseudostratified or stratified cuboidal epithelium. more distal parts lined with stratified columnar epithelium. Reflects many diverse functions: cells for ion reabsorption, cells for secretion of mucin and other proteins, enteroendocrine cells, and basal stem cells, few goblet cells. 4- The main Excretory duct Opens into the oral cavity. lined with nonkeratinized-stratified squamous epithelium. Dr.Hana Abusaida, Histology Department, Tripoli University Intralobular duct system of salivary glands Dr.Hana Abusaida, Histology Department, Tripoli University  Main excretory ducts of salivary glands Each of salivary gland has its own duct for releasing saliva into the mouth, these ducts are named: 1. Stensen's duct (parotid gland). 2. Wharton's duct (submandibular gland). 3. Bartholin's duct (sublingual gland). Dr.Hana Abusaida, Histology Department, Tripoli University  Types of major salivary glands 1- Parotid gland located in each cheek near the ear. branched acinar gland. the cells are purly serous with very small lumens. Produce 20 % of total saliva. Cells secerte amylase which responsible for the hydrolysis of ingested carbohydrates. and proline-rich proteins have antimicrobial properties. Dr.Hana Abusaida, Histology Department, Tripoli University  2- Submandibular gland (mixed gland) Branched tubuloacinar gland. The largest salivary glands, produce 65% of total saliva. Secretory portions containing both mucous and mainly serous cells. About 10% of mucous cells capped with serous cells called serous demilunes. Infoldings of the serous cells membrane increase the ion-transporting surface area. Secrete amylase, proline-rich proteins and lysozyme (bacteria hydrolysis). Dr.Hana Abusaida, Histology Department, Tripoli University 2- Submandibular gland (mixed gland) Dr.Hana Abusaida, Histology Department, Tripoli University  3- Sublingual gland (mixed gland) The smallest major glands Branched tubuloacinar gland. Formed of serous and mainly mucous cells. Produce only 5% of saliva. Serous cells demilunes on mucous tubules. The major product is mucus. Cells of serous demilunes secrete amylase and lysozyme. Dr.Hana Abusaida, Histology Department, Tripoli University  QUESTIONS: 1. Which one of the following is a major salivary gland? a) Labial b) Buccal c) Sublingual d) Lingual 2. Which of the following glands produce the most output of saliva? a) Parotid gland b) Sublingual gland c) Submandibular gland d) Buccal 3. Which one of the following is a minor salivary gland? a) Parotid b) Labial c) Sublingual d) Submandibular 4. Which of the following is a feature of mucous cells? a) Pyramidal in shape b) flattened basal nuclei c) Heavily basophilic cytoplasm d) All above 5. The sublingual gland produce about ____ of saliva? a) 65% b) 30% c) 50% d) 5% Dr.Hana Abusaida, Histology Department, Tripoli University  QUESTIONS: 6. Which one of the following lined by small Cuboidal cells? a) Striated Ducts b) Interlobular Ducts c) Main Duct d) Interclated Ducts 7. Amylase & lysozyme are produced by? a) Serous acini b) Mucous acini c) Mixed acini d) all of them 8. Which one of the following salivary glands is purely serous? a) Parotid gland b) Sublingual gland c) Submandibular gland 9. Which one of the following is the smallest salivary gland? a) Parotid gland b) Sublingual gland c) Submandibular gland 10. Which one of the following salivary glands is Produce only 20% of salivary output? a) Parotid gland b) Sublingual gland c) Submandibular gland Dr.Hana Abusaida, Histology Department, Tripoli University  The Pancreas Characters The main parts of the pancreas Is behind the stomach in the upper left 1. Head is C-shaped curve of abdomen. duodenum. It is spongy, pear shape. 2. Tail extends left to touch spleen. 25 cm long, 5 cm wide, and 1 to 2 cm 3. Body is the middle part. thick, weighs approximately 150 g 4. Main pancreatic duct runs the length of the pancreas, joins bile duct. Dr.Hana Abusaida, Histology Department, Tripoli University  The pancreas Is a mixed exocrine-endocrine gland that produces both digestive enzymes and hormones. (95%)of pancreas are exocrine tissue that produces pancreatic enzymes for digestion. The remaining tissue consists of endocrine cells called islets of Langerhans to produce hormones (insulin and glucagon) that regulate blood sugar, carbohydrate metabolism and regulate pancreatic secretions. Dr.Hana Abusaida, Histology Department, Tripoli University The pancreas: digestive enzymes These enzymes include: Proteases ( Trypsin and chymotrypsin), break