Sper' ma ry, the organ in which sperm cells are developed.
Sperm cells, the small, often motile, reproductive cell, which fuses with the egg cell.
Spic' ules, tiny needles of mineral substance found in the walls of many animals, notably sponges.
Spi' ra cle, an opening into the tracheal breathing organs of insects.
Spire, the coiled portion of a gasteropod shell.
Spore, a cell capable of developing into a new organism.
Sternum, a bone extending along the lower middle line of the chest region.
Stom' ach, the region of the alimentary canal especially adapted to digest food.
Stom' ach-in tes' tine, a region of the alimentary canal adapted to both digest and absorb food.
Sub cla' vi an, situated beneath the clavicle.