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CHAPTER 18 BODY FLUIDS AND CIRCULATION
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CHAPTER 18 BODY FLUIDS AND CIRCULATION
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Navas Cheemadan Factors for coagulation or clotting of blood
C HAPTER 18 are also present in the plasma in an
inactive form.
BODY FLUIDS AND CIRCULATION Plasma without the clotting factors is called
serum.
Need of a circulatory system in the body?
All living cells have to be provided with
nutrients, O2 and other essential substances.
b.Formed element
Also, the waste or harmful substances produced,
Erythrocytes, leucocytes and platelets
have to be removed continuously for healthy
are collectively called formed elements and
functioning of tissues. It is therefore, essential to
they constitute nearly 45 per cent of the
have efficient mechanisms for the movement of
blood
these substances to the cells and from the cells.
i)RBC (Red Blood cells/Erythrocytes)
Simple organisms like sponges and They are the most abundant of all the cells
coelenterates circulate water from their in blood.
surroundings through their body cavities to A healthy adult man has, on an average, 5
facilitate the cells to exchange these millions to 5.5 millions of RBCs mm–3 of
substances blood.
Blood is the most commonly used body RBCs are formed in the red bone marrow
fluid by most of the higher organisms in the adults. Formation of RBC is called
including humans for this purpose Erythropoiesis.
RBCs are devoid of nucleus in most of
BLOOD the mammals and are biconcave in shape.
Blood is a special fluid connective tissue They have a red coloured, iron containing
consisting of a fluid matrix, plasma, and complex protein called haemoglobin,
formed elements. hence the colour and name of these cells.
A healthy individual has 12-16 gms of
haemoglobin in every 100 ml of blood.
a.Plasma
These molecules play a significant role in
Plasma is the fluid part of the blood
transport of respiratory gases (oxygen
Plasma is a straw coloured, viscous fluid
and carbon dioxide).
constituting nearly 55 per cent of the blood.
RBCs have an average life span of 120
90-92 per cent of plasma is water and
days after which they are destroyed in the
proteins contribute 6-8 per cent of it.
spleen (graveyard of RBCs)
Fibrinogen, globulins and albumins are the
major proteins ii)WBC (White Blood Cells/Leucocytes)
Fibrinogens are needed for clotting or Leucocytes are also known as white blood
coagulation of blood. cells (WBC) as they are colourless due to
Globulins primarly are involved in defense the lack of haemoglobin.
mechanisms of the body They are nucleated and are relatively
The albumins help in osmotic balance. lesser in number which averages 6000-
Plasma also contains small amounts of 8000 mm–3 of blood.
minerals like Na+, Ca++, Mg++, HCO3 –, Cl–, Leucocytes are generally short lived.
etc. Glucose, amino acids, lipids, etc., are There are two main categories of WBCs
also present in the plasma. – granulocytes and agranulocytes
navas9895@gmail.com SOHSS-AREEKODE
, Navas Cheemadan
Granulocytes BLOOD GROUPS
Neutrophils, eosinophils and basophils are Various types of grouping of
different types of granulocytes. blood has been done. Two such groupings –
Neutrophils are the most abundant cells the ABO and Rh – are widely used all over
(60-65%) of the total WBCs and are the world.
involved in phagocytic reactions a) ABO Blood grouping
basophils are the least (0.5-1%) among ABO grouping is based on the presence
the WBC. Basophils secrete histamine, or absence of two surface antigens
serotonin, heparin, etc., and are involved in (chemicals that can induce immune
inflammatory reactions. response) on the RBCs namely A and B.
the plasma of different individuals contain
Eosinophils (2-3%) resist infections and
two natural antibodies (proteins produced
are also associated with allergic
in response to antigens). during blood
reactions.
transfusion, any blood cannot be used;
the blood of a donor has to be carefully
Agranulocytes
matched
Lymphocytes and monocytes are the
with the blood of a recipient before any
agranulocytes
blood transfusion to avoid severe problems
monocytes (6-8%) are phagocytic
of clumping (destruction of RBC)
cells which destroy foreign organisms
Blood Antigen Antibody Donor’s
entering the body
group on RBC in group
Lymphocytes (20-25%) are of two major plasma
types – „B’ and ‘T’ forms. A A Anti-B O,A
Both B and T lymphocytes are responsible B B Anti-A O, B
for immune responses of the body AB A, B Nil A,B,AB,O
O nil Anti-A, B O
iii) Platelets (Thrombocytes) ‘O’ blood can be donated to persons with
Platelets also called thrombocytes, are any other blood group (Because „O‟ blood
cell fragments produced from groud contains no antigen, so the recipient
megakaryocytes (special cells in the bone ody willnot make any antibody against it )
marrow). and hence „O‟ group individuals are called
Blood normally contains 1,500,00- „universal donors’.
3,500,00 platelets mm .–3 Persons with ‘AB’ group can accept blood
Platelets can release a variety of from persons with AB as well as the other
substances most of which are involved in groups of blood (AB blood group can
the coagulation or clotting of blood. receive any blood group because it
A reduction in their number can lead to contains no antibodies ). Therefore, such
clotting disorders which will lead to persons are called „universal recipients’.
excessive loss of blood from the body
navas9895@gmail.com SOHSS-AREEKODE
, Navas Cheemadan
b) Rh grouping
Another antigen, the Rh antigen similar to
one present in Rhesus monkeys (hence Coagulation of Blood
Rh), is also observed on the surface of We can see a dark reddish brown scum
RBCs of majority (nearly 80%) of formed at the site of a cut or an injury over
humans. Such individuals are called Rh a period of time. It is a clot or coagulam
positive (Rh+ve) and those in whom this formed mainly of a network of threads
antigen is absent are called Rh negative called fibrins in which dead and damaged
(Rh-ve). formed elements of blood are trapped.
An Rh-ve person, if exposed to Rh+ve Fibrins are formed by the conversion of
blood, will form specific antibodies against inactive fibrinogens in the plasma by the
the Rh antigens. Therefore, Rh group enzyme thrombin.
should also be matched before Thrombins, in turn are formed from
transfusions. another inactive substance present in the
Rh incompatibility- plasma called prothrombin. An enzyme
complex, thrombokinase, is required for
Erythroblastosis foetalis the above reaction.
This complex is formed by a series of
A special case of Rh incompatibility linked enzymic reactions (cascade
(mismatching) has been observed process) involving a number of factors
between the Rh-ve blood of a pregnant present in the plasma in an inactive state.
mother with Rh+ve blood of the foetus. An injury or a trauma stimulates the
Rh antigens of the foetus do not get platelets in the blood to release certain
exposed to the Rh-ve blood of the mother factors which activate the mechanism of
in the first pregnancy as the two bloods coagulation.
are well separated by the placenta. Certain factors released by the tissues at
However, during the delivery of the first the site of injury also can initiate
child, there is a possibility of exposure of coagulation. Calcium ions play a very
the maternal blood to small amounts of important role in clotting.
the Rh+ve blood from the foetus. In such Flow chart of blood coagulation
cases, the mother starts preparing
antibodies (Rh antibodies ) against Rh
antigen in her blood. In case of her
subsequent pregnancies, the Rh
antibodies from the mother (Rh-ve) can
leak into the blood of the foetus (Rh+ve)
and destroy the foetal RBCs. This could
be fatal to the foetus or could cause
severe anaemia and jaundice to the
baby. This condition is called
erythroblastosis foetalis.
This can be avoided by administering
anti-Rh antibodies to the mother
immediately after the delivery of the first
child.
navas9895@gmail.com SOHSS-AREEKODE
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