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INTERIOR OF HEART Dr. Ahmed Fathalla Ibrahim
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RIGHT ATRIUM
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RIGHT ATRIUM THE CAVITY IS DIVIDED INTO 3 PARTS:
The posterior (smooth) part: receives opening of coronary sinus, superior & inferior vena cava The anterior (rough) part: formed of parallel muscular ridges (musculi pectinati) extending to right auricle. It is separated from the posterior wall by a vertical ridge (crista terminalis) The septal wall: formed of an oval depression (fossa ovalis), bounded superolaterally by a margin (annulus ovalis)
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RIGHT ATRIUM OPENINGS:
Opening of SVC: opposite right 3rd costal cartilage, has no valves Opening of IVC: opposite right 6th costal cartilage, has a rudimentary valve Opening of coronary sinus: between opening of IVC & tricuspid orifice, has a functioning valve which prevents return of blood into coronary sinus during atrial contraction Openings of anterior cardiac veins Openings of venae cordis minimi
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RIGHT VENTRICLE
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RIGHT VENTRICLE THE CAVITY IS SEMILUNAR IN SHAPE & DIVIDED INTO 2 PARTS: The lower (rough) inflowing part: Formed of irregular muscular ridges (trabeculae carnae) Has 3 papillary muscles (anterior, posterior & septal): with a base attached to ventricular wall & an apex attached to cusps of tricuspid valve by chordae tendinae moderator band: a muscular ridge extending from interventricular septum to base of anterior papillary muscle. It carries the right branch of A-V bundle.
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RIGHT VENTRICLE The upper (smooth) outflowing part:
It is called the infundibulum or conus arteriosus It leads into pulmonary orifice
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ORIFICES & VALVES OF RIGHT VENTRICLE
RIGHT ATRIOVENTRICULAR (TRICUSPID): Lies between right atrium & ventricle Surrounded by a fibrous ring giving attachment to the bases of 3 triangular cusps (anterior, posterior & septal) Chordae tendinae of papillary muscles are attached to the adjoining free edges of cusps
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ORIFICES & VALVES OF RIGHT VENTRICLE
PULMONARY: Lies between infundibulum of right ventricle & pulmonary trunk Consists of 3 semilunar cusps Two situated in anterior wall: anterior & right cusps One situated in posterior wall: left cusp The wall of pulmonary trunk is slightly dilated above the 3 cusps forming 3 sinuses (two anterior & one posterior)
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LEFT ATRIUM COMPARED TO RIGHT ATRIUM:
Its cavity is smooth except the left auricle which have musculi pectinati Its posterior wall receives the openings of 4 pulmonary veins (have no valves)
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LEFT VENTRICLE
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LEFT VENTRICLE COMPARED TO RIGHT VENTRICLE:
Its cavity is circular in shape Its wall is 3 times thicker In its lower rough part: Trabeculae carnae are larger & more numerous Papillary muscles: are only 2, larger, has fewer but stronger chordae tendinae Its upper smooth part: called aortic vestibule, leads into aortic orifice
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ORIFICES & VALVES OF LEFT VENTRICLE
LEFT ATRIOVENTRICULAR (MITRAL): Lies between left atrium & ventricle Compared to tricuspid valve: Its orifice is narrower It has only 2 cusps (anterior & posterior) Cusps are larger & stronger
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ORIFICES & VALVES OF LEFT VENTRICLE
AORTIC: Lies between aortic vestibule of left ventricle & ascending aorta Compared to pulmonary valve: Consists of 3 larger semilunar cusps: One situated in anterior wall: right cusp Two situated in posterior wall: left & posterior cusps The wall of aorta is slightly dilated above the 3 cusps forming 3 sinuses (one anterior & two posterior)
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PULMONARY & AORTIC VALVES
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VENTRICULAR SEPTUM It is an oblique septum separating the ventricles
It is composed of two parts: An upper smaller membranous part A lower larger muscular part
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CONDUCTING SYSTEM
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CONDUCTING SYSTEM Consists of specialized cardiac muscle present in:
Sinoatrial node: in the wall of right atrium, in the upper part of sulcus terminalis, to the right of opening of SVC. It is the pacemaker of heart Atrioventricular node: in the lower part of atrial septum, above tricuspid valve Atrioventricular bundle: along the membranous part of ventricular septum, divides at the upper border of the muscular part of the septum into:
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CONDUCTING SYSTEM Right bundle branch: runs along the moderator band
Left bundle branch: pierces the ventricular septum to run on its left side Each branch divides into a network of branches giving a subendocardial plexus of fibers (Purkinje fibers) in the wall of each ventricle
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