Figure 1.

Heterogeneity of ejaculate fractions. This schematic representation depicts the proportional contribution and temporal (left to right) sequence of four sources of seminal fluid: first, urethral and bulbourethral glands (‘UB’), <10% of total ejaculate volume; second, prostatic, 20–40%; third, testicular-epididymal (‘TE’), <10%; finally, seminal vesicular, 50–80%. Collecting semen in sequential fractions results in heterogeneous composition of each fraction due to varied contributions from biochemically different glands