The Cardiac Cycle & The Pathway Of Blood

The Cardiac Cycle

The cardiac cycle is the sequence of events that occur in the heart during one heartbeat. It consists of two main phases:

Diastole:

Relaxation Phase: Both atria and ventricles are relaxed.
Blood Flow: Blood flows into the atria from the veins (vena cava and pulmonary veins).
Valve Position: Atrioventricular (AV) valves (tricuspid and bicuspid/mitral) are open, allowing blood to flow into the ventricles. Semilunar valves (pulmonary and aortic) are closed.

Systole:

Atrial Systole: Atria contract, pushing more blood into the ventricles.
Ventricular Systole: Ventricles contract. AV valves close to prevent backflow into the atria, and semilunar valves open to allow blood to be ejected from the heart.
Right Ventricle: Pumps deoxygenated blood into the pulmonary artery towards the lungs.
Left Ventricle: Pumps oxygenated blood into the aorta towards the rest of the body.

Deoxygenated Blood:

Superior and Inferior Vena Cava: Blood returns from the body to the right atrium.
Right Atrium: Blood flows into the right atrium.
Tricuspid Valve: Blood passes through this valve into the right ventricle.
Right Ventricle: Blood is pumped into the pulmonary artery through the pulmonary valve.
Pulmonary Arteries: Blood is carried to the lungs for oxygenation. Oxygenated Blood:
Pulmonary Veins: Blood returns from the lungs to the left atrium.
Left Atrium: Blood flows into the left atrium.
Bicuspid (Mitral) Valve: Blood passes through this valve into the left ventricle.
Left Ventricle: Blood is pumped into the aorta through the aortic valve.
Aorta: Blood is distributed to the rest of the body.

Oxygen Delivery: The cardiac cycle ensures a continuous supply of oxygenated blood to muscles during physical activity.
Efficiency: A well-functioning cardiac cycle supports the efficient removal of carbon dioxide and waste products.
Adaptation: Regular physical activity can improve the efficiency and strength of the heart, enhancing overall cardiovascular fitness.