GIT Glands Lec (1) PDF

12/9/24 GIT Associated Glands 1 Anatomy Of The Pancreas READ ONLY Retroperitoneal gland that is about 12–15 cm long and 2.5 cm thick. Lies posterior to the greater curvature of the stomach....

12/9/24 GIT Associated Glands 1 Anatomy Of The Pancreas READ ONLY Retroperitoneal gland that is about 12–15 cm long and 2.5 cm thick. Lies posterior to the greater curvature of the stomach. Pancreas consists of a head, a body, and a tail. Connected to the duodenum of the small intestine by two ducts. The head is the expanded portion of the organ near the curve of the duodenum, a central body and the tapering tail. 2 1  12/9/24 Histology Of The Pancreas Made up of small clusters of glandular epithelial cells. 99% of the clusters, called acini constitute the exocrine portion of the organ. Cells within acini secrete a mixture of fluid and digestive enzymes. 1% of the clusters, called pancreatic islets (islets of langerhans) form the endocrine portion of the pancreas. These cells secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide. 3 READ ONLY Liver And Gallbladder Liver is the heaviest gland of the body; 1.4 kg in an average adult. Ø Second only to the skin in size. Ø Liver is inferior to the diaphragm and occupies most of the right hypochondriac and part of the epigastric regions of the abdominopelvic cavity. The gallbladder is a pear-shaped sac located in a depression of the posterior surface of the liver. Ø It is 7–10 cm long and typically hangs from the anterior inferior margin of the liver. 4 2  12/9/24 READ ONLY Anatomy Of The Liver And Gallbladder The liver is almost completely covered by visceral peritoneum and is completely covered by a dense irregular connective tissue layer that lies deep to the peritoneum. The liver is divided into two principal lobes—a large right lobe and a smaller left lobe—by the falciform ligament, and smaller lobes: quadrate lobe and caudate lobe. The parts of the gallbladder include: the broad fundus (projects beyond the inferior border of the liver), the body (central portion) and the neck (tapered portion). 5 1.Hepatocytes: are the major functional cells of the liver Histology Of The Liver and perform: metabolic, secretory, and endocrine functions. Specialized epithelial cells with 5 to 12 sides that make up about 80% of the volume of the liver. Hepatocytes form complex three-dimensional arrangements called hepatic laminae. The hepatic laminae are plates of hepatocytes one cell thick bordered on either side by the endothelial-lined vascular spaces called hepatic sinusoids. Grooves in the cell membranes between neighboring hepatocytes provide spaces for canaliculi ( hepatocytes secrete bile in). Bile serves as both an excretory product and a digestive secretion. 6 3  12/9/24 Hepatocytes Large cuboidal or polyhedral epithelial cells, with large, round central nuclei. Eosinophilic cytoplasm rich in mitochondria. Cells are frequently binucleated. 50% of them are polyploid--- 2-8 times the normal chromosome number. 7 Hepatic lobules Hepatocytes form hundreds of irregular plates arranged radially around a small central vein. Peripherally each lobule has 3-6 portal areas --------contains three interlobular structures (portal triad): A venule branch of the portal vein, with blood rich in nutrients but low in O2, An arteriole branch of the hepatic artery that supplies O2, One or two small bile ductules. 8 4  12/9/24 Histology Of The Liver 2.Bile canaliculi: small ducts between hepatocytes that collect bile produced by the hepatocytes. From bile canaliculi, bile passes into bile ductules and then bile ducts. The bile ducts merge and eventually form the larger right and left hepatic ducts---unite---common hepatic duct The common hepatic duct joins the cystic duct from the gallbladder to form the common bile duct---bile enters the duodenum of the small intestine. 9 Histology Of The Liver 3.Hepatic sinusoids: highly permeable blood capillaries between rows of hepatocytes that receive oxygenated blood from branches of the hepatic artery and nutrient-rich deoxygenated blood from branches of the hepatic portal vein (blood from GIT,spleen). Hepatic sinusoids converge and deliver blood into a central vein--- to hepatic veins----to inferior vena cava Stellate reticuloendothelial cells (Kupffer): (hepatic macrophages) fixed phagocytes, destroy worn-out WBCs/RBCs, bacteria, and foreign matter in the venous blood draining from the gastrointestinal tract. Portal triad: a bile duct, branch of the hepatic artery, and branch of the hepatic vein. 10 5  12/9/24 LIVER 11 Blood Supply Of The Liver The liver receives blood from two sources: 1. The hepatic a. : Oxygenated blood. 2. The hepatic portal v. : Deoxygenated blood containing newly absorbed nutrients. Branches of both the hepatic a. And the hepatic portal V. Carry blood into hepatic sinusoids; oxygen, most of the nutrients, and certain toxic substances are taken up by the hepatocytes. Products manufactured by the hepatocytes and nutrients needed by other cells are secreted back into the blood---drains into the central vein---passes into a hepatic vein. 12 6  12/9/24 Hepatic Blood Flow 13 Histology Of The Gallbladder Mucosa consists of simple columnar epithelium arranged in rugae. The wall lacks a submucosa. The middle, muscular coat consists of smooth muscle fibers. Contraction of the smooth muscle fibers ejects the contents of the gallbladder into the cystic duct. The gallbladder’s outer coat is the visceral peritoneum. The functions of the gallbladder are to store and concentrate the bile produced by the liver (up to tenfold) until it is needed in the duodenum. In the concentration process, water and ions are absorbed by the gallbladder mucosa. Bile aids in the digestion and absorption of fats. 14 7