Week 11 - Healthy Human Body Systems

2 The Circulatory System

Lesson 10

Science in Action 8
Pages 135-140

ScienceFocus 8
Pages 146-147

Lesson 10: The Circulatory System

The circulation system's job is to transport materials around the body. It consists of the heart, arteries, veins, capillaries and blood. Each and every cell from the tip of your nose to the tip of your toes needs to be supplied with nutrients (food) and oxygen. These products allow your cells to carry on life processes called cellular respiration. During cellular respiration, waste products are created that could poison and kill the cells if they are not removed, so the blood collects these waste products and delivers them to the appropriate organ for removal from the body.
Visit the following websites for further information:

heart and circulation system

human circulation and blood
Background Information

The Heart
Every circulation system needs a pump to circulate materials around. Our heart is a four chambered pump.

If you look at the diagram of the heart in your text you will find that part is red and the other part is blue.

Do you know what that means? When blood carries fresh oxygen from the lungs it is quite a bright red so the diagrams show the oxygen rich blood flow in and away from the heart as bright red. This blood flows out to all the cells in your body. The blood arriving back at the heart that is low in oxygen is more purplish in colour and is indicated by the blue part of the diagram.
Click on the above image to learn about your heart


Arteries, Veins and Capillaries
Blood is carried away from the heart by arteries and back to the heart in veins . But what happens in between the arteries and the veins? As the blood flows away from the heart the arteries get smaller and smaller until they are so small you can no longer see them with your eyes. Just like the branches of a tree, the further you go from the heart, the more the arteries branch and branch again until each and every cell is near a small artery Each very small artery is called an arteriole . Now the blood vessels change to capillaries. Capillaries are very thin walled blood vessels that allow the exchange of oxygen, carbon dioxide, nutrient and wastes between the blood and the body's cells. Both carbon dioxide and oxygen are carried by the red blood cells.
This Diagram shows red blood cells rich in oxygen (red) passing through a capillary. On each side of the capillary are the cells of your body. As the red blood cell squeezes through, it gives oxygen to the body cells and collects the carbon dioxide waste from them. Notice the colour change in the blood as it leaves the capillary and heads back through the veins to the heart. The liquid part of your blood called plasma carries the nutrients to the cells and collects other cell wastes.

You can also see white blood cells in the diagram. They patrol your body looking for 'bad guys' like bacteria or viruses. They are part of your immune system that fights and kills anything that is 'not you'. The blood also carries particles called platelets . Platelets create patches to stop bleeding from cuts.
Immune System
At the website called cellsalive.com . watch the presentation called the anatomy of a splinter.

When you arrive at the site, click on cell gallery and then on ' anatomy of a splinter '.

Blood Pressure

Blood pressure can be defined as the measure of the pressure in the circulatory system. There are two pressure levels; the pressure in the system when your heart is beating - the systolic pressure, and the pressure when your heart is momentarily at rest - your diastolic pressure.
As we get older the pressure tend to climb higher. This can be dangerous as it can lead to heart disease and strokes. It is important to remain active, eat a balanced diet and try not to gain weight as we get older as these are the major variables that can affect blood pressure. The sphygmomanometer, otherwise know as a blood pressure cuff is displayed at the right.
Now watch the video to see how blood pressure is taken.
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Exercise 3.2: The Effect of Exercise

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