THE CIRCULATORY SYSTEM
“The heart and blood vessels of
the body…delivering oxygen
and nutrients, removing carbon
dioxide and waste products”
The Circulatory System
transports:
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Essential nutrients
 to the body tissues
Waste from tissues
 urinary system (as part of the plasma)
Gaseous waste (CO2)
 to the lungs to be eliminated
Oxygen from lungs
 is taken up and transported to the body
tissues
Gas exchange in the lungs
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Oxygen enters the
lungs via
INSPIRATION.
Carbon Dioxide leaves
the lungs via
EXPIRATION.
Gases move from high
to low concentration.
Regulation of the Metabolism
(homeostasis)
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Regulate the body’s fluid content
passing fluid from blood to tissues & vice versa
Regulate the body’s temperature
removal of heat (absorbing heat & carrying it to the
skin & lungs)
conserving heat -narrowing
(VASOCONSTRICTION) of the blood vessels)
Protection – White Blood Cells
fight foreign bodies (infection)
Composition of the Blood
The two sections of blood are:
 the solid section (45% blood
volume)
-- red blood cells
-- white blood cells
-- platelets
 the liquid section (55%
blood volume)-- plasma
Red Blood Cells
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Make up 99% of all blood
cells
Give blood the red colour
Produced in the bone
marrow
Have a life cycle of about
120 days (about 2 million
are destroyed & replaced
every second)
Contain haemoglobin (Hb),
which transports oxygen in
the blood
White Blood Cells
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Produced in the bone
marrow
Help the body fight
infection or disease
(they attempt to engulf
the invading microorganisms – pus is the
accumulation of dead
white blood cells)
Platelets
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Responsible for clotting the blood
Formed in the bone marrow
Stick to foreign particles or objects, & wounds
or damaged areas.
Plasma
Plasma is a yellowy solution containing:
 Water (absorbed into bloodstream from digestive
system)
 Nutrients
For example: Glucose, amino acids & lipids (fats)
 Hormones
(substances transported to target organs)
 Waste products
For example: (urea being taken from liver to
kidneys)
The Blood Vessels
(Vascular System)
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Blood vessels are
elastic tubes that
carry blood around
the body.
ARTERIES - Carry
oxygen rich
blood away from
the heart
High pressure
because blood is
being pumped
each heartbeat
Veins
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Carry blood toward the
heart
Low pressure because
blood is just flowing
back to the heart
Contain valves which
prevent a backflow
of blood
Capillaries
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Are fed by arterioles (small arteries)
Semi-permeable - allow oxygen, CO2, hormones &
nutrients to diffuse through walls into tissues
- allows waste products to pass from
tissues back to the blood
Blood flow through blood
vessels
Systemic Circuit
Heart  arteries  arterioles 
Capillaries (diffusion into tissues & from tissues)
 venules  veins  heart

Pulmonary Circuit
Heart  arteries arterioles 
Capillaries  Lungs (alveoli)  venules  veins 
heart

Systemic & Pulmonary Circuit
The Heart
The heart is a pump designed
to pump blood throughout the
circulatory system.
The heart has:
 2 Atria – upper chambers
which receive blood
 2 Ventricles – lower chambers
which pump blood
 The Septum – Divides the
heart into two pumps
 Left pump is the L.A &
L.V
 Right pump is the R.A &
R.V
Valves – located b/w the atria and ventricles and at the
entrance to the arteries from the heart
WHY??
They allow blood to travel in only one direction, stopping blood
in the ventricles flowing back into the atria.
Anatomy of the heart
The Heartbeat
The heartbeat is one contraction plus one
relaxation of the heart.
It consists of 2 sounds:
 A low-pressure sound, which is the closing
of the atrioventricular valves
 A high-pressure sound, which is the
closing of the aortic and pulmonary valves.
The Heart Rate
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Heart rate is the number of
beats per minute. (b.p.m)
It is measured by the pulse.
The average resting HR is
about 72bpm
Max HR is 220 – age
At rest the heart circulates
around 5L of blood around
the body in 1min.
At max work in a fit adult the
heart is able to pump over
30L
of blood around the body in
1min.
Heart Rate can increase due
to:
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Exercise
Excitement
Fear
Temperature changes
Ingestion of food
Smoking
Taking drugs
Body position
Gender
Cardiac Output
Cardiac Output is the amount of blood pumped out by
the heart in 1 minute.
CO = SV x HR
SV = stroke volume (the volume of blood pumped out
of the left ventricle each heart beat)
HR = heart rate (beats per minute)
The average resting value for Cardiac Output is 4-6L
per minute.
Blood Pressure
Blood pressure is an indicator of the body’s health,
indicating:
 How hard the heart has to work to push blood
through arteries and the other blood vessels.
 The health of the arteries and capillaries.
Blood Pressure
Blood pressure is measured
on a sphygmomanometer.
There are 2 readings:

Systolic pressure
(the pressure of the blood
being forced into the
arteries during left ventricle
contraction)

Diastolic pressure
(the pressure of the blood in
the arteries during left
ventricle relaxation)
Blood Pressure
Blood pressure is
expressed as:
systole
diastole
For example:
120
80
Blood Pressure
Blood pressure varies, depending
on:
 Gender
 Age
 Exercise
 Excitement
 Stress
High blood pressure is called
hypertension. This is due to a
loss of arterial wall elasticity,
that is hardening of the arteries.
Low blood pressure is a weakened
pressure within the artery.
Quiz Questions:
1.
2.
3.
4.
5.
6.
7.
8.
Which blood vessel carries blood toward the heart?
List three functions of the circulatory system.
Why is blood carried toward the lungs?
Why is there greater pressure in the arteries
compared to the veins?
What does Cardiac Output refer to?
How is Cardiac Output calculated?
What body organ does the word ‘pulmonary’ refer
to?
What is the smaller version of the artery called?
Quiz Questions:
9.
10.
11.
12.
13.
14.
Which is the largest artery in the body?
What is the role of platelets in the blood?
What specific part of the blood carries the
oxygen?
Why do our veins contain valves?
With reference to blood pressure, what
does systolic mean?
What part of our blood fights off infection
and disease?
Quiz Questions:
15.
16.
17.
18.
19.
20.
Does the left or the right side of the heart contain
oxygen rich blood?
Where are red blood cells produced in the body?
List 3 factors that can cause our heart rate to
increase.
What do the two readings in our blood pressure refer
to?
How many chambers does the heart have? List
them.
List one reason why exercise improves the function
of the circulatory system.