down proteins, and help keep the intestine free of parasites. Amylase breaks down carbohydrates (starch) into sugars which are more easily absorbed by the body, (is also found in saliva). Lipase break down fat molecules so they can be easily absorbed. Enzymes are produced as inactivate molecules , or zymogens , to prevent the risk of self digestion within the pancreas. Enzymes go to duodenum, where activated. Dr.Hana Abusaida, Histology Department, Tripoli University Histological structure of pancreas Stroma Capsule of C.T. Septa separating pancreatic lobules. Parenchyma pancreatic lobules Pancreatic islets (I) Pancreatic acini (A) Pancreatic ducts (D) Capillary network (V). Dr.Hana Abusaida, Histology Department, Tripoli University  Pancreatic exocrine part: Pancreatic acini Pancreatic acini characters  Consists of serous cells  With very small lumen,  Without myoepithelial cells The serous acinar cells:  Are typical protein-secreting cells  With nucleus at the basal third of the cell.  well developed RER, Golgi  basophilic cytoplasm  presence of zymogen granule (contains proenzymes, inactive precursor of an enzyme). at apex of the cell whose number decrease after a meal. Dr.Hana Abusaida, Histology Department, Tripoli University  Pancreas: Duct system 1) Intercalated ducts Connected with the acini Lined by simple squamous epithelium. penetrate the lumens of the acini forming larger Centroacinar cell of simple columnar epithelium, which are small pale-staining cells. Cells of the intercalated ducts secrete a large volume of fluid, rich in HCO3 (bicarbonate ions), which alkalinizes and transports enzymes produced in the acini. Dr.Hana Abusaida, Histology Department, Tripoli University Pancreas: Duct system 2) Intralobular ducts, is similar to the intercalated duct of salivary glands, lined by simple cuboidal epithelium. 3) Interlobular ducts, lined by simple columnar epithelia 4) Main pancreatic duct (duct of Wirsung), branches to accessory pancreatic duct (duct of santorini), which joins the common bile duct before opening in the duodenum at the ampulla of Vater.  Secretions into the duodenum are controlled by a muscular valve (the sphincter of Oddi). It surrounds the ampulla of Vater. Dr.Hana Abusaida, Histology Department, Tripoli University  Compare of the pancreas & parotid salivary gland. Pancreas Parotid salivary gland Capsule & Septa of C.T. Present Present Lobules Present Present Secretory portion Serous acini Serous acini Intercalated ducts Simple squamous epith. Simple cuboidal epith. Acini Present Present Islets Present Absent Myoepithelial cells Absent Present Striated duct Absent Present Centroacinar cells Present Absent Dr.Hana Abusaida, Histology Department, Tripoli University  Pancreatic secretions control Pancreatic acini secretion is controlled by hormone cholecystokinin (CCK) produced by enteroendocrine cells of the intestinal mucosa when chyme enters the duodenum. CCK promotes the exocytosis of enzymes from the pancreatic acini. Intercalated duct secretion (Bi-carbonate secretion) is Stimulated by the hormone secretin produced by enteroendocrine cells of the intestinal mucosa. CCK is called pancreozymin. Innervation of Pancreas Parasympathetic (vagus) nerve stimulate both exocrine and endocrine secretions. Sympathetic nerve inhibit secretions. Dr.Hana Abusaida, Histology Department, Tripoli University  Pancreatic endocrine function (Production of Pancreatic Hormones) * Islets of Langerhans “islet cells” are the hormone secreting cells. Hormones secreted by 3 types of cells: Dr.Hana Abusaida, Histology Department, Tripoli University  Medical application Acute pancreatitis, a sudden inflammation of pancreas that lasts for a short time, happens when the digestive proenzymes are activated before they are released into the small intestine and begin digest pancreatic tissues, leading to very serious complications. Causes include: infection, gallstones, alcoholism, drugs, and trauma. Most people recover completely after getting the right treatment. Severe pancreatitis can harm other vital organs such as the heart, lungs, and kidneys. Symptoms: severe abdominal pain which radiate to the back and cause nausea, vomiting and diarrhea. Chronic pancreatitis, is long-lasting inflammation of the pancreas. can produce progressive fibrosis and loss of pancreatic function. Heavy alcohol drinking is a big cause. Dr.Hana Abusaida, Histology Department, Tripoli University  Thank you END OF LECTURE 1 ‫قف على ناصية الحلم وقاتل‬  ORGANS ASSOCIATED WITH THE DIGESTIVE TRACT Lecture 2 Liver Dr. Hana Abusaida Department of Histology Faculty of Medicine, Tripoli University, 2024  Liver  Liver is the second largest organ in the body.  