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Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz Plasma and cells in suspension If blood is separated it no longer looks like the red liquid that we recognise. centrifuge 55% 45% The blood sample separates into two parts. The top half is a straw coloured liquid called plasma. The bottom half is a dark collection of blood cells. 2 of 50 How a suspension works As blood is 55% plasma and only 45% cells, the cells are actually suspended within the plasma, a little like people would be suspended within a swimming pool. Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz First function of plasma The plasma actually surrounds the cells and carries them along as it flows through the blood vessels. This is the first function of plasma. Blood flows around the body, transporting substances from one place to another. Transport role it usually picks up a substance from an exchange site takes it to a place where it is used a reaction occurs reaction a useful product and a waste product is made Shifting the product The blood then transports one or both of these substances to another place in the body. cell blood vessel useful/waste product The cycle then starts again. 7 of 50 Products dissolved in plasma Blood has to rely on its plasma to transport some of these useful or waste products. For example, plasma carries CO2 from the cells to the lungs. blood flowing along a capillary plasma CO2 CO2 CO2 blood cell CO2 CO2 blood cell Dissolved digestive products The third and fourth roles are also centred around the moving of a substance from one place to another. Plasma is responsible for carrying dissolved food. Remember! Our digestive system breaks down the food we eat to release the useful nutrients. Summary of absorption Mouth food is eaten Sugars Useful products of digestion are absorbed from the digestive system and enter the blood. Amino acids Glycerol Fatty acids Anus waste is excreted Leaving the plasma The soluble food dissolves into the plasma and is carried from the small intestine to the cells of the body. Here they diffuse into the cells and are used in various chemical reactions. glycerol sugars amino acids plasma body cell fatty acids Removing urea The final role of the plasma is to carry a particular waste product from the liver to the kidneys. The waste product is called urea. Urea is made in the liver by the breakdown of amino acids. As urea is toxic, it must be removed from the body as quickly as possible! The blood now has to help the body do this. Filtration and expulsion of urea Plasma carries the urea from the liver to the kidneys that filter the blood. Urea is removed from the plasma of the blood and passes down a tube to the bladder. kidney blood urea This urea in the bladder is stored before it is excreted. The urea will leave the body within the liquid urine. Reviewing the role of plasma Plasma – role summary In summary, plasma has a principle role in transporting substances around the body. substance moving from going to CO2 cells lungs Cells all over the body Dissolved food small intestine Urea liver cells kidney The full load All this is being carried in just the plasma! white blood cell platelets sugar fatty acids red blood cell amino acids urea carbon dioxide Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz Blood cells There are 3 types of blood cell within human blood. They have different shapes and carry out different functions. Platelets Red Blood Cells White Blood Cells (These are actually fragments of cells so we can’t really call them cells) Image of the 3 constituents red blood cells white blood cells platelets Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz Red blood cells: erythrocytes Of all the cells these are the most numerous. In fact, every cubic centimetre of blood contains… 1 cm 1 cm 1 cm 5 000,000,000 cells Basic diagram of a red blood cell Therefore, it is not hard to realise that each red blood cell is extremely small. In fact, each one is only on average 7 micrometers in diameter (one micrometer is a millionth of a metre). This is a basic diagram of a red blood cell. Inside the red blood cells Actually, although the red blood cell is a “cell”, it does not contain one of the 3 parts of a “normal” cell. Red blood cells have no nucleus. This may seem odd but, there is a reason for it. Red blood cells also contain a unique substance called haemoglobin. This is a special iron based pigment whose presence is essential if the red blood cell is to perform its job. Fe2+ Oxygen for carbon dioxide Red blood cells carry OXYGEN (O2). The story begins in the lungs because this is where the oxygen gas enters the bloodstream. Remember, during the process of breathing, oxygen gas enters the body and is exchanged for carbon dioxide gas. The oxygen gas will be needed for the process of respiration. O2 diffusion O2 oxygen is inhaled O2 O2 It passes through the breathing system and reaches an alveolus. O2 O2 O2 O2 The oxygen gas diffuses across the lining of the alveolus and the capillary. alveolus Inside the alveoli Here is a close up showing the diffusion of oxygen gas. As the oxygen gas diffuses across the lining of the alveolus, it dissolves in the moist layer. This speeds up the diffusion process. O2 moist layer lining of alveolus lining of capillary red blood cell O2 Oxyhaemoglobin If we now concentrate on one red blood cell, we can see how important the haemoglobin molecule is to the process of transporting oxygen. The oxygen molecule diffuses into the red blood cell. each red blood cell contains the pigment... Haemoglobin + O2 Oxyhaemoglobin These two molecules bind together to produce this new substance. Oxygen binding at the alveolus It is important to remember that this reaction is happening in red blood cells at the alveolus. This is how the red blood cells are able to bind hold of the oxygen and carry it within the blood. Oxyhaemoglobin Oxyhaemoglobin Oxyhaemoglobin Each red blood cell is now Oxyhaemoglobin loaded with oxygen molecules. Oxyhaemoglobin Oxyhaemoglobin Order the following events Offloading the oxygen to body cells Once these red blood cells reach the cells of the body, they are travelling through tiny capillaries similar to those found in the alveolus. capillary cells It is here that they offload their oxygen. In order for this to happen, the oxyhaemoglobin molecule must be broken down. Oxygen diffusion at the capillary bed Oxygen use in the body ENERGY In the cell, the oxygen is used in the process of respiration which produces…. It diffuses across the cell membrane and the lining of the capillary and into the cell. The oxyhaemoglobin breaks down to release the oxygen molecule. Features of red blood cells 1 There are vast numbers of them. The more cells there are, the more O2 can be carried and delivered to the cells. Features of red blood cells 2 They have no nucleus. This means they have more room for haemoglobin molecules and therefore each red blood cell can carry more oxygen gas. Features of red blood cells They have a large surface area compared to their 3 volume. large surface area small volume Through having a small volume compared to its surface area, the red blood cell is able to keep the oxygen close to its surface. Features of red blood cells This means it can quickly release its oxygen by reducing the time it takes for the gas to diffuse out of the cell. The distance for the gas to move is much smaller in a cell shaped like this. alternative cell design O2 O2 The overall effect of this means that the blood can cope with the oxygen demands of the body. Features of red blood cells 4 The diameter of red blood cells is slightly larger than the average diameter of a capillary. capillary red blood cell This means that the red blood cell is forced to slow down as it passes through the capillary. This means the exchange of the gas will definitely happen. It also means the surface of the red blood cell will be exposed to the surface of the capillary. Red blood cell features Useful or useless? Diffusion at the capillary bed level Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz White blood cell Let’s now consider the white blood cell. The white blood cell is bigger than the red blood cell. It has a much more varied shape and there are different types of white blood cell within the blood. Role in defence White blood cells play a part in the defence system of the body. There are far fewer white blood cells within the blood compared with red blood cells. They are designed to fight microbes such as bacteria and viruses. White blood cell count When the body fights disease, more white blood cells are produced. With some diseases, doctors can establish how healthy someone is by testing their blood to see how many white blood cells they have. Disease test white blood cell number is low test white blood cell number is higher Match the cells to the correct functions Blood cell differences Our final blood part is the platelet As we mentioned, the platelet is actually a fragment of a cell. Therefore it does not have a nucleus. They are also much smaller than both the white and red blood cells. Their role is to help to clot the blood when the body has a wound. cut skin Contents What is Blood? Plasma and cells in suspension Plasma functions Blood cells Red blood cells White blood cells Summary quiz Multiple-choice quiz