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Just in case you are wondering what MESS is about,
it is a collaborated educational blog.

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This blog is officially opened in 21 August 2009




-10 Recent Posts-
P4 Science: Air & the Respiratory System
P4 Chapter 3: The Water Cycle & Importance of Water
P4 Chapter 2: Water and Changes of States
P4 chapter 1: Matter & its 3 states
P3 Science Chapter 1: Diversity
P3 Science Chapter 7: Life Cycles Of Animals
P3 Science Chapter 8: Life Cycle Of Plants
P3 Science Chapter 9: Heredity
P3 Science Chapter 11: The Human Digestive System
P3 Science Chapter 12: The Skeletal & Muscular system


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Tuesday, August 25, 2009
P4 Science Chapter 5: Circulatory System @ 6:07 PM

P4 Science Chapter 5: Circulatory System
Our Circulatory System
Consists of: blood, heart, blood vessels
Helps us to: Transport food, water, oxygen & carry carbon dioxide, waste

Our heart is made up of a special heart muscle.It contracts & relaxes continuously.
The older we are, the slower the rate of our heartbeat.

Body does work = muscles work harder & need more energy = energy from food & oxygen needed = heart beat faster to circulate faster

Our blood:
1) Plasma: carries digested food, antibodies,hormones,waste materials
2) Red blood cells: transport oxygen from lungs, also a cell without a nucleus
3) White blood cells: keep the body healthy by fighting diseases
4) Platelets: Clots the blood, they are not cells, but cell fragments and do no have a nucleus.
  • Transports substances from small intestine to all parts of body
  • Transports carbon dioxide & waste materials fro removal
  • Transports oxygen from lungs to all parts of body
  • Transports heat produced by body tissure and distributes it throughout the body
Main functions of blood: Transportation, protection and regulation (distribute heat)

Why red blood cells do not contain a nucleus?
This increases the amount of space to pack more haemoglobin. (note that nuclei also occupy space) haemoglobin is a substance that can bind to oxygen and gives red blood cells its colour (red, duh). In fact, a single red blood cell may contain as many as 270,000,000 haemoglobin!

Our Blood Vessels:

1) Arteries: carry blood away from heart, and eqquiped with elastic walls and strong muscular layers to withstand the high pressure.

2) Veins: carry blood from body to heart, have thinner walls compared to arteries as the blood have lower presure. Valves are also present in the veins to ensure that the blood flows in only one direction.

3) Cappilaries: connect arteries to veins, walls of capillaries can be as thick as only one cell to allow quick and easy exchange of substances such as oxygen.

Plants

=> Xylem tubes Transports Water & Dissolved Mineral Salts

=> Phloem Tubes Transports food made by Leaves




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