What exactly is blood? What is it made up of? How are red blood cells adapted to carry oxygen? This article explains.

What is in Blood?

Blood is made up of 55% Plasma and 45% Cells.

These cells are suspended within the plasma.

This plasma surrounds the cells and carries them along as it flows through the blood vessels.

Blood flows around the body, transporting substances from one place to another. Blood has to rely on the plasma to transport some of the useful or waste products, like CO2.

Breakdown of Blood

There are 3 types of blood cell within the human blood :

  • Red Blood Cells
  • White Blood Cells
  • Platelets

The red blood cells are explained in the following paragraph, but white blood cells are bigger than red blood cells and have a more varied shape. Their job is to fight the bad bacteria and viruses within the body. They act very much like a defence system, really. When the body needs to fight disease, more white blood cells are produced.

Platelets however, are simply fragments of old cells. Their job is to aid the blood in clotting.

How are red blood cells adapted to carry O2?

Firstly, red blood cells are extremely small. In fact, each one is only an average of 7 micrometers in diameter. These red blood cells also have no nucleus. They also contain a unique substance called haemoglobin. This is an iron which is required to the cell to do its job.

The red blood cells carry oxygen, where the red blood cells collect it from the lungs. The oxygen gas is needed for respiration. This oxygen diffuses across the lining of the alveolus, dissolving the moist layer. The haemoglobin in the red blood cell catches the oxygen which makes the molecules; haemoglobin and oxygen bind together within the cell to make oxyhaemoglobin. Once they reach their destination, the oxyhaemoglobin is broken down again, where the oxygen is offloaded.

  • No Nucleus means that they can carry more substances.
  • A vast number of them means that more oxygen can be transported in less time.
  • They have a large surface area.
  • The distance that the gas has to move is minimised, meaning the cells can cope with the oxygen demands of the body.
  • The diameters of the cells are slightly larger than the diameter of the capillary – this means that the cell slows down, making the gas exchange a certainty.
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6 Responses to “Blood”
  1. brook Says...

    On March 23, 2010 at 10:00 am

    that is so wear didnt know dat………..!!!!!!!!!!!!!!!!!!!

  2. blah Says...

    On April 9, 2010 at 2:43 pm

    how r white blood cells adapted to their function?

  3. fatima Says...

    On September 19, 2010 at 11:02 am

    well, Phagocytes are white blood cells which engulf harmful micro-organisms in the body. They have a flexible cell membrane which means they can squeeze through small gaps in the capillaries to travel to where they are needed in the body. Their cytoplasm contains enzymes. This means that once a micro-organism is ingested by the cell, it will be digested by these enzymes.The cell membrane has a sensitive surface to enable the cell to detect foreign bodies and destroy.

  4. Liza Says...

    On December 14, 2010 at 10:42 am

    OMG thanks you so much!!!!! you are a genious/life savor whoever wrote this!!!!!

  5. jhon Says...

    On October 5, 2011 at 9:40 am

    how do they carry CO2 around and whats special about their shape??????

  6. Nai Says...

    On November 15, 2011 at 7:42 am

    RBCs have a biconcave shape which increases their surface area/volume ratio, making it able to carry more oxygen.
    as O2 moves out of the cell, the CO2 moves into the cell as a waste product

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