Define urine formation in the 3 stages ? 80 words.
Urine is a transparent, yellowish fluid that consists of dissolved waste substances excreted by the kidneys. Urine mainly consists of water (96%), nitrogenous wastes like urea and dissolved excesses in the body like glucose, salts, proteins etc.
Process of formation of urine formation
Urine process in human occurs by process of filtration, reabsorption and tubular secretion.
1) In filtration, glomeruli act as filters, passes water, glucose, salt and waste materials to Bowman’s capsule but prevent RBC to pass.
2) Reabsorption occurs in proximal tubule of nephron. Water, glucose, amino acids, sodium and other nutrients are reabsorbed into bloodstream. Water moves from high concentration to low concentration, process is osmosis.
3) Secretion is final step in which substances move directly from blood in distal and collecting tubules. Maintain pH, acid-base balance by secreting hydrogen ions. When blood is acidic more ions are secreted and less when alkaline. Urine formed by these processes passes to central part of kidney called pelvis, then flows to ureter and bladder.