The Circulatory System
In this lesson, you will Learn About…
 The functions of the circulatory system.
 How blood circulates through the body.
 How to keep your circulatory system healthy.
The Circulatory System
The Vocabulary terms for this lesson are:
 Circulatory system.
 Artery.
 Vein.
 Capillary.
 Pulmonary circulation.
 Systemic circulation.
 Plasma.
 Blood pressure.
Your Heart and Blood Vessels
The circulatory system is the group of
organs and tissues that transport
essential materials to body cells and
remove their waste products.
The circulatory system is also called the
cardiovascular system. It consists of the
following:
 The heart
 The blood vessels
 The blood
Your Heart and Blood Vessels
(cont’d.)
The heart is composed of cardiac muscle. It
pumps blood throughout the network of
blood vessels.
The blood flows through three types of
vessels:
 Arteries
 Veins
 Capillaries
How Circulation Works
Two types of circulation work together to
keep body cells supplied with nutrients
and free of waste products.
 Pulmonary circulation carries the blood from
the heart, through the lungs, and back to the
heart.
 Systemic circulation sends oxygen-rich blood
to all the body tissues except the lungs.
Pulmonary and Systemic Circulation
G.
F.
In the lungs, carbon dioxide
is removed from the blood
and is exhaled out of the
body. Oxygen is inhaled and
added to the blood, and
blood is sent back to the
heart through the
pulmonary vein to the left
atrium. Then the process
begins again.
The right atrium
sends the blood to
the right ventricle.
This part of the
heart sends the
low-oxygen, highcarbon dioxide
blood to the lungs.
E.
The veins carry
the blood back to
the right atrium of
the heart.
D.
The capillaries
deliver this lowoxygen blood to
veins.
A.
B.
C.
The left atrium receives
oxygen-rich blood from
the lungs and sends it
to the left ventricle.
The left ventricle
pumps oxygen-rich
blood to the aorta, the
body’s largest artery.
The aorta carries blood to
branching arteries that take
it to capillaries. Nutrients
and oxygen travel through
the walls of the capillaries
to cells. The cells send back
wastes such as carbon
dioxide.
What’s in Your Blood
Over half the volume of blood is plasma.
The rest of the volume of blood is made up
of three kinds of cells:
 Red blood cells
 White blood cells
 Cell fragments, called platelets
What’s in Your Blood (cont’d.)
The different parts of the blood carry out
several important functions in the body,
such as:
 Transporting various substances through the
body.
 Protecting the body from harm.
Parts of the Blood
Red Blood Cells
Platelets
Platelets are the smallest
type of blood cell. Platelets
help blood to clot, or thicken,
at the site of a wound.
Red blood cells, which look like little
disks or doughnuts, carry oxygen from
the lungs to all body parts.
White Blood Cells
Plasma
The three types of blood cells
are suspended in plasma, a
liquid that carries nutrients
to cells. It also carries
hormones, which are
chemicals that regulate body
processes. In addition,
plasma transports wastes to
the lungs and kidneys for
removal.
White blood cells fight
infection in the body. Some
white blood cells actually
create substances that
destroy foreign cells.
Others find and devour
disease-causing invaders
such as viruses.
Blood Pressure
When you have a medical checkup, the
nurse or doctor may take your blood
pressure.
Blood pressure is the force of blood
pushing against the walls of the blood
vessels.
Blood Pressure (cont’d.)
A blood pressure reading consists of two
numbers, usually written in the following
way:
110/70
The second number is the
lowest point of pressure, when
the heart relaxes to refill with
blood.
The first number is the pressure
at its highest point, when the
heart contracts and forces blood
into the arteries.
Blood Types
All blood is not the same. The four types–A,
B, AB, and O–are classified according to the
type of red blood cells they contain.
Some blood types are compatible and can
coexist in a person’s body. Compatible
blood types can be mixed safely.
Blood Types (cont’d.)
Blood Types (cont’d.)
Blood may also contain a substance called
an Rh factor.
People who are Rh-positive have this
substance. Rh-negative blood does not
contain this substance.
People with Rh-positive blood can receive
blood from people who are either Rhpositive or Rh-negative. Rh-negative
people can receive blood only from people
who are Rh-negative.
Caring for Your Circulatory System
You can take action now to care for your
circulatory system throughout your life.




Eat a balanced diet that is low in fats.
Learn to manage stress.
Avoid smoking.
Participate in activities that build heart and
lung endurance.
Reviewing Terms and Facts
1. List the two types of circulation.
 Pulmonary circulation
 Systemic circulation
Reviewing Terms and Facts
2. Define the term circulatory system.
The circulatory system is the group of organs
and tissues that transport essential materials to
body cells and remove their waste products.
Thinking Critically
3. Why is it necessary for hospital workers
to know patients’ blood types?
It is important to know the patients’ blood type
because incompatible blood types cannot be
mixed together. If blood types that are not
compatible are combined, the red blood cells in
one type of blood may clump together and block
blood vessels.
Vocabulary Review
The circulatory system is the group of
organs and tissues that transport
essential materials to body cells and
remove their waste products.
Vocabulary Review
An artery is a blood vessel that carries
blood away from the heart to all parts of
the body.
Vocabulary Review
A vein is a blood vessel that carries blood
back to the heart from all parts of the
body.
Vocabulary Review
A capillary is the smallest blood vessel
that provides body cells with blood and
connects arteries with veins.
Vocabulary Review
Pulmonary circulation carries the blood
from the heart, through the lungs, and
back to the heart.
Vocabulary Review
Systemic circulation sends oxygen-rich
blood to all the body tissues except the
lungs.
Vocabulary Review
Plasma is the yellowish fluid that is the
watery portion of blood.
Vocabulary Review
Blood pressure is the force of blood
pushing against the walls of the blood
vessels.