MUSCLE TISSUE 1- Skeletal muscle. 2- Cardiac muscle. 3- smooth muscle.
Muscle Tissue - Lazarov · Cardiac muscle tissue cardiomyocyte (Gr. cardia, heart) three types of...
Transcript of Muscle Tissue - Lazarov · Cardiac muscle tissue cardiomyocyte (Gr. cardia, heart) three types of...
Muscle Tissue
1.Muscle tissue – organization,
histogenesis and functions
2.Classification of muscle tissue
3.Smooth muscle tissue
4.Striated (skeletal) muscle tissue
5.Cardiac (heart) muscle tissue
6.Regeneration of muscle tissue
Prof. Dr. Nikolai Lazarov 2
Muscle tissue
body movements
digestion
blood circulation
respiratory movements
other movement activities, incl. cellular contraction
succession of relax and contraction:
transformation of chemical into mechanical energy
Textus muscularis: cells – myocytes extracellular matrix
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Muscle fibers – myofibers
muscle cells = myocytes (leiomyocytes, rhabdomyocytes, cardiomyocytes): elongated, cylindrical or fusiform = myofibers sarcolemma = plasmalemma sarcoplasm = cytoplasm sarcoplasmic reticulum =
smooth endoplasmic reticulum sarcosomes = mitochondria myoglobin: oxygen-binding protein connective tissue components:
endomysium (Gr. endon, within + mys, muscle) perimysium (Gr. peri, around, near + mys) epimysium (Gr. epi, upon + mys)
Gr. sarkos, flesh
myoepithelial cells pericytes myofibroblasts in healing wounds myoid cells of the testis
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Myofibrils and myofilaments
myofibrils: fill the muscle fibers
separated by sarcoplasmic reticulum
myofilaments: thick and thin filaments
(contractile proteins)
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Histogenesis
skeletal muscle – mesoderm somites – skeletal muscles
of the trunk
general mesoderm – muscles of the head and limbs
embryonic origin: smooth muscle –
mesenchyme
striated – mesoblast
myoepithelial cells – skin ectoblast
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Functions
movements of the body
as a whole
body posture stabilization
volume regulation of the
internal organs: sphincters
movement of substances
within living organisms:
blood, lymph, air, food and
fluids, urine, sperm
heat production: involuntary
contractions of the skeletal
muscles (trembling)
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Properties of muscle tissue
irritability the ability of a muscle to respond
to a stimulus
conductivity the ability of a muscle to conduct
electrical impulses across the membrane
contractility the ability of a muscle to shorten
and to produce energy
extensibility the ability of a muscle to lengthen
beyond its resting length
elasticity the ability of a muscle to return to
its original length without damage
NB: muscles can only pull or contract, not push!
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Types of muscle tissue
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Smooth muscle tissue
origin: mesenchyme
involuntary: ANS innervation
tonus
peristalsis
nonstriated
in the walls of hollow and tubular organs: blood vessels
(with exception of capillaries)
alimentary canal
respiratory tract
urogenital system
associated with hair follicles in the skin (arrector pili muscles)
Characteristics: Textus muscularis nonstriatus (glaber)
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Smooth muscle tissue
leiomyocyte (Gr. leios, smooth)
shape: fusiform or “spindle shaped”
length: 30-500 µm
thickness: 5-10 µm
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Ultrastructure
actin filaments (4.5 µm/7 nm):
actin, tropomyosin, calmodulin – Ca2+
myosin (2.2 µm/17 nm):
myosin II
dense bodies, corpora densa
(contain α-actinin = similar to the Z line)
caveolae (analogous to Т-tubule system)
intermediate filaments (10 nm):
desmin (skeletin), vimentin = non-contractile proteins
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Smooth muscle types
visceral (single-unit) smooth muscles in the walls of hollow organs small blood vessels
• relatively poor nerve supply • abundant gap junctions
function in syncytial fashion
multi-unit smooth muscles large arteries upper respiratory tract muscles of hair follicles iris and ciliary body of the eye
• rich nerve supply
• innervate individual cells
• allow for fine control
• provide very precise and graded contractions
two types of smooth muscle:
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Regulation of contraction and relaxation
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Skeletal muscle tissue
the most abundant tissue in the vertebrate body
– 40% of the body mass
origin: mesoblast (myotomes)
voluntary: CNS innervation strong, quick voluntary control
of contraction/relaxation
cross-striated
skeletal muscles
initial and end parts of the digestive tract
muscles of the head (incl. eye, ear)
muscles of respiration
Textus muscularis striatus (skeletalis)
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Skeletal muscle development
100 myoblasts (mononucleated) – 1 mature
muscle cell (multinucleated): syncytium (symplast)
satellite (myosatellite) cells: retain their potential for the formation of new cells (stem cells)
does not divide postnatally
muscle growth –
augmentation of
cell volume (hypertrophy)
Gr. syn, together + kytos, cell
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Skeletal muscle tissue
rhabdomyocyte (Gr. rhabdo, striped)
shape: elongated, cylindrical
length: 1-40 cm
diameter: 10-100 µm
numerous nuclei: 10-100/cell, located right up under the plasma membrane
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Organization of skeletal muscle