Is the largest gland. Anatomical structure:  Found in the abdominal cavity beneath the A large right lobe. diaphragm, protected by ribs. Smaller left lobe.  Weighing about 1-1.5 kg Plus 2 smaller inferior lobes  ( 2% of an adult's body weight). ( Quadrate & Caudate ).  Over 500 functions. Dr.Hana Abusaida, Histology Department, Tripoli University Histological structure of liver Stroma The outer surface of the liver is covered by a capsule of connetive tissue called Glisson’s capsule, covered by a layer of simple squamous mesothelium from the peritoneum. Septae, are C.T. continuous with the capsule, separates the liver to lobules. Hilum, (or porta hepatis), thickening of C.T. septae: where the portal vein and the hepatic artery enter the liver. where the right and left hepatic ducts and lymphatics exit. Dr.Hana Abusaida, Histology Department, Tripoli University Histological structure of liver Parenchyma 1) Liver (hepatic) lobules ( the functional units of liver), about one million, composed of: Hepatocytes (liver cells) around a central vein. 2) Reticular fiber network, surrounds and supports the liver cells and the sinusoidal endothelial cells of the liver lobules. Dr.Hana Abusaida, Histology Department, Tripoli University  Histological structure of hepatic lobule Each lobule is: Polyhedral, hexagonal. Each lobule is composed of: 1) Hepatocytes (Liver cells) plates. 2) A central vein, empty into the inferior vena cava. 3) Liver sinusoids (leaky capillaries), between hepatic plates. 4) Portal triads, at each of the six corners of the lobule, composed of: 1. A branch of the portal vein, supply the liver with nutrient rich blood, low O2 from small intestines. 2. A branch of the hepatic artery, supply the liver with O2 rich blood from the heart. 3. A branch of the bile duct, drains the bile. Dr.Hana Abusaida, Histology Department, Tripoli University Liver blood flow Dr.Hana Abusaida, Histology Department, Tripoli University  Hepatocytes (liver cells) Large polygonal epithelial cells. Able to regenerate life span is 5 months. Arranged as plates radially around the central vein. Binucleated, 50% of them are polyploid, with 2-8 times the normal chromosome number. Eosinophilic due to numerous mitochondria. Basophilic cytoplasm due to rich with RER in cells near portal areas, for protein synthesis. Rich with SER in cells near central vein, help produce bile salts, responsible for detoxification of substances before their excretion. With microvilli, emerge into the perisinusoidal space.  Each cell contain up to 50 Golgi complexes involved in the formation of lysosomes and the secretion of proteins, glycoproteins, and lipoproteins into plasma. Dr.Hana Abusaida, Histology Department, Tripoli University  Is the spaces between hepatocytes plates.  Lined with fenestrated endothelial cells. Perisinusoidal space (the space of Disse), between a hepatocyte and a sinusoidal endothelial cells.  Blood with nutrient from portal vein (from viscera) + blood with oxygen from hepatic artery mix in the sinusoids, running between hepatocyte plates from the portal areas to the central vein.  Microvilli in the perisinusoidal space and fenestration of endothelium allowing proteins and other plasma components from the sinusoids to be absorbed by the Dr.Hana Abusaida, Histology Department, Tripoli University hepatocytes.  Functions of liver: Hepatocyte the most versatile cell in the body (has many functions): Production of bile. Protein synthesis & Storage as albumin, fibrinogen, and others. Synthesis of cholesterol and phospholipids. Detoxification of alcohol, drugs and toxins. Storage of vitamin A and other fat-soluble vitamins(in hepatic stellate cells). Phagocytose dead red blood cells (by Kupffer cells). Clearance of bilirubin from red blood cells. Storage of iron & glucose. Converting lipids and amino acids into glucose by process called gluconeogenesis Dr.Hana Abusaida, Histology Department, Tripoli University  Cells associated with sinusoids 1- Endothelial cells Lining the sinusoids. Fenestrated for transport of proteins and other plasma components. 