Muscle
Undergraduate – Graduate
Histology Lecture Series
Larry Johnson, Professor
Veterinary Integrative Biosciences
Texas A&M University
College Station, TX 77843
Muscle – Introduction
Contractivity is one of the fundamental properties
of protoplasm and is exhibited in varying degree
by nearly all cell types.
In the cells of muscle, the ability to convert
chemical energy into mechanical work has become
highly developed.
Locomotion of multicellular animals, beating of
their hearts, and movement of their internal organs
depends on muscles of different types.
Cardiac muscle
Smooth muscle
Skeletal muscle
Objectives
Identify smooth, skeletal, and
cardiac muscle on route
histological preparations
Explain the morphological basis for
the different functions of these
three types of muscle
Distinguish between the modes of
excitation of these three types of
muscle
Four basic types of tissues
Epithelium (90% of tumors)
Muscular tissue
Connective tissue
Nervous tissue
Muscle
Function:
Generation of contractile force
Distinguishing features:
high concentration of contractile
proteins actin and myosin arranged
either diffusely in the cytoplasm
(smooth muscle) or in regular
repeating units called sarcomeres
(striated muscles, e.g., cardiac and
skeletal muscles)
Cardiac
muscle
Smooth muscle
Striated muscles
Muscle
- Histological identification
Skeletal muscle – very long
cylindrical striated muscle cells
with multiple peripheral nuclei
Cardiac muscle – short branching
striated muscle cells with
centrally located nuclei
Smooth muscle – closely packed
spindle-shaped cells with a single
centrally placed nucleus and
cytoplasm that appears
homogeneous by light microscopy
Dilator muscle of iris
Myoepithelial cells
Muscle
Distribution:
Skeletal – striated muscles
mostly associated with
the skeleton
Muscle
Distribution:
Cardiac – striated muscles
associated with the heart
large artery
of lung
Muscle
Distribution:
Smooth – fusiform cells associated
with the viscera, respiratory
tract, blood vessels, uterus, etc.
Smooth muscle
Ureter
Ductus deferens
Types of muscle
Skeletal muscle
– Voluntary, large and multinucleated cells,
striated
Cardiac muscle
– Involuntary, mononucleated and branched
cells, striated
Smooth muscle
– Involuntary, mononucleated, non-striated
Connective tissue layers of skeletal muscle
Epimysium - coarse CT
Perimysium - less coarse CT
Endomysium - delicate CT
Perimysium
Epimysium
Endomysium
Tongue, monkey
Skeletal muscle nuclei
Fasciculi
Endomysium
Muscle
cells
skeletal muscle nuclei,
Connective
tissue of
perimysium
striations
Connective
Tissue
connects cells
(muscle fibers) of
skeletal muscle
Endomysium
Connective Tissue Layers of
Skeletal Muscle
PERIMYSIUM
ENDOMYSIUM
Connective Tissue Layers of Skeletal Muscle
Endomysium
Individual
cell
Striated Muscle
Cardiac
Skeletal
A
“A” Band = dark band
Anisotropic = does
alter polarized light
(Birefringent)
“I” Band = light band
Isotropic = does not
alter polarized light
I
A
I
A
I
Polarized Light Micrograph Of
Human… High-Res Stock
Photography
...www.gettyimages.com
Striated Muscle (Skeletal)
Repeating A and I bands alone the cell’s length
creates repeating sarcomeres A
I
A
I
A
I
A
I
Striated
Muscle
(skeletal)
A
Sarcomeres are
organized for rapid
and highly controlled
contraction
I
Striated Muscle (Skeletal)
Sarcomere = structural unit and functional unit of striated muscle
Striated Muscle (Skeletal)
Thin filament = actin + actin-associated proteins
Actin-associated proteins dictate network or bundle
creating the Z line
Thick filament = myosin
Striated Muscle
Striated Muscle
Note uniform spacing of troponin
Striated Muscle
Unexplained complexity in skeletal muscle
13 isoforms of myosin
128 isoforms of troponin
• Footprints of evolution
– fossils
– comparative anatomy,
morphology and physiology
– biological macromolecules
• nucleic acids & proteins
• document evolutionary history
• provide insights into evolution of
form and function
– life
– biomolecules
• e.g., cytochrome c in rice & tuna
Slides adapted from Dr. Chris Collet
Queensland University of Technology
Australia
Based on scientific research, what three characteristics
do these mammals all have in common…
2. Mammary
with these mammals?
glands
1. Hair
3.Special
inner ear bones
Ear bones of mammals (including human) began as reptile jaws
This 125-million year old
fossil has inner-ear anatomy
intermediate (still attached to
the jaw) between reptiles and
mammals. In the early
embryonic stage of modern
mammals, the middle ear was
still attached to the jaw.
