The pathway of urine starting from when blood enters the kidney to the urethra is as follows:
1. Blood enters the kidney through the renal artery, which branches into smaller vessels called arterioles.
2. Arterioles further divide into tiny capillaries known as glomerulus, located within the nephrons, the functional units of the kidney.
3. In the glomerulus, blood is filtered under high pressure, allowing water, waste products, and dissolved substances to pass through into the renal tubules.
4. From the glomerulus, the filtered fluid, called filtrate, enters the renal tubules.
5. Within the renal tubules, the filtrate undergoes processes of reabsorption and secretion. Valuable substances like water, glucose, ions, and certain nutrients are reabsorbed back into the bloodstream, while waste products and excess substances are further concentrated in the tubules.
6. The refined fluid, now referred to as urine, travels down the renal tubules, eventually reaching the renal pelvis.
7. The renal pelvis is a funnel-shaped structure that collects urine from the tubules and funnels it into the ureter.
8. Ureters are muscular tubes that transport urine from the kidneys to the urinary bladder.
9. Urine accumulates in the urinary bladder until it reaches a certain volume, triggering the urge to urinate.
10. Upon urination, the urine is expelled from the urinary bladder through the urethra and exits the body.
This complete pathway ensures the filtration, reabsorption, and elimination of waste products from the bloodstream, maintaining proper fluid and electrolyte balance within the body.