The Cardiovascular System
Arteries and Veins
All veins carry blood
TO the heart. They
therefore carry
DEOXYGENATED
blood, with the
exception of the
pulmonary veins.
All arteries carry
blood AWAY from the
heart. They
therefore carry
OXYGENATED blood,
with the exception of
the pulmonary
arteries.
Primary Arteries Extending from the Aorta
right common carotid artery
right subclavian artery
left common carotid artery
left subclavian artery
brachiocephalic artery
abdominal aorta
(to arteries of abdomen and legs)
Note valves to
prevent backflow
of blood in veins,
which carry
blood under
relatively low
pressure.
Note smaller
internal
diameter and
thicker layer of
smooth muscle
in arteries.
Capillaries have thin,
semipermeable walls
that exchange O2 for
CO2 and nutrients for
waste with every cell
of the body.
Heart Sounds
• The first heart sound (lub) occurs
during ventricular contraction
when the tricuspid and bicuspid
valves close.
• The second heart sound (dub)
occurs during ventricular
relaxation when the pulmonary
and aortic valves close.
Rotating Heart – Valve Structure
Heart Pumping Animation
The coronary arteries supply blood from
the aorta to the heart muscle itself.
What is a Heart Attack?
• Myocardial Infarction (MI)
myocardial = pertaining to heart muscle tissue
infarction = tissue death due to oxygen starvation
• A blood clot completely blocks a coronary artery
cutting off supply of oxygen to that part of the heart.
• Results in cardiac tissue
death (no O2 – no ATP).
Heart Attack Animation
Angioplasty
CABG
Coronary Artery Bypass Graft
Bypass graft using
internal mammary
artery (from chest)
Bypass graft using
saphenous vein
(from leg)
Blocked coronary
arteries
Cardiac Conduction System
• While heart rate can be affected by neurons and
hormones, the heart muscle contracts on its own,
without outside stimulation.
• Contraction is initiated by the sinoatrial (SA) node
(the heart’s internal pacemaker).
– SA node is located in the right atrium.
– Cells of the SA node can reach threshold on their own,
initiating one action potential after another
(~70 times/min at rest).
Cardiac Conduction System
Sinoatrial
(SA) Node
Atrioventricular
(AV) Node
Bundle
Branches
5.
Electrical System / Arrhythmias
Purkinje
Fibers
Cardiac Conduction System
1. SA node depolarizes without nervous system
stimulation
2. Wave of action potentials spreads across L and R
atria, reaching AV node
Wave of action potentials propagates (spreads) via
intercalated discs!
3. AV node depolarizes
4. Action potentials travel down bundle branches to
Purkinje fibers, depolarizing ventricular walls
(contraction)
Pacemaker
• Electrodes are threaded through the
left subclavian vein and superior vena
cava into the right atrium of the heart.
• One electrode stimulates the AV node;
the other stimulates the Purkinje
fibers.
Electrocardiogram (ECG or EKG)
Action potentials through the myocardium during the cardiac
cycle produce electrical currents than can be measured.
Pattern
– P wave
• Atrial depolarization
– QRS complex
• Ventricular depolarization
• Atrial repolarization
– T wave:
• Ventricular repolarization
EKG animation
The Cardiac Cycle
The events associated with one heartbeat, lasting ~0.8 seconds.
During relaxation, ventricles
fill with blood (diastole).
During contraction, ventricles
expel blood (systole).
Blood Pressure
• Blood moves through circulatory system from areas of high
pressure to low pressure. (Contraction of the heart produces
the pressure.)
• Blood Pressure is a measurement of the force that blood
exerts against the inner walls of arteries.
• SYSTOLIC vs. DIASTOLIC pressure
The maximum pressure during ventricular contraction is the
systolic pressure. The systolic pressure is the peak arterial
pressure.
When ventricles relax (diastole) the arterial pressure drops.
The lowest pressure of blood in the arteries is called the
diastolic pressure.
Blood Pressure is determined by the sounds blood
makes as it is slowly released from an artery.
The systolic
pressure is the
top number.
The diastolic
pressure is the
bottom number.
example 120/80
Humans have ~5L of Blood
red blood cells (erythrocytes)
 biconcave discs, approx 7µ in diameter
 most numerous (5-6 billion / mL of blood)
 one RBC contains ~250 million molecules of
hemoglobin which carry O2
white blood cells (leucocytes)
 5 different types, some with granulated cytoplasm
 fight infection
 produce antibodies
to ‘tag’ foreign cells for
destruction
 perform phagocytosis
Y
WBC
platelets (thrombocytes)
 incomplete cells (cytoplasmic fragments)
 important for blood clotting (controlling blood loss from
damaged vessels)
plasma
 fluid matrix composed of 90% H2O, clear yellow in color
 transports glucose, electrolytes, hormones,
CO2, waste, proteins, lipids, etc
o
 helps regulate fluid and pH levels in blood