The Liver: An introduction to its Function

• Describe the anatomical position of the liver

  Right upper quadrant of the abdomen, primarily in the right hypochondrium and extending into the epigastric region. It is protected by the lower ribs and is situated inferior to the diaphragm.
• What is the peritoneal covering of the liver?

  Mostly covered by visceral peritoneum, except at the bare area, which is in direct contact with the diaphragm. The peritoneum forms ligaments that help support the liver.
• What are the major anatomical lobes of the liver?

  The liver is divided into four lobes:

  • Right lobe (largest)
  • Left lobe (smaller, extends across midline)
  • Caudate lobe (posterior, near the inferior vena cava)
  • Quadrate lobe (anterior, near the gallbladder)

  
• What is the function division of the gallbladder?

  The liver is divided into eight segments based on blood supply and bile drainage. These segments are defined by the branching of the portal vein, hepatic artery, and bile ducts.
• What structures are related to the liver?

  • Superiorly: Diaphragm
  • Inferiorly: Stomach, Duodenum, Right Kidney, Gallbladder, Pancreas
  • Anteriorly: Abdominal Wall
  • Posteriorly: Inferior vena cava, Oesophagus, Vertebral column
• What is porta hepatis?

  The "gateway" of the liver, located of the liver, located on its inferior surface. It contains:

  • Hepatic artery proper (oxygenated blood supply)
  • Portal vein (nutrient-rich blood from the gut)
  • Common hepatic duct (bile drainage)
• What ligaments support the liver?

  The liver is suspended by:

  • Falciform ligament (connects liver to anterior abdominal wall, contains ligamentum teres)
  • Coronary ligament (attaches liver to diaphragm)
  • Triangular ligaments (lateral stabilisation)
  • Lesser omentum (connects liver to stomach & duodenum)
• What is the microscopic structure of the liver?

  The liver is made up of lobules, which are hexagonal functional units. Each lobule contains:

  • Central vein (drains blood into hepatic veins)
  • Hepatocytes (liver cells performing metabolic functions)
  • Sinusoids (capillaries where blood mixes)
  • Kupffer cells (macrophages removing waste)
  • Bile canaliculi (small ducts collecting bile)
• What is the liver's role as a protective barrier?

  The liver acts as a protective barrier by detoxifying harmful substances, filtering blood from the gastrointestinal tract, and preventing pathogens and toxins from entering systemic circulation.
•  How does the liver filter blood to protect the body?

  The liver receives blood from the gastrointestinal tract via the hepatic portal vein, removing toxins, bacteria, and metabolic waste products before blood enters systemic circulation.
• What role do Kupffer cells play in the liver's protective barrier function?

   Kupffer cells, specialised macrophages in the liver, engulf and digest pathogens, dead cells, and toxins, helping to prevent infections and systemic inflammation.
•  How does the liver contribute to detoxification?

  The liver detoxifies harmful substances by biotransformation, converting toxins into less harmful forms via phase I (modification) and phase II (conjugation) reactions, which are then excreted in bile or urine.
• How does the liver protect against bacterial infections?

  Kupffer cells remove bacteria and debris from portal blood, reducing the risk of sepsis and preventing harmful microorganisms from entering systemic circulation.
• What is the role of bile in the liver’s protective function?

   Bile contains bile acids and antimicrobial substances that help neutralise ingested pathogens and support the elimination of lipid-soluble toxins through faeces.
• How does the liver help neutralise alcohol and drugs?

  The liver metabolises alcohol and drugs using alcohol dehydrogenase (ADH) and cytochrome P450 enzymes, preventing toxic accumulation and damage to body tissues.
• What happens when the liver’s protective function is impaired?

  Impaired liver function can lead to toxin accumulation, increased infection risk, jaundice, and systemic inflammation, as seen in conditions like cirrhosis and hepatic encephalopathy.
• What are the main storage functions of the liver?

  The liver stores glycogen, vitamins (A, D, B12, K), minerals (iron and copper), and triglycerides. These reserves help regulate energy metabolism and support physiological functions.
• How does the liver store and regulate glucose?

  The liver stores glucose as glycogen through glycogenesis and releases glucose into the bloodstream via glycogenolysis. This maintains blood sugar levels, especially during fasting.
• What is glycogenesis?