Skeletal muscle
Muscle fasciculus
Muscle fiber
Myofibril
Myofilaments
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Myofibril
85-90% of the myofiber volume
2500-3500/rhabdomyofiber
long cylindrical filamentous structure
with a diameter of 0.5-2 µm
system of transverse (T-) tubules –
encircle the boundaries of the А-I bands
“triad” = Т-tubule + 2 terminal cisternae:
depot of Ca2+
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Ultrastructure
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Sarcomere
Sarcomere (Gr. sarkos + meros, part):
length: 2-3 µm (~2.5 µm) – extends from Z line to Z line
А band (anisotropic, i.e., birefringent in polarized light) H zone (from the German “Hell”, bright) М line (mesophragm, "Mittel", middle of the sarcomere):
creatine kinase and myomesin I band (isotropic, does not alter polarized light, monorefrigent)
titin (3700 kDa) – connects thick filaments to the Z disc nebulin (600 kDa) – helps anchor thin filaments to α-actinin
Z disk (“Zwischenscheibe”, the band in between the I bands) = telophragm: α-actinin
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Sarcomere
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Sarcomere
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Myofilaments thin (actin) filaments – 1 µm long/8 nm wide:
actin – long filamentous polymers of F-actin; • 2 twisted strands of G-actin – globular monomer, 5.6 nm in diameter
tropomyosin – 40 nm in length extending over 7 G-actin molecules • 2 polypeptide chains
troponin – ТnT, TnI, TnC at intervals of 40 nm, attached to tropomyosin
thick (myosin) filaments – 1.6 µm long/15 nm wide: head (ATPase activity) + proximal 60 nm of tail = heavy meromyosin distal 90 nm of the tail = light meromyosin 2 identical heavy chains and 2 pairs of light chains
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Mechanism of contraction
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Mechanism of contraction
rigor mortis
Sliding Filament Hypothesis: Huxley
Sliding Filament Hypothesis: Sir Andrew F. Huxley (1917-2012)
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65-Year Anniversary of Sliding Filament
Huxley, A.F., and R. Niedergerke. 1954. Structural changes in muscle during contraction; interference microscopy of living muscle fibers. Nature. 173:971–973. Huxley, H., and J. Hanson. 1954. Changes in the cross-striations of muscle during contraction and stretch and their structural interpretation. Nature 173:973–976.
The improver of natural knowledge absolutely refuses to acknowledge authority, as such.
For him, skepticism is the highest of duties, blind faith the one unpardonable sin.
Thomas H. Huxley
On the Advisableness of Improving Natural Knowledge, 1866
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Motor end plate
Myasthenia gravis
myoneural junction – cholinergic (ACh)
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Neuromotor unit
motor unit = an individual somatic motoneuron and all the skeletal muscle fibers (cells) it innervates
a single nerve fiber (axon) can innervate up to 160 muscle fibers (cells), that all contract at the same time
the number of motor units and the variable size of each unit can control the intensity (force) of a muscle contraction
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Types of muscle fibers
Red fibers (slow oxydative) – type I
White fibers (fast glycolytic) – type IIb
Intermediate (slow oxydative) – type IIa
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Cardiac muscle tissue
origin: mesenchyme involuntary: ANS
quick continuous automatic contraction: conduction system
striated in the wall of the
heart (myocardium) some large vessels
Textus muscularis striatus cardiacus
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Cardiac muscle tissue
cardiomyocyte (Gr. cardia, heart)
three types of cardiac myocytes: contractile, conductive, secretory
shape: cylindrical, bifurcated
length: 85-100 µm
diameter: 15-20 µm
only 1 (or 2) centrally located pale-staining nuclei
delicate sheath of endomysial connective tissue containing a rich capillary network
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Cardiomyocyte Т-tubules: at the level of Z band
“diad” = Т-tubule + one SR cistern
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Cardiomyocyte
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Ultrastructure mitochondria: 40% of the cytoplasmic volume atrial granules (ANF and BNF): 300-400 nm
lipid droplets and lipofuscin glycogen granules intercalated discs:
fascia adhaerens – in the transverse portion macula adhaerens (desmosomes) – in the vicinity,
bind the cardiac cells together gap junction (nexus) – in the lateral portion,
provides ionic continuity between cells
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Myoepithelial cells
basket cells:
sweat gland
mammary gland
lacrimal gland
salivary glands
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Regeneration of muscle tissue
Cardiac muscle has almost no regenerative capacity beyond early childhood:
mature cardiac muscle cells do not divide
proliferation of connective tissue
myocardial scars
Skeletal muscle can undergo limited
regeneration
source of regenerating cells is believed
to be the satellite cell (stem cell)
Smooth muscle is still capable of an active
regenerative response (division)
viable mononucleated smooth muscle cells
and pericytes from blood vessels provide
for the replacement of the damaged tissue
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Thank you ...