Virtsankäynti

Virtsankäynti, also known as urination or micturition, is the process by which urine is expelled from the body. It is a vital physiological function for maintaining fluid balance and eliminating waste products. The process begins in the kidneys, where blood is filtered to remove waste materials and excess water, forming urine. This urine then travels down the ureters to the bladder, a muscular sac that stores it.

When the bladder fills with urine, stretch receptors in its walls send signals to the brain, creating the sensation of needing to urinate. The brain then signals the bladder muscles to contract and the sphincter muscles at the opening of the bladder to relax, allowing urine to flow out of the body through the urethra. This entire process is a complex interplay of the nervous system and muscular control.

The frequency and volume of urination can vary significantly among individuals and are influenced by factors such as fluid intake, diet, medications, and underlying health conditions. While generally an involuntary reflex, conscious control over urination is learned and maintained through sphincter muscle function. Deviations from normal urination patterns, such as increased frequency, difficulty urinating, or pain, can indicate medical issues and should be evaluated by a healthcare professional.