Muscle

Anatomy, general anatomy, Muscle in general

1. www.slideshare.net
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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 ARCHITECTURE
Parallel 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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33. ?
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