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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
Students should be able to:
 identify the main parts of the heart and the main blood vessels:
i) the four chambers: ventricles, atrium.
ii) pulmonary artery, pulmonary vein, aorta, vena cava.
iii) valves.
 state the function of the heart.
 briefly describe the transport (circulatory) system in human beings with reference to the heart and blood vessel.
 identify the components of blood i.e. white blood cells, red blood cells, platelets and plasma.
 state that the main function of blood is to transport food (nutrients) and oxygen to all parts of the body and to remove
carbon dioxide and waste products from the body.
 identify the three main types of blood vessels as arteries, veins and capillaries.
 describe the functions of arteries, veins and capillaries.
 show an awareness of the heartbeat, pulse and blood pressure.
1. The body of a mammal is made up of millions of cells which require oxygen and nutrients.
2. They also produce carbon dioxide and other waste products which must be removed.
3. Thus, in mammals including humans, the transport system carries oxygen and food substances to the cells and
removes waste products from the cells.
4. The transport system in humans is known as the blood
circulatory system.
5. It consists of the heart, blood vessels and blood.
The Heart
1. The human heart is about the size of our fist.
2. It lies in the chest between the two lungs.
3. It is a muscular organ and its main function is to pump blood
around the body. It pumps blood continuously from birth to
death.
How does the heart work?
Heart works by contraction and relaxation of the heart muscles as shown below:
When the heart muscles contract, blood is forced out
from the heart to other parts of the body.
When the heart muscles relax, blood fills the heart as it
flows from the other parts of the body into the heart.
The four chambers of heart
1. The heart consists of four chambers as follows:
a) The upper chambers are called the right and left atria (singular: atrium).
b) The lower chambers are called the right and left ventricles.
MSPSBS/Year 8 2013/ Lower Secondary Science
The left ventricle wall is the
thickest because this part
needs to pump oxygenated
blood (blood rich in oxygen)
throughout the body while
the right ventricle only pumps
blood to the lungs.
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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
2. The table below shows the comparison between the atria and the ventricles.
ATRIA
Receive blood
(where blood enters the heart)
CHARACTERISTIC
FUNCTION
WALL
SPACE
Thinner
Smaller
VENTRICLES
Pump blood from the heart
(where blood leaves the
heart)
Thicker
Bigger
Valves in the heart
1. There are four valves in the heart.
2. A valve ensures that blood flows in one direction only and to
prevent blood from flowing back.
Blood Vessels
1. There are three types of blood vessels in the human body. They
are the arteries, veins and capillaries.
2. The table below shows the differences between the artery, vein
and capillary.
Characteristics
Arteries
Veins
Capillaries
Cross
section
Carry blood into the heart
 Connect the arteries to the veins
 Allow the exchange of materials in
and out of the cells
Small
Thick, elastic and
muscular – to withstand
the high pressure
Large
Very small
Thin, not elastic and
muscular
Very thin
(One-cell thick)
Type of
blood
Oxygenated except
pulmonary artery
Deoxygenated except
pulmonary vein
Oxygenated and deoxygenated
Presence of
valve
Absent
Present
Absent
Rate of
blood flow
Fast and at high
pressure
Slow and at low pressure
Slow and at a low pressure
Function
Carry blood away from
the heart
Lumen size
Thickness of
the wall
3. The relation between artery, capillaries and vein:
 The artery and vein are joined by capillaries.
 The direction of the flow of blood is from an artery through the
capillaries then to the vein.
 (Heart  Artery  Capillaries  Vein  Heart)
Flow of blood
MSPSBS/Year 8 2013/ Lower Secondary Science
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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
Blood Vessels in the heart
Each chamber of the heart is connected with a big blood vessel as shown in the table below.
Heart chamber
(a)
Right atrium
Blood vessel
connected to it
Vena cava
(b)
Left atrium
Pulmonary vein
(c)
Right ventricle
Pulmonary artery
(d)
Left ventricle
Aorta
Blood Circulation – The flow of blood
1. The diagram shows the paths of blood flows in the heart.
2. On the left side of the heart as shown in the diagram carries the
oxygenated blood while on the right side carries the
deoxygenated blood.
