|
Plasma:
is the liquid part of
blood; it transports dissolved substances around the body and defends it
against disease.
The composition and functions of
plasma
There are a number of links on this page
to other pages in the web. I did not want to re-write these pages so if
you want to know more, jump to the appropriate page. You can do this by
clicking the appropriate flag P
or you can use the table at
the bottom of this page.
Composition of Blood:
 |
Red Blood Cells P |
|
White Blood Cells P |
|
Platelets |
|
Plasma which
contains:
 |
Glucose |
|
Amino-acids |
|
Vitamins P |
|
Hormones P |
|
Mineral
salts |
|
Antibodies |
|
Antitoxins |
|
Urea |
|
Phospholipids |
|
Lipoproteins |
|
Hydrogen
carbonate ions |
|
Fibrinogen |
|
Plasma is the liquid part of blood. It
contains many important substances which must be carried around the body.
Functions:
|
Transport of:
|
The
products of digestion P |
|
Carbon
dioxide P |
|
Hormones P |
|
Vitamins
P |
|
Urea |
|
Heat |
|
|
Defense:
|
Contains
antibodies and antitoxins |
|
Clotting |
|
Goodies in
plasma:
Please call them "useful substances".
The Plasma contains dissolved substances. Most of
these are useful and are carried to places where they are to be stored or
used. The products of digestion including glucose, amino acids, mineral
salts and vitamins are carried from the small intestines (ileum) to other
organs. Glucose is either stored in the liver and muscles as glycogen or
used in tissue respiration. Amino acids are used by all your tissues for
growth and repair. The liver is able to remove excess amino acids from
blood plasma and add some of those which are needed. The nitrogen from
excess amino acids is turned into a harmful substance called urea.
Vitamins are carried by plasma from the ileum to
all other parts of the body. They help keep your tissues healthy. Minerals
are also absorbed into blood plasma in the ileum and carried around the
body. Different minerals are required for different reasons. You must know
that calcium is needed for teeth and bones. It is also required for
muscles. Calcium ions are involved in the chemical mechanisms of muscle
contractions. So without enough calcium in your diet, your muscles are not
able to contract correctly.
Iodine is required by the thyroid gland in your
neck to make a hormone called thyroxine. This controls how fast your body
works. In particular, thyroxine affects the rate of tissue respiration.
Hormones are secreted by endocrine glands and carried in blood plasma to
target organs. Insulin is secreted by endocrine glands called "islets
of Langerhans". These are small groups of cells in your pancreas. The
main target organ for insulin is the liver. Insulin stimulates the liver
to convert excess glucose in your blood into glycogen. Insulin is also
necessary for tissue respiration.
Baddies:
Please call them "harmful substances".
The main baddies in your blood are urea and
hydrogen carbonate ions. Urea is the product of excess amino acids. It is
put into blood plasma by the liver and removed by the kidney. This process
is called excretion. Your kidneys also excrete excess water and salts from
your body. This process is called "osmoregulation". It is under
the control of the brain and involves chemical messengers ( hormones)
secreted by the pituitary gland.
Hydrogen carbonate ions are produced when carbon
dioxide produced by tissue respiration is absorbed by blood plasma. In
your lungs, hydrogen carbonate ions turn back to carbon dioxide which is
excreted when you exhale.
Antibodies kill bacteria. Antibodies are goodies
and bacteria are baddies.
If the goodies win, you live to a ripe old age. You may have a natural
immunity to some diseases, but other diseases are likely to kill you if
you do not receive medical attention. The problem is that the germs
multiply faster than you white blood cells kill them. If you cannot make
the right antibodies you will get very ill and could die. You can teach
your body to recognise diseases like smallpox by "inoculating"
yourself (get your doctor to do it) with a very similar disease like
cowpox. Edward Jenner discovered this. Cowpox does not make you very ill
and will certainly not kill you. When your white blood cells have learnt
how to make the antibodies needed to destroy cowpox they can also destroy
smallpox. Get yourself inoculated now especially if you are going to a
part of the world where smallpox is endemic.
When you cut yourself, the damaged blood vessels
trigger the clotting process. Fibrin, which is a soluble protein in your
blood, turns into fibrin which is an insoluble fibrous protein. Platelets
get caught in the network of fibrin and form a clot which dries up into a
scab. This is quite a good thing because it prevents any more blood from
getting out and it prevents germs from getting in. So fibrin is a goody.
Blood plasma contains lots of goodies
but you should call them "useful substances" and a few baddies
which you should call "harmful substances" in your exam
answers. |
