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Cardiac Muscle ١ 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 Dr. MOHAMMED SHAMIA ٢ 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). Myocardium: Formed of cardiac muscle fibers. Dr. MOHAMMED SHAMIA ٣ 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. Dr. MOHAMMED SHAMIA Characteristic of Cardiac Muscle ٤ 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 ٥ 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 ٦ 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) Dr. MOHAMMED SHAMIA INTERCALATED DISCS Intercalated Discs Cardiac Muscle Fibers (transverse section) ٧ Dr. MOHAMMED SHAMIA INTERCALATED DISCS Gap Junctions ٨ Desmosomes Dr. MOHAMMED SHAMIA ٩ 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 ١٠ 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 ١١ It is formed of modified cardiac muscle cells that are specialized to generate and to conduct cardiac impulses to all heart muscles. Consist of: 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. Dr. MOHAMMED SHAMIA The moderator Band ١٢ 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. Dr. MOHAMMED SHAMIA Purkinje Muscle Fibres ١٣ 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 ١٤ 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 ١٥ Dr. MOHAMMED SHAMIA Action Site Shape of fibers ١٦ 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 ١٧ Dr. MOHAMMED SHAMIA ١٨ Thank you Dr. MOHAMMED SHAMIA