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Muscular Tissue
Functions
1.Movement -Whole body or
parts of the body
2.Maintenance of body
posture.
3.Separates body cavities.
4. Respiration.
In animals there are two principle types of
muscles:
1. Striated muscles –their cells exhibit
cross
striations
under
light
microscopy. Based on the location
striated muscles are further divided
into:
a. Skeletal muscle
b. Cardiac
2. Smooth muscle. These cells have no
cross striations.
Myocytes / Muscle cells
These are the cells of
the muscle tissue.
They are elongated
cells whose primary
role is contraction.
Skeletal
Muscle
• Skeletal muscles are anchored
by tendons or by
aponeurosis to bone.
• Responsible for movement of
the skeleton, maintenance of
body posture.
• Voluntary-control of will.
• Components of skeletal muscle
tissue.
a. Muscle cells. These are long
unbranched cells (run parallel)
or myofibres. Have several
peripherally located nuclei.
b.Supportive connective
tissue.
• The skeletal muscle cells are
multinucleated. Their nuclei are
located in the cytoplasm
immediately beneath the plasma
membrane=sarcolema
• Each myofibre appears striated.
• That is, they have periodic
transverse bands.
• Within a myofibre are
myofibrils.
Skeletal muscle-longitudinal
and transverse sections.
Myofibrils
This is the basic contractile
unit.
Several myofibrils are located
within a muscle fibre.
They give the muscle fibre the
appearance of cross
striations.
• They are made up several
sarcomeres each of which
runs from one z band to the
next.
• They extend the entire length
of a muscle cell.
• When muscle contracts each
sarcomere shortens and
thickens.
Myofilaments
• These are the actual contractile elements
of skeletal muscle. Bundle of myofilaments
make a myofibril.
• Two types of myofilaments are associated
with muscle contraction.
• 1. Thin filaments. Composed of protein
actin
• 2. Thick filaments. Composed of protein
myosin II.
• The two myofilaments occupy most of the
cytoplasm =sarcoplasm.
Cross striations
• Arrangement of thick and thin
filaments results in the different
densities in the sarcomere=cross
striations.
• Under the light microscope, they
appear as alternate light and dark
bands=termed as A band and I
bands.
• The A and I bands are
bisected by narrow regions of
contrasting density.
• The light I band is bisected by
the Z line while the thick A
band is bisected by the M
band.
Skeletal muscle cellsLongitudinal section
Connective tissue in Muscle
Several myofibres are
grouped together to form a
fasciculus (bundle).
• Myofibre- endomysium
• Fasciculus- perimysium
• Whole muscle- epimysium
Cardiac muscle tissue
• It is found in the heart.
• Controlled by the autonomic
nervous system (ANS)involuntary.
• 1. Muscle has short striated
cells.
• 2. Fibres branch and
anastomose with adjacent fibres.
3. Each cell has 1-2 nuclei
which are centrally
located unlike the skeletal
muscles where the cells are
multinucleated with their
nuclei located below the
plasma membrane.
4. Have intercalated
discs which are
specialized intercellular
junctions where one cell
touches another cell.
They appear densely
staining under the light
microscope.
–During Increased
demand the cardiac
cells can hypertrophy.
–During decreased
demand the muscle
undergoes atrophy
Cardiac muscle tissue
Intercalated discs
Intercalated discs
PURKINJE FIBERS
• Specialized cardiac fibers.
• Involved in impulse conduction to the
various parts of the myocardium.
• Larger than the cardiac muscle cells.
• Myofibrils in these fibres are fewer
than in the typical cardiac muscle.
They are star-like in shape.
• They are lighter staining when
compared with normal cardiac cells.
PURKINJE FIBERS (cross-section)
Cardiac cells
Purkinje fibres
Smooth Muscle Tissue
• Location
• They line blood vessel walls, the
stomach, the intestines and urinary
bladder.
• They are involuntary.
• They have no cross striations.
• They are referred to as either;
– Smooth, un-striped , visceral or plain
muscles.
Structure
Smooth muscle is formed by
union of spindle shaped cells.
The cells are elongated and
taper on both ends.
- The nuclei are centrally
located.
-The cells are interconnected by
gap junctions.
-
Smooth Muscle cells -Longitudinal section
a).
b).
Smooth Muscle cells –
Longitudinal & cross section
Skeletal muscle cardiac muscle
smooth muscle
Location
Muscles of the
skeleton,
tongue,
oesophagus and
diaphragm.
Heart, superior
and inferior
Blood vessels,
vena cava,
intestines,
pulmonary
stomach.
veins.
Fibers
long and
unbranched
Short and
branching
Nuclei
Few and
peripheral
Single and
central
Sarcomeres
present
present
None
Cell to cell
junctions
None
Intercalated
discs.
Gap junctions
spindle
Single and
central