INTERIOR OF HEART Dr. Ahmed Fathalla Ibrahim

RIGHT ATRIUM

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)

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

RIGHT VENTRICLE

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.

RIGHT VENTRICLE The upper (smooth) outflowing part: It is called the infundibulum or conus arteriosus It leads into pulmonary orifice

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

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)

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)

LEFT VENTRICLE

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

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

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)

PULMONARY & AORTIC VALVES

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

CONDUCTING SYSTEM

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:

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