Cardiovascular System –
Pulmonary and Systemic Circuits
System Overview
• System consists of the
heart and the blood vessels
• Function: to bring oxygen
and nutrients to all body
cells and to remove waste
Heart Location
Coverings of the Heart
• Pericardium
• Fibrous pericardium
• Protects and
anchors heart
• Parietal pericardium
and Visceral
pericardium
• Make up the
pericardial cavity
• Pericardial
fluid reduces
friction
Walls of the Heart
• Epicardium
• Same as visceral
pericardium
• Lubricates heart
• Myocardium
• Layer that contracts
• Endocardium
• Lines heart
chambers
Heart Chambers
• 4 chambers of the heart
• Atria
• Thin walls
• Receive blood returning to
the heart
• Auricles
• Ventricles
• Thicker walls
• Receive blood from atria
• Force blood out of heart
• Interventricular Septum
• Divides chambers
Heart Valves
• Atrioventricular
valves
• Tricuspid – right
• Three flaps
• Bicuspid (mitral) – left
• Two flaps
• Semilunar valves
• Pulmonary – right
• Aortic – left
• Chordae tendinae
• Anchor AV valve flaps
Blood Supply to the Heart
• Coronary arteries
• Branch from aorta
and nourish heart
muscle
• Cardiac veins
• Drain blood from
heart muscle into
the coronary
sinus then into
right atrium.
Cardiac Cycle
• Cardiac cycle – series
of events that
constitute a complete
heartbeat
• Systole – contraction
• Prior to atrial systole
70% of blood follows
into ventricles without
contraction
• Diastole – relaxation
Cardiac Cycle
• Heart Sounds – “lub-dup”
• Lub – ventricular systole
• AV valves close
• Dup – ventricular diastole
• SL valves close
• Murmur – irregular heart sound
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Cardiac Conduction System
• Coordinates the
events of the
cardiac cycle
• Consists of clumps
and strands of
specialized cardiac
muscle that initiate
and distribute
impulses throughout
the myocardium
Nodes of Cardiac Conduction System
• Sinoatrial node –
AKA “pacemaker”
• Just beneath
epicardium
• Located in right
atrium near opening
of superior vena
cava
• Initiates impulses
without nervous
stimulation
Nodes of Cardiac Conduction System
• Atrioventricular node
• Located in inferior portion of
septum
• AV bundle (bundle of
His)
• Large fibers run through the
interventricular septum
• Purkinje fibers
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• Spread from septum into
papillary muscles
• Stimulate ventricular
contraction
Regulation of Cardiac Cycle
• Parasympathetic
and sympathetic
fibers from medulla
oblongata run to the
nodes
• Secrete
acetylcholine to
decrease heart rate
• Secrete
norepinephrine to
increase heart rate
Electrocardiogram (ECG)
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• Recording of the
electrical changes in
the myocardium
during the cardiac
cycle
• P – atrial systole
• QRS – ventricular
systole; covers atrial
diastole
• T – ventricular
diastole
Blood Vessels
Arteries
• Strong, elastic
vessels that carry
blood away from the
heart
• Lead to finer
branches called
arterioles
Artery Layers
• Tunica intima –
simple squamous
epithelium for smooth
surface
• Tunica media –
largest layer; smooth
muscle and elastic CT
• Tunica externa – CT
that attaches artery to
surrounding tissues
Capillaries
• Smallest diameter blood
vessels
• Extensions of inner lining of
arterioles (tunica intima)
• Connect arterioles and
venules
• Allow exchange between
blood and tissue fluid
• More abundant around
muscles and nerves
• Blood flow controlled by
precapillary sphincters
• Exchanges occur by
diffusion, osmosis, and
filtration
Veins
• Carry blood back to the
right atrium of the heart
• Form from microscopic
venules that are
continuous with
capillaries
• Structure similar to
arteries, but less
developed tunica media
• Many have valves to
prevent blood backflow
• Act as blood reservoirs
when hemorrhage causes
decrease in arterial blood
pressure
Blood Pressure
• The force blood exerts
against the inner walls of
blood vessels
• Refers primarily to arterial
blood pressure
• Increases during ventricular
systole – systolic pressure
(100-140)
• Decreases during
ventricular diastole –
diastolic pressure (70-90)
• Pulse
Factors that Affect Blood Pressure
• Heart action – how
much blood enters
arteries
• Blood volume
• Peripheral resistance –
friction between blood
and vessels
• Blood viscosity
• Hypertension and
stroke
• Emotions, exercise,
hormones & pain