• Footprints of evolution
– fossils
– comparative anatomy,
morphology and physiology
– biological macromolecules
• nucleic acids & proteins
• document evolutionary history
• provide insights into evolution of
form and function
– life
– biomolecules
• e.g., cytochrome c in rice & tuna
Slides adapted from Dr. Chris Collet
Queensland University of Technology
Australia
You can learn a lot about humans from studying animals
• Footprints of evolution
– fossils
– comparative anatomy,
morphology and physiology
– biological macromolecules
• nucleic acids & proteins
• document evolutionary history
• provide insights into evolution of
form and function
– life
– biomolecules
• e.g., cytochrome c in rice & tuna
Slides adapted from Dr. Chris Collet
Queensland University of Technology
Australia
Introduction: Pathways Of Protein Evolution
Protein Evolutionary Trees
Introduction: Pathways Of Protein Evolution
• Point mutation
– change of function to meet changing requirements
• Duplication
– simplest mechanism of evolving new proteins
– functional divergence of duplicates to meet new
requirements in biochemical pathways
• Exon shuffling
– creating novel proteins for new pathways of
development
• Alternate splicing
– protein diversity from existing genes
Exon Shuffling And Mosaic Proteins
If structural = functional modules then
– modules (domains) can be moved around genome
– fulfill new functions
– proteins show a mosaic history
Exon Shuffling and Mosaic Proteins
Many proteins are modular
– units derived from many sources
Alternate Pathways Of Transcript Splicing
• Different exons may be
joined to produce a related
set of mRNAs encoding a
small family of related
proteins
– protein isoforms
• Splicing patterns often
tissue-specific
• Related proteins may
perform similar, not
necessarily identical,
functions in different types
of cells
• Splicing is the norm in elks
as a means of producing
diversity
Unexplained complexity in skeletal muscle
13 isoforms of myosin
128 isoforms of troponin
Cell Structure of Skeletal Muscle
Myofiber = multinucleated cell
Myofibrils
Sarcomere
– Z Line (α-actinin)
– I Band (actin, tropomyosin,
troponins)
– A Band (myosin, overlaps actin)
– H Band (myosin with no overlap
of actin)
H
Cell Structure of
Skeletal Muscle
Individual cells
Individual cell
Cell Structure of Skeletal Muscle
Cell Structure of Skeletal Muscle
Skeletal Muscle
Wall Paper
Skeletal Muscle
Sarcomeres shorten
to create contraction
Skeletal Muscle
Remember the Intermediate Filaments on Epithelium
Structural support of
epithelial desmosomes
and
hemidesmosomes
Intermediate Filaments –
Function in Muscle Cells
Myofibril organization – Muscle cells
Cell =
Contraction of
the Sarcomere
Thin Filament
Actin (F-actin)
Tropomyosin
Troponin
T - attaches to
tropomyosin
C - binds calcium ions
I - inhibits actin-myosin
interaction
Thick Filament (myosin)
Sliding filament theory
of contraction
Sliding filament theory of
contraction of the sarcomere
Contraction (know five steps)
1. Troponin-C binds calcium
2. Troponin changes shape causing
conformational change in tropomyosin
exposing actin binding site
3. Myosin binds actin and released
inorganic phosphate inducing
4. Movement of myosin head (motor, power
stroke ) and sliding of actin filament in
relation to the myosin filament
5. ATP  ADP and inorganic phosphate
binds to myosin head cocking it
Contraction of the sarcomere
Contraction of the sarcomere
http://www.youtube.com/watch?v=gJ309LfHQ3M
https://www.youtube.com/watch?v=0kFmbrRJq4w
Calcium Regulation
Transverse (T) tubule
(invagination of sarcolemma)
transmit depolarization of
membrane deep into the cell
Sarcoplasmic reticulum (SER of
cell) release Ca++ for contraction
– then recovers Ca++ after
contraction
Triad = (T tubule
and two ends of SER)
