The movement of the cat hyoid during feeding

Abstract

The hyoid has generally been regarded as a basically static element in the jaw apparatus, moving only in swallowing. A regular patterned hyoid movement directly correlated with jaw movement occurs during feeding on soft food in the American opossum; the present study sought to establish whether: (i) hyoid movement was always linked to jaw movement and (ii) the pattern of hyoid movement could be correlated with jaw movement cycles associated with (a) transport and (b) chewing of food. Cats were fed foods varying in consistency from liquid (milk) to hard solids (cooked liver) and cinefluorographic recordings made of complete feeding sequences. The results showed that the hyoid not only moved continuously during feeding but had a generally upwards and forwards movement during early jaw opening (SO phase of jaw movement) and a generally backwards movement during later jaw opening (FO phase). This relationship was associated with movement of food through and within the mouth. In contrast, the hyoid orbit was attentuated and its phase relationship with that of the jaw movement cycle altered in some jaw movement cycles with short SO phases which occurred in the middle of sequences in which hard food was being processed. These changes are associated with a shift from a transport to a non-transport or chew function of the tongue and therefore a change in the behaviour of the hyoid in its base.