Anatomy, general anatomy, Muscle in general

1. www.slideshare.net 1
Maj Rishi Pokhrel
Anatomy
NAIHS

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
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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?
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4. MUSCLE
(Latin – Mus = Mouse)
(Gk = Mys)
• Myositis, myopathy, myology
• Resemble mouse - tapering
ends (tendons) - tail
• Contractile tissue - brings
about movement
• Motors of body
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5. Properties
• Excitability – nerve impulse stimulates contraction
• Contractility – Long cells shorten & generate pulling force
• Elasticity – Can recoil after being stretched
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6. Muscle tissue: types
 Skeletal
 Striated & voluntary
 Cardiac
 Striated & involuntary
 Smooth
 Nonstriated & involuntary
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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
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8. Skeletal muscles: microscopy
Connective tissue coverings:
 Epimysium – entire muscle
 Perimysium – fascicles
 Endomysium – muscle fibre
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9. Skeletal muscles: microscopy
• Multinucleated cylindrical cell, nucleus at periphery
• Exhibit cross striations
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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
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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. Aponeurosis
• Attachment of muscle by thin,
broad sheet
• Composed of parallel bundles of
collagen fibres
• E.g. External oblique
aponeurosis
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13. Raphe
• Fibrous band; interdigitating
fibres of aponeurosis
• Stretchable
• E.g. Mylohyoid raphe
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MR

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
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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
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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
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17. Classification of skeletal muscle
• Based on
– Architecture of fasciculi
– Action
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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
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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
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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
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Oblique fasciculi

21. Spiral / twisted fasciculi
– Trapezius
– Lattisimus dorsi
– Pectoralis major
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22. CRUCIATE FASCICULI
• Fasciculi are crossed
– Sternocleidomastoid (SCM)
– Masseter
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SCM
Masseter

23. Classification : action of muscle
• Prime mover
• Antagonist
• Fixator
• Synergist
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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
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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
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BF
QF
BF

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
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Deltoid

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
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Flexor tendon

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”
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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)
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30. • Muscular spasm – spontaneous / involuntary
contraction
• May be
– Localized – commonly caused by a “muscle pull”
– Generalized – seen in Tetanus & Epilepsy
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Applied anatomy

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• 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. • 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
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