Anatomy of the Heart

Study Notes

Right and left pulmonary arteries branch from the pulmonary trunk to carry deoxygenated blood to the lungs.
Major arteries include the right coronary artery and posterior interventricular artery, located in the atrioventricular and interventricular grooves, respectively.
Key veins include the great cardiac vein, posterior vein to the left ventricle, coronary sinus, and middle cardiac vein.

Atria serve as the receiving chambers; each atrium features a protruding auricle and pectinate muscles that define their walls.
Blood flows into the right atrium from the superior and inferior venae cavae, and coronary sinus, while the left atrium receives blood from pulmonary veins.
Ventricles are the discharging chambers with papillary muscles and trabeculae carneae forming the walls; the right ventricle pumps to the pulmonary trunk and the left ventricle to the aorta.

Myocardium varies in thickness: atria have thin walls to push blood into ventricles, while ventricles possess thicker walls for greater strength; left ventricle is the thickest for systemic circulation.
Right ventricle has lower resistance since it pumps to the lungs.

Pathway includes: Right atrium → tricuspid valve → Right ventricle → pulmonary semilunar valve → pulmonary arteries → lungs → pulmonary veins → Left atrium → bicuspid valve → Left ventricle → aortic semilunar valve → aorta → systemic circulation.

Supplies blood to the heart muscle itself, with collateral routes ensuring delivery despite major vessel blockages.
Key components of arterial supply involve right and left coronary arteries.

Ensure unidirectional blood flow; atrioventricular (AV) valves prevent backflow into atria during contraction, anchored by chordae tendineae.
Semilunar valves, including aortic and pulmonary valves, prevent backflow into ventricles after contraction.

Cardiac muscle is striated and interconnected through intercalated discs, ensuring coordinated contraction and function as a syncytium.

Cardiac muscle is self-excitable with a long refractory period, contracting as a unit similar to skeletal muscle.
Contraction is initiated by autorhythmic cells with pacemaker potentials.

The sinoatrial (SA) node is the primary pacemaker, generating impulses at 75 times per minute; the atrioventricular (AV) node delays impulses briefly for coordination.
Electrical activity is measured by ECG; P wave indicates atrial depolarization, QRS complex reflects ventricular depolarization, and T wave displays ventricular repolarization.

Comprises systole (contraction) and diastole (relaxation); includes phases of ventricular filling, contraction, and relaxation.
Dicrotic notch signifies a brief rise in aortic pressure from backflow when ventricles relax.

Cardiac output (CO) measures blood output per minute (CO = HR x SV, where HR is heart rate and SV is stroke volume).
Factors affecting stroke volume include preload (stretching of ventricles), contractility (force of contraction), and afterload (resistance in arteries).

Preload (degree of stretch) influences stroke volume, with increased return during exercise enhancing output, while blood loss or rapid heartbeat decreases it.

Influenced by autonomic nervous system: sympathetic stimulation increases heart rate (positive chronotropic effects), while parasympathetic (mainly via vagus nerve) decreases it (negative chronotropic effects).