Calcium Regulation
TRANVERSE (T) TUBULE
TRIAD = (T TUBULE +
TWO ENDS OF SER)
Calcium Regulation
Transverse Tubule
Stimulation
of Muscle
Cells
Innervation of Skeletal Muscle
Motor end-plate:
Synaptic cleft
Acetylcholine and
receptor
Junctional
Folds
Innervation of Muscle
Slide HISTO007 skeletal muscle cells
Nerve – muscle interface at the motor end plates
Note the motor end plates in several skeletal muscle cells
Innervation of Muscle
Innervation of Muscle
Innervation of Muscle
Innervation of
Muscle
Innervation of Muscle
Innervation of Muscle
Sensory
Innervation
of Muscle
Muscle Fiber / Cell
Muscle Spindle
Innervation of Muscle
Muscle Spindle
Muscle Spindle
Intracapsular fibers
Tongue Muscle spindle
Muscle spindles
Intrafusal
fibers inside the capsule
capillaries
nerve
fibroblasts
Types of Fibers in
Skeletal Muscle
Red (Slow, Oxidative)
– High Myoglobin
– High Cytochromes/
Mitochondria
– Posture, flight
muscle in birds
Types of Fibers
in Skeletal
Muscle
White (Fast, Glycolytic)
– Low Myoglobin
– Fewer Mitochondria
Types of Fibers in Skeletal Muscle
Intermediate (Fast, Oxidative, and Glycolytic)
http://www.youtube.com/watch?v=pbTah5NVOtU&feature=r
elated
Cardiac Muscle
Cardiac Muscle is Striated Muscle
Differences From Skeletal Muscle
– Mononucleated vs. Multinucleated
– Central vs. Peripheral Nuclei
– Diad vs. Triad
Cardiac Muscle is Striated Muscle
Intercalated Disc
– Fascia Adherens
– Maculae Adherens
– Gap Junctions - Lateral Portion
Cardiac Muscle
Intercalated Disc
Intercalated Disc
Fascia Adherens
Maculae Adherens
Gap Junctions
Lateral Portion
Intercalated discs
Cardiac Muscle
Intercalated
Disc
Cardiac Muscle is
Striated Muscle
Cardiac Muscle
Cardiac Muscle – Diad located at Z line
Diad = (T tubule +
one end of SER)
Cardiac Muscle
Cardiac Muscle
Cardiac Muscle has Organized
Contractions
PURKINJE FIBERS
Heart
Internodal connections
Cardiac Muscle has Organized
Contractions
Purkinje Fibers
Cardiac Muscle
Purkinje Fibers
Cardiac Muscle
Purkinje Fibers
Nexus
(gap junction)
Smooth Muscle
Cell organization
Myofilament organization
Intermediate filaments and
fusiform dense regions
Smooth Muscle
Smooth Muscle
MUSCULAR ARTERY
Smooth Muscle
Arrector Pili Muscle in Skin
Smooth Muscle
Has a PAS +
basement membrane
Smooth
Muscle
Actin
Myosin
Smooth
Muscle
Intracellular caveolae
Smooth
Muscle
Smooth Muscle
Smooth Muscle
Regeneration of Muscle
Cardiac – None
Skeletal – Some
Smooth - Lots
Muscle
Striated - Smooth
Summary of Muscle
shapes and excitations of types
Many illustrations in these VIBS Histology YouTube videos were modified from
the following books and sources: Many thanks to original sources!
Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA.
Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY.
Don W. Fawcett. 1986. Bloom and Fawcett. A textbook of histology. W. B. Saunders Company,
Philadelphia, PA.
Don W. Fawcett. 1994. Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY.
Arthur W. Ham and David H. Cormack. 1979. Histology. J. S. Lippincott Company, Philadelphia, PA.
Luis C. Junqueira, et al. 1983. Basic Histology. Lange Medical Publications, Los Altos, CA.
L. Carlos Junqueira, et al. 1995. Basic Histology. Appleton and Lange, Norwalk, CT.
L.L. Langley, et al. 1974. Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY.
W.W. Tuttle and Byron A. Schottelius. 1969. Textbook of Physiology. The C. V. Mosby Company, St. Louis,
MO.
Leon Weiss. 1977. Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY.
Leon Weiss and Roy O. Greep. 1977. Histology. McGraw-Hill Book Company, New York, NY.
Nature (http://www.nature.com), Vol. 414:88,2001.
A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13th ed. McGraw
Internet images and videos on biological presentations
Next time
Peripheral Nervous System