Topic 3: Exchange: The Heart

Cardiac muscle

Heart has thick layer of cardiac muscle (myogenic). It never fatigues as long as it has an adequate supply of oxygen

Myogenic

Meaning it can contract and relax without nervous or hormonal stimulation

Coronary arteries

• Blood vessels that supply oxygenated blood directly to heart muscles

• Come out of aorta

• Blocked coronary arteries lead to cells dying (myocardial infarction) → heart attack (common language)

The left side of the heart has a thicker muscular wall

Also allows larger contraction. As it has oxygenated blood that have high pressure to reach all body

Aorta

Carries oxygenated blood to the body

Superior vena cava/ inferior vena cava

Brings deoxygenated blood from the body

Pulmonary artery

Right lung

Right ventricle

Sends deoxygenated blood to the lungs

Pulmonary artery

Deoxygenated to left lung

Pulmonary veins

Come from the left lung so oxygenated

Left ventricle

Pumps blood to the body (oxygenated)

4 major blood vessels

• vena cava

• Pulmonary vein

• Pulmonary artery

• Aorta

Pathway of blood through the heart

Rest of body → vena cava → right atrium → atrioventricular tricuspid valve → right ventricle → pulmonary semi-lunar valve → pulmonary artery → lungs → pulmonary vein → left atrium → atrioventricular valve bicuspid valve → left ventricle → aorticsemilunar valve → aorta → rest of body

Heart valves

Prevents backflow of blood

Values will only open if the pressure is higher behind them, compared to thefront

If the pressure is higher in front, then the valve remains closed

AV open when pressure is higher in the atria than the ventricles → close when higher in ventricles

Semi-lunar open when pressure higher in ventricles then arteries → close when pressure higher in artery than ventricle

Septum

Separates the oxygenated and deoxygenated blood. Muscle that runs down the middle of the heart.

The difference between the atria and ventricles

1. Atria - the top chambers in the heart that collect blood from blood vessels (veins)

2. Ventricles - the bottom chambers in the heart that pump blood into blood vessels (arteries)

The left side of the heart contains oxygenated blood, and the right side contains deoxygenated blood.

This forms two separate pumping mechanisms

The heart has two separate pumping mechanisms because:

• Blood pressure drops in the lungs as it flows through the capillaries

• A single pump would slow the blood flow to the body cells

• Two pumps increase the pressure before the blood circulates

The atrioventricular values:

1. The tricuspid value is located between the right atrium and right ventricle

2. The bicuspid (mitral) valve is located between left atrium and left ventricle

3. Both values prevent backflow of blood into the atria when the ventricles contract

The semi-lunar valves

1. These are located between the ventricles and the pulmonary artery and the aorta

2. They prevent the backflow of blood into the ventricles when they relax

A major blood vessel connects to each of the four chambers of the heart

1. The pulmonary vein- this moves oxygenated blood into the left atrium from the lungs

2. The aorta - this moves oxygenated blood from the left ventricle to the body

3. The vena cava - this moves deoxygenated blood into the right atrium from the body

4. The pulmonary artery - this moves deoxygenated blood from the right ventricle to the lungs

The ventricle walls are thicker than the atria walls (with more muscle). This is because:

1. The atria only need enough pressure to pump blood a short distance into the ventricles

2. The ventricles need a lot of pressure to pump blood a long distance out of the heart to other organs

The left ventricle walls is thicker than the right ventricle wall (with more muscle). This is because:

1. The right ventricle only needs enough pressure to pump deoxygenated blood a short distance to the lungs

2. The left ventricle needs a lot of pressure to pump oxygenated blood to the other more distant organs of the body