3. Differences between oxygenated and deoxygenated blood:
Oxygenated blood
Rich in oxygen
Deoxygenated blood
Poor in oxygen
Poor in carbon dioxide
Rich in carbon dioxide
MSPSBS/Year 8 2013/ Lower Secondary Science
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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
4. The diagram shows the circulation (movement) of blood around the human body.
5. The diagram shows that the blood circulates in two paths:
(a) From the heart to the lungs and back to the heart again, [Pulmonary circulation]
(b) From the heart to the rest of the body and back to the heart again. [Systematic circulation]
6. As the blood circulates around the body, it passes through the heart twice. This is called double circulation. It
takes about one minute for blood to circulate around the body once.
7. In the lungs, blood collects oxygen and loses carbon dioxide. The
oxygen is carried by the red blood cells.
8. As the blood moves around the body, it supplies oxygen to the
cells
and collects carbon dioxide from the cells.
9. The exchange of gases takes place in the lungs. Oxygen from the
air
sacs diffuses into the blood. At the same time, carbon dioxide
diffuses
out of the blood into the air sacs. The blood becomes
oxygenated.
10. As the oxygenated blood moves around the body, oxygen diffuses from the blood into the cells.
11. Carbon dioxide, which is produced in the cells diffuses out from the cells into the blood. The blood now becomes
deoxygenated.
12. The deoxygenated blood moves back to the lungs where the
carbon dioxide is removed and more oxygen is taken
into the blood system.
13. The diagram shows the exchange of substances
between blood and the surrounding cells. The process
by which these substances go in and out is called diffusion.
MSPSBS/Year 8 2013/ Lower Secondary Science
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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
Human Blood
1. One important function of blood is to act as a transport medium.
2. The functions of blood are:
(a) It carries nutrients from the small intestines and oxygen from
the lungs to every cell in the body.
(b) It removes carbon dioxide produced in the cells and carries it
back to the lungs.
(c) It carries other waste products such as urea to the kidneys to be
removed from the body.
(d) It helps to ingest bacteria or to fight diseases and to produce
antibodies.
(e) It helps in blood clotting process
Additional Information
1. Human blood consists of four components:
a) plasma (55%)
b) blood cells (45%) [red blood cells, white blood cells and platelets].
2. The four components of blood:
Plasma
Structure
Function
Red Blood Cells
White Blood Cells
Platelets
Tiny, biconcave discs in
shape
Colourless and
irregular in shape
Colourless and
irregular in shape
Pale yellow liquid
transport
nutrients into the
cells and waste
products out of
the cell
carry oxygen from the
lungs to all the cells in
the body
ingest bacteria or to
fight diseases and to
produce antibodies.
to help in blood
clotting process
HEARTBEAT, PULSE & BLOOD PRESSURE
The heart beats about 70
times a minute. This is
called the heartbeat rate.
MSPSBS/Year 8 2013/ Lower Secondary Science
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UNIT 11 TRANSPORT SYSTEM IN HUMAN BEINGS 2013
1. During each heartbeat, the muscles of the heart contract causing a wave of pressure which forces blood
through the arteries.
2. This wave of pressure that expands the artery a little is known as a pulse. There is one pulsation for
each heartbeat.
3. The pulse can be felt at various points on the body where the arteries are just under the skin, such as
the temples, neck, crook of the elbow, wrist, back of the knee, and the inside back of the ankle.
The number of pulses per minute is called the pulse
rate.
This is the same as the heart rate.
4. With exercise or physical activity, the heart rate increases to supply the muscles and cells with more
nutrients and oxygen to produce extra energy.
5. A baby may have a pulse rate of more than 100 beats per minute.
6. The heart beats faster so that more nutrients and oxygen can reach the cells.
Therefore, the heart beats faster or pulse rate increases.
7. The heart can beat up to 200 times per minute with extreme exercise.
Therefore the heart or pulse rate increases.
8. Heart beat can be heard using a stethoscope
BLOOD PRESSURE
1. As blood flows along the arteries, it pushes on the walls of the arteries. This push exerts a force called
the blood pressure.
Blood pressure is the force of the blood against the walls of the
arteries.
2. Blood pressure results from two forces.
(a) It is created by the heart as it pumps blood into the arteries and through the circulatory system.
(b) The other is the force of the arteries as they resist the blood flow.
3. During exercise, the heart pumps with more force and hence the blood pressure also increases.
4. The blood pressure is increased by certain factors such as: overeating, diet, stress.
5. In overweight people, the heart has to pump harder. So the blood pressure is often too high. Long-term high
blood pressure can cause damage to the heart, blood vessels, the brain and kidneys.
6. Blood pressures can be measured in the artery of the arm by an instrument called the
sphygmomanometer.
MSPSBS/Year 8 2013/ Lower Secondary Science
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