Cardiac Muscle Tissue
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Walls of the heart (cardia: heart);
myocardium.
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Cardiac muscle fibers
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Other components;
not as densely packed as skeletal
cardiac muscle tissue is highly
vascularized
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dense C.T. septa, larger blood
vessels, lymphatic vessels, and
small nerves.
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Cardiac Muscle Tissue
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Cardiac muscle fiber; 1/3 to 1/6 as wide as
skeletal
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much shorter
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5 to 10 times longer than wide.
Typically branched
1-2 nuclei
nuclei are larger, lighter-staining, elongate
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are centrally-located in the fiber
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Cardiac Muscle Tissue
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Myofibrils align with the main axis of the
muscle fiber
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centrally-located myofibrils of the
fiber swerve around the nucleus
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void areas just beyond the ends of the
nucleus-spaces; lacking myofibrils
Fibers are cross-striated.
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Components tend to be much shorter
and smaller
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Cross-striation pattern is a much
finer
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A-bands and I-bands narrower.
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Cardiac Muscle Tissue
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Cardiac fibers interconnect at their ends
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THREE-DIMENSIONAL
NETWORK of fibers
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Ends are flat and wide
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Zone of gap junctions stains
more darkly than crossstriations
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Called an intercalated disc.
Spaces contain capillaries
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Cardiac Muscle Tissue
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Intercalated disc
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Zone of electrical connection
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Membrane impulse spreads through
the network of fibers
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one huge all-or-none unit of
contraction.
Cardiac muscle tissue is an
interconnected network of cardiocytes
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Void in
cytoplasm
Central
nucleus
Cross banding
pattern
Intercalated
discs
Overall; more
disorganized than
skeletal muscle
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Intercalated
discs
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Cardiac Muscle Tissue
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Cardiac muscle fibers do not require
exogenous stimulation
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Rhythmically self-stimulating
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Occurs more quickly at the
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sino-atrial node (the
"pacemaker")
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Spreads rapidly, causing contraction
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Impulse is conducted from adjacent
fibers
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Cardiac Muscle Tissue
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Nervous and endocrine system are able to
modulate contraction
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speed up or slow down
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stronger contraction or weaker
contraction.
If cardiac muscle tissue has 02 and chemical
energy (glucose and lactate)
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it will continue to rhythmically contract.
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Cardiac Muscle Tissue
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Produce ATP aerobically only
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Do not reach a high level of contraction
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Never rest for more than about 1 sec
of time
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Highly vascularized
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High myoglobin concentration
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very dark in life compared to
skeletal
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Contracts more slowly
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somewhat greater strength.
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Cardiac Muscle Tissue
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On low power;
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Bark of trunk of elm trees
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Branching-and-interconnecting system of cells.
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light-stained Nuclei, evenly distributed
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more oval than skeletal and smooth muscle
fibers
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not in single-file.
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Cardiac Muscle Tissue
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Capillaries very abundant
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oriented obliquely to longitudinally.
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Cardiocytes are eosinophilic.
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Cross-striations very fine; not distinct.
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Intercalated discs not distinct w/o special
staining.
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Septa typically scarce
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larger blood vessels typically scarce
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small to medium-sized nerves not obvious
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Cardiac Muscle Tissue
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Structure and appearance of cross sections of
cardiac muscle tissue
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Variable in diameter and shape
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Are branched.
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Central nuclei, round and lightly stained
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One-half the diameter of the fiber
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Cardiac Muscle Tissue
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Many fibers (or fiber branches) crosssectioned at location other than at
nucleus
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cross-section near nucleus
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Capillaries abundant
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fiber has a void
mainly cross-sectioned
look for isolated RBC
Need special stain for intercalated discs
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silver, orscein, toludine blue, etc.
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Smooth muscle tissue
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Smooth muscle tissue is found in the
walls of tubular organs
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blood vessels, digestive tract,
respiratory organs, urinary ducts,
reproductive ducts,
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controls the diameter and/or the
length
Made of smooth muscle fibers (SMFs)
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Parallel, densely packed
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Poorly vascularized, contains CT
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Smooth muscle tissue
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Structure and function of the smooth muscle
fiber
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Ancient and primitive
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Elongate, narrow and spindle shape
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diameter < cardiac muscle fiber.
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Mono-nucleated
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elongate, light-staining nucleus in middle
of SMF
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Nucleus diameter ~ 2/3 to 3/4 of SMF
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Smooth muscle tissue
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Moderately eosinophilic
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H&E; more pink than orange
collagen fibers nearby, orange
cytoplasmic : slightly basophilic ; slightly
violet-pink.
Not cross-striated.
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Fiber contains myofibrils
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myofibrils at a slight angle to axis
Different bundles, different directions
SMFs contract more slowly
but with greater strength per gram
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Smooth muscle tissue
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Anaerobic
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low metabolic rate
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fewer mitochondria and lower
myoglobin.
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Adjust tone.
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No T-tubule-system.
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Smooth muscle tissue
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Tone ; sustained partial depolarization of
the sarcolemma
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No full magnitude membrane impulses.
Several ways to stimulated contraction
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Stimuli:
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histamine, CO2, 02, prostaglandins,
hormones
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stretching
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direct neural input (autonomic;
involuntary)
depolarization from adjacent smooth
muscle fibers
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Smooth muscle tissue
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Structural and functional types of smooth
muscle tissue
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Vascular smooth muscle tissue
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Walls of blood vessels and
larger lymphatic vessels.
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Each fiber has an autonomic
nerve ending (sympathetic)
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electrically insulated by
reticular fibers
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no membrane depolarization
from fiber to fiber
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Smooth muscle tissue
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Visceral smooth muscle tissue
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Walls of digestive tract organs.
Autonomic nerve endings
throughout tissue;
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not all fibers have a nerve
ending
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membrane depolarization
is conducted from fiber
to fiber.
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Smooth muscle tissue
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Structure and appearance, longitudinal
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Homogeneously stained eosinophilic
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elongate, lightly stained nuclei
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random distribution ; oriented in the
same direction
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H&E: pink to violet-pink.
Capillaries, CT elements, nerves, etc., very
scarce to absent.
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Smooth muscle tissue
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Structure and appearance of cross section
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homogeneously stained
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Most difficult tissues to identify
moderately eosinophilic
Sparse, very small, round, light-stained nuclei
H&E: pink to violet-pink.
Cell membranes; not distinguishable.
Capillaries, CT elements, etc., very scarce to
absent.
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Smooth muscle tissue
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Smooth muscle fibers are sometimes found as
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isolated fibers; one to two fibers thick
are not smooth muscle tissue, need a mass of cells several cells
thick.
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