“Basic Cardiac Anatomy and Physiology” by Nancy Braudis for OPENPediatrics

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. Please help us improve the content by providing
us with some feedback.


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