Vol. 3, Issue 1, Part A (2018)

A comparative gross anatomical study and linear measurements of the two types of masticatory muscles were conducted on slaughtered sheep heads. The physiological cross- sectional area (PCSA), maximal isometric force, torque and kinetic energy were calculated. were calculated. The study showed that the sheep jaw-closing muscles were the masseter and temporal muscles whereas the digastricus was a jaw-opening muscle. The physiological cross- sectional area (PCSA) was 3.1, 2, 3.1 cm² for the masseter, temporal and the digastric muscle, respectively. The maximal isometric force for those muscles was 6.2, 4, 6.2 cm², respectively. The force of those muscles was 0.49, 0.098, 0.196 N, respectively. The torque of those muscles was 0.49, 0.098, 0.196 Nm, respectively. While the kinetic energy of the jaw-closing group was 90 Joule, that of the jaw-opening group was 30 Joule. The values of the PCSA, force, maximum isometric force, torque and kinetic energy of the jaw-closing group were higher than those of the jaw- opening. This is suggested to be due to the increased activity of the jaw-closing muscles.