Muscle tissue
Dr. Amam Ali Amam
PhD: Periodontal Disease

Muscle tissue
Composed of: differentiated cells containing contractile
proteins.
Most muscle cells are of mesodermal origin,
They are differentiated mainly by a gradual process of
lengthening, with simultaneous synthesis of myofibrillar
proteins.

Muscle tissue
General characteristics
The sarcoplasm : it’s the cytoplasm of muscle .
The sarcolemma : is the cell membrane, or plasmalemma .
The sarcoplasmic reticulum : the smooth endoplasmic
reticulum

Muscle tissue morphological and functional characteristics
1-Smooth Muscle Tissue 2- Striated Muscle Tissue
Skeletal muscle
Cardiac muscle

Structure of the 3 muscle type, cross section
Muscle types
Activity Composed of:
Skeletal muscle
Strong , quick dis continuous voluntary contraction
Large, elongated, multinucleated fibers
Cardiac muscle
Strong , quick continuous involuntary contraction
Smooth muscle
Weak , slow contraction involuntary
Irregular branched cells bound together longitudinally by intercalated disks
An agglomerate of fusiform cells.

Skeletal muscle consists of muscle fibers , bundles of very long (up to 30 cm) cylindrical multinucleated cells with a diameter of 10-100
µ m.
Nuclei : The oval nuclei are usually found at the periphery
of the cell under the cell membrane.
Activity: Strong , quick discontinuous voluntary contraction
Location: Upper & lower limbs

Each muscle fiber is itself surrounded by a delicate layer of connective tissue, the endomysium .
The connective tissue around each bundle of muscle fibers
is called the perimysium.
The masses of fibers are arranged in regular bundles
surrounded by the epimysium.

Skeletal Muscle tissue
General characteristics
The sarcoplasm is filled with long cylindrical filamentous
bundles called myofibrils.
The myofibrils : which have a diameter of 1-2 µm
and run
parallel to the long axis of the muscle fiber
One of the most important roles of connective tissue is to mechanically transmit the forces generated by contracting
muscle cells. vessels penetrate the muscle within the connective tissue
septa and form a rich capillary network .

Skeletal muscle
Voluntary M., Striated M.
Plasma membrane or plasmalemma = sarcolemma
Cytoplasm = sarcoplasm
Endoplasmic reticulum = sarcoplasmic reticulum
Smooth muscle
Involuntary M., Visceral M.
Cardiac muscle
Involuntary M.
Continuous , rhythmic contractility of the heart

the light-colored areas among and above the muscle fibers contain
connective tissue, Nuclei are stained by hematoxylin.

• Longitudinal
• Peripheral Nuclei
• Striations
• No Branching
• Cross Section
• Peripheral Nuclei
• Massive Cytoplasm

• Longitudinal skeletal muscle is nonbranching and can be identified by peripheral nuclei. The large white vertical lines are knife marks from sectioning
(artifact).
• At higher magnification, the striations become visible. I-bands (isotropic) are light while A-bands (anisotropic) are dark.

Cardiac muscle works all the time.
Consists of tightly knit bundles of cells.
15
µm
in diameter and from 85 to 100
µ m in length .
Big amount of communication, big cells.
Nuclei : 1-2 centrally located, pale-staining nuclei.
Cardiac muscle cells: contain numerous mitochondria,
Surrounding the muscle cells is a delicate sheath of endomysial connective tissue containing a rich capillary network.
Force: high (regular beating because of circulation)
Can’t regenerate

Intercalated disks: represent junctional complexes found at the interface between adjacent cardiac muscle cells
Two regions can be distinguished in the steplike junctions:
1- a transverse portion : which runs across the fibers at
right angles.
2- a lateral portion : which runs parallel to the myofilaments.

Cardiac muscle
Involuntary M. rhythmic contractility of the heart
Contractions are:
strong & utilise a great deal of energy
continuous
modulated by external autonomic & hormonal stimuli

Cardiac muscle fibres are cylindrical cells with one or two nuclei
Intercalated discs Between the muscle fibers collagenous tissue similar to the endomysium

Composed of: elongated, nonstriated cells,
each of which is enclosed by a basal lamina and a network of reticular fibers.
Smooth muscle cells : are fusiform , they are Largest at their midpoints and taper toward their ends.
Cell size : from 20
µ m in small blood vessels
to 500
µ m in the pregnant uterus.
The borders of the cell: become scalloped when smooth
muscle contracts, and the nucleus becomes folded or
has the appearance of a corkscrew . at the poles of the nucleus are mitochondria , polyribosomes,
cisternae of rough endoplasmic reticulum , and the Golgi complex .

Contractile: Continuous, involuntary.
Nucleus :one central elongated, centrally.
Cells shape : fusiform (elongated spindle-shaped )
At the poles of the nucleus are:
- mitochondria polyribosomes,
-
cisternae of rough endoplasmic reticulum,
-
the Golgi complex.
These bundles consist of thin filaments nm) containing actin and tropomyosin and thick filaments (12-16 nm) consisting of myosin

Smooth muscle
Involuntary M., Visceral M.
•
Is specialized for continuous contractions of relatively low force .
•
Influences of the autonomic nervous system, hormones & local metabolites .
Elongated spindle-shaped cells with one central elongated nucleus.

• Longitudinal smooth muscle is identified by long, thin central nuclei, a more scattered tissue layout, and an absence of striations.
• In cross section, smooth muscle can be identified by central nuclei and a small ring of surrounding cytoplasm.

Regeneration of Muscle Tissue:
They have different potentials after injury
1- Cardiac muscle has almost no regenerative capacity
beyond early childhood. Defects or damage (eg, infarcts) in heart
muscle are generally replaced by the proliferation of connective tissue , forming myocardial scars.
2- skeletal muscle : although the nuclei are incapable of undergoing mitosis, the tissue can undergo limited
regeneration.
3- Smooth muscle is capable of an active regenerative response after injury . (pericytes from blood vessels undergo
mitosis and provide for the replacement of the damaged tissue).

Contractile
Location
Cells shape
Nucleus
Nucleus Location
Cells interaction
Skeletal M. voluntary
Upper & lower limbs cylindrical
Smooth M.
Continuous involuntary
Intestine , digestive System,
Visceral fusiform
Cardiac M.
Continuous , rhythmic involuntary
Heart cylindrical multinucleated multinucleate peripherally one central elongated centrally centrally
Regeneration
+
No (limited)
-
Active
+
No