The Heart Flashcards
Describe the two major divisions (circuits) of the heart.
The heart has two major divisions.
The pulmonary circuit consists of the right side of the heart and veins. This division is responsible for transporting unoxygenated blood to the lungs for gas exchange (oxygen and carbon dioxide).
The systemic circuit supplies oxygen rich blood to all the organs. This circuit consists of the left side of the heart and arteries.
Describe the characteristics of the heart (in terms of shape, positioning in the thorax, and size).
The heart is located in the mediastinum (middle of the thorax posterior to the sternum and anterior to the thoracic vertebrae); its base is superior and the apex is the narrow pointed area inferior. The base is shifted/tiled toward the right. The size of the heart (as a general rule) is about the size of the individual’s fist.
The heart is responsible for pumping blood. It has four chambers that assist in this function. What are the chambers and which one(s) is responsible for the pumping blood out of the heart and which one(s) is responsible for receiving blood?
The four chambers of the heart are - in order that blood flows:
right atrium, right ventricle, left atrium, left ventricle. The ventricles are responsible for pumping blood away from the heart and the atria are responsible for receiving blood.
What is the name of the septum that separates the right ventricle from the left ventricle and the right atrium from the left atrium?
The interatrial septum separates the atria and the interventricular septum separates the ventricles.
What are the four valves located in the heart and where are they located? Name them in the order in which an erythrocyte would pass through (start in the right atrium).
The right atrioventricular (AV) valve is located between the right atrium and right ventricle.
The pulmonary semilunar valve is located in the pulmonary artery
The left atrioventricular valve is located between the left atrium and left ventricle.
The aortic semilunar valve is located in the aorta.
The function of valves is to prevent blood from flowing backwards into the chamber from which it just exited.
What vessel is responsible for delivering blood to the right atrium and left atrium?
The inferior and superior vena cava deliver blood to the right atrium. The pulmonary vein delivers blood to the left atrium.
Describe what happens to the valves of the heart when the ventricles are relaxed.
When the ventricles are is diastole, the right and left AV valves are open allowing blood to flow into and fill the ventricles. The pulmonary and aortic semilunar valves are closed preventing back flow of blood.
The heart is a muscle that needs oxygen in order to sustain its function. What vessels deliver blood to the myocardium?
The coronary arteries supply blood to the myocardium.
Describe how the electrical pathway makes its way through the heart. In doing so, know where it begins and when it ends.
The sinoatrial (SA) node is located in the superior aspect of the right atrium. The SA node is considered the pacemaker because it initiates the shock. The electrical current envelopes the entire inner surface of the right atrium (part of the current is transitioned to the left atrium at this point). The electrical current then comes to a focal point in the right atrium called the atrialventricular (AV) node where the current is slowed down. The current then moves to the atrioventricular septum via the AV bundles where is splits into right and left bundles. The current then continues to the apex of the heart and travels upward along the myocardium via the Purkinje fibers; it is at this point that the ventricles contract. The current ends once the ventricles maximally contract (ventricular systole). The cycle begins again at the SA node.
Describe what the cardiac cycle is.
The cardiac cycle is one complete contraction and relaxation of all four chambers.
Describe what happens to the atrium in relation to the ventricles when the heart “beats”.
The atria are in diastole when the ventricles are in systole. The atria are in systole when the ventricles are in diastole.
In auscultation of the heart describe what happens on each sound: “lubb” “dubb”
The first sound of the heart beat is the “lubb” sound. This sound signifies the atrioventricular valves closing (ventricles are in systole).
The second sound of the heart beat is the “dubb” sound. This sound signifies the closure of the aortic and pulmonary semilunar valves (ventricles are in diastole). There may be a 3rd sound heard; this sound mimics a “swish” and indicates a heart murmur.
When the ventricles contract (ventricular systole), the atria relax (atrial diastole). However, there a phase between the when the reverse happens; what is this phase called and what is happening to the chambers?
This period is called the quiescent period. All 4 chambers are relaxed. The AV valves are open and blood is allowed to move into the ventricles.
When is ejection fraction the highest?
Ejection fraction is the amount of blood ejected from the ventricles with each contraction. The ejection fraction is highest with exercise.
Define cardiac output (CO).
Cardiac output (CO) is the amount of blood ejected from each ventricle in 1 minute. CO = heart rate X stroke volume.
