It is carried put by the neutrophils and the macrophages
- Antibodies in the blood attach to foreign antigens in the body.
- Receptors on the phagocytes bind to to antigens and the membrane of the phagocyte begins to fold inwards to trap the pathogen.
- When the membrane folds over completely, a vaccum called a phagosome is created and the pathogen is trapped here.
- Lysosomes inside of the phagocyte then release lysins which are hydrolitic enzymes that digest the pathogen.
- The end products are harmless nutrients that are absorbed into the cytoplasm.
The specific immune response
- After some macrophages engulf the pathogen, they do not digest it completely. Instead they seperate out the antigens and expose them on the surface membrane of the macrophage and becomes known as an antigen presenting cell. These then activate the T lymphocytes.
- T lymphocytes are another type of white blood cells which are covered in receptors. When the receptor on the T lymphocytes meet a complimentary antigen, it binds to it. This activates the T lymphocytes causing it to divide and differentiate into different types of T lymphocyte and the selection of the correct lymphcyte is called clonal selection.
- Different T lymphocytes carry out different functions:
- T helper - relese cytokines which stimulate B cells to develop.
- T killer - attack and kill any infected body cell.
- T memory - remain in the body after an infection
- Once the right T lymphocyte is selected,many copies of it are made and this is called Clonal Expansion.
B lymphocytes are covered in antibodies with each B lymphocyte having a differently shaped antibody. When the antibody on the surface of the B lymphocyte meets a complimentary shaped antigen, it binds to it. This, together with the interleukins released from the T lymphocytes, activates the B lymphcytes causing them to divide into:
- B Plasma Cells- flow around the body manufactoring and secreting antibodies
- B Memory Cells- remain in the blood after infection and provide the immunological memory
Short term effects of Tar
Tar is made of a combination of chemicals which settle on the linigs of the airways and alveoli. in the short term this causes:
- This increases the diffusion distance for gasses entering and leaving the blood.
- many of these chemicals cause allergic reactions where the smooth muscle in the walls of the airways contracts reducing the size of the lumen and reducing the flow of air.
- Tar paralyses cillia so they become unable to move the mucous up of the airways .
- Tar stimulates the goblet cells and mucus secreting glands so greater amounts of mucus is secreted and builds up in the airways.
- The bacteria and viruses that are trapped in the,mucus are not removed. They multiply in the mucus and eventually the combination of mucus and bacteria can block the bronchioles.
- The presence of bacteria and viruses means that the lungs are more suseptible to infection.
Long term effects of Tar
- Smokers cough is an attempt to shift the bacteria laden mucus that collects in the lungs. It results from the irritation of the airways by the mucus and also the need for air to reach the alveoli.
- The constant cough causes the linings of the airways and alveoli to be damaged and the damaged areas get replaced by scar tissue which is thicker and less flexible.
- The layer of smooth muscle in the wall of the bronchioles which reduces the lumen of the airway and the flow of air is permenantly restricted.
- The presence of bacteria and viruses imflame the linigs of the airways causing damage especially to the epithelium. White blood cells are attracted to the area to deal with the pathogenic microorganisms. In order for the white blood cells to get to the airway lining, they have to leave the blood vessels and in order to do these, they release enzymes to digest part of the lung linings. This damages the elastic tissue in the lining of the lungs. los of the elastic tissue reduces the elasticity of the alveolous walls so they do not recoil during exhilation so air is not forced out. The bronchioles collapse, trapping the air in the alveoli which can cause the alveoli to burst as the pressure in the lungs increases.