Penis urethra. Coloured scanning electron micrograph (SEM) of a section through a penis showing the wall of the urethra (purple). The urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids from the body. In males (as here), the urethra travels through the penis, and carries semen as well as urine. Magnification: x660, when printed 10 centimetres wide.