Dr Ahmed Fathalla Ibrahim RIGHT ATRIUM RIGHT ATRIUM

Dr. Ahmed Fathalla Ibrahim

RIGHT ATRIUM

RIGHT ATRIUM • THE CAVITY IS DIVIDED INTO 3 PARTS: 1. The posterior (smooth) part: receives opening of coronary sinus, superior & inferior vena cava 2. 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) 3. The septal wall: formed of an oval depression (fossa ovalis), bounded superolaterally by a margin (annulus ovalis)

RIGHT ATRIUM • OPENINGS: 1. Opening of SVC: opposite right 3 rd costal cartilage, has no valves 2. Opening of IVC: opposite right 6 th costal cartilage, has a rudimentary valve 3. 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 4. Openings of anterior cardiac veins 5. 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 1. Two situated in anterior wall: anterior & right cusps 2. 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: 1. Trabeculae carnae are larger & more numerous 2. 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 • • • 1. 2. LEFT ATRIOVENTRICULAR (MITRAL): Lies between left atrium & ventricle Compared to tricuspid valve: Its orifice is narrower It has only 2 cusps (anterior & posterior) 3. 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: 1. One situated in anterior wall: right cusp 2. 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: 1. An upper smaller membranous part 2. A lower larger muscular part

CONDUCTING SYSTEM

CONDUCTING SYSTEM • Consists of specialized cardiac muscle present in: 1. 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 2. Atrioventricular node: in the lower part of atrial septum, above tricuspid valve 3. 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