  Glycogenesis is the process of converting excess glucose into glycogen for storage in the liver and muscles, regulated by insulin
• What is glycogenolysis?

  Glycogenolysis is the breakdown of glycogen into glucose when blood sugar levels drop, stimulated by glucagon and adrenaline.
• How does the liver contribute to long-term energy storage?

  The liver stores excess energy as triglycerides, which can be broken down into fatty acids and used for energy during fasting or starvation.
• Which vitamins are stored in the liver?

  The liver stores fat-soluble vitamins A, D, K, and B12 (a water-soluble vitamin), ensuring their availability when dietary intake is insufficient.
• Why is vitamin A storage in the liver important?

  The liver stores vitamin A in stellate cells, releasing it as needed for vision, immune function, and cellular growth.
• How does the liver regulate vitamin D?

  The liver converts vitamin D into 25-hydroxyvitamin D (calcidiol), which is further processed in the kidneys to its active form, calcitriol, for calcium homeostasis.
•  What is the role of the liver in vitamin B12 storage?

  The liver stores vitamin B12 (cobalamin) in large amounts, ensuring long-term supply for red blood cell formation, DNA synthesis, and nerve function.
• How does the liver store and regulate iron?

  The liver stores iron in ferritin and haemosiderin, releasing it as needed for haemoglobin synthesis and preventing iron deficiency or overload.
• What is the role of the liver in copper storage?

  The liver stores copper bound to metallothionein, incorporating it into ceruloplasmin for transport and excreting excess copper into bile.
• What is the liver’s role in coagulation?

  The liver synthesises most of the coagulation factors essential for blood clotting, helping maintain haemostasis and prevent excessive bleeding.
• Which coagulation factors are synthesised by the liver?

  The liver synthesises clotting factors I (fibrinogen), II (prothrombin), V, VII, IX, X, XI, and XII, as well as proteins C, S, and Z.
• Which coagulation factors require vitamin K for activation?

  The vitamin K-dependent coagulation factors are II (prothrombin), VII, IX, and X, along with protein C and protein S (anticoagulants).
• How does vitamin K affect the synthesis of coagulation factors?

  Vitamin K is required for the γ-carboxylation of coagulation factors II, VII, IX, and X, allowing them to bind calcium and participate in clotting.
• How does liver disease affect coagulation?

  Liver disease impairs coagulation factor synthesis, leading to prolonged bleeding times, increased risk of haemorrhage, and a raised prothrombin time (PT)/INR.
• What is fibrinogen, and what is its role in coagulation?

  Fibrinogen (factor I) is a plasma protein synthesised by the liver. It is converted into fibrin by thrombin, forming a mesh that stabilises blood clots.
• Which anticoagulant proteins are synthesised by the liver?

  The liver produces protein C, protein S, and antithrombin III, which regulate coagulation and prevent excessive clot formation.
• Why is prothrombin time (PT) used to assess liver function?

   PT measures the time taken for blood to clot, reflecting the synthesis of factor I, II, V, VII, and X. A prolonged PT indicates liver dysfunction.
• What are the key functions of the liver?

  The liver is responsible for:

  • Bile production for fat digestion
  • Regulating metabolism (glucose, lipids, proteins)
  • Detoxification of drugs and toxins
  • Storage of vitamins and minerals
  • Synthesis of plasma proteins (e.g., albumin, clotting factors)
  • Immune function via Kupffer cells
• What is bile, and what are its main components?

  Bile is a digestive fluid produced by the liver, essential for fat digestion and absorption. It contains:

  • Bile salts (derived from cholesterol)
  • Bilirubin (a breakdown product of haemoglobin)
  • Cholesterol
  • Phospholipids (mainly lecithin)
  • Water and electrolytes
• How does bile aid in fat digestion and absorption?

  Bile emulsifies dietary fats by breaking them into smaller droplets, increasing the surface area for enzymatic digestion by pancreatic lipase. This process forms micelles, which help transport fatty acids and monoglycerides across the intestinal epithelium.
• What is the function of the gallbladder?

  The gallbladder stores and concentrates bile, releasing it into the duodenum in response to cholecystokinin (CCK) during digestion.
• What triggers bile release from the gallbladder?

  Bile release is stimulated by cholecystokinin (CCK), which is secreted by the small intestine in response to fats in the duodenum.