Functions of the Liver - PPT/PDF
Download notes (PPT/PDF) detailing the diverse functions of the liver. These notes cover the liver's crucial roles in carbohydrate metabolism, protein metabolism, fat metabolism, vitamin synthesis, bile production, blood-related functions, storage, and heat regulation. Suitable for B.Pharm and related health science programs.
Keywords: Liver, Functions, Carbohydrate Metabolism, Protein Metabolism, Fat Metabolism, Vitamin Synthesis, Bile Production, Blood, Storage, Heat Regulation, Human Anatomy and Physiology, B.Pharm, PPT, PDF, Download.
Functions of the Liver - Detailed Explanation
1. Introduction
The liver is the largest internal organ in the human body and plays a vital role in maintaining homeostasis. It's located in the upper right quadrant of the abdomen, below the diaphragm. The liver performs a remarkable array of functions, impacting nearly every system in the body. It receives blood from two sources: the hepatic artery (oxygenated blood) and the hepatic portal vein (nutrient-rich blood from the digestive tract).
2. Functions of the Liver
1. Carbohydrate Metabolism
The liver is central to maintaining blood glucose homeostasis. It performs several key processes:
- Glycogenesis: The conversion of glucose to glycogen for storage. This occurs when blood glucose levels are high (e.g., after a meal).
- Glycogenolysis: The breakdown of glycogen to glucose. This occurs when blood glucose levels are low (e.g., between meals or during fasting).
- Gluconeogenesis: The synthesis of glucose from non-carbohydrate sources, such as amino acids and glycerol. This is important during prolonged fasting or starvation.
2. Protein Metabolism
The liver plays a critical role in protein metabolism:
- Synthesis of Plasma Proteins: The liver synthesizes most plasma proteins, including:
- Albumin: The most abundant plasma protein, important for maintaining osmotic pressure and transporting various substances.
- Clotting Factors: Most of the proteins involved in blood clotting (e.g., prothrombin, fibrinogen).
- Globulins: Various globulins, except for immunoglobulins (antibodies).
- Amino Acid Metabolism:
- Deamination: The removal of the amino group (-NH2) from amino acids. This is necessary for amino acids to be used for energy or converted to other compounds. The amino group is converted to ammonia (NH3), which is then converted to urea by the liver.
- Transamination: The transfer of an amino group from one amino acid to another. This allows the liver to synthesize non-essential amino acids.
- Urea Synthesis: The liver converts toxic ammonia (NH3) to urea, a less toxic waste product that can be excreted by the kidneys.
3. Fat Metabolism
The liver is involved in several aspects of fat metabolism:
- Fatty Acid Oxidation: The liver breaks down fatty acids to produce energy (ATP).
- Lipoprotein Synthesis: The liver synthesizes lipoproteins (e.g., VLDL, HDL, LDL), which transport lipids (fats) in the blood.
- Cholesterol Synthesis: The liver synthesizes cholesterol, which is a component of cell membranes and a precursor for steroid hormones and bile salts.
- Ketogenesis: During periods of fasting or starvation, the liver converts fatty acids into ketone bodies, which can be used as an alternative energy source by the brain and other tissues.
4. Synthesis of Vitamins
While the liver doesn't synthesize *all* vitamins, it plays important roles in vitamin metabolism:
- Vitamin A: The liver stores vitamin A and converts beta-carotene (from plants) into vitamin A.
- Vitamin D: The liver participates in the activation of vitamin D (converting it to 25-hydroxycholecalciferol).
- Vitamin K: The liver uses vitamin K to synthesize certain clotting factors.
5. Manufacture of Bile
The liver produces bile, a greenish-yellow fluid that is essential for the digestion and absorption of fats. Bile contains:
- Bile Salts: Emulsify fats, breaking them down into smaller droplets that can be more easily digested by lipases.
- Bilirubin: A breakdown product of heme (from red blood cells). Gives bile its color.
- Cholesterol: Excreted in bile.
- Phospholipids: Help solubilize cholesterol.
Bile is stored and concentrated in the gallbladder and released into the duodenum (the first part of the small intestine) when needed.
6. Functions Related to Blood
- Detoxification: The liver detoxifies harmful substances, such as drugs, alcohol, and toxins, by converting them into less harmful forms that can be excreted. This often involves enzymatic reactions (e.g., cytochrome P450 enzymes).
- Phagocytosis: Kupffer cells (specialized macrophages in the liver) phagocytose (engulf and destroy) old red blood cells, bacteria, and other foreign substances.
- Blood Reservoir: The liver can store a significant amount of blood and release it into circulation when needed.
- Hematopoiesis (in the fetus): In the developing fetus, the liver is a major site of blood cell formation (hematopoiesis).
7. Storehouse
The liver acts as a storage site for several important substances:
- Glycogen: The storage form of glucose.
- Vitamins: Fat-soluble vitamins (A, D, E, K) and vitamin B12.
- Minerals: Iron (stored as ferritin) and copper.
8. Heat Regulation
The liver is a highly metabolically active organ, and its metabolic processes generate a significant amount of heat. This heat contributes to maintaining body temperature.
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