Describe the structure and function of the gallbladder and liver and state the role of bile in digestion.
Gross Anatomy of the Liver:
• Largest gland in the body
• Located under the diaphragm and lies almost entirely within the rib cage
• Four Primary Lobes:
1. Right Lobe (largest lobe)
2. Left Lobe (separated by a fissure)
3. Caudate Lobe
4. Quadrate Lobe
• The falciform separates the right and left lobes and round ligament
• The hepatic portal vein and hepatic vein enter the liver at the porta hepatis ("gateway to the liver") and the common hepatic ducts, which runs inferiorly from the liver, all travel through the lesser omentum to reach their destination
Microscopic Anatomy of the Liver:
• The liver is composed of sesame seed-sized structure and functional units called liver lobules
• Liver lobules consist of hepatocytes (liver cells)
• Hepatocyte plates radiate outward from a central vein running in the longitudinal axis of the lobules
1. Process bloodborne nutrients in various ways (e.g. they store glucose as glycogen and use amino acids to make plasma proteins)
2. Store fat-soluble vitamins
3. Play important roles in detoxification, such as ridding the blood of ammonia by converting it to urea.
• Portal triad (portal tract region) contains:
1. A branch of the hepatic artery (supplying oxygen-rich arterial blood to the liver)
2. A branch of the hepatic portal vein (carrying venous blood laden with nutrients from the digestive viscera)
3. A bile duct
• Liver Sinusoids: between the hepatocyte plates
Function of the Liver:
• Hematological Regulation: Phagocytosis and antigen presentation [kupffer cells], synthesis of plasma proteins, removal of circulating hormones, removal of antibodies, removal or storage of toxins.
• Synthesis and secretion of bile [mostly water, with minor amounts of ions, bilirubin, cholesterol and an assortment of lipids know as bile salts, that function in the emulsification of lipids.
• Rests in a recess on the inferior surface of the right liver lobe
• Stores and concentrates bile
2. alkaline solution containing bile salts
• Bile salts and phospholipids aid in digestive process
• bile salts are primarily cholic and chenodeoxycholic acid, are cholesterol derivatives
• They emulsify fats