Heart Flashcards
Auricles (auricular appendages)
outpouchings from the walls of the right and left atria
Borders of the heart
• right border = right atrium
• Left border = left atrium
• Inferior border = right ventricle and part of left ventricle
Surfaces of the heart
• base/ posterior surface = left atrium, part of right atrium
• Inferior / diaphragmatic surface = left ventricle, part of the right ventricle
• Anterior / sternocostal surface = right ventricle
• Left pulmonary surface = left ventricle
• Right pulmonary surface = right atrium
Coronary circulation
major muscular arteries lie in sulci (grooves on external surface of heart)
• Left and right coronary arteries arise from ascending aorta and then branch further to supply specific heart regions
• Cardiac veins return venous blood to coronary sinus which enters right atrium
Right coronary artery
supply parts of the conducting system of the heart, the right atrium, right ventricle, part of the left ventricle, and part of the interventricular septum.
• Branches to the sinoatrial node and atrioventricular node supply these major components of the electrical conducting system of the heart.
• The right marginal artery supplies the inferior border of the heart.
• The posterior interventricular artery (PIV) is the continuation of the right coronary artery on the inferior (diaphragmatic) surface of the heart - runs in the posterior interventricular sulcus and supplies both ventricles.
posterior interventricular artery (PIV)
continuation of the right coronary artery on the inferior (diaphragmatic) surface of the heart - runs in the posterior interventricular sulcus and supplies both ventricles.
Left coronary artery
supply parts of the conducting system of the heart, the left atrium, most of the left ventricle, part of the right ventricle, and part of the interventricular septum.
• only runs a short course before it divides into 2 large terminal branches:
1. Anterior interventricular artery (or the left anterior descending; ‘LAD’)
2. Circumflex artery (abbreviated to ‘Cx’).
• The anterior interventricular artery (LAD) runs in the anterior interventricular sulcus towards the apex- supplies both ventricles.
• One or two diagonal branches arise from the LAD.
• circumflex artery runs around the heart onto the inferior / diaphragmatic surface- supplies the left atrium, part of the right ventricle and the left ventricle.
• left marginal artery arises from the circumflex and supplies the left ventricle.
2 terminal branches of left coronary artery
- Anterior interventricular artery (or the left anterior descending; ‘LAD’)
- Circumflex artery (abbreviated to ‘Cx’).
Anterior interventricular artery (or the left anterior descending; ‘LAD’)
runs in the anterior interventricular sulcus towards the apex- supplies both ventricles.
• One or two diagonal branches arise from the LAD.
- septal branches arise from LAD as well
Circumflex artery (abbreviated to ‘Cx’).
runs around the heart onto the inferior / diaphragmatic surface- supplies the left atrium, part of the right ventricle and the left ventricle.
• obtuse marginal artery arises from the circumflex and supplies the left ventricle.
Right marginal artery
supplies the inferior border of the heart.
posterior interventricular artery (PIV)
continuation of the right coronary artery on the inferior (diaphragmatic) surface of the heart - runs in the posterior interventricular sulcus and supplies both ventricles.
Right dominant circulation
the PIV arises from the right coronary- both the right and left coronary arteries supply the left ventricle.
occlusion of the left main stem would impair blood flow to part of, but not the entire left ventricle.
Left dominant circulation
the PIV arises from the circumflex artery; the left coronary artery supplies the entire left ventricle.
blockage of the left main stem occludes blood flow to the entire left ventricle.
Right atrium
receives deoxygenated blood from the body via the superior and inferior venae cavae, and from the heart via the coronary sinus
Main features of right atrium
Interatrial septum
Fossa ovalis
Crista terminalis
Tricupsid valve
Interatrial septum
separates right atrium from the left atrium
Fossa ovalis
a depression in the interatrial septum, remnant of the foetal foramen ovale. In the foetus the foramen ovale shunts oxygenated blood from the right atrium to the left atrium- bypassing the lungs.
Crista terminalis
muscular ridge that separates the smooth-walled posterior part of the atrium from the anterior part, which has a ridged, muscular wall. The ridges are pectinate muscles and extend into the right auricle. The parts of the right atrium on either side of the crista have different embryological origins.
Right ventricle
pumps the deoxygenated blood that it receives from the right atrium into the pulmonary trunk, which bifurcates into a left and right pulmonary artery.
• The pulmonary valve at the entrance of the pulmonary trunk prevents backflow of blood into the right ventricle.
• As contraction of the right ventricle propels blood into the pulmonary trunk, the wall of the right ventricle is thicker than that of the right atrium.
Right ventricle contains:
interventricular septum
trabeculae carneae
papillary muscles
chordae tendineae
moderator band
interventricular septum
Separates left and right ventricle
papillary muscles
modified regions of trabeculae carneae, which project into the lumen of the ventricle
trabeculae carneae
muscular ridges on the internal wall
chordae tendineae
fibrous cords which connect the tips of the papillary muscles to the valve
moderator band
modified region of the trabeculae carneae which connects the interventricular septum to one of the papillary muscles.
Left atrium
receives oxygenated blood from the lungs via the pulmonary veins (2 from each lung).
• it has a thinner wall compared to the ventricles and internally has a smooth-walled posterior part and an anterior part bearing pectinate muscles.
• From the left atrium, blood flows into the left ventricle via the left atrioventricular valve (mitral valve)- flow of blood is mostly passive, but the left atrium does contract to empty fully.
Left ventricle
pumps the oxygenated blood that it receives from the left atrium into the aorta.
• The first branches from the aorta are the coronary arteries.
