The Cardiovascular System

-The function to deliver oxygen and nutrients 

and to remove carbon dioxide and other waste 

products

•Blood vessels allow blood to circulate to all 

 parts of the body

•A closed system of the heart and blood vessels

•The heart pumps blood

The Heart

•About the size of your fist

•Pointed apex directed toward left hip

•Thorax between the lungs

•Location

•Hollow

•Weighs less than a pound

•Sits on the diaphragm

•Apex is at the 5th intercostal space

The Heart: Coverings

•Serous fluid fills the space between the layers 

 of pericardium

•Outside layer

•Tough; Prevents overdistension

•Fibrous pericardium

•Two layers

○ Parietal 

○ Visceral = Epicardium

•Serous Pericardium

•Pericardium – a double serous membran

The Heart: Heart Wall

•Endothelium

•Inner layer

•Endocardium

•Mostly cardiac muscle

•Middle layer

•Myocardium

•Connective tissue layer

•This layer is the visceral pericardium

•Outside layer

•Epicardium

•Three layers

Clinical Applications

Pericarditis- Inflammation of the pericardium. 

Caused by either buildup of fluid or extensive 

bleeding. This compresses the heart.

Cardiac Tamponade- compression of the heart due to 

fluid/blood buildup

The Heart: Chambers

•Left ventricle

•Right ventricle

•Discharging chambers

•Ventricles

•Left atrium

•Right atrium

•Receiving chambers

•Atria

•Four chambers

•Right and left side act as separate pumps

The Heart: Valves

•Aortic semilunar valve

•Pulmonary semilunar valve

•Semilunar valves - between ventricle and 

artery

•Tricuspid valve (right)

•Bicuspid valve (left)

•Atrioventricular valves – between atria 

 and ventricles

•Four valves

•Allow blood to flow in only one direction

The Heart: Valves

•Close to prevent backflow

•Held in place by chordae tendineae 

 (“heart strings”)

•Valves open as blood is pumped through

Blood Pathway

Right Atrium

Tricuspid Valve

Right Ventricle

Pulmonary Semilunar Valve

Pulmonary Trunk

R/L Pulmonary arteries

Lungs

R/L pulmonary Veins

Left Atrium

Bicuspid Valve

Left Ventricle

Aortic Semilunar Valve

Aortic Arch

Arteries

Arterioles

Capillaries

Venules

Veins

Superior/Inferior Vena Cava

The Heart: Associated Great Vessels

•Enter left atrium

•Pulmonary veins (four)

•Enters right atrium

•Vena cava

•Leave right ventricle

•Pulmonary arteries

•Leaves left ventricle

•Aorta

Coronary Circulation

•Blood empties into the right atrium via the 

 coronary sinus

•Cardiac veins

•Coronary arteries

•The heart has its own nourishing circulatory 

 system

•Blood in the heart chambers does not nourish 

 the myocardium

The Heart: Conduction System

•Heart muscle cells contract, without nerve 

 impulses, in a regular, continuous way

•Intrinsic conduction system (nodal system)

○ will beat without brain

The Heart: Conduction System

•Purkinje fibers

•Bundle branches

•Atrioventricular bundle

•Atrioventricular node

•Sinoatrial node

•Pacemaker

Heart Contractions

•Sequential stimulation occurs at other 

•autorhythmic cells

•Contraction is initiated by the sinoatrial node

The Heart: Cardiac Cycle

•Diastole = relaxation

•Systole = contraction

•Atria relax, then ventricles contract

•Atria contract simultaneously

The Heart: Cardiac Cycle

•Early diastole – atria finish re-filling, 

 ventricular pressure is low

•Ventricular systole – blood pressure builds 

 before ventricle contracts, pushing out blood

•Mid-to-late diastole – blood flows into 

 ventricles

•Cardiac cycle – events of one complete 

 heart bea

The Heart: Cardiac Cycle

•Early diastole – atria finish re-filling, 

 ventricular pressure is low

•Ventricular systole – blood pressure builds 

 before ventricle contracts, pushing out blood

•Mid-to-late diastole – blood flows into 

 ventricles

•Cardiac cycle – events of one complete 

 heart beat

The Heart: Cardiac Output

•Volume of blood pumped by each ventricle 

 in one contraction

•Stroke volume

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

•Amount of blood pumped by each side 

 of the heart in one minute

•Cardiac output (CO)

The Heart: Regulation of Heart Rate

•Changing heart rate is the most common 

 way to change cardiac output

•Starling’s law of the heart – the more that 

 the cardiac muscle is stretched, the 

 stronger the contraction

•Stroke volume usually remains relatively 

 constant

The Heart: Regulation of Heart Rate

•Decreased blood volume

•Exercise

•Thyroxine

•Epinephrine

•Hormones

•Low blood pressure

•Crisis

•Sympathetic nervous system

•Increased heart rate

The Heart: Regulation of Heart Rate

•Decreased venous return

•High blood pressure or blood volume

•Parasympathetic nervous system

•Decreased heart rate

Blood Pressure

•Pressure in blood vessels decreases as the

 distance away from the heart increases

•Diastolic – pressure when ventricles relax

•Systolic – pressure at the peak of 

 ventricular contraction

•Measurements by health professionals are 

 made on the pressure in large arteries

Blood Pressure: Effects of Factors

•Renin – hormonal 

control

•Regulation by altering blood volume

•Renal factors

•Autonomic nervous system adjustments 

 (sympathetic division)

•Neural factors

Blood Pressure: Effects of Factors

•Diet

•Various substances can cause increases 

 or decreases

•Chemicals

•Cold has a vasoconstricting effect

•Heat has a vasodilation effect

•Temperature

Variations in Blood Pressure

•Can be dangerous if it is chronic

•High systolic (above 140 mm HG)

•Hypertension

•Often associated with illness

•Low systolic (below 110 mm HG)

•Hypotension

•80–75 mm Hg diastolic

•140–110 mm Hg systolic

•Normal

•Human normal range is variable

Heart Disorders

Atherosclerosis – progressive hardening of the 

arteries due to plaque buildup

Myocardial infarction (MI) – heart attack

result of a blockage in one of the coronary

arteries

Angina – pain felt from an MI

Fibrillation – a condition of the conduction 

system; the heart is useless as a pump

Congestive Heart Failure

• condition where the myocardium progressively 

weakens due to atherosclerosis or multiple 

myocardial infarctions.

Examples:

Pulmonary Congestion – CHF on the left side of 

the heart; blood pools in the lungs

Peripheral Congestion – CHF on the right side of

the heart; blood pools in the extremities

causing edema

Murmur – condition of the valves were blood 

flows in the opposite direction of the valve

due to incompetent valves. 

Heart Rate Variations

• Tachycardia- Heart Rate HIGH

• Bradycardia- Heart Rate LOW