Liver Anatomy PDF

LIVER ~ 1500 g Livers exocrine Largest gland function is limited to filtration of toix material. False Both end...

LIVER ~ 1500 g Livers exocrine Largest gland function is limited to filtration of toix material. False Both endocrine & exocrine (bile) functions (same cell: hepatocyte) Convert noxious substances into nontoxic materials  General Hepatic Structure Glisson’s capsule: dense irregular connective tissue Loosely attached except at porta hepatis (blood & lymph vessels & bile ducts) Sparse connective tissue  General Hepatic Structure & Vascular Supply Porta hepatis Left & right hepatic artery Portal vein (nutrients, iron-rich blood from spleen) Right and left hepatic ducts Hepatic veins BLOOD SUPPLY Hepatic artery distributing arterioles inlet arterioles  Peribiliary capillary plexus around interlobular bile ducts Portal vein larger distributing veins smaller inlet venules Central vein: initial branch of hepatic vein Hepatocytes radiate from central vein & separated from each other by hepatic sinusoids inlet arterioles, inlet venules & branches from peribiliary capillary plexus hepatic sinusoids central vein sublobular vein collecting veins right and left hepatic veins  TYPES OF LIVER LOBULES Classical lobule Portal lobule Hepatic acinus (acinus of Rappaport)  Classical Lobule Closely packed classical lobules (hexagon- shaped) Boundaries can only be approximated 3 lobules contact: portal areas (triads) Hepatic artery Portal vein Bile duct  Classical Lobule Limiting plate (modified hepatocytes) Space of Möll (Mall) separates limiting plate from connective tissue of portal areas around each lobule in a random section  Classical Lobule Blood flows from periphery to center into central vein Bile enters into bile canaliculi between hepatocytes & flows to periphery to interlobular bile ducts  Portal Lobule All hepatocytes that deliver their bile to a particular bile duct constitute a portal lobule Triangular region Portal area at the center Imaginary straight lines connecting 3 central veins  Hepatic Acinus (Acinus of Rappaport) Based on blood flow from distributing arteriole On the order in which hepatocytes degenerate subsequent to toxic or hypoxic insults Ovoid to diamond-shaped lobule Zone 1 Zone 2 Zone 3  Persons who have consumed hepatotoxic substances, such as alcohol, diasplay an increased number of lipid deposits in zone 3 hepatocytes. Persons who are taking barbiturates display an increase in SER content of zone 3 cells. Since zone 3 has the lowest oxygen levels of the 3 zones, this is the region of the liver acinus that is most susceptible to necrosis in case of severe liver injury.  Hepatic Sinusoids & Hepatocyte Plates Plates of hepatocytes radiate from central vein toward periphery of classical lobule Spaces between plates: sinusoids Sinusoidal lining cells Gaps between lining cells Fenestrae in clusters: sieve plates  Kupffer cells in Sinusoids Endocytose particulate matter and cellular debris, defunct erythrocytes  Perisinusoidal Space of Disse Narrow space between a plate of hepatocytes and sinusoidal lining cells Microvilli of hepatocytes, exchange of materials between blood & hepatocytes  Perisinusoidal Space of Disse Type 3 collagen (reticular) fibers, supporting sinusoids Type 1 & 4 collagen fibers No basal lamina Nonmyelinated nerve fibers  Space of Disse Hepatic stellate cells (Ito cells): fat storing Which actions of below is not abservered in scapse of disse cells Store vitamin A Manufacture & release type 3 collagen Secrete growth factors Form fibrous connective tissue to replace damaged hepatocytes Pit cells Natural killer cells  Hepatic ducts Bile canaliculi Canals of Hering (Cholangioles) Interlobular bile ducts Right & left hepatic ducts  Hepatocytes 5-12 sided polygonal cells 20-30 m diameter Closely packed to form one or two cell- thick plates Show variations in their structural, histochemical & biochemical properties depending on their location within lobules  Domains of Hepatocyte Plasmalemma Lateral domains Formation of bile canaliculi Bile leakage prevented by tight junctions High levels of Na, K-ATPase activity & adenylate cyclase Gap junctions  Domains of Hepatocyte Plasmalemma Sinusoidal domains Microvilli projecting into space of Disse Increase surface area, facilitating exchange between hepatocyte and plasma in perisinusoidal space Mannose-6-phosphate receptors Na, K-ATPase Adenylate cyclase Endocrine secretions of hepatocytes released & enter sinusoidal blood Material from blood transported into hepatocyte cytoplasm  Hepatocyte organelles and inclusions Manufacture primary bile Abundant free ribosomes, RER, Golgi 2000 mitochondria Rich in endosome, lysosome & peroxisome SER Certain drugs & toxins increase SER  Continued long-term usage of certain drugs, such as barbiturates, decreases their effectiveness, requiring prescription of increased doses. This drug tolerance is due to hypertrophy of SER complement of hepatocytes and concominant increase in their mixed- function oxidases.  