Heart Physiology

Atrioventricular (AV) valves

prevent blood backflow into the atria when ventricles contract

• located between: atria and venticles

Two types of AV valves

• Tricuspid valve

• Bicuspid (mitral) valve

Tricuspid valve

allows blood to flow from the right atrium into the right ventricle

• located between: right atrium and right ventricle

Bicuspid (mitral) valve

allows blood flow from the left atrium and the left ventricle

• located between: left atrium and left ventricle

In the cardiac cycle, during diastole, AV valves

open, allowing blood to fill the ventricles

In the cardiac cycle, during systole , AV valves

close, preventing back flow into the atria

Chordae tendineae

attatch AV valve flaps to papillary muscles

Papillary muscles

contract to tighten chordae tendineae, preventing valve eversion (flipping inside out like an unmbrella)

Chordae tendineae and papillary muscles are only found in

AV valves

How do the chordae tendineae and papillary muscles work together?

• Chordae tendineae attach AV valve flaps to papillary muscles.

• Papillary muscles contract, tightening chordae tendineae to prevent eversion (flipping inside out like an umbrella).

• This anchors the AV valves, ensuring one-way blood flow and preventing backflow

Semilunar (SL) valves

control blood flow preventing backflow into the heart

• between the ventricles and arteries

Two types of SL valves

• Pulmonary valve

• Aortic valve

Pulmonary valve

sends deoxygenated blood to the lungs

• located between: right ventricle and pulmonary artery

Aortic valve

sends oxygenated blood to the body

• located between: left ventricle and aorta

In the cardiac cycle, during diastole, SL valves

close, preventing back flow into the ventricles

In the cardiac cycle, during systole, SL valves

open, allowing blood to the ejected from the ventricles

Blood flow through the heart

“Very Red Turtles - Run Past Peaceful Lakes - Passing Little Boats - Long Adventures Await”

The vena cava and the pulmonary veins do not have

valves where they enter the atria

Both ventricles contract together to

push blood into the pulmonary artery and aorta

Both atria contract together to

push blood into the ventricles

Heart is in systole when

ventricle contract

Heart is in diastole when

ventricles relax

The “bump or “lub” sound is caused by

AV valves closing at the beginning of ventricular systole

The “dump or dub” sound is caused by

SL valves closing at the beginning of ventricular diastole

What are the phases of the cardiac cycle?

1. Mid-to-late Diastole (Heart Filling)

2. Ventricular Systole (Pumping)

3. Early Diastole (Relaxation)

Step 1 of Cardiac Cycle: Ventricular Filling (Mid-to-Late Diastole)

• AV Valves open

• Blood flows from atria to ventricles

Step 2 of Cardiac Cycle: Atrial Contraction (Mid-to-Late Diastole)

Atria contract, pushing remaining blood into ventricles

Step 3 of Cardiac Cycle: Isovolumetric Contraction (Ventricle Systole)

• Ventricles contract but all valves are closed initially

• Pressure builds up

Step 4 of Cardiac Cycle: Ventricular Ejection (Ventricle Systole)

• SL valves open

• blood is pumped into the pulmonary artery (right side) and aorta (left side)

Step 5 of Cardiac Cycle: Isovolumetric Relaxation (Early Diastole)

• ventricles relax

• SL Valves close (prevents backflow)