Detailed Summary
Excretory products include nitrogenous wastes and other metabolites that must be eliminated to maintain homeostasis. The main forms of nitrogenous wastes are ammonia, urea, and uric acid, each reflecting an organism's evolutionary adaptation to its environment, especially concerning water availability.
In humans, the excretory system consists of two kidneys and associated structures like ureters, urinary bladder, and urethra. Each kidney comprises numerous nephrons, the functional units tasked with urine formation. During urine formation:
1. Filtration occurs in the glomerulus, where blood is filtered to form a protein-free fluid.
2. Reabsorption occurs across various nephron segments, with significant water and solute recovery occurring,
3. Secretion in the tubules helps maintain acid-base balance and excrete unwanted ions.
Moreover, a counter-current mechanism within the nephron aids in concentrating urine, allowing humans to conserve water effectively. The urine, once formed, is stored in the bladder before being released through the urethra during micturition.
Other organs, such as the liver, lungs, and skin, participate in excretion, ensuring a comprehensive elimination process. Kidney malfunctions can lead to significant health issues, such as uremia, necessitating interventions like dialysis or transplantation.