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					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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