• The aortic valve at the entrance to the aorta prevents backflow of blood into the left ventricle.
• Because contraction of the left ventricle propels blood into the systemic circulation, the wall of the left ventricle is thicker than that of the right ventricle.
Left ventricle contains:
• trabeculae carneae
• papillary muscles; two in the left ventricle
• chordae tendineae that connect the tips of the papillary muscles to the mitral valve.
Atrioventricular valve
When the ventricles contract (ventricular systole), pressure rises inside the ventricles. This rise in pressure has the potential to force blood back into the atria.
• The tricuspid and mitral valves close during ventricular contraction and prevent regurgitation of blood back into the atria, ensuring that blood can only flow out the ventricles via the great vessels (the pulmonary trunk and aorta).
• The papillary muscles and chordae tendineae allow the closed valves to resist the pressure generated inside the ventricles during contraction and prevent them from being forced open.
As pressure rises in the ventricles, the valve cusps, which project into the ventricle, start to close passively. When the ventricles contract, the papillary muscles also contract. The papillary muscles tense the cords, which in turn ‘pull’ on the valve cusps and prevent them everting into the atria.
Semilunar valves
aortic and pulmonary valves are called semilunar valves, as their cusps are semi-circular (half-moon) shaped.
• They prevent the backflow of blood from the aorta and pulmonary trunk into the left and right ventricles, respectively, that would otherwise occur at the end of ventricular contraction.
• Each semilunar valve has 3 semi-circular cusps.
• Each cusp is attached to the inner wall of the vessel, with a free edge that projects into the vessel lumen forming a pocket, or sinus, between its free edge and the vessel wall. When blood is forcefully propelled from the ventricles during ventricular systole, the valve cusps are ‘flattened’ onto the vessel wall and blood flows through the valve unimpeded. At the end of ventricular systole, pressure in the ventricles drops. Once pressure in the ventricle is less than that in the vessel (aorta or pulmonary trunk), blood in the vessel starts to flow back towards the heart. As it flows back, blood is immediately ‘caught’ in the valve cusps. The sinuses rapidly fill with blood and the cusps balloon out into the lumen. The free edges of the three valve cusps contact each other in the lumen and close the valve orifice.
• In the aorta, the right and left coronary arteries arise from two of the three aortic sinuses, hence the coronary arteries fill during ventricular relaxation (diastole).
How many cusps does each semilunar valve have
3
Each cusp is attached to the inner wall of the vessel, with a free edge that projects into the vessel lumen forming a pocket, or sinus, between its free edge and the vessel wall. When blood is forcefully propelled from the ventricles during ventricular systole, the valve cusps are ‘flattened’ onto the vessel wall and blood flows through the valve unimpeded. At the end of ventricular systole, pressure in the ventricles drops. Once pressure in the ventricle is less than that in the vessel (aorta or pulmonary trunk), blood in the vessel starts to flow back towards the heart. As it flows back, blood is immediately ‘caught’ in the valve cusps. The sinuses rapidly fill with blood and the cusps balloon out into the lumen. The free edges of the three valve cusps contact each other in the lumen and close the valve orifice.
Heart sound positions
• Aortic = 2nd intercostal space, just to the right of the sternum.
• Pulmonary = 2nd intercostal space, just to the left of the sternum.
• Tricuspid = 5th intercostal space, just to the left of the sternum.
• Mitral = 5th intercostal space, left midclavicular line.
listen to the heart sounds in the regions where sound is transmitted, rather than directly over the valve
Conducting system of the heart
• Specialised cells in the heart generate and conduct the electrical impulses that stimulate myocardial contraction.
• Cells in the sinoatrial (SA) node spontaneously generate electrical impulses; it is the ‘pacemaker’ of the heart. It is located at the superior end of the crista terminalis.
• Impulses from the SA node stimulate contraction of the atria.
• Impulses are conducted to the atrioventricular (AV) node, located at the inferior end of the interatrial septum.
• From the AV node, conducting fibres form the atrioventricular bundle (Bundle of His).
• The atrioventricular bundle divides into two groups of fibres - the right and left bundle branches.
• The left and right bundle branches give rise to Purkinje fibres that enter the myocardium of the left and right ventricles, respectively, and stimulate contraction.
Rate of impulses from SAN
• The SA node generates impulses at a rate of approximately 70 per minute.
Percentage of SAN supplied by left or right coronary artery
The SA node is supplied by the RCA in approximately 60% of people and by the LCA in approximately 40% of people.
Blood supply to the conducting system
The SA node is supplied by the RCA in approximately 60% of people and by the LCA in approximately 40% of people.
• The AV node is usually supplied by the posterior interventricular artery. In most people, the PIV arises from the RCA.
• In most people, the LCA supplies the Bundle of His
• Occlusion of either coronary artery can therefore result in conduction abnormalities, in addition to myocardial ischaemia.
Innervation of the heart
innervated by sympathetic and parasympathetic fibres- act upon the SA node and can change the rate and force of myocardial contraction.
• Sympathetic stimulation increases the heart rate and force of contraction.
• Parasympathetic stimulation slows the heart rate and force of contraction.
• also innervated by visceral afferent fibres- convey sensory information from the heart back to the CNS.
Referred pain
if the myocardium is ischaemic, this visceral sensory information is relayed back to our conscious perception and may be perceived as pain, burning, tightness or pressure in the chest. Typically, the pain cannot be pinpointed, but is felt generally in the chest, the left side of the neck and / or the left arm.
3 main sulci of the heart
Coronary sulcus (atrioventricular groove)
Anterior interventricular sulcus
Posterior interventricular sulcus
