Download Cardiac Muscle 2

Cardiac Muscle
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The heart is formed of two thin atria & two ventricles.
Cardiac muscle form wall of the heart known
myocardium.
Wall of the heart is formed of 3 layers:
1- Epicardium
2- Myocardium
3- Endocardium
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Dr. MOHAMMED SHAMIA
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Epicardium:
- Visceral layer of pericardium formed of simple
sq.epithelium & layer of connective tissue.
- The epicardium is the layer immediately outside of
the heart muscle proper (the Myocardium).
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Myocardium:
Formed of cardiac muscle fibers.
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Dr. MOHAMMED SHAMIA
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Endocardium:
- Lines the heart from inside.
- Having four layers from inside:
1- Simple squamus endothelium.
2- Subendothelial layer of dense fibrous C.T.
3- Dense elastic & collagenous membrane.
4- Loose of C.T. layer contain BV. & Purkinje muscle fiber.
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Dr. MOHAMMED SHAMIA
Characteristic of Cardiac Muscle
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Individual muscle cells surround by C.T endomysium
contain B.v. & lymphocytes.
Small diameter.
Branch & join each other forming sheets.
Contract spontaneous(involuntary in action).
Striation: have irregular striation.
Nuclei are large, central in position & oval in shape.
Dr. MOHAMMED SHAMIA
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Thin sarcolemma.
Cytoplasm granular acidophilic sarcoplasm rich in
glycogen, mitochondria & lipochrome granules.
The cardiac muscle transversed by dark staining
discs which extend across the fibers called
Intercalated Discs.
Dr. MOHAMMED SHAMIA
The Intercalated Disc
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The cardiac muscle fibers are joined end to end by the
intercalated discs.
There are 3 types of junctional complex at the
intercalated discs:
1- Desmosomal type of junction which prevent separation
of the muscle cells.
2- Adherens type of junction.
3- Gap type of junction impulses between heart muscles
The atrial muscle fibres secret Atrial natriuretic Diuretic
Hormone (ANDH)
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Dr. MOHAMMED SHAMIA
INTERCALATED DISCS
Intercalated Discs
Cardiac Muscle Fibers
(transverse section)
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Dr. MOHAMMED SHAMIA
INTERCALATED DISCS
Gap Junctions
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Desmosomes
Dr. MOHAMMED SHAMIA
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Cardiac muscle have the ability to undergo rhythmic
contraction.
Valves of the heart are formed of dense CT. rich in
elastic & collagenous fibers and covered by simple
sq. endothelium.
Dr. MOHAMMED SHAMIA
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Phagocytic histiocyte cells are present in the CT. of
the valves in order to engulf any micro-organism.
Fibrous skeleton of the heart formed of dense
fibrous tissue.
Cardiac muscle & valves are attached to the fibrous
skeleton.
Dr. MOHAMMED SHAMIA
The conducting system of the heart
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It is formed of modified cardiac muscle cells that are
specialized to generate and to conduct cardiac
impulses to all heart muscles.
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1- Sino-atrial node(SA) in the Rt.atrium,its pacemaker of
the heart .
2- Atrio-ventricular(AV) node present in septal wall of
Rt. atrium.
3- Atrio-ventricular bundles of His: branches into Rt. &Lt.
bundles.
4- Rt&Lt. Bundles branches: the Rt. Branch is called
moderator Band.
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Dr. MOHAMMED SHAMIA
The moderator Band
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It is a bundle of cardiac muscle fibers through which
the right branch of the artio-venticular bundle
traverse the cavity of the right ventricle to reach the
lateral wall of the heart.
Formed of:
Cardiac muscle bundles, fat cells, Blood capillaries,
Purkinje muscle fibers and bundles of nerve fibers.
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Dr. MOHAMMED SHAMIA
Purkinje Muscle Fibres
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The atrio-venticular bundle & its brunches are
composed of elongated cells called Purkinje Cardiac
Muscle fibers.
They are larger in diameter than the cardiac fibers.
They are paler in color.
They are usually grouped into bundles & surrounded
by C.T. sheath.
Each purkinje fiber is formed of separate, short, thick,
elongated cylindrical cells.
Dr. MOHAMMED SHAMIA
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The sarcolemma of purkinje fibers is thin and
irregular.
Cytoplasm is granular and rich in glycogen. Has
myofibrils which are peripherally situated (parallel
to sarcolemma)
The intercalated discs are absent in Purkinje muscle
fibers.
Eccentric nuclei and many gap junction.
The fibers are non striated.
Dr. MOHAMMED SHAMIA
PURKINJE FIBERS
Purkinje Fibers
(specialized
conducting
tissue)
PF
Purkinje Fibers (trans. section)
glycogen
stores
adipocyte
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Dr. MOHAMMED SHAMIA
Action
Site
Shape
of fibers
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Striations
Sarcolemma
Sarcoplasm
Size
Branching fibers
Length of fibers
Diameter of fibers
Nuclei
Intercalated Discs
Myofibrils
Triad of tubular system
Satellite cells
Regeneration
Smooth
Skeletal
Cardiac
Involuntary
viscera
Spindle -shaped
Non-striated
Very thin
Pale cytoplasm
Small in size
Non-branching fibers
From 30-500 microns
Up to 10 microns
Single & central
Absent
With no sarcomeres
Absent
Absent
From the pericytes
Voluntary
Attached to bone
Cylindrical
Well striated
Very thick
Red & pale cytoplasm
Large size
Involuntary
In the heart
Cylindrical
Non-clear striation
Very thin
Red cytoplasm
Medium-sized
Branch & anastomosing
Form continous sheet
Up to 25 microns
Central nuclei
Present
Irregular sarcomeres
Presence & Diad system
Absent
Cannot regenerate
Branch in face &tongue
Variable
Up to 100 microns
Multiple ,peripheral
Absent
Regular sarcomeres
Present
Present
From satellite
Dr. MOHAMMED SHAMIA
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Dr. MOHAMMED SHAMIA
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Thank you
Dr. MOHAMMED SHAMIA