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

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

The wall of the left ventricle is noticeably thicker than the wall of the right ventricle

Problems

This allows the left ventricle to develop the pressure needed to force the blood out of the heart and around the whole body

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