2- Stellate macrophages, or Kupffer cells Phagocytic cells, cleaning the blood. Found between sinusoidal endothelial cells and mainly near the portal areas. Break down aged erythrocytes into globin and heme. Globin digested by peptidases to produce amino acids (which recycled or metabolised by liver cells) Heme groups are broken down to give iron (for re- use) and bilirubin. Remove bacteria may enter the portal blood. Act as antigen-presenting cells Dr.Hanain immunity. Abusaida, Histology Department, Tripoli University  Cells associated with sinusoids 3- Stellate fat storing cells (or Ito cells)  Lipocyte, fat storing cell.  Store vitamin A in small lipid droplets.  5-8% of the total number of liver cells.  Found in the perisinusoidal space.  Mesenchymal cells, produce extracellular matrix components of liver cells (becoming myofibroblasts after liver injury).  Produce cytokines that regulate Kupffer cell activity. Dr.Hana Abusaida, Histology Department, Tripoli University Cells associated with sinusoids  Stellate fat storing cells (or Ito cells) Dr.Hana Abusaida, Histology Department, Tripoli University Process of Erythrocyte and Haemoglobin Recycling Dr.Hana Abusaida, Histology Department, Tripoli University  MEDICAL APPLICATION Cirrhosis Damaged of liver cells and replaced by fibrosis (scar tissue), It is the third most common cause of death in adults between 45 and 65 ages. Mostly caused by alcoholism, hepatitis B and hepatitis C, obesity. Symptoms: weakness, loss of appetite, jundice. Complications: hemorrhage, liver cancer, coma due to liver failure, sepsis (blood poisoning), death. Dr.Hana Abusaida, Histology Department, Tripoli University Dr.Hana Abusaida, Histology Department, Tripoli University Thank you END OF LECTURE 2  ORGANS ASSOCIATED WITH THE DIGESTIVE TRACT Lecture 3 Bile & Gallbladder Dr. Hana Abusaida Department of Histology Faculty of Medicine, Tripoli University, 2024  Bile juice Definition Bile is a digestive juice secreted by the liver and stored in the gallbladder. Components: Water, bile acids, bile salts, bilirubin, cholesterol, fatty acids, bicarbonate ions, electrolytes, phospholipids. Functions  Assists in breakdown and emulsification of fats to allow absorption in dudenum.  Bile serves as a route for the excretion of bilirubin from the body, (Bilirubin is a pigmented breakdown product of heme), SER enzymes (glucuronosyl transferases) in hepatocytes changes bilirubin to bilirubin glucuronide, which is more soluble in water and facilitating its excretion by kidney.  Bile salts neutralize acids that come from the stomach. Dr.Hana Abusaida, Histology Department, Tripoli University  Bile duct system 1- Bile canaliculi Formed from apical surfaces of the hepatocytes. long spaces between two hepatocytes. With junctional complex, short microvilli. Is the site of exocrine secretion by hepatocytes (secrete bile). The bile flow direction is opposite of the blood, ie, from the center of the lobule to its periphery. Dr.Hana Abusaida, Histology Department, Tripoli University  Bile duct system 2- Bile canals of Hering Bile canaliculi empty into bile canal of hering. Composed of cuboidal epithelial cells called cholangiocytes. 3- Bile duct (ductule)  In the portal spaces.  Lined by cuboidal or columnar epithelium cholangiocytes.  Have a distinct C.T. sheath.  Enlarge, and form right and left hepatic ducts leaving the liver. Dr.Hana Abusaida, Histology Department, Tripoli University  Hepatic lobules Hepatocytes near the portal areas (rich with RER) can depends on aerobic metabolism and active in protein synthesis, The more central hepatocytes (rich with SER) are exposed to lower concentrations of nutrients and oxygen and are involved in detoxification and glycogen metabolism. The smaller apical surfaces of the hepatocytes form bile canaliculi and are involved in secretion of bile. These different categories of hepatocyte functions led to three ways of liver lobule structure: Dr.Hana Abusaida, Histology Department, Tripoli University  Hepatic lobules 1- Classic hepatic lobule Hexagonal; with a central vein, 6 portal triads, hepatocytes, sinusoids. blood flowing from the six portal triad areas to a central vein. Endocrine function (producing of plasma proteins). Dr.Hana Abusaida, Histology Department, Tripoli University  Hepatic lobules 2- Portal lobule Triangular; Centered on one portal triad, With central veins of three classic lobules, Exocrine function ( bile secretion) draining bile into portal area. Dr.Hana Abusaida, Histology Department, Tripoli University  Hepatic lobules 3- Acinus lobule The smallest functional unit of the liver, Irregular oval or diamond-shaped; divided into: 1) Zone 1 (periportal), encircles the portal area where the blood rich with oxygen & nutrients from hepatic arteries enters hepatocytes, show high metabolic activity 2) Zone 3 (pericentral), is located around central veins, where oxygen & nutrients is poor, it is site of glycolysis, lipid formation, and drug detoxification, zone III is the first hepatocytes to undergo fatty accumulation and liver necrosis. 