Muscular System
Muscles are responsible for all types
of body movement – they contract
or shorten and are the machine of
the body
The action of the
muscle on the joint can be
worked out from its
attachments and from its
relation to the joint.
The Muscular System
Three basic muscle types are found in the
body
 Skeletal muscle
 Cardiac muscle
 Smooth muscle

Function of Muscles
1. Support the
body
 2. Allow for
movement by
making bones and
other body parts
move
 3. Maintain
constant body
temperature

4. Assist in
movement of
cardiovascular
veins and lymph
 5. Protect internal
organs and
stabilize joints

Coverings of a Skeletal Muscle

Skeletal muscles are
organs



They contain muscle
fibers, nerves, and blood
vessels
Connective tissue
membranes separate each
muscle structure
Fascia – layer of fibrous
tissue that separates
muscles from each other
and from the skin
Coverings from largest to smallest
Epimysium –
covers the entire
skeletal muscle
 Perimysium –
surrounds a
bundle of muscle
fibers (fascicle)
 Endomysium –
surrounds a
single muscle
fiber (cell)

Skeletal Muscle Attachments

Epimysium blends into a connective tissue
attachment


Tendon – cord-like structure
Sites of muscle attachment



Bones
Cartilages
Connective tissue coverings
Classification of muscle(appearance)
Classification of muscle on the basis
of direction of muscle fibers
Parallel muscles
 Pennate muscle
 Spiral muscles
 Cruciate muscles

Parallel muscles

Circumpennate :
Spiral muscle
Cruciate muscles
Classification of muscle on the basis
of force of action
Naming of Skeletal Muscles

Direction of muscle fibers


Relative size of the muscle


Example: maximus (largest), minimus
(smallest), longus (long), brevis (short)
Location of the muscle


Example: rectus (straight), orbicularis (circular)
Example: pectoralis (chest), external (outside),
frontalis (frontal)
Number of origins

Example: triceps (three heads)

Location of the muscles origin and
insertion


Shape of the muscle


Example: sterno (on the sternum)
Example: deltoid (triangular)
Action of the muscle

Example: flexor and extensor (flexes or
extends a bone)
Microscopic Anatomy of Muscle Fiber
(muscle cell)
Cells are multinucleate
 Nuclei are just beneath the membrane

Sarcolemma – specialized plasma
membrane
 Sarcoplasmic reticulum – specialized
smooth endoplasmic reticulum involved in
muscle contraction


Myosin and actin
overlap somewhat
in the sarcomere

Myosin filaments
have heads
(extensions) that
can ‘grab’ onto
actin forming a
crossbridge

Muscle force depends upon the
number of fibers stimulated

More fibers contracting results in
greater muscle tension
Muscles and Body Movements
Movement is
attained due to a
muscle moving an
attached bone
 Muscles are attached
to at least two points

Blood supply
Nerve supply
Disorders relating to the Muscular
System
Muscular Dystrophy: inherited, muscle
enlarge due to increased fat and
connective tissue, but fibers degenerate
and atrophy
 Duchenne MD: lacking a protein to
maintain the sarcolemma
 Myasthemia Gravis: progressive
weakness due to a shortage of
acetylcholine receptors

Sprain verses Strain

Strain – overstretching of
a muscle near a joint

Sprain – twisting of a joint
leading to swelling and
injury to ligaments,
tendons, blood vessels and
nerves
Myalgia and Tendinitis

Myalgia –
inflammation of
muscle tissue
(arthritis on previous
slide)

Tendinitis –
inflammation of the
tendon due to strain
of repeated activity
TENDONS
Tendons take the form of whitish-looking
cords or straps, with a round or oval crosssection.
 60% of their dry weight consists of large
crimped fibres of collagen type I .
 Other components of their matrix include
collagen types II and V, elastin,
glycoproteins and proteoglycans


Loose connective tissue between fascicles
provides a conduit for small vessels and
nerves; it condenses on the surface as a
sheath or epitendineum.

The loose attachments between this
sheath and the surrounding tissue present
little resistance to movements of the
tendon.
Aponeurosis

Aponeuroses are sheet-like elastic tendon
structures that cover a portion of the
muscle belly and act as insertion sites for
muscle fibers while free tendons connect
muscles to bones