WEEK 10

SUBJECT: BASIC SCIENCE AND TECHNOLOGY

TERM: 1ST TERM

CLASS: PRIMARY 6

TOPIC: THE HUMAN BODY (BLOOD CIRCULATION)

BEHAVIOURAL OBJECTIVES: AT THE END OF THE LESSON, PUPILS SHOULD BE ABLE TO:

Define human heart

State the functions of the heart 3. Mention the types of blood circulation

INSTRUCTIONAL MATERIALS:

A chart showing the human heart

REFERENCE MATERIALS

Scheme of work

All relevant materials

9-Years Basic Education Curriculum

BUILDING BACKGROUND/CONNECTION TO PRIOR KNOWLEDGE:

Pupils are familiar with the topic in their previous classes.

CONTENT OF THE LESSON

The Human Heart

The heart is the muscular organ that pumps blood round the body. It contains four chambers namely:

Right auricle

Left auricle

(Hi) Right ventricle

(iv) Left ventricle

The major difference between the auricles and the ventricles is that the walls of the ventricles are
thicker and more muscular than those of the auricles.

FIG. 1

Functions of the Heart

The functions of the heart include the following:

(ii) It also keeps blood in continuous flow round the body.

Blood Vessels

Blood vessels are tubes through which blood moves round the body. These vessels are; arteries, veins,
and capillaries and they have various functions in the body. Arteries carry blood away from the heart,
while veins carry blood towards the heart.

Capillaries join arteries to the veins.

Arteries: These are blood vessels that carry blood away from the heart. That is, blood flows from the
heart to all parts of the body through arteries.

Veins: These are blood vessels that carry blood from other parts of the body to the heart.

Capillaries: They are the tiny network of blood vessels that connect the veins to the arteries. They carry
blood between arteries and veins.

Blood Circulation

The circulatory system is the route by which blood moves round the body. It is made up of the heart
blood, and blood Vessels.

Functions of the blood circulatory system

The blood circulatory system in the human body has several functions. They are as follows:

Transport
The blood system carries oxygen, absorbed into the blood in the lungs, to all the living cells in all parts of
the body.

The blood system carries food substances, after digestion, from the alimentary canal to all the living cells
in the body.

The blood system carries the white blood corpuscles to all parts of the body where they defend the body
against infection.

The blood system carries antibodies all round the body. The antibodies defend the body against
infection.

The blood system carries waste products, such as carbon dioxide, urea, water and excess salts from
living cells where they are produced to the parts of the body, such as the lungs and kidneys where they
are removed.

Defense of the body against infection

When disease-causing organisms enter the human body, the white blood cells attack and swallow them,
or produce chemicals called antibodies that kill the disease-causing organisms.

Blood clotting

By clotting at the point of an injury, the blood protects the body against further loss of blood.

Distribution of heat

Some parts of the body, e.g. the muscles produce more heat than others. The blood circulatory system
distributes heat evenly throughout the body. There are two types of blood circulation in the body. These
are: Pulmonary circulation and Systemic circulation.

Pulmonary Circulation This is one in which blood flows from the heart to the lungs and back to the heart.

Systemic Circulation: This is one in which blood is pumped from the heart to the other parts of the body
and back to the heart.

The right auricle and ventricle contains blood with less oxygen and more scarbon dioxide. The left
auricle and ventricle contains blood with more oxygen that comes from the lungs.
The heart is filled with blood, as a result of the relaxation of the involuntary muscles of the heart called
cardiac muscle. When the muscles of the heart contract, it (the heart) pumps blood out through the
right and left ventricles into the pulmonary arteries and aorta respectively.

The blood in the pulmonary arteries goes to the lungs and the blood in the aorta goes to other parts of
the body.

The presence of valves prevent the blood from flowing back to the heart.: When the heart is relaxed,
blood returns to the heart from the veins through vena-cava to the right auricles and through the
pulmonary veins to the left auricles. The blood that moves into the body cells is more oxygenated
because the blood flows by the indication of the arrows.

Functions of the arteries and veins

The arteries carry blood away from the heart and the veins carry blood towards the heart.

Functions of the capillary blood vessels

If blood were to flow all the time within the blood vessels, it would not be of much use to the body. The
capillaries have thin walls through which the liquid part of the blood can diffuse out of the blood vessels
to reach the living cells in the various organs. In this way, the capillaries make it possible for the cells of
the body to be supplied with food, water, oxygen and all other essentials. They are also useful in the
removal of waste products from the cells

Differences between

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Arteries
Veins

1. They carry blood away from the heart.

They carry blood towards the heart.

2. They have thick elastic walls.

They have thin, not very elastic walls.

3. They carry blood that contain oxygen (except the pulmonary artery)

They carry blood in which oxygen has been used up (except the pulmonary vein)

4. Pressure of blood in the vessels is high

Pressure of blood in the vessels is low.

5.They do not have valves.

They have valves to prevent the back-flow of blood.

6. Arteries are located deeper in the surface of the body than veins.
Veins are located nearer the flesh than arteries.

7. Pulse is detectable.

Pulse is usually not detectable.

Assessment & Evaluation:

Define human heart

State the functions of the heart

Mention the types of blood circulation

(WRAP-UP CONCLUSION)

Teacher goes over the topic once again to enhance better understanding Answer these questions

List the things that make up the human blood.

Name the four chambers that make up the human heart.

Describe the paths along which blood circulates round the human body.

Describe the functions of the human heart.

State four differences between arteries and veins.

Explain the importance of blood capillaries.

Describe the functions of the blood circulatory system.

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