From day ___, the blastocyst begins to elongate bilaterally. It extends the length of the pregnant horn by day ___ in bovine, and by day ___ in the sheep. Later, after extending into the nonpregnant horn, it reaches a length of ___ cm and a width of ___ mm (bovine); in the bovine, the tips of the extended blastocyst are slightly bulbous. The elongated portions of the blastocyst later become folded in a concertina-like fashion; the embryonal disc is visible as a slight swelling in the middle.