anatomy of the heart

Anatomy of the heart

Blood flow

Superior and inferior vena cava > right atrium > tricuspid valve> right ventricle> pulmonary valve>pulmonary arteries> lungs> pulmonary veins> left atrium>mitral valve > left ventricle> aortic valve> aorta> body

Right atrium (RA)
• forms the right border of the heart
• deoxygenated blood enters R.A through 1 of 3 vessels
• superior and inferior vena cava: deliver blood to the heart from the body
• coronary sinus: returns blood from the walls of the heart itself
• superior vena cava: enters the upper posterior portion of the RA
• inferior vena cava and coronary sinus: enter by lower posterior portion of RA
• blood exits the RA into RV via right atrioventricular orifice during ventral diastole
• the tricuspid valve between RA and RV closes during ventricular systole
• note that there are also numerous openings of the smallest cardiac veins on the walls of RA for drainage of blood from the myocardium into the RA

Tricuspid valve
• right atrioventricular orifice is closed during ventricular contraction by the tricuspid valve to prevent the back flow of blood
• the contraction of the papillary muscles attached to the valve cusps by the chordae tendinae prevent the cusps from being everted back into the RA during ventricular systole

Right ventricle (RV)
• most anterior surface of heart
• in relation to RA, RV is located in front of and to the left of the right atrioventricular orifice
• blood entering RV from RA moves in a horizontal and forward direction
• 3 papillary muscles( derived from trabeculae carneae on RV wall) have only one end attached to ventricular surface while the other end serves as the point of attachment for tendon-like fibrous cords called chordae tendinae which connect to the free edges of the cusps of the tricuspid valve

Pulmonary valve
• 3 semi lunar cusps
• Each cusp form a pocket-like sinus, after ventricular contraction, the recoil of blood fills the pulmonary sinuses and forces the cusps close hence preventing blood from flowing back into the RV


Left atrium
• LA receives 4 pulmonary veins
• Interatrial septum is part of the anterior wall of LA
• Thin area in the septum is the valve of the foramen ovale (if not closed properly at birth, causes a “hole in the heart”)


Mitral valve also known as bi-cuspid valve
• has two cusps
• the bases of these cusps are secured to a fibrous ring surrounding the opening between LA and LV( left atrioventricular orifice)
• the coordinated action of the chordae tendinae and papillary muscle (same as in RA and RV) keep the valve closed

Left ventricle
• lies anterior to LA
• forms the apex of heart
• blood enters LV in a forward direction to the apex
• has the thickest layer of myocardium
• the papillary muscle found in LV are larger than those in RV

Aortic valve
• opening from the LV into aorta is closed by aortic valve
• 3 semilunar cusps: right, left and posterior
• The right and left coronary arteries originate from the right and left cusps

Stenosis: a narrowing of the orifice, caused by the valve’s inability to open fully