Blood Circulation Pathways
Blood is pumped from the heart to different parts of the body through two main circuits:
Systemic Circuit:
Blood leaves the left side of the heart.
Begins at the aorta and branches out into major arteries that supply the body's tissues, excluding the lungs.
Blood reaches capillary beds where gas, nutrients, and waste exchange occurs in body tissues (skeletal muscle, glands, gut).
Returns through veins to the vena cava, re-entering the heart's right side.
Pulmonary Circuit:
Blood leaves the right side of the heart.
Heads towards the lungs through the pulmonary trunk for gas exchange (O2 and CO2) in the pulmonary capillary beds.
Unidirectional Blood Flow:
Blood flow through the heart is unidirectional due to heart valves.
Comprises:
Atrioventricular (AV) Valves: separate atria from ventricles (right AV valve and left AV valve).
Semilunar Valves: located at the exits of the ventricles (pulmonary and aortic valves).
Valves ensure one-way flow, preventing backflow.
Valve Anatomy:
Composed of flaps (also called leaflets) that open and close to regulate blood flow.
Connected to the heart wall via chordae tendineae (cord-like tendons) and papillary muscles (muscle projections from the heart wall).
Chordae tendineae prevent flaps from inverting when ventricles contract.
Cardiac Cycle Phases:
Atrial Contraction:
Increases pressure in the atria, opening AV valves, allowing blood flow into ventricles.
Ventricular Contraction:
Initiated by the QRS complex on an EKG.
Increases ventricular pressure, which causes blood to be ejected into the aorta.
As pressure rises above atrial pressure, AV valves close (S1 heart sound).
Ventricles eject blood until pressures equalize with the aorta.
Ventricular Relaxation:
Reduces pressure in the ventricles, allowing AV valves to open when atrial pressure exceeds ventricular pressure.
Blood flows passively into ventricles during relaxation.
Heart Sounds:
S1 (Lub): Sound made when AV valves close during ventricular contraction.
S2 (Dub): Sound made when semilunar valves close after blood ejection.
Murmurs indicate abnormal sounds due to backflow or structural issues with heart valves.
Electrical and Pressure Changes:
Blood flow is driven by pressure gradients between chambers:
Blood flows from high-pressure areas to low-pressure areas.
This pressure change drives the heart's mechanics and valve function.
Pressure Gradients:
Following electrical activation (EKG waveforms), observe corresponding pressure changes in the atria, ventricles, and aorta indicating contraction and relaxation phases.
Valve Damage:
Issues with chordae tendineae or valve flaps can lead to regurgitation (blood flowing backward).
Symptoms range from mild fatigue to severe heart function impairment, necessitating valve replacement surgery, often using pig valves or artificial options.
Importance of preserving heart valve integrity highlighted through aging effects on connective tissue, causing hardening and inefficiency over time.
cardiac heart cycle 2_14
Blood Circulation Pathways
Blood is pumped from the heart to different parts of the body through two main circuits:
Systemic Circuit:
Blood leaves the left side of the heart.
Begins at the aorta and branches out into major arteries that supply the body's tissues, excluding the lungs.
Blood reaches capillary beds where gas, nutrients, and waste exchange occurs in body tissues (skeletal muscle, glands, gut).
Returns through veins to the vena cava, re-entering the heart's right side.
Pulmonary Circuit:
Blood leaves the right side of the heart.
Heads towards the lungs through the pulmonary trunk for gas exchange (O2 and CO2) in the pulmonary capillary beds.
Unidirectional Blood Flow:
Blood flow through the heart is unidirectional due to heart valves.
Comprises:
Atrioventricular (AV) Valves: separate atria from ventricles (right AV valve and left AV valve).
Semilunar Valves: located at the exits of the ventricles (pulmonary and aortic valves).
Valves ensure one-way flow, preventing backflow.
Valve Anatomy:
Composed of flaps (also called leaflets) that open and close to regulate blood flow.
Connected to the heart wall via chordae tendineae (cord-like tendons) and papillary muscles (muscle projections from the heart wall).
Chordae tendineae prevent flaps from inverting when ventricles contract.
Cardiac Cycle Phases:
Atrial Contraction:
Increases pressure in the atria, opening AV valves, allowing blood flow into ventricles.
Ventricular Contraction:
Initiated by the QRS complex on an EKG.
Increases ventricular pressure, which causes blood to be ejected into the aorta.
As pressure rises above atrial pressure, AV valves close (S1 heart sound).
Ventricles eject blood until pressures equalize with the aorta.
Ventricular Relaxation:
Reduces pressure in the ventricles, allowing AV valves to open when atrial pressure exceeds ventricular pressure.
Blood flows passively into ventricles during relaxation.
Heart Sounds:
S1 (Lub): Sound made when AV valves close during ventricular contraction.
S2 (Dub): Sound made when semilunar valves close after blood ejection.
Murmurs indicate abnormal sounds due to backflow or structural issues with heart valves.
Electrical and Pressure Changes:
Blood flow is driven by pressure gradients between chambers:
Blood flows from high-pressure areas to low-pressure areas.
This pressure change drives the heart's mechanics and valve function.
Pressure Gradients:
Following electrical activation (EKG waveforms), observe corresponding pressure changes in the atria, ventricles, and aorta indicating contraction and relaxation phases.
Valve Damage:
Issues with chordae tendineae or valve flaps can lead to regurgitation (blood flowing backward).
Symptoms range from mild fatigue to severe heart function impairment, necessitating valve replacement surgery, often using pig valves or artificial options.
Importance of preserving heart valve integrity highlighted through aging effects on connective tissue, causing hardening and inefficiency over time.