Liver_Structure_and_Function_Styled.pptx

Definee liver structute and function and the 2 pdf defines iodine deficinecy and its effect on human

1. Structure and Function of the Liver The Body's Largest and Most Versatile Gland

2. Structure: The Hepatic Lobule • Largest gland in the body (~1.5 kg in adults). • Divided into lobes made of **hepatic lobules** – the basic functional units. • Each lobule has columns of **hepatocytes** arranged around a central vein. • Blood flows through **sinusoids** between hepatocyte columns. • **Kupffer Cells:** Specialized macrophages that destroy bacteria/debris. • The liver can regenerate up to **75%** of its mass after damage. • Covered by a fibrous capsule called **Glisson’s capsule**.

3. Dual Blood Supply and Zonation • **Dual Blood Supply:** - **Portal Vein (≈80%)**: Nutrient-rich, low in oxygen (from GI tract). - **Hepatic Artery (≈20%)**: Oxygen-rich blood. • Blood mixes in **sinusoids**, drains into the **central vein → hepatic vein → inferior vena cava**. • **Zonation:** - **Zone 1 (Periportal):** Highest O₂ & nutrients, most active metabolism. - **Zone 2:** Intermediate. - **Zone 3 (Pericentral):** Lowest O₂, more prone to toxic damage. • **Bile flow** is opposite to blood flow.

4. Liver: The Central Organ of Metabolism 1. **Carbohydrate Metabolism:** - **Glycogenesis:** Glucose → Glycogen (storage). - **Glycogenolysis:** Glycogen → Glucose. - **Gluconeogenesis:** Formation of glucose from non-carbohydrates. 2. **Protein Metabolism:** - Deamination & transamination of amino acids. - **Urea formation** to remove ammonia. - Synthesizes **plasma proteins** (albumin, fibrinogen). 3. **Fat Metabolism:** - **β-Oxidation** of fatty acids. - Synthesis of **lipoproteins, cholesterol, phospholipids**. - Converts excess nutrients into **triglycerides**.

5. Synthesis, Storage, and Protection • **Synthetic Functions:** - Produces **plasma proteins** (Albumin maintains osmotic pressure). - Synthesizes **clotting factors** (Prothrombin, Fibrinogen, Factors VII, IX, X). • **Storage Functions:** - Stores **Vitamins A, D, K, B12** and **Iron (as ferritin)**. - Glycogen storage for energy. • **Detoxification:** - Converts toxic substances (drugs, alcohol, hormones) into harmless forms. - Uses **conjugation** with sulfate/glycine to make toxins water-soluble. • **Kupffer Cells:** Destroy bacteria from portal circulation.

6. Bile: Production, Composition, and Role • **Production:** Secreted by **hepatocytes** into bile canaliculi. • **Storage:** Collected in **gall bladder** during fasting. • **Composition:** Bile salts, bile pigments (bilirubin), cholesterol, phospholipids, water, electrolytes. • **Functions:** - **Emulsifies fats** for digestion. - Aids absorption of **fat-soluble vitamins (A, D, E, K)**. - **Excretes bilirubin** and cholesterol. - Helps neutralize gastric acid entering duodenum.

7. When the Liver Fails (Clinical Signs) • **Jaundice:** Accumulation of bilirubin (yellowing of skin/eyes). • **Bleeding Disorders:** Reduced synthesis of clotting factors. • **Edema/Ascites:** Low albumin → decreased plasma oncotic pressure. • **Hepatic Encephalopathy:** Ammonia buildup affects brain function. • **Fatty Liver:** Triglyceride accumulation. • **Portal Hypertension:** High portal vein pressure due to cirrhosis. • **Other Signs:** Muscle wasting, nausea, itching (bile salts).