An apparatus for sorting and orienting sperm cells includes a pair of walls in confronting arrangement and forming a flow chamber having an inlet, a downstream outlet, and an intermediate detector region. The inlet receives first and second spaced apart streams of input fluid and a third stream of sample fluid containing the cells to be sorted. The first and second streams have respective flow rates relative to the third stream, such that the third stream is constricted, forming a relatively narrow sample stream, so that the cells are oriented parallel to the walls. A detector detects the desired cells and a sorter downstream of the detector, sorts the desired cells from the stream.