The Transport System in Humans
•All cells in our body need nutrients, oxygen and water.
Meanwhile carbon dioxide and other waste materials
produces by the cells must be removed.
•An internal transport system is needed to deliver
useful materials to the body cells and remove the
waste materials from them.
•The internal transport system is often called the
circulatory system because useful as well as waste
materials circulate the body.
•A circulatory system has four basic characteristics:
a. Circulating fluid – this circulating fluid is called
blood. The blood transports useful and waste
b. Pumping device – the pumping device is the
heart. Blood is moved through the body by
muscular contractions of the heart.
c. Blood vessels – a complex network of blood
vessels carries materials to the tissues and back to
the heart. There are three main types of blood
vessels, namely arteries, veins and capillaries.
d. Valves – valves are present in some blood vessels
to prevent backflow and ensure that blood flows
in one direction only.
•The human circulatory system is a double
circulatory system. This means that in each
complete circuit of the body, the blood must flow
through the heart twice.
•The human double circulatory system consists of:
a. The pulmonary circulation which transports
blood between the heart and the lungs and
a. The systematic circulation which transports
blood between the heart and all other parts of
•The advantage of having a double circulatory system is that it
increase the pressure of the blood and the rate of flow, thereby
speeding up the delivery of materials to the tissues.
The human double circulatory system
Structure of the human heart
•An adult human heart is about the size of a clenches
•The heart lies in the chest between the two lungs.
•The heart is a muscular organ with walls made of
•The coronary arteries supply nutrients and oxygen
wastes from the muscles.
•The heart is divided into four chambers. The two upper
chambers are called auricles and atria ( atrium) and the
two lower chambers are called ventricles.
•The septum divides the heart into the right and left
•The auricles have thinner walls than the ventricles.
When the auricles contract, blood is pushed into the
•The left ventricle has a much thicker muscular wall
than the right ventricle. The right ventricle pumps blood
to the lungs , which lie next to the heart. The left
ventricle has to pump blood from the heart to the rest
of the body.
•The right atrium is connected to the right ventricle by
the tricuspid valve. The left atrium is connected to the
left ventricle by the bicuspid or mitral valve.
•Semilunar valves are
situated at the
entrances of the aorta
and the pulmonary
artery to prevent to
backflow of blood into
• The chordae
tendineae prevent the
valves from turning
inside out when the
ventricles contract The structure of the human heart
Function of the human heart
•The heart is made up of two pumps located
side by side.
•The right side of the heart pumps
deoxygenated blood it receives from the lungs
to the rest of the body. Oxygen is removed at
the tissues for respiration
a. Arteries are blood vessels which carry blood
away from the heart.
b. Arteries deliver oxygenated blood except
c. The walls of the arteries are much thicker and
stronger than those of veins because they
have to withstand the high pressure of blood
coming from the heart.
The blood vessels
a. Veins are blood vessels which carry blood
back to the heart.
b. Veins deliver deoxygenated blood except
c. Veins have thinner walls than arteries
because blood pressure in the veins is much
lower than that in the arteries. Since the
blood in the veins may be moving against
gravity, the contain valves to present the
blood from flowing back.
a. Capillaries are tiny blood vessels which
connect arteries and veins. They have walls
which are only one cell thick.
b. Oxygen and nutrients move from the blood
through the capillary walls into the body cells.
At the same time carbon dioxide and other
waste products move from the cells into the
Artery Vein Capillary
Cross section Circular Oval Circular
Size of wall Has thick
Has very thin
one cell- thick
Differences of artery, vein and
Lumen Narrow Fairly wide Very
Colour Red Bluish – red Bluish – red
blood to the
•Heart disease is one of the major cause of death in
•Factors that increase the risk of getting heart disease:
a. Heredity – the risk is increase if there is a family
history of heart disease.
b. Cholesterol and obesity – high cholesterol and
obesity are major heart disease risk factor.
c. Lack of exercise – low level of physical activity
increase the risk of getting heart disease.
d. Smoking – smoking damages blood vessels and
leads to heart disease. Smoking also decreases the
amount of oxygen that reaches the heart.
Heridity Cholesterol and obesity
Lack of ExerciseSmoking
e. Stress – people who are stressed are more prone to
f. Alcohol – excessive alcohol intake can elevate blood
pressure, thus making heart attacks more likely.
a. Avoid high cholesterol foods. Eat more fruits and
b. Regular aerobic exercises help to keep body weight
down. Lower blood pressure and strengthen the
c. Lose weight to a desirable weight range and keep
within it with moderate eating and exercise.
d. Relax and get enough sleep.
e. Quit smoking.
f. Reduce alcohol consumption.
Eat more fruits Aerobics Lose weight
Get enough sleep Quit Smoking Reduce Alcohol