The Circulatory System

The Heart…..a muscular organ, the center of emotions,
or a suit in a deck of cards?
Let’s take a closer look at this magnificent system
The Discovery of the Human Circulatory
 The earliest known writings about the circulatory system
can be found in the Ebers Papyrus (16th century BCE)
**Papyrus is an ancient writing material made from a plant
in Egypt** Even then it was attributed to not just a physical
but a spiritual and emotional aspect of humanity.
 Though the circulatory system was written about and
contemplated about throughout history it was still not
 Separate and distinct parts of the system would be
identified but not understood on how each part
 Most early Greek physicians believed that arteries
delivered only air and nothing else.
 A Greek physician, Herophilus (335-280
BCE)discovered a clear difference in veins and arteries
through dissection of dead corpses
 It was 500 years later that Galunus (AD 129 200/217)
concluded that the venous system carried blood that
held nutrition and the arterial system carried “body
 Enter: Dr. William Harvey, an English physician,
named the “Father of Cardiovascular Medicine”
 In 1628 he published his findings in the role of the
heart and circulation of blood in a closed system. He
felt his studies were complete.
 Thirty years later it would take an Italian physician,
Malpighi, to identify the capillary system that
connects arteries to veins.
 “While anatomically, the circulatory system had finally
been mapped, true understanding of it’s function
would not be achieved until the 20th century” (20022012 Helium, Inc.)
 “Even as late as the early 1900’s physicians were still
prescribing bloodletting and leech therapy” (20022012 Helium, Inc.)
The Anatomy of the Heart
 The heart is the size of your fist and lies usually on the left
side of the chest.
 It is protected by the sternum, the spine, and the rib cage.
 It has 4 chambers, the right atrium, the right ventricle, the
left atrium and the left ventricle. (the heart of a pig is the
same with 4 chambers)
 The normal heartbeat for an adult is 60-100 beats per
 The heart is encased in a sac known as the “pericardial
sac” this sac protects the heart from infection and
trauma, anchors the heart and protects it from friction
while pumping.
 The heart chambers are separated by four valves and
help keep blood from flowing backwards in the heart.
 The valves between the atria and ventricles are the
tricuspid valve (right) and the mitral valve (left)
 The valves which connect the ventricles out to the
body are the Pulmonary valve (to the lungs) and the
Aortic valve (to the body)
Let’s see it in
Blood Flow in the Heart
 Each of the four chambers have specific jobs in blood flow.
 The atria receives blood into the heart and the ventricles
pump blood out of the heart.
 The right side of the heart moves de-oxygenated blood to
the lungs
 The left side of the heart moves oxygenated blood out to
the body.
 The amount of blood pumped out of the heart per minute
is referred to as “cardiac output”. Normal cardiac output for
an adult is 4-8 liters per min.
Let’s look at it in 3D
The rest of the system: Vasculature
 The circulatory system is comprised of the heart and
the vascular system.
The vascular system is comprised of 5 different vessels,
arteries, arterioles, veins, venuoles, and capillaries.
Arteries carry blood away from the heart.
Veins carry blood towards the heart.
Capillaries are responsible for the joining of the 2 and
the delivery of oxygen to the tissues and the removal of
carbon dioxide.
 Arteries are muscular and can contract to
accommodate changes in blood flow and pressures
 Arteries produce pulses. Let’s see what pulses we can
Find these pulses:
Post tibial
 Arteries connect to arterioles which connect to the
 Capillaries then connect to venuoles which connect to
the veins thus completing the closed system.
 Veins are not muscular, they cannot change size due to
pressure or blood flow and do not have a pulse.
 Veins contain valves which help to prevent back flow
of blood in the system.
The Great Vessels
 The “Great Vessels” are the major vessels in the body,
they consist of arteries and veins.
The largest artery in the body (this is often a crossword
clue) is the Aorta.
The Aorta is divided into different sections, the
ascending aorta, the aortic arch, the descending aorta
and the descending abdominal aorta.
The coronary vessels (arteries around the heart) are
fed first before the ascending aorta or the arch.
The aortic arch feeds the brain via the carotid arteries
(hence where a pulse is checked when giving CPR to an
 The Pulmonary artery is another “great vessel”, which
is responsible for carrying de-oxygenated blood from
the right ventricle to the lungs where carbon dioxide is
exchanged for oxygen. (interestingly enough, this is
the only artery that carries de-oxygenated blood)
 The oxygenated blood is returned to the left atrium
through the pulmonary veins (these are the only veins
in the body that carry oxygenated blood)
TIP: Arteries always carry blood “away” from the heart
and Veins always carry blood “toward” the heart
 The venous system also has “great vessels”. The Inferior
and Superior Vena Cava are the great veins that return
deoxygenated blood from the tissues to the heart.
Let’s take another 3D look…
The Conductor :
How does the Heart know when to pump?
 The heart is regulated by an
electrical conduction system.
 A bundle of highly sensitive
nerve endings in various areas
of the heart stimulate the
heart to pump at specific rates
 A diagnostic tool used to
monitor the electrical activity
in the heart is called an
Electrocardiogram (EKG)
•The Sinus Node (SA Node)
regulates a normal heart rate 60100. It stimulates the atrium to
contract and empty all the blood
from it.
•The Atrioventricular Node (AV
Node) takes over if the SA node
fails, it regulates the heart rate at
40-60, this usually means the
atrium may not have emptied
•Lastly, (the sign of a dying
heart) if both the above nodes
fail, the ventricles will beat at 2040 via the purkinje fibers
 This is a life sized model of
the heart of a blue whale,
the largest animal on
Earth. A blue whale heart
is the size of a small car
and weighs around a ton.
They only beat 8-10 times a
minute, but pump an
astonishing 2000 to 5000
liters through the whale's
blood vessels.
Abnormalities of the Heart
 Arrhythmias
 Heart attack
 Heart failure
(abnormal heart
• Ventricular Fibrillation- the
most common rhythm seen
in cardiac arrest
•Heart blocks- cause slower
heart rates when the
conduction system of the
heart gets blocked.(i.e. SA
node doesn’t fire so the AV
node takes over.)Commonly
results in patient getting a
Heart Attacks
•Heart attacks are also
called “MI”s or Myocardial
•Heart attacks or MI’s are
caused from a blockage to
the blood flow to the heart
muscle. The coronary
arteries are blocked by
plaque or blood clots
Heart Failure
•As people age, their heart
muscle can weaken which
makes it pump less
•Weakening heart muscle
can result in blood pooling
in the ventricles, this is
known as heart failure.
•Sometimes blood can pool
enough to even back up
into the lungs. Signs of
heart failure can include
heart murmurs, shortness
of breath and even cool
extremities causing lower
oxygenation of tissues due
to low blood flow.
Note to self: Always check for a
 Cardiac Cycle: By Regina Bailey, Guide:
 Blood Vessels: By Regina Bailey, Guide:
The Heart and the Circulatory System, William Harvey-Father of cardiovascular
Medicine: By Regina Bailey, Guide:
 The history of discovery of the human circulatory system: by Theresa Cobb : Helium,
 Visible Body 3D Heart & Circulatory Premium 2:
 Far Side cartoon, by Gary Larson:

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