Liver Anatomy & Physiology PDF

Liver Dr. Rimaz Elhag Gurashi Jul 2024 Anatomy & Physiology General anatomy of the liver  1 ▪ The weight of a normal liver comprises about 1/18 (5%) of the newborn child’s body weight ▪ About 1/50 (2 to 3.3%)of the adult’s bodyweight. ▪ Varying in men from 1,500 to1,800 g and in women...

Liver Dr. Rimaz Elhag Gurashi Jul 2024 Anatomy & Physiology General anatomy of the liver  1 ▪ The weight of a normal liver comprises about 1/18 (5%) of the newborn child’s body weight ▪ About 1/50 (2 to 3.3%)of the adult’s bodyweight. ▪ Varying in men from 1,500 to1,800 g and in women from 1,300 to 1,500 g. ▪ The weight of the liver relative to body weight decreases  2 ▪ size, the liver is on average 25 to 30 cm in width, 12 to 20 cm in length, and 6 to10 cm in thickness. ▪ The surface is smooth and shiny. ▪ The colour is brownish red. ▪ The lobular structure can be seen distinctly upon close inspection.  3 ▪ Position is intraperitoneal located beneath in the right upper quadrant of the abdominal cavity and is attached to the diaphragm. ▪ Lies to the right of the stomach and overlies the gallbladder, is protected by the lower rib cage 6 4  5 ▪ The topography of the liver is characterized by the (smaller) left lobe and the (about six times larger) right lobe, which are separated by the (translucent) falciform ligament. ▪ There is no known functional difference between the lobes, and communication flows freely between all areas of the liver  6 ▪ Round ligament It runs in the free edge of the falciform ligament, it is a remnant of the umbilical vein of the foetus. ▪ Quadrate lobe lying anteriorly between the gall bladder and round ligament. ▪The caudate lobe with papillary tubercle and caudate process , lying posteriorly along the inferior vena cava in front of the hepatic porta  7 ▪ This hilum of the liver in the center of the inferior liver surface consists of the proper hepatic artery, portal vein, common hepatic duct, lymph vessels, and hepatic nerve plexus. ▪ These are held together by the perivascular fibrous capsule.  Anatomical Divition of the liver 11 8 hepatic artery and portal vein, lymph nodes right lobe left lobe 1 2  Segmental subdivisions 10 ▪ The boundaries regarding physiological topography are marked by the distribution pattern of the portal vein, the hepatic artery and the bile ducts, or according to the origin of the three large hepatic veins. ▪ The result is a clear and precise subdivision of the liver in the sense of a functional lobulation. 11 Surgical Classification of the liver 12 Structure and histology of the liver ▪ Structurally and histologically, the liver can be divided into four tissue systems: (1.) Intrahepatic vascular system. (2.) Stroma. (3.) Sinusoidal cells. (4.) Hepatocytes. 14 (1.) Intrahepatic vascular system: ▪ Hepatic artery ▪ Portal vein ▪ Hepatic vein ▪ Biliary system ▪ Lymph vessels  12 (1.) Intrahepatic vascular system: 1.1 Hepatic artery carries Oxygenated blood from the aorta & is responsible for providing approximately 25% of the total blood supply to the liver. 13 (1.) Intrahepatic vascular system: 1.2 Portal vein Nutrient-rich blood flows carries blood containing digested nutrients from the entire gastrointestinal tract , and it is responsible for providing approximately 75% of the total blood supply to the liver. 19 (1.) Intrahepatic vascular system: 1.3 Hepatic vein The venous drainage from the liver converges into the hepatic veins, which join the inferior vena cava near its entry into the right atrium. 9 21 22 14 ▪Approximately 1,500 mL of blood passes through the liver per minute. ▪The liver is drained by a collecting system of veins that empties into the hepatic veins and ultimately into the inferior vena cava. ▪These blood vessels subdivide into capillaries, which then lead to a lobule. ▪Each lobule is made up of millions of hepatic cells ( basic metabolic cells). 24  25 (1.) Intrahepatic vascular system: 1.4 Biliary system ▪The excretory system of the liver begins at the bile canaliculi. ▪The bile canaliculi are small spaces between the hepatocytes that form intrahepatic ducts, where excretory products of the cell can drain. ▪The intrahepatic ducts join to form the right and left hepatic ducts, which drain the secretions from the liver.  16 ▪The right and left hepatic ducts merge to form the common hepatic duct, which is eventually joined with the cystic duct of the gallbladder to form the common bile duct. ▪Combined digestive secretions are then expelled into the duodenum 27 (1.) Intrahepatic vascular system: 1.5 Lymph vessels ▪The liver forms more lymph than any other organ of the body. ▪Lymph capillaries take up lymph from Disse’s space and thereafter from Mall’s space ,which lies between the limiting plate and the portal connective tissue. ▪Disse’s space is also considered to be the main source of lymph.  15 ▪ Lymph vessels possess valves which permit the lymph to flow only in one direction. Lymphatic vessels are present in all portal fields. ▪ They are found exclusively in the peri- vascular connective tissue and in the capsule of the liver. ▪ Drainage is effected by the hepatic lymph nodes in the area of the porta hepatis. ▪ Lymph reaches the thoracic duct via large valved lymphatic trunks and interconnected lymph nodes. ▪ Thus it enters the systemic circulation. 