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.