1) Zone 2 (transition) located in between. Dr.Hana Abusaida, Histology Department, Tripoli University Liver Regeneration * Liver has a strong capacity for regeneration. Increases tissue mass after damage or partial resection (surgical removal of a liver portion) by two ways: 1) Compensatory hyperplasia; That maintains the original tissue mass but increasing number of cells by mitosis in the remaining healthy hepatocytes. 2) Stem cells; By the development of new cells from stem cells called oval cells present in the epithelium of hering duct, which can give rise to hepatocytes and cholangiocytes. Dr.Hana Abusaida, Histology Department, Tripoli University  MEDICAL APPLICATION Jaundice or (Hyperbilirubinemia) Yellowing of the skin and the whites of the eyes caused by an accumulation of bile pigment (bilirubin) in the blood; can be results of: gallstones, liver infection or anemia. The SER of hepatocytes detoxify bilirubin to a water-soluble nontoxic bilirubin. Neonatal hyperbilirubinemia Jaundice of newborns due to undeveloped SER in their hepatocytes. Treatment for these cases is exposure to blue light fluorescent, which transforms bilirubin into a water-soluble, to excreted by kidneys. Dr.Hana Abusaida, Histology Department, Tripoli University  Biliary Tract & Gallbladder Left & right hepatic ducts, leaving the liver. Is a hollow, saclike, pear-shaped organ. Cystic duct serving the gall bladder. attached to the lower surface of Common bile duct continues to the duodenum. the liver. Main pancreatic duct + common bile duct merges at Storing 30–50 mL of bile. hepatopancreatic ampulla (ampulla of Vater). Bile and pancreatic juices are secreted from the major duodenal papilla into the duodenal lumen. The common hepatic, cystic and common bile ducts are: Lined by simple columnar epithelium (cholongiocytes) Lamina propria and submucosa are thin, with mucous glands.in some areas of the cystic duct. Thin muscularis becomes thicker near the duodenum forms a sphincter (of oddi) that regulates bile & enzymes flow Dr.Hana Abusaida, Histology Department, Tripoli University  Histology of gallbladder Mucosa composed of : 1- Simple columnar epithelium (no goblet cells). 2- Lamina propria (LP), rich with elastic fibers & BV. 3- Has many folds when the gallbladder is empty. Muscularis externa (M)  Thin, with bundles of circular muscles oriented in several directions. Adventitia, in area connected with liver or serosa in suspended area. The lining epithelial:  Very thin basment membrane.  Microvilli, for water absorption.  Prominent mitochondria, for pumping process.  Intercellular spaces. Dr.Hana Abusaida, Histology Department, Tripoli University Histology of gallbladder Dr.Hana Abusaida, Histology Department, Tripoli University Histology of gallbladder Dr.Hana Abusaida, Histology Department, Tripoli University  Function of gallbladder:  Store bile, concentrate it by absorbing its water, and release it when necessary into the duodenum (by active sodium-transporting ).  To move stored bile into the duodenum, contraction of the gallbladder muscularis is induced by cholecystokinin (CCK) released from enteroendocrine cells of the small intestine. Dr.Hana Abusaida, Histology Department, Tripoli University  MEDICAL APPLICATION Cholelithiasis (Gallstones) The presence of gallstones in the gallbladder or bile ducts. i.e. concentration of cholesterol or bilirubin. Causes: Genetics, body weight, decrease motility of the gallbladder, diet. Removal of the gallbladder due to obstruction or chronic inflammation leads to direct flow of bile from liver to duodenum, with few problems in digestion. Dr.Hana Abusaida, Histology Department, Tripoli University  Summary Table Salivary Glands Pancreas Liver 1- Parotid Exocrine gland Bile * Serous secretion 100% * Serous secretion * Metabolic Waste 2- Sublingual * Digestive * Stored in Gall * 80% Mucous secretion enzymes Bladder * 5% Serous secretion Endocrine gland 3- Submandibular * Insulin * 60% Serous secretion * Glucagon * 30% Mucous secretion Dr.Hana Abusaida, Histology Department, Tripoli University Dr.Hana Abusaida, Histology Department, Tripoli University  Thank you END OF LECTURE 3 ‫قف على ناصية الحلم وقاتل‬