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The Cardiovascular System

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Organization of the Cardiovascular System: Circuits

Blood alternates between pulmonary circuit &

systemic circuit

Pulmonary Circuit Systemic Circuit

Carries blood to & from the lungs

Right side of heart → pumps blood to lungs

Carries blood to & from the body

Left side of heart → pumps blood to body

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Location of the Heart Muscular organ ~ size of fistThoracic cavityApex → points toward left side of bodyBase → points toward right shoulderMedial to R/L lungs

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Major Functions of the Heart

• keeps oxygen poor blood separate from oxygen rich blood

• keeps blood flowing in one direction

• generates blood pressure

• moves blood throughout body

• serves as an endocrine gland (ANP/ANH → BP

regulation)

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Endocardium – innermost layer → simple squamous epithelium (endothelium)

Myocardium – thickest layer → cardiac muscle

Epicardium – outermost layer → also part of the pericardium

myocardium (heart wall)

epicardium

endocardium

heart chamber

Layers of Heart Wall

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PericardiumFibrous pericardium – outermost layer

• anchors & protects heartSerous pericardium – 2 layers

• parietal layer• visceral layer = epicardium

“heart”

pericardium

6

serous pericardium

parietal layer

visceral layer(epicardium)

pericardial cavity

Pericardial cavity – fluid reduces friction

fibrous pericardium

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Chambers of the Heart

Four Chambers

• Two Atria → superior

• divided by interatrial septum

• receiving chambers

• Two Ventricles → inferior

• divided by interventricular

septum

• pump blood out of heart

LA

LV

RA

RV

interventricular septum

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Valves of the Heart

Four Valves → ensure 1-way flow of blood

• Two Atrioventricular Valves

• separate atria from ventricles

• Two Semilunar Valves

• separate ventricles from major

arteries

Which valves are the AV valves? SL valves?

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Valves of the Heart

Atrioventricular Valves

1) Right AV valve (tricuspid valve)

2) Left AV valve (bicuspid, mitral valve)

Semilunar Valves

3) Pulmonary SL valve

4) Aortic SL valve

1

2

3

4

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3

4

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Pathway of Blood Through the Heart Chambers & Valves

2

2 4

4

R atrium L atrium

R (AV) valve L (AV) valve

R ventricle L ventricle

PulmonarySL valve

AorticSL valve

lungs body

1 3

1

3

(pulmonary circuit) (systemic circuit)

http://www.mayoclinic.com/health/circulatory-system/MM00636

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Pulmonary Circuit

Systemic Circuit

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Heart SoundsHeart sounds (“lub-dup”)

• 1st sound - AV valves closing (louder/stronger sound)• 2nd sound - SL valves closing (shorter/sharper sound)• Can distinguish sounds of 4 valves

Heart murmurs• ineffective, “leaky” valves• allows backflow of blood• clicking/swishing sound

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Great Vessels of the Heart

Arteries

• Pulmonary trunk

• carries O2 poor blood to lungs

• Aorta

• carries O2 rich blood to body

Veins

• Superior/Inferior Vena Cavae

• carry O2 poor blood to heart

• Pulmonary veins

• carry O2 rich blood to heart

Why is the pulmonary trunk an artery? Why is it blue?

Pulmonary trunk

AortaSuperior Vena Cava

Inferior Vena Cava

Pulmonary Veins

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Right atrium → tricuspid valve → right ventricle

Right ventricle → pulmonary semilunar valve → pulmonary trunk → lungs

Lungs → pulmonary veins → left atrium

Left atrium → bicuspid valve → left ventricle

Left ventricle → aortic semilunar valve → aorta

Aorta → systemic circulation

Pathway of Blood

1

2 3

4

5

6

7

15

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Group question: Why is the left ventricle larger than the right ventricle?