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Various electrolytes
as Na+
K+
Hco3-
Ca++
Po4--
Others2 %
Lipids, enzymesHormones, nutrients
Waste products
Plasma proteins
7.1
Plasma
Water dissolved solutes blood gases 90% 10% O2 and Co2
In-organic substances organic substances 9.1 % 0.9 %
Albuminglobulins FibrinogenProthrombin
%3.5 -5.0 gm%2.5 – 3.5 gm%0.3 gm%0.01 gm%
TypesOne typeSeveral typesOne typeOne type
M.W6900090000 - 156000340000
Site of formation
liver
Liver except γ globulins
synthesized in lymphoid tissues by
plasma cells
liverLiver
Main function
Maintaining plasma colloidal.
Enzymatic functionDefense function
Blood clottingBlood viscosity
Blood clotting
Plasma Proteins
PlasmaTissues
Liver
Plasma Proteins Amino acids
Dynamic state of plasma proteins
When the level of plasma proteins decrease as in hemorrhage:
it can be regenerated in two phases:
Rapid phase
( few hours )
from tissue proteins.
Slow phase
)days(
tissue proteins and dietary proteins
re-synthesis from
Albumin / Globulin ratio (A / G)
It is the ratio between plasma levels of albumin and globulins.
The normal value for A/G ratio ranges from 1.2 – 1.6.
A / G decreases in:
1 -Decrease plasma albumin level as in:
synthesis by the liver as in liver cirrhosis.
Intake as in malabsorption and mal nutrition
loss by the kidney as in nephrosis
loss by the skin in severe burns
Loss
2 -Increase plasma globulins level as in severe infections.
Congenital agammaglobulinemia where the globulin fraction is decreased.
A / G increases in:
Functions of plasma proteins1-Osmotic function.
2-Buffer function.
3-Defensive function.
4-Blood clotting.
5-Blood viscosity.
6-Regulation of capillary permeability.
7-Transport and conservation of important elements.
8-Source of amino acids for the tissues
1-Osmotic function.
Plasma proteins
Cells
Venous endArterial end
Capillary B.P. 32 mm.Hg 12 mm.Hg
No plasma proteins
Lymph
The osmotic pressure of the plasma = 5000 mmHg
Is due to
Crystalloids = Na, Cl, K … Colloids = plasma proteins
Crystalloids are present in the plasma and tissue fluid in the same concentration.
And So
The net osmotic effect of crystalloids is zero
The plasma proteins are present only in the plasma.
The tissue fluid is almost free of proteins
Albumin is responsible for most ( 80 % ) of the osmotic pressure of the plasma due to:
Highest concentration
Smallest molecular size = great number of molecules
So, some fluid is reabsorbed from tissue fluid to the plasma by the osmotic effect of plasma proteins.
The plasma proteins are responsible for 25 – 30 mmHg of the plasma O.P.
2-Buffer function:
Buffer system is composed of weak acid + its salt with a strong base
At normal Ph of blood ( 7.4, slightly alkaline) :
Plasma proteins are present in the form of proteinic acid ( weak acid ) and Na proteinate ( its salt with strong base).
Thus it acts as a buffer system preventing
excessive changes in Ph .
Lactic acid (relatively strong) + Na protinate Na lactate + proteinic acid ( weak acid )
NaOH (strong alkali) + proteinic acid Na proteinate + H2O
Gamma globulins are responsible for
defending the body against micro-organisms
and their toxins {humoral immunity}.
3-Defensive function.
4-Blood clotting.
Fibrinogen, prothrombin and other protein clotting factors
are essential for the coagulation process.
5-Blood viscosity.
Blood
plasma
Water
3.0
1.5
1.0
Viscosity is important in the production of the peripheral
resistance and maintenance of arterial blood pressure.
The fibrinogen molecule contributes more than other
plasma proteins to the viscosity of the blood because of its
elongated shape.
RBC’s are the main cause of blood viscosity because it
is the main cellular element of the blood
6-Regulation of capillary permeability
Most of the pores in the capillary wall are closed by
plasma proteins.
Decrease plasma proteins is associated with increasing
Capillary permeability.
7-Transport and conservation of important
elements.
**carriers for important substances as hormones
**Bind harmful substances to prevent their hazards e.g. bilirubin.
Significance:
The combined form acts as reservoir from which the free substance is slowly releases e.g. Free T3
Prevent filtration of substances in the kidney and their loss in urine.
8- Plasma proteins as a source of amino acids for
the tissues
Plasma proteins act as a source for
rapid replacement of tissue proteins
in case of tissue protein depletion.