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Organising plants and animals, Vena cava - brings deoxygenated blood from…
Organising plants and animals
Blood
Blood plasma
Blood plasma is a yellow liquid which transports all of your blood cells and other substances around your body
Waste carbon dioxide produced by the cells is carried to the lungs
Urea formed by the liver from breakdown of excess proteins is carried to your kidneys where it's removed from the blood and turned into urine
Small, soluble products from digestion pass into the plasma and are transported to individual cells
Red blood cells
More red blood cells than any other blood cell in your body
They pick up oxygen from the air in your lungs and carry it to the cells where it's needed
Adaptations
Biconcave discs - being biconcave increases the surface area to volume ratio for diffusion
Packed with haemoglobin that binds to oxygen
No nucleus, which makes more space for haemoglobin
White blood cells
Form part of the immune system:
lymphocytes
form antibodies against microorganisms, some form antitoxins and
phagocytes
engulf and digest bacteria and viruses
Much bigger than red blood cells and there are fewer of them
Platelets
Small fragments of cells with no nucleus
Help the blood clot at the site of a wound
Formed when the enzyme reaction produces protein fibres that capture lots of red blood cells and platelets to form a clot that stops you bleeding to death
Blood vessels
Arteries
Carry blood
away
from the heart to the organs of the body
Contain thick walls containing muscle and elastic fibres
Blood is under high pressure in an artery which makes it dangerous if one is cut - the blood will spurt out very rapidly
Arteries stretch as blood goes through and then goes back afterwards. This is felt as a pulse where the arteries are close to the skin
Veins
Carry blood
towards
the heart and away from the organs
Low in oxygen and a deep purple-red colour
Do not have a pulse
Much thinner walls than arteries
Have valves to prevent the backflow of blood
Valves open as the blood flows through and then close if the blood starts to flow backwards.
Capillaries
Form a huge network of tiny vessels linking arteries and veins
Narrow with very thin walls - one cell thick
Enables substances, like oxygen and carbon dioxide, to diffuse easily out of your blood and into your cells
Double circulation
Blood vessels are arranged in a double circulatory system
One transport system carries blood from your heart to your lungs and back again. This allows oxygen and carbon dioxide to be exchanged with the air in the lungs
The other transport system carries blood from your heart to all the other organs of your body and back again
Vital in warm-blooded animals and it makes our circulatory system very efficient
The heart
The heart is supplied with oxygen by the coronary arteries
The two sides of the heart fill and empty at the same time, giving a strong, coordinated heartbeat
The wall of the left ventricle is noticeably thicker than the wall of the right ventricle
This allows the left ventricle to develop the pressure needed to force the blood out of the heart and around the whole body
Problems
In
Coronary Heart Disease
, the coronary arteries that supply the heart with blood become narrow. If the blood flow is reduced, then the amount of oxygen that the heart gets is also reduced. A common cause is build up of fatty materials and it can cause pain, a heart attack or even death
Coronary heart disease is often solved using stents, bypass surgery or statins
A
stent
is a piece of metal mesh which is placed into your artery to keep them open and allow blood to flow through freely. A balloon is inflated into the stent to keep the artery and stent open; when it is deflated the stent stays open. Many also release drugs to stop the blood from clotting.
Bypass surgery
is replacing the narrowed or blocked arteries with bits of veins from other parts of the body. This is carried out on heavily damaged arteries and when stents cannot be used. However, it is extremely expensive and comes with the risks of anaesthetic
Statins
are drugs which reduce blood cholesterol levels and slows down the rate at which fatty materials are deposited into your arteries. These are prescribed to people at risk of coronary heart disease.
Helping the heart
Leaky valves
Heart valves have to withstand a lot of pressure and over time may become leaky or stiff, which reduces the heart's efficiency
People affected may become breathless and without treatment, die
Mechanical valves
Used to replace faulty valves and are made out of titanium and polymers
Last a very long time
However, have to take medicine for the rest of your life to prevent the blood from clotting around it
Biological valves
Based on valves taken from animals: eg, pigs or cattle, or even humans
Work extremely well and patient doesn't need to take any medication
However, only last 12-15 years
Artificial pacemakers
The heart beats at a healthy rhythm of around 70 bpm and is controlled by the natural pacemaker cells
If these stop working, they can cause serious problems
If the heart beats too slow, the body won't get enough oxygen, but if it beats too fast, the heart can't pump blood properly
Artificial pacemaker
Electrical device implanted into the chest that weighs 20-50g
Attached to the heart by two wires
Sends strong, regular electrical signals to the heart that stimulate it to beat properly
Modern pacemakers are often very sensitive to what your body needs and only work when the natural rhythm goes wrong. Many stimulate the heart to beat faster during exercise
Artificial heart
Heart transplants
When the heart fails, a donor heart or heart and lungs may need to be transplanted
However, you have to wait for a tissue match and this can take years. Many people die before this can happen
Vena cava
- brings deoxygenated blood from the head and body
Right atrium
Right ventricle
Pulmonary artery
- takes deoxygenated blood to the lungs
Pulmonary vein
- brings oxygenated blood to the heart from the lungs
Left atrium
Left ventricle
Aorta
- carries oxygenated blood around the body