liver physiolgy

• The liver is a large, meaty organ located in the upper right quadrant of the abdomen, responsible for filtering blood from the digestive tract, producing bile, and storing carbohydrates

  
• The liver is the largest gland of the body, weighing about 1.4 kg in an average adult, located below the diaphragm on the right side of the body
• The main function of the liver is the secretion of bile, making it part of the hepatobiliary system along with the gallbladder and bile ducts
• The liver is organized into functional units called lobules, each a hexagon structure consisting of hepatocytes arranged around a central vein, with portal spaces at each corner containing branches of bile duct, portal vein, and hepatic artery
• Within a hepatic plate, bile canaliculus accumulates bile from hepatocytes and drains it into the bile duct in the portal space, while the sinusoid vessel receives blood from the portal vein and hepatic artery, draining it into the central vein
• Liver sinusoids are wide, highly permeable capillaries containing venous blood from the portal vein and arterial blood from the hepatic artery, delivering blood to the central vein
• The liver receives blood from the hepatic artery (oxygenated blood) and the portal vein (venous blood with nutrients, drugs, and possibly microbes and toxins from the GIT), serving as a filter before blood enters systemic circulation
• The liver's functions include bile secretion for fat digestion, detoxification of blood, synthesis of plasma proteins and clotting factors, storage of blood, and metabolism of carbohydrates and lipids
• Hepatocytes secrete about 1 liter of bile daily, a yellow-green liquid with a pH of 7.6-8.6, isotonic to blood plasma, released into the duodenum to neutralize gastric acid and aid in digestion
• Bile is composed of water, bile pigments, bile salts, cholesterol, lecithin (phospholipid), and several ions (Na+, bicarbonate, etc)
• Bile acids, primary (synthesized by the liver from cholesterol) and secondary (produced in the duodenum), are conjugated with glycine and taurine to form bile salts, aiding in fat digestion by making fat water-soluble and emulsifying it
• Micelles, simple and mixed, are formed by bile salts interacting with lipid droplets, aiding in the digestion of fats by increasing the surface area for enzyme action
• Bile salts reduce surface tension, emulsifying fat by creating shells of negative charge around lipid droplets, preventing them from coalescing into large globules
• The digestive system is a group of organs that work together to break down food into nutrients and absorb them into the body

  
• The digestive process starts in the mouth where food is chewed and mixed with saliva containing enzymes that break down carbohydrates
• Food then travels to the stomach where acids and enzymes further break it down before moving to the small intestine, where it mixes with bile from the liver and enzymes from the pancreas
• In the small intestine, bile helps break down fats and enzymes break down proteins, carbohydrates, and fats, allowing absorption into the bloodstream
• Undigested food moves to the large intestine, where it forms feces and is expelled from the body
• The liver, located in the upper right quadrant of the abdomen, filters blood from the digestive tract, produces bile, and stores carbohydrates

  
• The liver lobule is the structural and functional unit of the liver, composed of hepatocytes, Kupffer cells, and endothelial cells, supplied with blood by the hepatic artery and portal vein, and drained by bile canaliculi

  
• Bile salts in the small intestine aid in absorption of lipid hydrolysis products like free fatty acids and glycerol
• Micelles carry fatty acids and glycerol through the watery layer of the intestine for absorption by enterocytes and transport to the blood
• The gallbladder stores bile produced by the liver, concentrating it through water absorption while sphincter of Oddi closure prevents bile from entering the duodenum between meals
• Jaundice is a yellow discoloration of the skin and sclera caused by hyperbilirubinemia, with types including prehepatic, hepatic, and extrahepatic jaundice
• The liver detoxifies blood, synthesizes proteins, regulates carbohydrate metabolism, and is involved in lipid metabolism