General Anatomy • Introduction to muscle • Histological Classification • Functions of muscles in general • Type of skeletal muscles

1. The Muscular
System
Dr, Syed Altaf Assistant Professor

2. Derivation of name
Muscle (Latin Mus=
mouse) are so named
because many of
them resemble a
mouse, with their
tendons representing the
tail.

4. The Muscular System
 Muscles are responsible for all types of
body movement – they contract or
shorten and are the machine of the
body
 Three basic muscle types are found in
the body
Skeletal muscle
Cardiac muscle
Smooth muscle

5. Characteristics of Muscles
Slide 6.2
 Muscle cells are elongated
(muscle cell = muscle fiber)
 Contraction of muscles is due to the
movement of microfilaments
 All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle

6. Skeletal Muscle:
Characteristics
Slide 6.3
 Most are attached by tendons to bones
 Cells are multinucleate
 Striated – have visible banding
 Voluntary – subject to conscious control
 Cells are surrounded and bundled by
connective tissue = great force, but tires
easily

7. Connective Tissue Wrappings of
Skeletal Muscle
Slide 6.4a
 Endomysium –
around single
muscle fiber
 Perimysium –
around a
fascicle
(bundle) of
fibers Figure 6.1

8. Connective Tissue Wrappings of
Skeletal Muscle
Slide 6.4b
 Epimysium –
covers the
entire skeletal
muscle
 Fascia – on the
outside of the
epimysium
Figure 6.1

9. Skeletal Muscle Attachments
Slide 6.5
 Epimysium blends into a connective
tissue attachment
Tendon – cord-like structure
Aponeuroses – sheet-like structure
 Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings

10. Smooth Muscle Characteristics
 Has no striations
 Spindle-shaped
cells
 Single nucleus
 Involuntary – no
conscious control
 Found mainly in
the walls of hollow
organs
 Slow, sustained
and tireless Figure 6.2a

11. Cardiac Muscle Characteristics
 Has striations
 Usually has a
single nucleus
 Joined to another
muscle cell at an
intercalated disc
 Involuntary
 Found only in the
heart
Figure 6.2b

14. Skeletal
muscles
SSyynonyms
1. Striped muscles
2. Striated muscles
3. Somatic muscles
4. Voluntary muscles

15. Parts of a skeletal muscle
A. Two ends
1.Origin is one end of the
muscle which remains fixed
during its contraction.
2. Insertion is the other end
which moves during its
contraction.
In the limb muscles, origin is
usually proximal to insertion.

16. 1. Fleshy part is contractile,
and is called the ‘belly’.
2. Fibrous part is non-
contractile and inelastic.
When cord-like or rope-like,
it is called ‘tendon’ ;
3. when flattened it is called
‘aponeurosis’.
B. Two parts

17. BASIC PROPERTIES
• IRRITABILITY
– Sensitive to stimuli
• CONTRACTILITY
– When stimulated, the contracts
lengthwise leading to its shortening

18. BASIC PROPERTIES
• EXTENSIBILITY
– The Ability to stretched without Any tissue
damage .
• ELASTICITY
– Muscle assumes a desired shape.

19. Microscopic Anatomy of Skeletal
Muscle
Slide 6.9a
 Cells are multinucleate
 Nuclei are just beneath the sarcolemma
Figure 6.3a

20. Microscopic Anatomy of Skeletal
Muscle
 Sarcolemma – specialized plasma
membrane
 Sarcoplasmic reticulum – specialized
smooth endoplasmic reticulum
Figure 6.3a

21. Microscopic Anatomy of Skeletal
Muscle
 Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distinct bands
I band =
light band
A band =
dark band
Figure 6.3b

22. Microscopic Anatomy of Skeletal
Muscle
 Sarcomere
Contractile unit of a muscle fiber
Figure 6.3b

23. Nerve Stimulus to Muscles
 Skeletal
muscles must
be stimulated
by a nerve to
contract (motor
neruron)
 Motor unit
One neuron
Muscle cells
stimulated by
that neuron
Figure 6.4a

24. Energy for Muscle Contraction
 Anaerobic glycolysis
(continued)
This reaction is not as
efficient, but is fast
Huge amounts of
glucose are needed
Lactic acid produces
muscle fatigue
Figure 6.10b

25. Energy for Muscle Contraction
 Aerobic Respiration
Series of metabolic
pathways that occur in
the mitochondria
Glucose is broken down
to carbon dioxide and
water, releasing energy
This is a slower reaction
that requires continuous
oxygen
Figure 6.10c

26. Slow and Fast Muscle Fibres
1. Type I (slow,red) fibres
•
•
•
• show a slow ‘tonic’ contraction
characteristic of postural muscles.
They are red in colour because of large
amounts of myoglobin.
The fibres are rich in mitochondria and
oxidative enzymes but poor in
phosphorylases.
Because of well developed metabolism,
slow fibers are highly resistant to fatigue.

27. •
2. Type II (fast,white) fibres
• show a fast ‘phasic’ contraction required for
large-scale movements of body segments
(non- postural muscles)
These are paler (white) in color because of
small amounts of myoglobin.
•
•
These fibres are rich in glycogen and
phosphorylases, but poor in mitochondria and
oxidative enzymes.
Because of anaerobic glycolytic respiration, the
fast fibres are quite easily fatigued.

