Crystals in seminal fluid. Polarised light micrograph of a sample of abnormal seminal fluid. The sample contains crystals, which may indicate a problem with the prostate. For example, if the crystals are composed of uric acid, this may be caused by an infection of the prostate (prostatitis). The prostate is a male sex gland thatsurrounds the urethra just below the bladder and secretes seminal fluid, an alkaline liquid that forms part of the semen. Magnification: x570 when printed 10 centimetres wide.