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Muscle

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Anatomy, general anatomy, Muscle in general

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Muscle

  1. 1. www.slideshare.net 1 Maj Rishi Pokhrel Anatomy NAIHS
  2. 2. At the end of this class, you should be able to .. • Describe skeletal muscle • Classify skeletal muscles • Understand concepts: motor point, motor unit • Describe Laws of innervation • Appreciate importance of skeletal muscles in clinical practice 2
  3. 3. • A male child born to healthy parents with normal pregnancy – Walking was delayed … 4 years – Calf muscles grew unusually large – Couldnot walk after 11 years – Died at the age of 20 – respiratory failure – His elder brother was fine • What went wrong? 3
  4. 4. MUSCLE (Latin – Mus = Mouse) (Gk = Mys) • Myositis, myopathy, myology • Resemble mouse - tapering ends (tendons) - tail • Contractile tissue - brings about movement • Motors of body 4
  5. 5. Properties • Excitability – nerve impulse stimulates contraction • Contractility – Long cells shorten & generate pulling force • Elasticity – Can recoil after being stretched 5
  6. 6. Muscle tissue: types  Skeletal  Striated & voluntary  Cardiac  Striated & involuntary  Smooth  Nonstriated & involuntary 6
  7. 7. Skeletal muscle: features • Striped / Striated / Somatic / Voluntary • Most abundant • Attached to skeleton • Supplied by somatic nerves; voluntary control • Responds quickly to stimuli • Capable of rapid contraction; easily fatigued • Help in adjusting to external environment • Under highest nervous control of cerebral cortex 7
  8. 8. Skeletal muscles: microscopy Connective tissue coverings:  Epimysium – entire muscle  Perimysium – fascicles  Endomysium – muscle fibre 8
  9. 9. Skeletal muscles: microscopy • Multinucleated cylindrical cell, nucleus at periphery • Exhibit cross striations 9
  10. 10. SKELETAL MUSCLE: PARTS • Fleshy, Contractile - Belly • Fibrous, Non contractile – Tendon (cord like) – Aponeurosis (flattened sheet) • Origin: relatively fixed during contraction • Insertion: moves during contraction • Origin & insertion / attachments 10
  11. 11. 11 Tendon • Fibrous, cord like, non-contractile • Composed of bundles of collagen fibres • Surrounded by epi-tendineum • Supplied by sensory nerve • Vascular needs- minimal • Tendon transfer & transplantation • Heals very slowly
  12. 12. Aponeurosis • Attachment of muscle by thin, broad sheet • Composed of parallel bundles of collagen fibres • E.g. External oblique aponeurosis 12
  13. 13. Raphe • Fibrous band; interdigitating fibres of aponeurosis • Stretchable • E.g. Mylohyoid raphe 13 MR
  14. 14. Nomenclature of skeletal muscles • Shape: Trapezius, Rhomboideus, Deltoid • Number of heads: Biceps, Triceps, Quadriceps • Structure: Semimembranosus, Semitendinosus • Location: Temporalis, Supraspinatus • Attachments: Stylohyoid, Cricothyroid • Action: Adductor longus, Flexor carpi ulnaris • Direction of fibres: Rectus abdominis, Transversus abdominis • Relative position: Medial & lateral pterygoids 14
  15. 15. Nerve supply • Nerve supplying a muscle - motor nerve • Motor point – Site where motor nerve enters muscle – May be one or more – Electrical stimulation at this point is more effective • Sensory supply: proprioception 15
  16. 16. MOTOR UNIT • Motor unit - motor neuron & all muscle fibres it supplies • Fine movements (fingers, eyes) - small motor units: 5-10 fibres • Large weight-bearing muscles (thighs, hips) - large motor units :100-200 fibres • Hybrid muscles 16
  17. 17. Classification of skeletal muscle • Based on – Architecture of fasciculi – Action 17
  18. 18. Fascicular architecture • Force - directly proportional to number & size of muscle fibres • Range - directly proportional to length of fibres • Classified: According to arrangement of fasciculi – Parallel – Oblique – Spiral – Cruciate 18
  19. 19. FASCICULAR ARCHITECTUREParallel fasciculi •Fasciculi are parallel to line of pull •Range of movements is maximum •Subtypes – Quadrilateral -Thyrohyoid – Strap like - Sartorius – Strap like with tendinous intersections - Rectus abdominis – Fusiform - Biceps brachii 19
  20. 20. • Fasciculi oblique to line of pull • Power increased, range decreased • Subtypes – Triangular - Temporalis – Unipennate - Flexor pollicis longus – Bipennate - Rectus femoris – Multipennate – Deltoid (middle fibres) – Circumpennate - Tibialis anterior 20 Oblique fasciculi
  21. 21. Spiral / twisted fasciculi – Trapezius – Lattisimus dorsi – Pectoralis major 21
  22. 22. CRUCIATE FASCICULI • Fasciculi are crossed – Sternocleidomastoid (SCM) – Masseter 22 SCM Masseter
  23. 23. Classification : action of muscle • Prime mover • Antagonist • Fixator • Synergist 23
  24. 24. Prime mover • Muscle or group of muscles that bring about a desired movement • Gravity may also assist • E.g. Brachialis as flexor at elbow joint 24
  25. 25. Antagonist (opponent) • Muscle or group of muscles that directly oppose movement under consideration • Relax & control movement to make it smooth, jerk free & precise. • Prime mover & antagonist cooperate • E.g. Triceps in elbow flexion 25 BF QF BF
  26. 26. Fixators (fixation muscles) • Stabilize parts & thereby maintain position while prime movers act • E.g.: Muscles holding scapula steady are acting as fixator while deltoid moves humerus 26 Deltoid
  27. 27. Synergists • Special fixation muscles • Partial antagonist to prime mover • When a prime mover crosses two or more joints, synergists prevent undesired actions at intermediate joints 27 Flexor tendon
  28. 28. Laws of innervation • Hilton’s law: “the nerve supplying the muscles extending directly across and acting at a given joint also innervate the joint & skin overlying the joint • “Only actions are represented in cortex” • “Spinal segments supplying the antagonists are in a sequence” • “Spinal segments supplying immediately distal group of muscles are in sequence” 28
  29. 29. Applied anatomy Paralysis / paresis • Loss of power of movement • Muscles are unable to contract • Damage to motor neural pathways – Upper motor neuron (UMN) – Lower motor neuron (LMN) 29
  30. 30. • Muscular spasm – spontaneous / involuntary contraction • May be – Localized – commonly caused by a “muscle pull” – Generalized – seen in Tetanus & Epilepsy 30 Applied anatomy
  31. 31. 31 • Disuse atrophy – Muscles not used for long time, become thin & weak – Reduction in size (muscular wasting) – Seen in paralysis & generalized debility • Hypertrophy – Excessive use of a particular muscle results in better development or hypertrophy (Body builders & Athletes) Applied anatomy
  32. 32. • Regeneration – Capable of limited regeneration – Large regions damaged- regeneration does not occur & replaced by CT • Muscular dystrophy – Inherent defect in cell membrane of muscle – Rupture of muscle fibers – X- linked recessive – Duchene’s & Baker’s 32
  33. 33. ? 33

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