12 Structure and histology of the liver ▪ Structurally and histologically, the liver can be divided into four tissue systems: ✓ (1.) Intrahepatic vascular system. (2.) Stroma. (3.) Sinusoidal cells. (4.) Hepatocytes.  (2.) Stroma. 30 The term stroma comprises the interstitial connective tissue of an organ. In the liver, four types of tissue structure are differentiated: (2.1) capsule of the liver. (2.2) perivascular connective tissue. (2.3) reticular network. (2.4) portal tract.  31 Capsule of the liver. ▪ It consists of the endothelial coating and a network of collagenous and elastic fibers. 43 to76 µm thickness. ▪ The capsule and the falciform ligament contain sensitive of the nerve. ▪ Blood and lymph vessels as well as bile ducts are present in the capsule.  Perivascular connective tissue 32 ▪ The perivascular fibrous capsule as a tree-like branching framework of connective tissue surrounding the interlobular vessels. ▪ It surrounded the central hepatic vein, which are joined to the parenchyma by radial fibers ▪ This prevents a suction-induced collapse of the venous vessels as a result of respiration- dependent negative pressure in the pleural cavity.  33 Reticular Network ▪ The reticular network consists fibers which lie on the hepatic cell plates and serve as a mechanical support for the sinusoids and in hepatocyte regeneration.  34 Portal Tract ▪ In the portal tract, the perivascular connective tissue with its enclosed (and protected) radicles of the portal veins, the hepatic arterioles, bile ducts, lymph vessels and nerve fibers terminates in the connective tissue covering of the perivascular fibrous capsule.  12 Structure and histology of the liver ▪ Structurally and histologically, the liver can be divided into four tissue systems: ✓ (1.) Intrahepatic vascular system. ✓ (2.) Stroma. (3.) Sinusoidal cells. (4.) Hepatocytes.  (3.) Sinusoidal Cells. 36 Although the sinusoidal cells make up only a relatively small proportion of the liver volume (6.3%) ▪ Endothelial cells ▪ Kupffer cells ▪ Ito cells ▪ PIT cells  37 ▪Endothelial cells Constitute the greatest proportion (70%) of the sinusoidal cells. They are in loose connection with both the neighbouring endothelial cells and the microvilli of the hepatocytes. They are located on a fine layer of extracellular matrix ▪Ito cells Also known as fat-storing cells, hepatic stellate cells or lipocytes. Constitute about 38% of the total liver cell number  38 ▪ Kupffer cells 25% of the sinusoidal cells. They probably derive from monocytes and are released by stem cells in the bone marrow. line the sinusoids of the liver and act as active phagocytes capable of engulfing bacteria, debris, toxins, and other substances flowing through the sinusoid. ▪PIT cells It is proportion to Kupffer cells is 2 : 10. Natural killer cells destroy tumor cells or foreign cells and, necrosed cells. 12 Structure and histology of the liver ▪ Structurally and histologically, the liver can be divided into four tissue systems: ✓ (1.) Intrahepatic vascular system. ✓ (2.) Stroma. ✓ (3.) Sinusoidal cells. (4.) Hepatocytes.  40 Hepatocytes ▪ Making up approximately 80% of the volume ▪ of the organ. ▪ Hepatocytes are polygonal epithelial cells with six or more faces corresponding to their ▪ individual position in the overall cell structure. ▪ The usual life span of hepatocytes is at least ▪ 150to200 days. ▪ This programmed death of the old hepatocytes is designated apoptosis  41 They have a clearly contoured cell membrane which is divided into 3 compartments defined by morphological and functional cellular polarization: (1.) About 37% of the external area of the hepatocyte membrane is sinusoidal surface, the absorptive and secretory function (2.)About 12% of the outer hepatocyte membrane consist of canaliculi, termed canalicular surface. This area is the secretory pole of the cell. (3.)The remaining 50% of the external hepatocyte membrane constitute the smooth intercellular fissure  42 Biliary epithelial cells They constitute some 3.5% of all hepatic cells. Depending on the size of the biliary ducts in which they are located, they show distinct histological and histochemical variations. These biliary cells probably play a role in biligenesis.  43 Subcellular Structures Endoplasmic Reticulum: Essential organelle for protein and lipids synthesis ▪The smooth ER: is the site of hepatic drug metabolism, drug detoxification, bilirubin conjugation, and cholesterol synthesis. ▪The rough ER : Synthesis and conjugation of protein, metabolism of lipids and steroids, detoxification and metabolism of drugs, glycogen breakdown.  44 Golgi complex: ▪ Receives proteins and modifies them to attach carbohydrates and lipids, forming glycoproteins and lipoproteins. VLDL is produced in the Golgi complex. Lysosomes: Active in protein breakdown (proteolysis) and other degradation functions. Mitochondria: Active in oxidative phosphorylation and fatty acid oxidation. 45 46  What does the liver do? 47 Multi-function, blood-processing “factory” 48 Amazing fact about the liver With only 1/6th of our liver present our bodies could continue to function. 80% of our liver could be cut away and it would grow back to full size in approximately three months. Because the liver is designed by this way , it is usually hard to determine if the liver is damaged until the damage is quite advanced.