Blood Flow Through the Heart
Simultaneous Flow Concept
Blood flows through both sides of the heart at the same time.
Each heartbeat involves coordinated contractions:
o Both atria contract together, pushing blood into the ventricles.
o Both ventricles contract together, pumping blood into the pulmonary and
systemic circulations.
Understanding simultaneous flow is essential for interpreting heart function, including
electrical activity, pressure changes, and heart sounds.
Right Side of the Heart – Pulmonary Circulation
Receives deoxygenated blood from the body via the superior and inferior vena
cava.
Blood enters the right atrium, then moves through the tricuspid valve into the right
ventricle.
The right ventricle contracts, sending blood through the pulmonary valve into
the pulmonary arteries, which carry it to the lungs for oxygenation.
Left Side of the Heart – Systemic Circulation
Receives oxygenated blood from the lungs via the pulmonary veins.
Blood enters the left atrium, then passes through the mitral (bicuspid) valve into
the left ventricle.
The left ventricle contracts, pumping blood through the aortic valve into the aorta,
which distributes it to the rest of the body.
Coordination of Both Sides
The right and left sides of the heart work in perfect coordination.
This ensures continuous and balanced circulation:
o Pulmonary circulation carries blood to the lungs for oxygenation.
o Systemic circulation delivers oxygen-rich blood to tissues.
Proper timing is critical for maintaining efficient blood flow and pressure balance.
Clinical Relevance
, Knowing that blood flows simultaneously through both sides is essential for
understanding:
o Electrocardiography (ECG/EKG) patterns
o Heart sounds (S1, S2)
o Pressure changes in chambers during the cardiac cycle
Blood Flow Through the Heart – Detailed
Notes
Right Side of the Heart
1. Entry of Deoxygenated Blood
o Blood enters the relaxed right atrium from:
Systemic circulation via the superior and inferior venae cavae
, Heart wall via the coronary sinus
2. Movement into Right Ventricle
o Most blood flows into the relaxed right ventricle.
o Right atrium contraction pushes remaining blood into the right ventricle,
completing right ventricular filling.
3. Right Ventricle Contraction
o Contraction pushes blood against the tricuspid valve, forcing it closed to
prevent backflow into the atrium.
o Blood also pushes against the pulmonary semilunar valve, forcing it open.
o Blood flows into the pulmonary trunk, which branches into pulmonary
arteries carrying blood to the lungs for gas exchange (CO₂ released, O₂
picked up).
Left Side of the Heart
1. Entry of Oxygenated Blood
o Blood returns from the lungs into the left atrium via four pulmonary veins.
2. Movement into Left Ventricle
o Most blood flows through the bicuspid (mitral) valve into the relaxed left
ventricle.
o Left atrium contraction completes left ventricular filling.
3. Left Ventricle Contraction
o Contraction pushes blood against the bicuspid valve, closing it to prevent
backflow into the atrium.
o Blood also pushes against the aortic semilunar valve, opening it.
o Blood enters the aorta, which distributes it to all parts of the body, except
areas of the lungs served by pulmonary vessels.
Autorhythmicity of Cardiac Muscle
The heart is autorhythmic because it stimulates itself to contract at regular intervals.
o “Auto” = self
o “Rhythmic” = at regular intervals
Even if the heart is removed from the body and kept under physiological
conditions (proper nutrients and temperature), it will continue to beat
autorhythmically for a long time.
This property allows the heart to maintain a consistent heartbeat without external
neural input.
Simultaneous Flow Concept
Blood flows through both sides of the heart at the same time.
Each heartbeat involves coordinated contractions:
o Both atria contract together, pushing blood into the ventricles.
o Both ventricles contract together, pumping blood into the pulmonary and
systemic circulations.
Understanding simultaneous flow is essential for interpreting heart function, including
electrical activity, pressure changes, and heart sounds.
Right Side of the Heart – Pulmonary Circulation
Receives deoxygenated blood from the body via the superior and inferior vena
cava.
Blood enters the right atrium, then moves through the tricuspid valve into the right
ventricle.
The right ventricle contracts, sending blood through the pulmonary valve into
the pulmonary arteries, which carry it to the lungs for oxygenation.
Left Side of the Heart – Systemic Circulation
Receives oxygenated blood from the lungs via the pulmonary veins.
Blood enters the left atrium, then passes through the mitral (bicuspid) valve into
the left ventricle.
The left ventricle contracts, pumping blood through the aortic valve into the aorta,
which distributes it to the rest of the body.
Coordination of Both Sides
The right and left sides of the heart work in perfect coordination.
This ensures continuous and balanced circulation:
o Pulmonary circulation carries blood to the lungs for oxygenation.
o Systemic circulation delivers oxygen-rich blood to tissues.
Proper timing is critical for maintaining efficient blood flow and pressure balance.
Clinical Relevance
, Knowing that blood flows simultaneously through both sides is essential for
understanding:
o Electrocardiography (ECG/EKG) patterns
o Heart sounds (S1, S2)
o Pressure changes in chambers during the cardiac cycle
Blood Flow Through the Heart – Detailed
Notes
Right Side of the Heart
1. Entry of Deoxygenated Blood
o Blood enters the relaxed right atrium from:
Systemic circulation via the superior and inferior venae cavae
, Heart wall via the coronary sinus
2. Movement into Right Ventricle
o Most blood flows into the relaxed right ventricle.
o Right atrium contraction pushes remaining blood into the right ventricle,
completing right ventricular filling.
3. Right Ventricle Contraction
o Contraction pushes blood against the tricuspid valve, forcing it closed to
prevent backflow into the atrium.
o Blood also pushes against the pulmonary semilunar valve, forcing it open.
o Blood flows into the pulmonary trunk, which branches into pulmonary
arteries carrying blood to the lungs for gas exchange (CO₂ released, O₂
picked up).
Left Side of the Heart
1. Entry of Oxygenated Blood
o Blood returns from the lungs into the left atrium via four pulmonary veins.
2. Movement into Left Ventricle
o Most blood flows through the bicuspid (mitral) valve into the relaxed left
ventricle.
o Left atrium contraction completes left ventricular filling.
3. Left Ventricle Contraction
o Contraction pushes blood against the bicuspid valve, closing it to prevent
backflow into the atrium.
o Blood also pushes against the aortic semilunar valve, opening it.
o Blood enters the aorta, which distributes it to all parts of the body, except
areas of the lungs served by pulmonary vessels.
Autorhythmicity of Cardiac Muscle
The heart is autorhythmic because it stimulates itself to contract at regular intervals.
o “Auto” = self
o “Rhythmic” = at regular intervals
Even if the heart is removed from the body and kept under physiological
conditions (proper nutrients and temperature), it will continue to beat
autorhythmically for a long time.
This property allows the heart to maintain a consistent heartbeat without external
neural input.
