Comparative Myology Lecture 3 LEARNING OUTCOMES 1.Classify muscle types 2.Differentiate between structures of tendon and aponeurosis 3.Describe implications of no./length of muscle fibers on force generation 4.Describe implications of sites of muscle insertion on range of motion 5.Describe evolutionary adaptations of muscle arrangements in various species MUSCLE TYPES Smooth Muscle – Weak, sustained and rhythmic contractions Cardiac Muscle – Continuous, involuntary Skeletal Muscle – Dark fibers – tonic contractions Pale fibers – phasic contractions STRUCTURE OF TENDON AND APONEUROSIS Tendon – Consolidated masses of CT at the end of muscles STRUCTURE OF TENDON AND APONEUROSIS Aponeurosis – A thick sheet of CT giving attachment to muscles FORCE GENERATION AND NUMBER/LENGTH OF MUSCLE FIBERS Greater the number of muscle fibers, greater the contraction force Greater the length of muscle fibers, greater the ROM IMPLICATIONS OF MUSCLE ATTACHMENT SITES ON ROM Uniarticular / Biarticular / Multiarticular mm. IMPLICATIONS OF MUSCLE ATTACHMENT SITES ON ROM Proximal insertion site on bone – Rapid, extensive excursion of distal end of bone Distal insertion site on bone – Powerful, slow and less extensive excursion EVOLUTIONARY ADAPTATIONS OF MUSCLE ARRANGEMENTS IN VARIOUS SPECIES Portion of a muscle or the muscle itself may be absent e.g. loss of forearm rotators in ungulates A portion may be represented in a different form or may shift to another muscle group e.g. rearrangement of clavicular muscles in quadrupeds EVOLUTIONARY ADAPTATIONS OF MUSCLE ARRANGEMENTS IN VARIOUS SPECIES As the number of digits reduces, some of the muscles disappear or are represented as ligaments e.g. mm. interossei EVOLUTIONARY ADAPTATIONS OF MUSCLE ARRANGEMENTS IN VARIOUS SPECIES The muscles of mastication are composed differently in different animals side to side vs tearing and biting movements Biting - Temporalis Side to side – Masseter Sternoceph.
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