Basic Cardiac Anatomy and Physiology by Nancy Braudis.
My name is Nancy Braudis and I am a clinical nurse specialist at Children's Hospital of
Boston, and I will be going over cardiac anatomy and physiology.
Normal Cardiac Anatomy.
The right side of the heart receives venous blood from the body through the superior and
inferior vena cava, which enter the right atrium.
Blood flows through the tricuspid valve into the right ventricle.
Blood leaves the right ventricle through the pulmonary valve into the main pulmonary artery.
The pulmonary artery divides into right and left pulmonary arteries to transport deoxygenated
blood from the right side of the heart to the right and left lungs.
The pulmonary arteries branch further into the pulmonary capillary bed where oxygen and
carbon dioxide exchange occurs.
The four pulmonary veins, two from the right lung and two from the left lung, carry oxygenated
blood from the lungs to the left side of the heart.
The oxygenated blood flows from the left atrium through the mitral valve and into the left
ventricle and out through the aortic valve and into the aorta and to the body.
Cardiac Valves.
This picture shows the individual heart valves.
The heart valve openings are protected by flaps of tissue called leaflets or cusps that
are attached to the papillary muscles by the chordae tendineae.
The papillary muscles are extensions of the heart muscle that pull the cusps together
and downward at the onset of ventricular contraction.
As the pressure increases in the ventricles, the valves close, and the papillary muscles
prevent the valves from opening.
Coronary arteries.
The branch of circulation that supplies oxygen and other nutrients to the cells of the heart
is called the coronary circulation.
The major coronary arteries are the right coronary artery and the left coronary artery.
The left coronary artery originates from a single opening behind the left cusp of the
aortic valve and divides into the left anterior descending artery and the circumflex artery.
The right coronary artery originates from an opening behind the right cusp of the aortic
valve and divides into three major branches, the conus, the marginal-- the right marginal
branch, and the posterior descending branch.
Coronary Veins.
After flowing through an extensive network of capillaries, blood from the coronary arteries
drain into the cardiac veins.
The veins follow into the great cardiac vein and coronary sinus.
Blood empties from the coronary sinus into the right atrium.
Cardiac conduction system.
Electrical impulses originate in the sinoatrial node located at the junction of the right
atrium and superior vena cava.
Each electrical impulse generated from the SA node travels through the right and left
atrium, causing the atria to contract.
The impulse then travels to the atrioventricular node, AV node, then to the bundle of His,
and finally through the right and left bundle branches of the ventricles, causing the ventricles
to contract.
Electrocardiogram.
The P-wave of electrocardiogram represents atrial contraction.
The PR interval is a measure of time from the onset of atrial contraction to the onset
of ventricular contraction.
The QRS complex represents the complete depolarization of the ventricles.
The ST segment represents the complete repolarization of the ventricles.
Elevation or depression of this segment may indicate heart muscle ischemia.
The QT interval represents the complete depolarization and repolarization of the ventricles.
A prolonged QT interval is a risk factor for ventricular arrhythmias and sudden death.
Intracardiac Pressures.
Pressures on the left side of the heart are usually three times greater than the right
side of the heart.
A normal right atrial pressure is usually around 3, with a range of 2-8.
And left atrial pressure is usually 8, with a range of 6-12 millimeters of mercury.
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