Gastrointestinal System PDF

Gastrointestinal System Accessory organs Assistant Prof. Tarek Abdelkader Accessory organs of the digestive system In this lecture we’ll discuss the following in details: 1. Contents of oral cavity 2. Liver 3. Gall bladder 4. Pancreas We’ll also talk about the spleen which is N...

Gastrointestinal System Accessory organs Assistant Prof. Tarek Abdelkader Accessory organs of the digestive system In this lecture we’ll discuss the following in details: 1. Contents of oral cavity 2. Liver 3. Gall bladder 4. Pancreas We’ll also talk about the spleen which is NOT a part of the digestive system. Teeth Gingivitis, Tooth decay or caries Gingivitis Tooth decay or caries Tongue  Tongue Filiform papillae Circumvallate papillae Fungiform papillae  Tongue functions of the tongue (1) mechanical processing (2) manipulation of food (3) sensory analysis by touch, temperature, and taste receptors (4) secretion of mucins and the enzyme lingual lipase Ankyloglossia, Tongue ulcers, Tongue lesions and White discoloration of the tongue Salivary glands  Salivary glands Parotid salivary glands produce a serous secretion containing large amounts of salivary amylase. This enzyme breaks down starch Sublingual salivary glands are covered by the mucous membrane of the floor of the mouth. These glands produce a mucous secretion that acts as a buffer and lubricant Submandibular salivary glands lie along the inner surfaces of the mandible within a depression called the mandibular groove. Cells of the submandibular glands secrete a mixture of buffers, glycoproteins called mucins, and salivary amylase. Saliva (70% Submandibular, 25% Parotid and 5% Sublingual) Saliva is 99.4 % water & 0.6 % electrolytes (Na+, Cl−, and HCO3), buffers, glycoproteins, antibodies, enzymes, and waste products. The salivary glands produce 1.0–1.5 litres of saliva each day. Functions of saliva: ✓ Lubricating and moistening food in the mouth and the oral cavity ✓ Dissolving chemicals that can stimulate the taste buds and provide sensory information about the food ✓ Beginning the digestion of complex carbohydrates before the food is swallowed (salivary amylase) mumps Mumps, Salivary duct obstruction  Liver The liver lies primarily in the right hypochondrium and epigastric region, extending into the left hypochondrium Surfaces of the liver: 1. Diaphragmatic surface lies against the inferior surface of the diaphragm. Two lobes can be seen from that surface, right and left lobe. This surface is in close relations to the subphrenic and hepatorenal recesses The subphrenic recess separates the diaphragmatic surface of the liver from the diaphragm and is divided into right and left areas by the falciform ligament The hepatorenal recess (Morison’s pouch) is a part of the peritoneal cavity on the right side between the liver and the right kidney and right suprarenal gland. 2. Visceral surface It is mostly covered with visceral peritoneum except in the fossa for the gallbladder and at the porta hepatis. Plus the right and left lobes, caudate lobe can be seen on this surface near the superior border of the liver and quadrate lobe can be seen near the inferior border as well. Liver ligaments They stabilize the liver in its place by attaching it to the surrounding structures 1. Falciform ligament 2. Coronary ligament (anterior and posterior) 3. Triangular ligaments (left and right) 4. Lesser omentum Liver  The porta hepatis serves as the point of entry into the liver for the hepatic arteries and the portal vein, and the exit point for the hepatic ducts The liver has a special blood supply system as It receives arterial blood from right & left hepatic arteries from the hepatic artery proper which is a branch from celiac trunk It also receives venous blood from the hepatic portal vein for detoxification Three hepatic veins drain the liver into the inferior vena cava The hepatic lymph nodes, lying in the lesser omentum, are responsible for draining the anterior part of the liver. The posterior part drains the lymph into the phrenic and posterior mediastinal lymph nodes. The liver is innervated by hepatic plexus which contains both sympathetic and parasympathetic nerve fibers  Left Hepatic A Celiac Trunk Right Hepatic A Proper Hepatic A Common Hepatic A  Right Hepatic V Left Hepatic V Left Hepatic Portal V Intermediate Hepatic V Hepatic Portal V Right Hepatic Portal V Main functions of the Liver The liver is a very important organ in the body as it’s involved with more that 200 functions which can be categorized into three main categories 1) Metabolic regulation store iron, some lipids, and heavy metals, store and release glucose, store