Animal Physiology Blood Mr G Davidson

Components of Blood On average, we have approximately 5 litres of blood in our body. It is used to carry a large variety of substances around the body. Blood is a mixture of cells suspended in a fluid. 10 May 2019 Mr G Davidson

Components of Blood The main components of blood include: A straw coloured liquid called plasma. Red blood cells. White blood cells. 10 May 2019 Mr G Davidson

Plasma Plasma contains proteins such as antibodies. It also carries soluble food substances such as amino acids and glucose. Plasma also carries other substances such as urea, vitamins, minerals and hormones to where they are needed in the body. Some carbon dioxide is also carried in the plasma. 10 May 2019 Mr G Davidson

Red Blood Cells Red blood cells carry oxygen. They are biconcave in shape which increases their surface area. There are approximately 5 million red blood cells in every 1ml of blood. 10 May 2019 Mr G Davidson

Red Blood Cells Red blood cells contain a pigment called haemoglobin, which is used to carry the oxygen. They have no nucleus to allow more room in the cells for the haemoglobin. They are extremely small cells and also very flexible which allows them to pass through very narrow blood capillaries. 10 May 2019 Mr G Davidson

Red Blood Cells 10 May 2019 Mr G Davidson

Oxygen Transport Oxygen is absorbed by the blood capillaries in the lungs. The haemoglobin associates with the oxygen to make oxyhaemoglobin. When the blood gets to the cells, the surrounding oxygen concentration is low and the oxyhaemoglobin disassociates from the oxygen. 10 May 2019 Mr G Davidson

Disassociation in the body tissues Oxygen Transport + Haemoglobin Oxygen Disassociation in the body tissues Association in the Lungs Oxyhaemoglobin 10 May 2019 Mr G Davidson

Oxygen Transport Haemoglobin is said to have a high affinity for oxygen when the oxygen concentration is high. It has a low affinity for oxygen when the oxygen concentration is low. 10 May 2019 Mr G Davidson

Oxygen Disassociation Curve Oxygen concentration in the surroundings Oxygen concentration in the blood Respiring tissue Alveoli Dropping off oxygen Picking up oxygen 10 May 2019 Mr G Davidson

Body Defences Another function of the blood is to defend the body from foreign organisms. Organisms which cause disease, such as bacteria and viruses, are called pathogens. 10 May 2019 Mr G Davidson

Body Defences These pathogens have to firstly get through the body’s first lines of defence, which include: Skin Mucus Acid Tears Saliva 10 May 2019 Mr G Davidson

Body Defences Once the first line of defence is breeched, the second line takes over. This includes white blood cells. These are much fewer than red blood cells and they also contain a nucleus. 10 May 2019 Mr G Davidson

Body Defences There are several types of white blood cell which includes monocytes and macrophages. The cells engulf and destroy any foreign organisms. This process is called phagocytosis. 10 May 2019 Mr G Davidson

Body Defences The bacteria is engulfed and kept in a vacuole. There are lysosomes in the cytoplasm of the phagocyte which contain powerful digestive enzymes. The lysosomes join with the vacuole containing the bacteria and release their enzymes destroying the bacteria. 10 May 2019 Mr G Davidson

Body Defences Phagocytosis comes under the heading of “general immunity”. It is non-specific. i.e. it protects us from many different bacteria. We also have specific immunity which involves the production of antibodies. 10 May 2019 Mr G Davidson

Body Defences Antibodies are produced by another type of white blood cell called lymphocytes. An antibody is a Y-shaped molecule with receptor sites on 2 points of the Y. The receptor sites are shaped to fit a specific antigen, which is a protein recognised by the body as foreign. 10 May 2019 Mr G Davidson

Body Defences 10 May 2019 Mr G Davidson

Body Defences 10 May 2019 Mr G Davidson

Body Defences Once the antibody and antigen are locked together the foreign organism is rendered harmless. They can now be engulfed by a phagocyte. 10 May 2019 Mr G Davidson

Body Defences This type of defence is useful because the lymphocytes can then “remember” the organism and produce antibodies much quicker the next time it appears. E.g. if you are infected by the measles virus, lymphocytes will begin multiplying and producing antibodies to fight off the disease. 10 May 2019 Mr G Davidson

Body Defences You will be ill for a time but the antibodies will eventually destroy the viruses and you will recover. Some of the lymphocytes, however, remain as memory cells, and should the same virus enter your body again, it will have the antibodies to fight it off before it can make you ill. This is called specific immunity. 10 May 2019 Mr G Davidson

Body Defences The first time the body is infected is called the primary response. The second time it is infected is called the secondary response. It is more rapid than the primary response It produces more antibodies The antibodies last longer 10 May 2019 Mr G Davidson

Body Defences There are 2 ways to gain specific immunity. Passive immunity is when a ready-made antibody gets into the body, e.g. through breast milk. Active immunity is when antibodies are made in response to disease or vaccination. 10 May 2019 Mr G Davidson

Body Defences A vaccination is an injection of treated antigens which stimulate the lymphocytes into producing antibodies, but does not cause the disease. This is called artificial immunity or immunisation. 10 May 2019 Mr G Davidson