GRADE SIX SCIENCE

Hello Boys and Girls, How was your past week? Was it filled with lots of activities? Have you been learning new things at school? Have you been revising? Good, keep on learning. It’s a good thing to do! Also remember to THINK.

Last week we looked at the Circulatory System. Let’s find out how much you have learnt.

Answer these questions below.

1. An average person has body. (A) more than 6 (C) less than 4

2. In the body the red blood cells are blood cells (A) less than (B) more than

3.

Which set of blood vessels is in the correct order of size? (A) Vein, artery, capillary (C) Capillary, artery, vein (B) Vein, capillary, artery (D) Artery, vein, capillary

Name the blood vessels that (A) join together to form others ...................................... (B) have very thin walls .................................................... (C) take blood away from the heart ................................. (D) that have thick elastic walls .........................................

We will continue to examine the circulatory system this week. It is so interesting. We ended last week’s article by looking at the blood vessels. Let’s look at the information below and find some differences between arteries and veins.

Arteries ◊

.................. Litres of blood in his/her

Carry blood away from the heart

Carry blood with high amounts of oxygen (except for one of the blood vessels)

Walls are thick, muscular and elastic

Valves are absent (except in one case).

Tend to lie deeper in the body

(C) between 1 and 3 (D) about 5

(C) same in number as (D) about 5

Veins ◊

.............................. white

Carry blood towards the heart.

Carry blood with low amounts of oxygen

Some Differences between Arteries and Veins

Let’s look at some of the functions of the blood. How many did you list in your homework? The blood carries oxygen to all the organs and other parts of the body. Every cell in the body needs oxygen in order to carry out its functions. The blood takes waste materials to the organs responsible for getting rid of them. What do you think would happen if the body does not get rid of the waste material? Yes, death would occur eventually. The blood distributes food from the small intestine to all parts of the body for nourishment. (The blood also distributes other types of substances. Can you name any of the substances?) The blood helps us in the fight against disease. Find out how.

Did you think of any other functions? Have you ever heard of the term ’heartbeat’? What is a heartbeat? The heart serves to maintain a constant circulation of blood around the body with its constant pumping action. It contracts approximately 70 times per minute throughout our lives. How many times per day would that be? That’s right, over 100,000 times a day! Each contraction is followed by relaxation. When it relaxes, blood is sucked into the heart from the veins. When it contracts, blood is pumped out of the heart into the arteries. One contraction and relaxation is called a heartbeat.

If you put your finger on your skin just above the artery in the wrist, you will feel it as a slight throb. Doctors and nurses often feel a patient’s pulse to find out if the patient’s heart is beating at the normal rate. You can also hear the heartbeat by putting your ear against a person’s chest. What is the name of the instrument that the doctor uses to do this? Do you remember?

Examine the picture which follows. Note where the different fingers are placed.

Have you ever heard the term ‘blood pressure’? Find out about it. The pumping action of the heart (among other things) results in a considerable pressure being built up in the arteries. Whenever you hear the term, blood pressure, you will know that it really is this.

A person’s blood pressure varies according to what he or she is doing. Exercise often results in increasing the rate at which the heart beats.

Some foods help us to have ‘healthy’ blood. Can you name a few? There are some diseases that are associated with the malfunctioning of the blood. Name at least two.

Answer the following questions. 1. Name the parts that make up the Circulatory System. 2. Under normal circumstances what happens when your heart stops beating? How many chambers does the heart of the human being have? We often refer to the heart as a __________. At what rate does the heart beat? Name at least two times when the rate of beating of the heart increases. Blood is made up ____________. What is the approximate weight of the heart? An average person has 5 litres of blood: True or False. There are more white blood cells than red ones in a healthy human body: True or False. Put the blood vessels in descending order of size 3. 4. 5. 6.

7.

8. 9. 10.

11.

a. b. c.

Arteries Capillaries Arteries of __________, ___________ and

capillaries veins veins

veins arteries capillaries

Where are most blood cells formed? List at least three functions of the blood. Which type of blood vessel usually takes the blood away from the heart? Make up a word search with the following words. Blood veins cells arteries capillaries heart chambers vessels

Let your friend help you to do it. Until next week when we shall look at another system of the body, goodbye Boys and Girls!