Hepatocyte Lipid droplets mostly VLDLs Glycogen Electron-dense granules 20-30 nm in size Abundant after eating, fewer after fasting Glycogen  Alcoholics and people who suffer from obstruction of the biliary tract or chronic poisoning are at risk for development of cirrhosis. Fibrosis Degeneration of hepatocytes Disintegration of normal organiztion of the liver Cirrhosis  Wilson’s disease Hereditary condition Liver does not eliminate copper by transferring it into bile Copper accumulates in eyes, brain, liver causing cirrhosis Fatal if left untreated Chelating agent, penicillamine, binds with copper and facilitates its elimination from body  GALLBLADDER Simple columnar epithelium Mucinogen Short microvilli Lamina propria Smooth muscle Mucosa highly folded into tall parallel ridges Serosa/adventitia As gallbladder distended, plication reduced to few short folds & mucosa becomes smooth Epithelial cells: Basally positioned oval nuclei Short microvilli coated by glycocalyx Basal region rich in mitochondria, providing abundant energy for Na-K ATPase pump in basolateral membrane Deep diverticula called ROKITANSKY-ASCHOFF SINUSES Intercellular spaces at basal aspect Feature associated with transport of fluid across epithelium Commonly seen in intestinal absorptive cells  Lamina propria Loose connective tissue Elastic & collagen fibers Neck: simple tubuloalveolar glands (mucus)  We do not seee musculars mucosa and submucosa in gallbladder Smooth muscle layer Mostly obliquely oriented fibers Others longitudinally oriented Adventitia attached to Glisson’s capsule Nonattached surface invested by peritoneum  Extrahepatic ducts Right hepatic duct left hepatic duct Common hepatic duct Cystic duct Common bile duct pancreatic duct Ampulla of Vater PANCREAS  Posterior body wall deep to the peritoneum Four regions Uncinate process Head Body Tail 25 cm long, 5 cm wide, 1-2 cm thick, 150 g  Exocrine Digestive juices Secretory acini Endocrine Hormones Islets of Langerhans  EXOCRINE PANCREAS Compound tubuloacinar gland Produces bicarbonate-rich fluid & digestive proenzymes (1200 ml/day) 40-50 acinar cells form a round to oval acinus Lumen occupied by 3-4 centroacinar cells (distinguishing characteristic, beginning of duct system) Surrounded by BL supported by reticular fibers  Acinar cell serous cells Like a truncated pyramid Base positioned on BL separating cell from CT Basally located round nucleus, surrounded by basophilic cytoplasm Apex faces the lumen Apex filled with zymogen granules, eosinophilic Number diminishes after meal Golgi region between nucleus and zymogen granules varies in size in inverse relation to zymogen granule concentration  Base contains many Ultrastructure of acinar cell parallel cisternae of GER (basophilic staining in LM) Golgi apparatus fluctuates in size (smaller when zymogen granules numerous, larger after granules release their content) Microvilli from apical surface Z. occludentes  very thin connective tissue capsule invaginates into gland to form septae (vascular and nerve supply, ducts travel in connective tissue) septae divide pancreas into distinctive lobules  Compound tubuloacinar gland The cells that synthesize and secrete digestive enzymes are arranged in grape-like clusters called acini, very similar to what is seen in salivary glands.  Secretory Portion Basal cell membranes of acinar cells have receptors for CCK & ACh. EM: abundance of basally located RER Rich supply of polysomes Numerous mitochondria Golgi well developed  Duct System Begins within center of acinus with terminus of intercalated ducts (ICD) Pale, low cuboidal centroacinar (CA) cells CA cells & ICDs have receptors on basal plasmalemma for secretin & possibly for ACh Pancreatic Ducts ICD Intralobular duct Interlobular duct Main pancreatic duct Common bile duct Papilla of Vater  Intercalated ducts receive secretions from acini flattened to cuboidal epithelium that extends up into the lumen of the acinus to form centroacinar cells Note the low cuboidal, almost squamous epithelium.  Intralobular ducts cuboidal epithelium within lobules receive secretions from intercalated ducts Longitudinal section through an intercalated duct emptying into an intralobular duct. Note the cuboidal epithelium in the intralobular duct.  Interlobular ducts between lobules, within the connective tissue septae vary considerably in size smaller forms have cuboidal epithelium larger ducts have columnar epithelium transmit secretions from intralobular ducts to major pancreatic duct Small interlobular ducts: Note the columnar epithelium. A thin interlobular septum is seen running horizontally immediately above the duct. A large interlobular duct in association with a pancreatic artery (A) and vein (V). D: Intralobular duct.  The main pancreatic duct receives secretion from interlobular ducts receives secretion from penetrates through the wall of duodenum interlobular ducts joins the bile duct prior to entering the intestine penetrates through the wall of duodenum joins the bile duct prior to entering the intestine  Acute pancreatitis Pancreatic digestive enzymes become active within cytoplasm of acinar cells Often fatal İnflammatory reaction, necrosis of blood vessels, proteolysis of parenchyma, enzymatic destruction of adipose cells  Islets of Langerhans Scattered among acini Richly vascularized Spherical conglomeration of 3000 cells 1 million islets Greater number in tail Surrounded by reticular fibers  Islets of Langerhans Lightly stained polygonal or rounded cells arranged in cords separated by a network of fenestrated capillaries Both parenchymal cells & blood vessels are innervated by ANS  Cells of Islets 5 types: Beta Alpha Delta (D&D1) PP (pancreatic polypeptide-producing) G (gastrin-producing) Differences from parotid gland Exocrine part similar in structure to parotid gland Distinction: Absence of striated ducts Presence of islets of Langerhans Initial parts of ICDs penetrate lumens of acini Centroacinar cells (nuclei surrounded by pale cytoplasm)  Diabetes mellitus Hyperglycemic metabolic disorder Lack of insülin production from B cells or, Defective insülin receptors If uncontrolled; circulatory disorders, renal faiilure, blindness, gangrene, stroke, myocardial infarct  Type 1 diabetes Usually affects persons 40 years of age  Verner-Morrison syndrome (pancreatic cholera) Explosive, watery diarrhea Hypokalemia Hypochlorhydria Caused by excessive manufacture and release of VIP due to adenoma of D1 cells Frequently, tumors of D1 cells are malignant