B3- Transporting substances

this is a word document of the secound topic in B3, gcse

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  • Created on: 13-11-11 15:30
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B3-2 : Transporting Substances Around the
The Circulatory System
The blood circulation system we have is made up of
three main components: blood vessels, the heart and the blood. It is
made up of two different blood systems ­ a double circulation. The
diagram shows that one transports blood from the heart to the lungs and
back again, the other takes blood around the rest of the body. Having a
double circulation is vital in animals like ourselves because we are
constantly active and in need of a rich blood supply ­ and with this system,
we are constantly receiving oxygenated blood from the lungs which is sent
around the body in one cycle.
There are three main blood vessels in the system, which have all adapted to
carry out specific functions. The diagram below shows each of them...

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The arteries (left diagram)carry blood away from the heart to the organs
in the body. This is usually oxygenated blood, explaining the red tubes.
When you feel your pulse, that is the arteries stretching as blood is forced
through them and returning back into their original shape.
The veins carry blood towards the heart, usually low in oxygen and
hence are deep purple-red in colour. No pulse in veins, but they do contain
valves usually which prevent the backflow of blood.…read more

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Urea, a waste product formed in the liver is carried in the plasma to the
kidneys. In the kidneys, urea is removed from the blood and transformed
into urine. All the small, soluble products of digestion pass into the blood
from the gut, which are carried around the body by plasma to the
individual cells which need the certain substances.
Red blood cells are the most common cell
type in the human body. There are around 5 million per each square
milimetre of blood.…read more

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When resting, your muscles are using up a certain amount of oxygen, but
when exercising your muscles contract harder and faster, so need more
glucose and oxygen to supply their energy needs. More carbon dioxide is
obviously produced ­ which has to be removed to keep muscles working
efficiently. So during exercise...…read more

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Another example is that water balance in the body must be maintained
because too much water (turgid) or too little water (flaccid) in cells can
destroy them ­ so the kidneys can remove excess water and release it from
the body in urine. Similarly, the kidneys can remove excess salt from the
body in the same way.
The kidneys filter the blood and then reabsorb (take back) everything
your body needs.…read more

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There are two ways we can deal with this
problem, the first being dialysis. The machine used in dialysis is called the
dialysis machine, and relies on a process called dialysis to clean the blood.
A person's blood leaves their body and flows into the machine, through
partially permeable membranes. After the membranes comes the dialysis
fluid, which contains a certain concentration of substances to ensure
diffusion of unwanted substances from the blood into the fluid. However,
glucose remains in the blood.…read more

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Unfortunately, the majority of the time this is not the case. One issue is
that the kidney the recipient receives was not originally theirs, so the
antigens on its surface will differ from the antigens they already have. Of
course, the problem with this is that the recipient's immune system may
reject the new kidney ­ which means your body will destroy it. During a
transplant, everything is done to prevent such a thing, but it is always a
risk.…read more


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