The urge to urinate is controlled by nervous signals that regulate the contraction and relaxation of the muscles in the urinary bladder. These signals are under conscious control, allowing individuals to suppress or initiate urination voluntarily.

The urinary bladder acts as a temporary storage reservoir for urine. It expands as urine accumulates and contracts when it’s time to urinate, exerting pressure that triggers the urge to pass urine through the urethra.

The ureter is a long tube that connects each kidney to the urinary bladder. Its primary function is to transport urine from the kidneys to the bladder for storage.

During re-absorption, essential substances like glucose, amino acids, salts, and water are selectively re-absorbed from the initial filtrate back into the bloodstream. This process helps maintain the body’s balance of water and electrolytes while eliminating waste products.

Nephrons are the filtration units in the kidneys responsible for filtering waste products from the blood and producing urine. They selectively re-absorb substances like glucose, amino acids, salts, and water from the initial filtrate as urine flows through the tubules.