Muscle Tissue.pdf

 State the general features of muscle tissue
 State the classification of muscular tissue
 Describe the histological features of different types of
muscular tissue
 State the arrangement of connective tissue around
muscular tissue
Objectives

Tissue
 Collections of specialized cells and cell
products that perform a specific function.
Four Primary Tissue
Epithelial tissue
Connective tissue
Nervous tissue
Muscular tissue

• Epithelial
covers exposed surfaces, lines passageways, forms glands.
• Connective
fills internal space, structural support, storage of energy.
• Muscle
contracts for specific movements.
• Neural
carries information from one part of the body to another.
Four Primary Tissue

Muscular tissue – embryological origin
Primitive mesenchyme
irregular cells + slender processes

 muscle fiber = muscle cell (elongated and thread like)
 sarcoplasm = cytoplasm of the muscle fiber
 sarcolemma = muscle fiber plasma membrane
 sarcoplasmic reticulum = smooth endoplasmic
reticulum of the muscle fiber
Terminology

General features of muscle tissue
 Consists of highly differentiated cells; muscle
fibers
 Organized as muscle fiber bundles, sheaths
 Arrangement of connective tissue is important
 Characteristic ultra-structural arrangement
helping the contraction
 Chief structural proteins are actin and myosin

General features of muscular tissue
 Chief action is contraction – active process
 Contraction is due to rearrangement of molecular
bonds
 Contractile force, power and range differ
 Muscle fibers able to change shape during
contraction
 Convert chemical energy to mechanical energy

Classification of muscular tissue
• Striated
• non -striated
Base on
structure
• voluntary
• involuntary
Base on
function
functional
&
structural
• striated & voluntary = skeletal muscle
• striated & involuntary = cardiac muscle
• smooth & involuntary = smooth/visceral muscle

Muscular Tissue Types
Skeletal muscle
Smooth muscle
Cardiac muscle

 Single cell- muscle fibre
 Bundle of fibres- single muscle fascicle
 Many fascicles- single muscle
eg: Biceps, triceps
Skeletal muscle

• Long and cylindrical shape
– Cross section – polygonal
• Length : 10-100μm
• Unbranced fibre
• Multinucleated
• Peripheraly located oval euchromatic nuclei
• Nuclei located under sarcolemma
• Fibers can increase in size but not in number
Muscle fibre

Muscle fibre
Contractile proteins arranges in cylindrical
myofibrils
each fiber contains dozens of myofibrils
each myofibril is about 1-2 µm in diameter
contains myofilament bundles

• Cylindrical
• Diameter 1 μm
• Densely stained
transverse lines- Z
lines
• Area between two
consecutive Z
lines- Sarcomere
( Contractile unit )
Myofibril structure

Feature Description
A band Thick filament and lengths of thin filaments
I band Thin filaments of adjacent sarcomeres
H zone Central paler region of A band without thin
filaments present
M line Transverse link of thick filaments in a
sarcomere

Sarcomere
• Functional unit of a muscle fibre
• The segment between two successive densely
stained Z lines
• Includes one A band and half of two
contiguous I bands

• Alternating light and dark bands
• Light band- I band
• Dark band- A band
Muscle fibre stucture

• Myosin-most abundant, forms the thick filaments
• Actin – forms thin filament
• Tropomyosin & troponin
Contractility regulating proteins
• Dystropin- stabilizes muscle fiber and transmit
force to the extracellular matrix
– Defective synthesis result in Duchenne muscular
dystrophy
Important muscle proteins

Connective tissues of muscle
• Provides structural covering and
support
• Maintains the shape of the muscle
• Act as attachments with the bone
• Transmit contractile force to the
action site (eg joint movement)

 Thin , delicate reticular fiber network
 Surrounds each muscle fiber
 Forms immediate external environment
of the muscle fiber
 Site of metabolic exchange between
muscle and blood
 Continuous with the perimysium
Endomysium

• Ensheaths groups of muscle fibers
• Inward extensions of the epimysium
• Therefore forms a muscle fasciculi
• Carries larger blood vessels and
neuromuscular spindles
Perimysium

• Forms the entire outer covering of the
muscle bulk
• Numerous collagen fibers arranged
regularly
Epimysium

 Uniform contraction is maintained by system of
T tubules
 T tubules are deep invaginations of the sarcolemma
encircle every myofibril at A-I junction
 On either side of T tubule are expanded terminal
cisternae of smooth endoplasmic reticulum
SER
T tubule Muscle Triad
SER
Muscle Triad

 Found only in the myocardium of heart &
roots of large vessels
 Consists of branching network of individual
cells
 Cylindrical fibers - intermediate size
 Anastomoses with adjacent fibers
 Therefore functions as a unit
 usually one nucleus
 Nucleus located centrally
Cardiac Muscle

 myofilaments organized into myofibrils
 Similar to skeletal muscle
 Cross striations present but faint

 fibers are arranged as
interwoven bundles
 contractions in all dimensions
 highly vascular
 many mitochondria
 fibers capable of hypertrophy
 but not hyperplasia
Cardiac Muscle - cell structure

 Intercalated discs : functional syncytium
 unique to cardiac muscle fibers
 interdigitating fold of sarcolemma at the ends of
adjacent fibers
 linking them structurally and functionally by
gap junctions and desmosomes
Cardiac Muscle - cell structure

 Intercalated discs
 A: fascia adherens
terminal actin filaments
anchored sarcolemma
 B: macula adherens
desmosomes
binds cells
 C: gap junctions
ionically couple cells
Cardiac Muscle – cell structure

Contractile apparatus is as same as skeletal muscle
fibers
 T-tubule system similar:
 T-tubules at the level of the Z-line
 no triads sarcoplasmic reticulum not
Muscle diad well developed
no terminal cisterns
 ionic coupling regulates contraction
through gap junctions

Smooth Muscle
• Involuntary action
• Spindle shape cells/tapering towards the end
• non-branching
• Single, centrally placed nucleus often twisted due to
contraction
• Muscle cells arrange themselves longitudinally as
sheaths
• smallest fiber type with many gap junctions
• Rudimentary sarcoplasmic reticulum but lack T tubles

 No sarcomeres
 Myofilaments : actin and myosin filaments
 No proper organization
 Myofilaments: criss-cross obliquely through the
sarcoplasm
 Attached to dense bodies via actinin (like z line)
 Myofilaments are inserted to dense bodies
to transmit force of contraction
 Lack troponin, rich in calmodulin
Smooth Muscle

• Typically found in walls of tubular structures
– Blood vessels, bronchial tree (regulating the flow of
blood and air)
– Ureteric wall , hepatic duct, intestine muscularis
propria (propels liquids and solids)
– Urinary bladder , uterine myometrium (expels
contents)
– Secretory ducts
Arrangement of cells depends on the site and function
of the organ
Smooth Muscle

Myometrium
Muscularis propria
Urinary bladder wall

SUMMERY
Skeletal muscle Smooth muscle Cardiac muscle
Contractile
unit

REFFERENCES
 Burkit, H.G, young, B. (1993). Wheaters
functional histology. 4 th ed.,
london:Churchill livingstone
 Junqueira, L.C., Carneiro (1998). Basic
histology. 9 th ed., stamford: Appleton &
lange

Muscle Tissue.pdf

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