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The Circulatory System
Definition:
Transportation system by which oxygen and
nutrients reach the body's cells, and waste
materials are carried away.
Also carries substances called hormones,
which control body processes, and antibodies
to fight invading germs.
Parts of the Circulatory System
• Divided into three major parts:
– The Heart
– The Blood
– The Blood Vessels
 The Heart has the job of pumping these things
around the body.
 The Heart pumps blood and substances around
the body in tubes called blood vessels.
The heart
• The heart is an organ made up of muscle
tissue
• It is about the size of your fist and has thick
muscular walls
• It is divided into two pumps
• The heart has 4 chambers: 2 atria in the
upper part and 2 ventricles in the lower part
• The atria are smaller than the ventricles
The Structures of the Heart
Superior Vena Cava
Large vein that brings oxygen-poor blood
from the upper part of the body to the right
atrium
Aorta
Brings oxygen-rich blood from the left ventricle
to the rest of the body
Pulmonary Arteries
Bring oxygen-poor blood to the
lungs
Pulmonary Veins
Bring oxygen-rich blood
from each of the lungs to
the left atrium
Left Atrium
Pulmonary Valve
Prevents blood from flowing back
into the right ventricle after it has
entered the pulmonary artery
Aortic Valve
Prevents blood from flowing back
into the left ventricle after it has
entered the aorta
Mitral Valve
Prevents blood from flowing back into the
left atrium after it has entered the left
ventricle
Tricuspid Valve
Right Atrium
Prevents blood from
flowing back into the right
atrium after it has entered
the right ventricle
Inferior Vena Cava
Vein that brings oxygen-poor
blood from the lower part of
the body to the right atrium
Left Ventricle
Right Ventricle
Septum
Wall that divides the heart
into left and right
• Valves control blood flow from one chamber to
the other
• The valves also prevent movement from going
opposite to its normal flow (called reflux)
• The ventricles, of the heart, contract to push
blood out of the heart
• The left ventricle has walls that are thicker than
the right ventricle. Can you think why this is?
• The reason is that the left ventricle is responsible
for pumping blood to the entire body, while the
right ventricle only pushes blood to the lungs
Blood Vessels
• These are the channels that blood flows
through
• 3 types of vessels
– Arteries
– Capillaries
– Veins
Arteries:
carries blood Away from heart
-
Carry blood from the heart to the other organs
in the body
The aorta is that largest artery
Arteries:
–
–
–
Have thick-walls and are muscular
Are elastic
Carry oxygenated blood
•
–
–
Exception Pulmonary Artery
Blood in the arteries are carried under great
pressure
Arterioles: smaller vessels, enter body tissue
The ARTERY
the elastic fibres allow the
artery to stretch under
pressure
thick muscle and
elastic fibres
the thick muscle can
contract to push the
blood along.
Capillaries
-
Form networks of tiny vessels across cells,
tissues and organs; they transport blood from
the arterioles to the venules
smallest vessel (Microscopic; walls are one cell
thick)
Exchanges of nutrients and gases diffuse here
 cells collect nutrients and oxygen and get rid
of their waste (CO2 and water)
Capillary walls allow the entry (exit) of some
blood cells – this allows WBCs to destroy
bacteria and other elements before returning to
the circulatory system
The CAPILLARY
Capillaries link Arteries with Veins
they exchange materials
between the blood and
other body cells.
the wall of a capillary
is only one cell thick
The exchange of materials
between the blood and the
body can only occur through
capillaries.
The CAPILLARY
A collection of capillaries is known as a capillary bed.
artery
vein
capillaries
body cell
Veins:
Carries blood to heart
– Carries blood that contains waste and CO2
• Exception pulmonary vein
– Less elastic than arteries because the blood
pressure is much weaker
– They have valves to prevent blood from
moving backwards
– Blood will not return to the heart on its
own
Venules: larger than capillaries
The VEIN
Veins carry blood from organs towards from the heart.
veins have valves which
act to stop the blood from
going in the wrong
direction.
thin muscle and
elastic fibres
body muscles surround the veins so
that when they contract to move the
body, they also squeeze the veins and
push the blood along the vessel 
these contractions increase with
physical activity
Our circulatory system is a double circulatory system.
This means it has two parts.
Lungs
the right side of the
the left side of the
system
system
deals with
deals with
deoxygenated blood.
oxygenated blood.
Body cells
Circulation
• The circulatory system is actually made up of
three distinct parts:
– Systematic circulation
– Pulmonary circulation
– Coronary circulation
•
Systemic Circulation: It's All
Throughout the Body
• Systemic circulation supplies nourishment to all
of the tissue located throughout your body, with
the exception of the heart and lungs because
they have their own systems.
• Major part of the circulatory system
• The blood vessels (arteries, veins, and capillaries)
are responsible for the delivery of oxygen and
nutrients to the tissue.
• Oxygen-rich blood enters the blood vessels
through the heart's main artery called the aorta.
• The forceful contraction of the heart's left
ventricle forces the blood into the aorta which
then branches into many smaller arteries
which run throughout the body.
• The oxygen-rich blood enters the capillaries
where the oxygen and nutrients are released.
• The waste products are collected and the
waste-rich blood flows into the veins in order
to circulate back to the heart where
pulmonary circulation will allow the exchange
of gases in the lungs.
Pulmonary Circulation --It's All in the
Lungs
• Pulmonary circulation is the movement of blood from
the heart, to the lungs, and back to the heart again.
• The veins bring waste-rich blood back to the heart,
entering the right atrium throughout two large veins
called vena cavae.
• The right atrium fills with the waste-rich blood and
then contracts, pushing the blood through a one-way
valve into the right ventricle.
• The right ventricle fills and then contracts, pushing the
blood into the pulmonary artery which leads to the
lungs.
• In the lung capillaries, the exchange of carbon
dioxide and oxygen takes place.
• The fresh, oxygen-rich blood enters the
pulmonary veins and then returns to the
heart, re-entering through the left atrium.
• The oxygen-rich blood then passes through a
one-way valve into the left ventricle where it
will exit the heart again through the main
artery, called the aorta for systematic
circulation to occur
Path of Nutrients in the Blood
Coronary Circulation: It's All in the
Heart
• Coronary circulation refers to the movement
of blood through the tissues of the heart
• Serious heart damage may occur if the heart
tissue does not receive a normal supply of
food and oxygen.
• The heart tissue receives nourishment
through the capillaries located in the heart.
Blood Pressure
• Measured as the force of blood against the walls
of arteries.
• Blood pressure is recorded as two numbers—the
systolic pressure (as the heart beats) over the
diastolic pressure (as the heart relaxes between
beats).
• The systolic pressure refers to the pressure
recorded while the ventricles pump the blood.
• The diastolic pressure refers to the pressure
recorded as the ventricles fill with blood.
• A normal blood pressure is 120/80