In previous classes, we learnt about the breathing system, the digestive system and the reproductive system.
In this class, we shall learn about the circulatory system. In circulatory system blood circulates materials throughout the body. Therefore, the blood system is known as the circulatory system.
The circulatory system is made up of the heart, arteries, capillaries and veins. The system transports blood and other materials all over the body.
Parts of the circulatory system
- Watch a video of blood circulation in human beings.
- Watch the video very carefully. Note how the blood flows and the various organs involved.
- Now, look at the charts provided.
- Try to identify the organs in the video using the charts. List them down and give their roles in the whole process.
The circulatory system in human beings is responsible for transporting blood and other dissolved materials in the body. It is made up of the:
- heart
- blood
- blood vessels
The heart
Activity 1.2: To find out various parts of the heart
- Refer to the video you watched in Activity 1.1. Can you identify the heart? What does it do?
- Now, look at the model of the heart.
- Identify the various parts of the heart, use the charts provided.
- Draw the diagram of the heart in your notebook. Label the various parts.
The heart is a muscular organ that pumps blood throughout the body. It lies in between the lungs, slightly to the left side of the body, in the chest cavity. The heart is protected from injury by the chest.
The heart has thick and strong muscles. These muscles can relax and contract. When the muscles contract, the heart pumps blood out under high pressure. This contracting and relaxing of the heart muscles is called then heartbeat.
- Put your palm firmly on the left side and over the centre of your chest. Can you feel something pumping or beating on your hand?
- Place your right hand fingers firmly on your left hand wrist as shown below.
Do you feel the same as in 1 above?
Use a watch or clock to count the number of beats in one minute.
- Put your finger on one side of your neck; just underneath your jaw bone.
Do you feel any heart beats?
Use a watch or clock to count the number of beats in one minute. - Go outside and run very fast then stop running suddenly.
Place your right hand on your left wrist. Count the number of heartbeats in one minute.- Does the number of heartbeats change?
The heart of an adult beats approximately 72 times in one minute. The heartbeats are also called pulses. The number of times the heart beats in a minute is called the pulse rate.
The heart beats faster when we are active. This is to provide more oxygen to the active muscles so as to help generate more energy. It also beats faster in children, when people are excited, ill or fearful people.
Blood
When one has an injury, the red liquid that flows out of the injured part is called blood.
Blood contains:
- water
- blood cells
- digested food
- waste products
- hormones
Hormones are chemicals that control growth and other activities in the body.
An adult human being has about five litres of blood flowing in the body.
Blood vessels
Blood is contained in tubes called blood vessels. These tubes carry blood to all parts of the body.
Avoid touching other people’s blood because blood can spread HIV; the virus that causes AIDS. You should wear protective gloves when assisting an injured person.
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