What is the definition of micturition?

Micturition refers specifically to the process of expelling urine from the urinary bladder through the urethra to the outside of the body. This process is an essential part of the urinary system's function, allowing for the elimination of waste products and the regulation of body fluids.

During micturition, several physiological mechanisms are involved, including the contraction of the bladder's smooth muscle and the relaxation of the sphincters, which facilitates the movement of urine. This process is also subject to neural control, allowing individuals to have some degree of voluntary control over when they urinate. Understanding micturition is crucial for appreciating how the urinary system maintains homeostasis in the body.

The other options involve different functions related to the urinary system but do not define micturition itself. For example, the formation of urine occurs in the kidneys, while the absorption of nutrients and blood filtration are processes primarily associated with the digestive and circulatory systems, respectively.