virtsarakkoa

Virtsarakko, or the urinary bladder, is a hollow, muscular organ that stores urine before elimination. In humans it sits in the pelvic cavity behind the pubic symphysis. Its position varies by sex: in males it lies anterior to the rectum and above the prostate; in females it lies anterior to the uterus and vagina.

Anatomy: The bladder wall contains the detrusor muscle, a layer of smooth muscle, and a urothelium-lined mucosa. It is highly distensible, with a typical functional capacity around 400–600 ml; the sensation to void is often felt at roughly 150–300 ml.

Control: Storage is maintained by the sympathetic nerves (hypogastric, T11–L2) that relax the detrusor and constrict the internal urethral sphincter, plus somatic input to the external sphincter via the pudendal nerve. Voiding (micturition) is triggered by parasympathetic activation (pelvic nerves S2–S4) causing detrusor contraction and internal sphincter relaxation; voluntary initiation involves higher brain centers.

Blood supply and innervation: The bladder receives arterial blood from branches of the internal iliac arteries (vesical branches). Venous drainage is via vesical venous plexuses. Lymphatics drain to pelvic nodes.

Clinical notes: Common conditions include urinary incontinence, overactive bladder, cystitis, bladder stones, and bladder cancer. Developmentally, the organ originates from the urogenital sinus; congenital anomalies such as bladder exstrophy can occur. Treatments range from behavioral strategies and medications to surgical procedures in more complex cases.