Overview of the Heart and Circulatory System

Study Notes

Average weight of the heart is approximately 300 grams.
Beats at a rate of 75 per minute, leading to 108,000 beats daily.
Estimated to beat over 35 million times per year and 2.5 billion times over a lifetime.
Pumps about 70 ml of blood per beat, resulting in a daily output of around 7,200 liters.
The heart's workload equals lifting approximately 30 tons to the peak of Mount Everest.

Right Heart:
- Receives deoxygenated blood from systemic circulation via the superior and inferior vena cava into the right atrium.
- Pumps blood to pulmonary circulation through the right ventricle.
Left Heart:
- Receives oxygenated blood from pulmonary circulation.
- Pumps blood into systemic circulation through the left ventricle.

Atrioventricular Valves:
- Tricuspid valve: located between the right atrium and right ventricle, consisting of three leaflets.
- Mitral valve: located between the left atrium and left ventricle, consisting of two leaflets.
Semilunar Valves:
- Pulmonic valve: features three leaflets governing blood flow from the right ventricle to the pulmonary artery.
- Aortic valve: also consists of three leaflets regulating blood from the left ventricle to the aorta.
Valves function to prevent backward blood flow and ensure low resistance to forward movement.

Defined as the period spanning one heart contraction to the next.
Diastole lasts longer than systole, with distinct phases of contraction and relaxation.

Isometric Contraction:
- Ventricular contraction occurs, raising ventricular pressure and closing atrioventricular valves (0.05 seconds).
- Raises pressure to match aortic pressure (after-load).
Ejection Phase:
- Ventricles contract further, increasing pressure above arterial pressure and opening semilunar valves.
- Comprises a rapid ejection phase (0.10 seconds) and a reduced ejection phase (0.15 seconds).
Isometric Relaxation:
- Ventricular muscle relaxes, causing ventricular pressure to fall below aortic pressure, resulting in closure of the aortic valve (0.06-0.08 seconds).
Ventricular Filling:
- Ventricles continue to relax; pressure drops, allowing atrioventricular valves to open and blood from the atria to fill the ventricles.
- Includes a period of rapid filling (0.11 seconds) and reduced filling (0.22 seconds).
Atrial Systole:
- Contributes 30% to ventricular filling and is crucial for maximizing cardiac output during high demands or heart failure.

A-Wave: Reflects atrial contraction.
C-Wave: Occurs due to bulging of the atrioventricular valves at the onset of ventricular contraction.
V-Wave: Observed at the end of ventricular contraction; results from blood accumulation in the atria with closed atrioventricular valves.