Liver Functions and Anatomy

Liver Functions

• The liver processes digested food from the intestine
• The liver stores glucose as glycogen
• The liver produces bile and synthesizes cholesterol and lipoproteins
• The liver removes harmful substances from the blood through detoxification
• It regulates hormones by producing clotting factors and processing steroid hormones
• The liver stores vitamins A, D, E, and K, as well as iron and copper
• Albumin is produced and is a major contributor to osmotic balance
• It assists in wound healing and regulates blood volume and pressure

Liver Anatomy

• The liver is the largest gland in the body and weighs approximately 3 lbs
• It is located under the diaphragm and within the rib cage
• The liver has four lobes: right, left, caudate, and quadrate lobes
• The lesser omentum anchors the liver to the lesser curvature of the stomach
• The Hepatic Artery, Hepatic Portal Vein, and Common Hepatic Duct runs through the lesser omentum
• The Porta Hepatis is where these three structures enter and leave the liver

Bile Flow

• Bile exits the liver through the left and right hepatic ducts
• The right and left hepatic ducts merge to form the common hepatic duct
• The common hepatic duct fuses with the cystic duct that drains the gallbladder
• This forms the common bile duct

Enterohepatic Circulation of Bile Salts

• Bile salts are recirculated through enterohepatic circulation
• A HIDA scan, or hepatobiliary iminodiacetic acid scan, can be used to assess the liver and bile ducts

Microscopic Liver

• The liver is composed of liver lobules
• The portal triad consists of the portal vein, hepatic artery, and bile duct
• The lobules contain a central vein and sinusoids
• Hepatocyte cords and bile canaliculi are present
• Stellate macrophages (Kupffer cells) line the sinusoid walls

Hepatocytes

• Hepatocytes secrete 900 ml of bile daily where blood and bile flow in opposite directions
• They process bloodborne nutrients and can store glucose as glycogen
• They store fat-soluble vitamins like vitamin K and detoxify blood, converting ammonia to urea

Bile Composition and Function

• Bile is yellow-green and alkaline
• It is composed of bile salt, bile pigments, cholesterol, triglycerides, phospholipids, and electrolytes
• Bile salts are salts of cholic and chenodeoxycholic acids, which are cholesterol derivatives
• Bile salts are recycled through enterohepatic circulation and reabsorbed into the portal vein from the ileum
• Bile salts are recirculated 4-12 times per day

Bilirubin

• Bilirubin is the chief bile pigment
• It is a yellow waste product of heme from hemoglobin
• Liver cells absorb bilirubin from the blood and excrete it into bile
• In the small intestine, bilirubin is metabolized and includes stercobilin, which gives feces their brown color

Hepatitis and Cirrhosis

• Hepatitis is the inflammation of the liver
• It can be caused by alcohol, drugs, and viruses like Hepatitis A through F
• Non-alcoholic fatty liver disease (NAFLD) affects 30% of North Americans and 70% of the obese population
• Cirrhosis is the final stage of chronic hepatic inflammation where the liver becomes fibrous or develops scar tissue

Gallbladder

• The gallbladder is about the size of a kiwi
• It is green when filled with bile and stores bile that is not immediately needed for digestion

Gallstones (Cholelithiasis)

• Bile salts help keep cholesterol dissolved in bile
• Too much cholesterol, or too few bile salts, causes cholesterol to crystallize and form gallstones
• The "5 F's" of cholelithiasis includes Family history, Fat, Female, Fertile, and Forty
• This is more prevalent in Hispanic and Native American populations

Pancreas

• The pancreas produces enzymes that break down foodstuffs
• It is tadpole-shaped, retroperitoneal, and lies deep to the greater curvature of the stomach
• The pancreas has both exocrine and endocrine functions

Exocrine Pancreas

• Acini, which are clusters of acinar cells, produce enzymes that make up pancreatic juice
• Pancreatic juice contains inactive proteases, amylase, lipases, and nucleases
• Ducts transport secretions from acinar cells

Gallstone Pancreatitis

• Gallstones can obstruct the pancreatic duct, leading to pancreatitis