Dr Shabana Ali
Associate Professor Anatomy
MBBS Mphil Anatomy, PGDE, MHPE

• Each muscle fibre is actually a single muscle cell
• approx 10-100 µm in diameter & few mm- many cm long.
• have many nuclei
• Muscle cells must be insulated from one another by specialized membranes.
nuclei stripes myofibrils

• Each muscle fiber (muscle cell), is composed of many myofibrils.
• Organized system of cytoskeleton filaments of actin
and myosin proteins that do the actual contraction.
• A sarcomere is one segment of a myofibril .
• The series of sarcomeres produce the striated appearance of muscles

Contractile proteins
• Actin
• Myosin
Regulatory proteins
• Tropomyosin
• Troponin
Structural proteins
• Dystrophin
• Titin

Morphology
Group action
• Myoglobin content
Mode of attachment
Extent of muscle

• Muscles with fibers parallel to line of pull
Muscles with fibers oblique to line of pull
Cruciate muscles
Circular muscles
Spiral muscles

A. Muscles with fibers parallel to line of pull
• Great range of movement
• Less power
• Classified into three subgroups
 Strap like muscles
 Quadrilateral muscles
 Fusiform muscles

Strap like muscles
Quadrilateral muscles
Sartorius,
Sternohyoid
•
Length greater than width
Thyrohyoid muscle
Short length
Fusiform muscles
Bicep brachii
Fibers taper at both ends

B. Muscles with fibers oblique to line of pull
• Greater power
• Less range of movement
• Classified into three groups
 Triangular muscles
 Pennate muscles
 Radial muscles

Triangular/
Convergent muscle
Broad origin
Pennate muscles
Narrow insertion
Temporalis,
Deltoid
Feather like fibers obliquely attached to tendon
Classified into
• Unipennate
• Bipennate
• Multipennate
Radial muscles
Fibers originate from wall of osteofacial compartment
Converge on central tendon
Tibialis anterior

• Broad origin
• Narrow insertion
• Twist as they pass from origin to insertion
• Some muscles twist around bones
• Supinator spirals obliquely around shaft of radius

• Have two planes of fibers
• Two planes cross each other
• Masseter
• Sternocleidomastoid

• Circular arrangement of fibers
• Enclose body orifices
• Orbicularis oculi
• Orbicularis oris

• One action of the joint is not only the responsibility of one muscle but it is the responsibility of different groups of muscles, which can be classified as
Agonist
Fixators
Muscle action
Antagonist
Synergists

Tonic muscles
Reflexive muscles
Phasic muscles

Tonic muscles (stabilizers):
• Demonstrate continuous low level of contractile activity which is required to maintain a given
posture.
• Prevent muscle from getting flaccid.

Reflexive muscles:
• Contract automatically Eg., Diaphragm
• Contraction of muscles by subjecting it to stress
• Eg., contraction of Quadriceps Femoris in knee jerk

• Demonstrates rapid (fast twitch) activity which is required when changing from one position to another

Red fibers
• Smallest diameter
• Abundant myoglobin
• Abundant mitochondria
White fibers
• Larger diameter
• Less myoglobin
• Few mitochondria
Intermediate fibers
• Posses intermediate characteristics

• Slow oxidative fibers with small diameter
• Red due to myoglobin and rich vascularity
• Rich in mitochondria and oxidative enzymes
• Poor in phosphorylases
• Undergo extensive repetitive movement without fatigue.
• Responsible for maintenance of posture.
• Soleus, Erector spinae

• Larger diameter and white in color
• Less myoglobin and few mitochondria
• Contract rapidly but also fatigue very quickly due to glycolytic respiration.
• Biceps brachii, extraocular muscles of eye

 In appearance, resemble fast fibers, for they contain little myoglobin and are relatively pale.
 They have a more extensive capillary network around them and are more resistant to fatigue than are fast fibers.
 Most fibers in body belong to this variety

1.
Spurt
▫ mainly rotator muscles which have their origin away from the joint and their insertion near to the joint e.g
. Biceps muscle .
2.
Shunt
▫ mainly stabilizer muscles which have origin near the joint and their insertion away from the joint e.g
. Brachioradialis
3.
Spin muscles
• Muscles having predominantly spin movement.
Pronator
quadratus.

5.Based on the Extent of the Muscles
• EXTRINSIC MUSCLES
• Extensive muscles having some attachment in the concerned region and some in other region
• Consist of thick and course fasciculi
• Gross types of movement
• INTRINSIC MUSCLES
• Smaller muscles having all attachments in the same region
• Consist of thin fasciculi
• Fine and precision types of movement

Intrinsic muscles
Extrinsic muscles

• Loss of motor power is called paralysis
• Cause can be damage of motor neuronal pathway or inherent disease of muscle
• Spastic paralysis
• Flaccid paralysis

• Is an involuntary contraction of a muscle that can cause a great deal of pain.

• Neuromuscular disorder
• Fatigue of skeletal muscles
• Flaccid paralysis
• Acetylcholine receptors decrease in number

• Ingestion of insecticides
• Inhibit action of acetylcholine
• Accumulation of acetylcholine leads to hyperexcitation of muscle
• Death occurs due to spastic paralysis of muscles of respiration

• Bursitis is the inflammation of one or more bursa in the body.
• Vary from localized warmth and erythematous, joint pain and stiffness, to stinging pain that surrounds the joint around the inflamed bursa.