cholesterol and engulf pathogens 1) Hematological regulation Production of certain proteins for blood plasma, processing for use of its iron content, clearing the blood of drugs and regulating blood clotting (like I fibrinogen, II prothrombin…) 1) Bile production. Which helps carry away waste and break down fats in the small intestine during digestion The functional unit of the liver is the liver lobule Hepatitis, Alcoholism, Portal hypertension, Cirrhosis  Jaundice Ascites  Gall bladder It is present on the visceral surface of the right lobe of the liver, specifically, in a fossa between the right and quadrate lobes. It has three main parts: 1. Fundus of the gallbladder It is the most rounded end, which may project from the inferior border of the liver. 2. Body of the gallbladder The major part in the fossa, which may be against the transverse colon and the superior part of the duodenum. 3. Neck of the gallbladder The narrow part with mucosal folds forming the spiral fold. The gall bladder receives blood supply through the cystic artery which is a branch from the right hepatic artery and drains into the cystic vein which empties into the right hepatic portal vein. While the lymph drains into the cystic lymph nods. The main function of gall bladder is to store and concentrate the bile synthesized in the liver The Biliary Tree The bile is synthesized in the liver lobule. It is then collected into the bile canaliculi inside the liver lobule which empties into the bile duct in the portal area. These converge together to form the right and left hepatic bile ducts which drain from the right and left lobes of the liver respectively. The two hepatic ducts combine to form the common hepatic duct, which runs near the liver, with the hepatic artery proper and portal vein in the free margin of the lesser omentum. The common hepatic duct is joined by the cystic duct from the gall bladder to form the bile duct. The bile duct continues to descend, passing posteriorly to the superior part of the duodenum and through the head of the pancreas before joining with the pancreatic duct to enter the descending part of the duodenum.  Common hepatic A Common hepatic duct Cystic duct Gall bladder Hepatic portal vein Bill duct Ultrasound showing stones in the gall bladder  Pancreas The pancreas lies mostly posterior to the stomach. It consists of four parts: Head It lies within the C-shaped concavity of the duodenum Neck Positioned anterior to the superior mesenteric vessels Body It is elongate and extends from the neck to the tail of the pancreas Tail It passes between layers of the splenorenal ligament Blood Supply Greater pancreatic artery & dorsal pancreatic artery, both from splenic artery. There is separate blood supply to the head of Pancreas: superior and inferior pancreaticoduodenal arteries which are branches of the gastroduodenal artery & Superior mesenteric arteries respectively. The superior mesenteric branches of the hepatic portal vein drains the head of pancreas. The pancreatic veins draining the rest of the pancreas into the splenic vein. There are two main functions of the pancreas 1. Endocrine function To control the glucose level in blood > pancreatic islets (islets of Langerhans) secrete insulin and glucagon into the bloodstream 2. Exocrine function To help in digestion by secreting digestive enzymes > the acinar cells and the epithelial cells that line the duct system, secrete pancreatic juice (an alkaline mixture of digestive enzymes, water, and ions) into the small intestine.  Spleen The spleen is NOT a part of digestive system and it develops as part of the vascular system in the part of the dorsal mesentery It is located in the left hypochondrium, of the abdomen against the diaphragm, in the area of rib IX to rib X The spleen is connected to the: 1. greater curvature of the stomach by the gastrosplenic ligament, which contains the short gastric and gastro-omental vessels. 2. left kidney by the splenorenal ligament, which contains the splenic vessels. The spleen is surrounded by visceral peritoneum except in the area of the hilum. The splenic hilum is the entry point for the splenic vessels, and occasionally the tail of the pancreas reaches this area. It receives blood supply from the splenic artery which gives five different branches allowing for (subtotal splenectomy). It drains into the splenic vein then superior mesenteric vein. Spleen CT showing enlarged spleen (splenomegaly) May occur in cases of leukemia, lymphoma and certain infections  Thank you Sources: Grays Anatomy for Students 3rd edition Fundamentals of Anatomy & Physiology-Pearson Visible Body; Human Anatomy Atlas