The Circulatory Sytem
- The Circulatory System transports substances around the body
- It is made up of the heart, blood vessels and the blood.
- Substances (food ans oxygen) are transported from where they are taken into the body to the cells, or waste products (carbon dioxide and urea) are transported from the cells to where they are removed from the body.
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The Double Circulatory Sytem
- Humans have a double circulatory system.
- One pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart.
- The other pumps oxygenated blood around all the other organs in the body. The blood gives up the oxygen at the body cells and the deoxygenated blood returns to the heart.
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- The Heart is an organ
- It pumps the blood around the body
- Much of the wall of the heart is made from muscle tissue
- There are four main chambers: the left and right atrium; the left and right ventricle
- Valves in the heart ensure the blood flows in the correct direction
How it works:
- Blood flows into the two atria from the vena cava and the pulminary vein.
- The atria contracts, pusching the blood into the ventricles.
- the ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart.
- The blood then flows to the organs through arteries, and returns through veins.
- The atria fill again and the whole cycle starts over.
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Blood vessels are designed for their functions.
There are three types:
- Arteries - carry the blood away from the heart
- Capillaries - Involved in the exchnge of materials at the tissues.
- Veins - carry the blood to the heart
The arteries branch into capillaries, and capillaries join up to form veins.
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- Carry the blood away from the heart
- Have thick walls, containing muscles and elastic fibres allwoing them to stretch and pring back.
- This is needed as they carry the blood under high pressure
- Has a tiny lumen (hole)
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- Carry the blood to the heart
- Veins have thinner walls than arteriets as the blood is at a lower pressure.
- Often have valves to prevent back-flow of blood
- Bigger lumen, to help the blood flow despite the low pressure
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- Invloved in the exchange of materials at the tissues.
- Capillaries are very narrow, thin- walled blood vessels.
- They carry blood really close to every cell in the body to exchange substances with them.
- Substances needed by cells in body tissues pass out of the blood, and substance produced by the cells pass into the blood by diffusion through the walls of the capillaries.
- They have permeable walls, so substances can diffuse in and out
- Their walls are usually only one cell thick, increasing the rate of diffusion by decreasing the sistance on which it occurs.
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- The blood is a tissue
- It consist of a fluid called plasma in which red blood cells, white blood cells and platelets are suspended.
The Blood Plasma Transports:
- Red blood cells, white blood cells and platelets
- Carbon dioxide from the organs to the lungs
- Soluble products (glucose and amino acids) of digestion from the small intestine to other organs.
- Urea form the liver to the kidneys
- Antibodies and antitoxins produced by white blood cells
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Red Blood Cells
- Red Blood Cells transport oxygen from the lungs to the organs.
- Thay have a concave shape to give a large surface area for absorbing oxygen
- They are packed full with a red pigment called haemoglobin that absorbs oxygen
- They have no nucleus, leaving more room for haemoglobi to carry oxygen.
- In the lungs, haemoglobin combines with oxygen to form oxyhaemoglobin
- In other organs, oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to the cells
White Blood Cells
- White blood cells form part of the body's defense system against microorganisms
- They can change shape to engulf and digest microorganisms.
- They produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by microorganaisms.
- They have a nucleus.
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- Platelets are small fragments of cells
- They have no nucleus
- Platelets help blood to clot as the site of a wound - stopping blood loss and microorganisms getting in.
- Lack of platelets can cause excess bleeding and bruising.
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- Artificial blood is a blood substitiute, which is used to replace a lost volume of blood.
- When someone loses a lot of blood, their heart can still pump the remaining blood around the body as long as the volume of their blood can be topped up.
- Artificial blood is safe as long as no bubbles get in the blood.
- It can keep people alive even if they lose 2/3 of their red blood cells
- It may five the patient will need a blood transfusion
- Ideally, an artifical blood product would replace the function of the red blohat tod cells, so there's no need for a blood transfusion.
- Problem: Side-effects
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- Artifical Blood
- Artifical Parts
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- Artifical hearts are mechanical devices that pump blood if someone's heart fails.
- They are normally temporary until a donor heart is found
- Sometime perminent, reducing the need for a donor heart.
- They're not rejected by the body's immune system, becasue they are meade from metals or plastics, so the body doesn't recognise them as 'foreign' and attack.
- Surgery to fit an artifical heart can lead to bleeding and infection
- They don't work as well as healthy, natural hearts as parts wear out and the electric motor could fail.
- Blood doesn't flow through an artifical heart smoothly, which can cause blood clots and lead to strokes.
- Patient has to take drugs to thin blood, which can cause problem with bleeding if they get hurt
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Stents/Coronary Heart Disease
Coronary Heart Disease:
- Is when arteries that supply blood to the muscles of the heart get bloocked by fatty depositis.
- This causes the arteries to become narrow and blood flow is restricted, which can lead to a heart attack.
- Are tubes that are inserted inside arteries to keep them open, making sure blood can pass through to the heart muscle. This keep the heart beating and the person alive.
- Stents are a way of lowering the risk of a heart attack in people with coronary heart disease.
- However, over time the artery can narrow again as stents can irritate the artery and make scar tissue grow.
- Patients also have to take drugs to stop blood clotting on the stent.
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