28. Muscle Tone
 Some fibers are contracted even in a
relaxed muscle.
 Different fibers contract at different
times to provide muscle tone
 The process of stimulating various
fibers is under involuntary control

29. Naming Skeletal Muscles
• Location of muscle – bone or body region
associated with the muscle
• Shape of muscle – e.g., the deltoid muscle
(deltoid = triangle)
• Relative size – e.g., maximus (largest),
minimus (smallest), longus (long)

30. • Direction of fibers – e.g., rectus (fibers run
straight), transversus, and oblique (fibers run at
angles to an imaginary defined axis)
• Number of origins – e.g., biceps (two origins)
and triceps (three origins)
• Location of attachments – named according to
point of origin or insertion
• Action – e.g., flexor or extensor, as in the names
of muscles that flex or extend, respectively
Naming Skeletal Muscles

31. Naming of Skeletal Muscles
 Direction of muscle fibers
Example: rectus (straight)
 Relative size of the muscle
Example: maximus (largest)

32. Naming of Skeletal Muscles
 Location of the muscle
Example: many muscles are named
for bones (e.g., temporalis)
 Number of origins
Example: triceps (three heads)

33. Naming of Skeletal Muscles
 Location of the muscles origin and
insertion
Example: sterno (on the sternum)
 Shape of the muscle
Example: deltoid (triangular)
 Action of the muscle
Example: flexor and extensor (flexes or
extends a bone)

36. ATTACHMENTS e.g.,
stylohyoid, cricothyroid, etc.
FUNCTION e.g., adductor
longus, flexor carpi ulnaris,
abductor pollicis longus,
etc.
DIRECTION OF FIBRES
e.g., rectus abdominis,
oblique abdominis,
transversus, etc.

37. FASCICULAR ARCHITECTURE OF MUSCLES
• The arrangement of muscle fibres varies
according to
–direction,
–force
–range of movement at joint.

38. CLASSIFICATION OF MUSCLE ACCORDING TO
THE ARRANGEMENT OF THE FASCICULI
A.Parallel Fasciculi
B.Oblique Fasciculi
C.Pennate Fasciculi
D.Spiral or Twisted Fasciculi

39. Fascicular arrangement

40. Pennate Fasciculi
1. Unipennate-
e.g. flexor pollicis
longus, extensor
digitorum longus,
peroneus tertius
2. Bipennate-
e.g. rectus femoris,
dorsal interossei,
peroneus longus,
flexor hallucis longus

42. Types of Muscle Contractions
 Isotonic contractions
Myofilaments are able to slide past each
other during contractions
The muscle shortens
 Isometric contractions
Tension in the muscles increases
The muscle is unable to shorten

44. A. Prime movers (agonists) Bring about the
desired movement.
B. Antagonists (opponents) Produce
movement opposite to prime mover. They
help the prime movers by active controlled
relaxation.
C. Fixators They stabilize the origin of prime
mover so it can act efficiently.
D. Synergists When the prime movers cross
more than one joint, the undesired actions at
the proximal joints are prevented by certain
muscles known as synergists
GROUP ACTION OF MUSCLES

45. Types of Ordinary Body Movements
 Flexion – decreases angle of joint and
brings two bones closer together
 Extension- opposite of flexion
 Rotation- movement of a bone in
longitudinal axis, shaking head “no”
 Abduction/Adduction

46. Body Movements
Slide 6.33Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

47. Blood supply of skeletal muscle
• Blood supply is derived from muscular branches
from neighbouring arteries.
• The arteries, veins and motor nerve pierce the
muscle at a fairly constant point called
neurovascular hilum.
• The arteries divide repeatedly to form arterioles
in the perimysium, and capillaries in the
endomysium for nutritive circulation.

48. Nerve supply of skeletal muscle
The nerve supplying a muscle is called a
motor nerve.
In fact it is a mixed nerve.
MOTOR FIBRES (60%)
SENSORY FIBERS (40%)

50. • MOTOR POINT:
Site where motor nerve enters the muscle.
It may be one or more than one.
• MOTOR UNIT (MYONE):
Single alpha motor neuron together with the
muscle fibres supplied by it. The size of motor
unit depends upon the precision the muscle
control.
Small motor units (5-10 muscle fibres) are found in
muscles of fine movements (extra-ocular muscles).
Large motor units (100-2000 muscle fibres) are found
in muscles of gross movements (proximal limb
muscles).

51. Effects of Exercise on Muscle
 Results of increased muscle use
Increase in muscle size
Increase in muscle strength
Increase in muscle efficiency
Muscle becomes more fatigue resistant

52. APPLIED ANATOMY
PARALYSIS
Loss of motor power (power of
movement)
This is due to inability of
muscles to contract either
because of damage to motor
pathways or by inherent
disease of muscles (myopathy).

53. APPLIED ANATOMY
MUSCULAR SPASM
Localized muscle spasm is commonly caused by a
‘muscle pull’.
Generalized muscle spasms occur in tetanus and
epilepsy.
DISUSE ATROPHY
muscles which are not used for a long time become
thin and weak. This is called disuse atrophy.

56. APPLIED ANATOMY
OVERUSE HYPERTROPHY
Excessive use of a
particular muscle causes
that muscle evident
the better development of
by
increase in size and bulk.
MUSCLE REGENERATION
Muscles have a limited
capability of regeneration.

57. Disorders relating to the Muscular System
• Muscular Dystrophy: inherited, muscle
enlarge due to increased fat and connective
tissue, but fibers degenerate and atrophy.
• Duchenne : lacking a protein to maintain the
sarcolemma.

59. Myasthemia Gravis:

60. Dr, Syed Altaf Assistant Professor