1. Definition: Micturition, commonly known as urination, is the process by which the body expels urine from the bladder through the urethra. This process involves a complex interplay between the nervous system, muscles, and the urinary tract.
2. Anatomy and Physiology:
Bladder: The bladder is a muscular sac that stores urine until expelled. It can expand to accommodate urine and contracts during micturition.
Urethra: The urethra is a tube that connects the bladder to the external environment. It serves as a passageway for urine to exit the body.
Sphincters: The urinary sphincters are ring-like muscles that control urine flow. The internal urethral sphincter is involuntary, while the external urethral sphincter is under voluntary control.
3. Control of Micturition:
Nervous System: Micturition is regulated by both the autonomic (involuntary) and somatic (voluntary) nervous systems.
Storage Phase: During this phase, the bladder fills with urine, and the detrusor (bladder wall muscle) relaxes. The internal urethral sphincter remains contracted to prevent urine leakage.
Voiding Phase: When the bladder is full and micturition is desired, sensory signals from stretch receptors in the bladder wall are sent to the brain. The detrusor muscle contracts in response, and the internal urethral sphincter relaxes. The external urethral sphincter can be voluntarily controlled.
Clinical Significance: Proper micturition is vital for maintaining overall health and preventing urinary retention, urinary incontinence, and related complications. Micturition disorders can arise due to neurological conditions (e.g., spinal cord injuries), structural abnormalities, or urinary tract infections.
