ANAT30007 Lecture Notes - Lecture 6: Scapula, Biomet, Masseter Muscle

• School: University of Melbourne
• Department: Anatomy and Neuroscience
• Course: ANAT30007
• Professor: All

Document Summary

Such a shallow socket, but large range of motion. Motion comes at the cost of stability. Moment arm = length b/w a joint axis and the line of force acting on that joint. The torque capacity of a muscle (eg. in elevation) is determined by its moment arm. Larger muscles that are further from the joint have more leverage: eg. A muscle"s instantaneous moment arm can be measured from the instantaneous gradient of the muscle"s tendon excursion vs. joint angle curve: tells where the muscle is a prime mover. In early abduction, supraspinatus has the longest moment arm -> indicates supraspinatus (on top of scapula) has greatest leverage and is an initiator of abduction. Lat. dorsi has negative moment arm -> indicating it is a depressor (good for climbing) Middle deltoid kicks in in later elevation mid-range and high motion. 50% of ppl in there 7th decade, and over 80% over 80 will suffer a full-thickness rotator cuff tear.