THE CIRCULATORY SYSTEM
• THE ADULT HUMAN BODY CONTAINS ONLY
ABOUT 5 LITRES OF BLOOD
© PDST Home Economics
COMPOSITION OF THE
BLOOD
BLOOD IS MADE UP OF:
1. A LIQUID PART CALLED PLASMA
2. CELLS THAT ARE SUSPENDED IN THE PLASMA
COMPOSITION OF THE
BLOOD
THE PLASMA IS MADE UP OF:
1. 90% WATER
2. There are many substances dissolved in the
water,
e.g. Sugar, Protein, Hormones, Enzymes,
Minerals etc.
COMPOSITION OF THE
BLOOD
THERE ARE 3 TYPES OF CELLS SUSPENDED IN
THE PLASMA:
1. RED BLOOD CELLS
2. WHITE BLOOD CELLS
3. PLATELETS
Functions of the Blood
THE BLOOD HAS THREE MAIN FUNCTIONS:
1. TRANSPORT
2. FIGHTING INFECTION
3. CLOTTING
TRANSPORT:
The blood carries very many substances
around the body.
For example:
• Blood carries oxygen from the lungs to the
cells.
• Blood carries carbon dio0xide from the
cells to the lungs.
• Blood carries digested food products from the
intestines to the cells.
• Blood carries waste from the cells to the liver and
the kidneys.
• Blood carries hormones and enzymes around the
body.
FIGHTING INFECTION:
• The blood destroys bacteria, and viruses that may
infect the body.
CLOTTING:
• Sometimes a tear occurs in a blood vessel e.g.
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•
when you are cut
Blood will leak out
Infection may enter
•It is vital that such tears are repaired quickly
•The blood does this by forming a clot that seals
the wound
• Another function of the blood is to help maintain
normal body temperature.
• THIS IS 37° C
• The function of red blood cells is to
carry oxygen around the body
Red blood cells
• The function of white blood cells is to
fight infection
• Some white blood cells produce substances called
antibodies that identify and destroy bacteria,
viruses
• Other white blood cells kill bacteria by engulfing
them and digesting.
• The function of the platelets is to help the
blood to clot.
THE CIRCULATORY SYSTEM
• On leaving the heart, the blood passes into all of
the organs and limbs of the body before being
returned to the heart.
The
Circulatory
System
THE HEART
• The heart is located in the centre of the chest,
behind the breast bone.
• The function of the heart is to pump blood.
• The heart is made up of muscle called cardiac
muscle.
The Structure of the Heart
• The heart is divided into two sides, left and right,
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separated by a wall of muscle called the septum.
Each side has two chambers.
The top chambers are called atria.
The lower chambers are called ventricles.
THE HEART
left atrium
right atrium
right ventricle
left ventricle
septum
THE FOUR CHAMBERS OF THE HEART
The heart acts as if it were two
separate pumps:
1. The right ventricle pumps blood to the
lungs.
2. The left ventricle pumps blood all round
the rest of the body.
• Since the lungs are very close to the
heart, the right ventricle doesn`t
pump blood very far.
• Since it must pump blood much
further, the muscle of the left
ventricle is much thicker than of the
right ventricle.
BLOOD VESSELS OF THE
HEART
THE HEART
• The Vena Cava carry deoxygenated blood
•
•
from all over the body to the right atrium.
The Superior Vena Cava collect
deoxygenated from the upper parts of the
body.
The Inferior Vena Cava collect the blood
from the lower parts of the body.
• The blood then flows into the right
ventricle.
• It is then pumped into pulmonary
artery.
Pulmonary Circulation
• The Pulmonary Artery carries deoxygenated blood
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from the right ventricle to the lungs.
It divides in two, one to each lung.
This blood is oxygenated in the lungs.
The Pulmonary Veins carry oxygenated blood from the
lungs to the left atrium of the heart.
There are four pulmonary veins, two from each lung.
Systemic or General Circulation
• The left ventricle contracts and pumps blood out
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of the heart through the aorta.
The aorta is the major artery of the body.
It carries blood all over the body.
It collects carbon dioxide.
The deoxygenated blood travels back to the right
atria through the vena cava.
Blood Flow Through the Heart
Superior
Vena Cava
Pulmonary Artery
Aorta
Pulmonary Veins
Inferior
Vena Cava
BLUE =
deoxygenated blood
RED =
oxygenated blood
Blood Flow Through the Heart
Blood Flow Through the Heart
BLOOD VESSELS
• The tubes that carry blood are known as blood
vessels.
• There are three types:
 Arteries
 Veins
 Capillaries
BLOOD VESSELS
• Arteries carry blood away from the heart.
• Veins carry blood towards the heart.
• Capillaries connect arteries to veins.
THE DIFFERENCES BETWEEN
ARTERIES AND VEINS
• The blood in the arteries is under much higher
pressure than in veins.
• This means that the wall of an artery is much
thicker than that of a vein.
• This also means that the passage through an
artery is much narrower than in a vein.
THE DIFFERENCES BETWEEN
ARTERIES AND VEINS
• Arteries do not have valves because the blood
is under high pressure.
• To prevent low pressure blood flowing
backwards, veins have valves.
THE DIFFERENCES BETWEEN
ARTERIES AND VEINS
• The blood in arteries is oxygenated
except for the pulmonary artery.
•The blood in veins is deoxygenated
except for the pulmonary vein.
Structure of Arteries
• They are thick-walled tubes. They all
have the same basic construction:
• A fibrous outer covering
• A middle layer of muscle and elastic
tissue
• An endothelial layer (a single layer of
flattened cells)
Structure of Capillaries
• The capillaries are the smallest blood
vessels.
• Their walls are one cell thick and
porous, thus allowing the passage og
gases and nutrients.
Structure of Veins
• They have three-layered walls similar
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to that of arteries.
Their walls are much thinner and the
lumen is larger.
They have a fibrous outer coating
A middle layer of muscle and elastic
tissue
An endothelial layer
They have valves to prevent the back
flow of blood.
THE HEARTBEAT
• When the heart pumps, a pulse of
blood is sent down the arteries.
• This pulse can be felt in several
places, e.g. the wrist, the temples
and the neck.
What is Pulse
• The rate at which your heart pumps
blood through your circulatory
system.
• When blood is pumped from the left
ventricle into the aorta, the aorta
swells.
• The elastic wall of the aorta contacts
thus forcing the blood to move on.
• This sets up a wave of swelling and
contracting which continues along all
the elastic tissues.
• It can be felt wherever an artery
passes close to the surface of the
skin and over a bone.
• Most adults heartbeat is 72 – 80
beats per minute.
• Babies have a beat of 130 times a
minute.
Anaemia
• Is a reduction in the bloods ability to
carry oxygen.
• It may be caused by :
 Loss of blood,
Lack of iron in the diet,
A failure of the bone marrow to
produce the normal level of red blood
cells.
THE HEARTBEAT
• The normal human heartbeat is
seventy beats per minute.
• The normal human adult breathing
rate is 16-17 breaths per minute.
THE HEARTBEAT
• If more oxygen is needed by the muscles
and the brain the rate of the heartbeat
increases.
• Extra blood is pumped to these organs and
so they get extra oxygen.
• Carbon dioxide is also removed faster.
FACTORS THAT INCREASE THE RATE
OF THE HEARTBEAT INCLUDE:
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EXERCISE
A FRIGHT
SMOKING
EXCITEMENT
• FACTORS THAT
DECREASE THE RATE OF
THE HEARTBEAT
INCLUDE:
• REST AND SLEEP