Caption

Bladder and prostate. Coloured ultrasound image of a human bladder and prostate gland. This sagittal section shows the bladder as a sac-shaped black object at upper centre and the prostate gland as a red rounded structure at lower centre. The bladder is a sac made of smooth muscle where urine is stored. The prostate gland is a male accessory sex gland which creates a component of semen. Ultrasound scanning uses extremely high frequency sound waves to create images of structures inside the body.