blood and circulation

• Atherosclerosis Risk factors include smoking, inactivity, stress, salt intake, high blood

  cholesterol and alcohol consumption.
• Atherosclerosis includes the following sequence of events:

  • The endothelium lining the artery becomes damaged. This can result from high blood pressure-extra strain on the cells. It may be caused by toxins in tobacco smoke.
  • causes an inflammatory response. Macrophages leave the blood vessel, move into the artery wall. They accumulate chemicals from blood, e.g. cholesterol. A deposit builds up which is called an atheroma.
  • fibrous tissue also build up- causes hard swelling called plaque( inner wall of the artery). This means that artery wall loses elasticity and “hardens”
• In atherosclerosis Plaques cause the artery walls to narrow and it is also difficult for the vessel to constrict or dilate. This can make it difficult for the heart to pump blood around the body causing an increase in blood pressure. If the arteries become very narrow or completely blocked they then cannot supply enough blood.
• Coronary Thrombosis is when Blood platelets collect at the damaged surface of an artery and release factors that trigger blood clotting.
• A clot that formed inside a

  damaged but intact blood vessel is called a thrombus

  and the condition is called a thrombosis.
• If a thrombus happens in the coronary arteries it is called a

  coronary thrombosis.
• In coronary thrombosis, the heart doesn't get oxygen. If this happens for too long they will be permanently damaged. This results in myocardial infarction (heart attack)
• cardiac arrest can happen for coronary thrombosis if a large artery is blocked as it may cause the heart to stop beating
• Atherosclerosis can lead to weakening of a section of

  the artery wall which, due to the pressure of the blood,

  bulges outwards, forming a balloon like sac called an

  aneurysm.
• If the weakening is severe enough in a artery wall from atherosclerosis, the aneurysm may burst, causing a bleed. A small

  aneurysm in the brain can lead to a stroke.
• In angiography, a special dye is released into an artery making the blood vessels visible when an X-ray is taken. The angiogram shows the blood flow through the blood vessels and allows abnormalities to be detected –
• What are some abnormalities in a angiogram?

  Aneurysm, where sections of blood vessels bulge due to weakness in wall

  Atherosclerosis, where blood flow is restricted or blocked
• Irregular heartbeat can be detected using an electrocardiogram (ECG). An abnormal heartbeat, called arrhythmia, can involve change in rhythm producing an uneven heartbeat, or a change in rate.
• Capillaries Walls one cell thick composed of squamous

  endothelium with gaps between cells
• cappilaries tissue fluid is forced out at artery end of capillary, across capillary walls to supply cells with food and oxygen. It is

  forced out through the high hydrostatic pressure of the blood coming from the heart.
• After tissue fluid is forced out of the capillary through hydrostatic pressure, It then can return into venous end of capillary. It can bring waste products such as CO2 and urea.

  It is drawn back into the capillary by osmosis.

  This is because its contents remain concentrated due to the presence of large plasma proteins which were not filtered out at the artery end.