The Cardiovascular SystemThe Cardiovascular System

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A closed system of the heart and blood vessels The heart pumps blood

Blood vessels allow blood to circulate to all parts of the body

Function: to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

The HeartThe Heart

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Location Thorax between the lungs

Pointed apex directed toward left hip

Base points toward right shoulder

About the size of your fist

The HeartThe Heart

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Figure 11.1

The Heart: CoveringsThe Heart: Coverings

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Pericardium – a double serous membrane Visceral pericardium

Next to heart

Parietal pericardium

Outside layer

Serous fluid fills the space between the layers of pericardium

The Heart: Heart WallThe Heart: Heart Wall

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Three layers Epicardium

Outside layer This layer is the parietal pericardium Connective tissue layer

Myocardium Middle layer Mostly cardiac muscle

Endocardium Inner layer Endothelium

External Heart AnatomyExternal Heart Anatomy

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The Heart: ChambersThe Heart: Chambers

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Right and left side act as separate pumps Four chambers

Atria Receiving chambers

Right atrium Left atrium

Ventricles Discharging chambers

Right ventricle Left ventricle

Slide 11.6

Internal Heart AnatomyInternal Heart Anatomy

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Blood CirculationBlood Circulation

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Figure 11.3

Pulmonary CircuitPulmonary Circuit

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Function—carry blood to lungs for gas exchange and return it to the heart

Blood vessels involved

Pulmonary arteries—carry oxygen-poor blood to the lungs away from the heart

Pulmonary veins—carry oxygen-rich blood to the heart from the lungs

Systemic CircuitSystemic Circuit

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Function—carries oxygen- and nutrient-rich blood to all body organs, and carries oxygen-poor blood back to heart

Blood vessels involved

Arteries—carries oxygen-rich blood from heart to body

Veins—carries oxygen-poor blood from body to heart

The Heart: ValvesThe Heart: Valves

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Allow blood to flow in only one direction Four valves

Atrioventricular valves – between atria and ventricles Bicuspid valve (left) Tricuspid valve (right)

Semilunar valves between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve

The Heart: ValvesThe Heart: Valves

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Valves open as blood is pumped through

Held in place by chordae tendineae (“heart strings”)

Close to prevent backflow

Operation of Heart ValvesOperation of Heart Valves

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Figure 11.4

The Heart: Associated Great VesselsThe Heart: Associated Great Vessels

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Aorta Leaves left ventricle

Pulmonary arteries Leave right ventricle

Vena cava Enters right atrium

Pulmonary veins (four) Enter left atrium

Coronary CirculationCoronary Circulation

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Blood in the heart chambers does not nourish the myocardium

The heart has its own nourishing circulatory system

Coronary arteries

Cardiac veins

Blood empties into the right atrium via the coronary sinus

Circulatory homeostatic imbalancesCirculatory homeostatic imbalances

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Angina pectoris

Myocardium is deprived of oxygen when there is not enough blood supply, resulting in crushing chest pain

Myocardial infarction

“heart attack” or “coronary”

Ischemic (decrease in blood supply) heart cells die forming an infarct (region of dead tissue)

The Heart: Conduction SystemThe Heart: Conduction System

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Intrinsic conduction system (nodal system)

Heart muscle cells contract, without nerve impulses, in a regular, continuous way

Enforces contraction rate of ~75 beats/min

The Heart: Conduction SystemThe Heart: Conduction System

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Special tissue sets the pace

1. Sinoatrial node—pacemaker (highest rate of depolarization, starts each heartbeat)

2. Atrioventricular node

3. Atrioventricular bundle (Bundle of His)

4. Bundle branches (right and left)

5. Purkinje fibers

Heart ContractionsHeart Contractions

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Figure 11.5

The Heart: Cardiac CycleThe Heart: Cardiac Cycle

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Cardiac cycle – events of one complete heart beat (~0.8 sec)

Atrial systole and diastole followed by ventricular systole and diastole

Atria contract simultaneously

Atria relax, then ventricles contract

Most pumping is done by ventricles

Systole = contraction

Diastole = relaxation

The Heart: Cardiac CycleThe Heart: Cardiac Cycle

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Mid-to-late diastole (relaxation) – blood flows into ventricles

Ventricular systole – blood pressure builds before ventricle contracts, pushing out blood (atria are relaxed and filling with blood)

Early diastole – atria finish re-filling, ventricular pressure is low, semilunar valves shut

Slide 11.17

The Heart: Cardiac CycleThe Heart: Cardiac Cycle

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Mid-to-late Diastole Ventricular Systole Early Diastole1. PRESSURE LOW

2. AV VALVES OPEN

3. SEMILUNAR VALVES CLOSED

4. BLOOD FLOWS INTO VENTRICLES

5. ATRIA CONTRACT, VENTRICLES RELAX

1. PRESSURE HIGH

2. AV VALVES CLOSE

3. SEMILUNAR VALVES FORCED OPEN

4. BLOOD PUSHED OUT OF VENTRICLES INTO PULMONARY TRUNK/AORTA

5. ATRIA RELAX, VENTRICLES CONTRACT

1. PRESSURE LOW

2. AV VALVES OPEN

3. SEMILUNAR VALVES SNAP SHUT

4. VENTRICLES REFILL WITH BLOOD

5. ATRIA BEGIN TO CONTRACT, VENTRICLES RELAX

Filling of Heart Chambers – Filling of Heart Chambers – the Cardiac Cyclethe Cardiac Cycle

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Figure 11.6

Heart SoundsHeart Sounds

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Lub-dup, pause, lub-dup, pause…

Lub-first sound louder and longer when AV valves close

Signifies start of systole when ventricular pressure rises above atrial pressure

-dup-sharp sound when SL valves snap shut

Signifies start of ventricular diastole

The Heart: Cardiac OutputThe Heart: Cardiac Output

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Cardiac output (CO)

Amount of blood pumped by each side of the heart in one minute

CO = (heart rate [HR]) x (stroke volume [SV])

Stroke volume

Volume of blood pumped by each ventricle in one contraction

Cardiac Output RegulationCardiac Output Regulation

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Figure 11.7