Learning objectives for plasma
To understand:
• Plasma and its composition.
• Plasma proteins – types, normal values and
physical characteristics.
• Separation of plasma proteins
• Functions of plasma proteins.
• Sites of synthesis of plasma proteins
• Edema and other applied aspects.
Plasma
•It is a clear straw colored fluid portion of the blood.
It contains:
91% water
9% solids1% inorganic molecules
7% plasma proteins
1% other substances
Plasma proteins
Total proteins: 7.3gm% (6.4 to 8.3gm%)
Serum albumin: 4.7gm%
Serum globulin: 2.3gm%
Fibrinogen: 0.3gm%
•Serum is the fluid part of the blood after clotting.
•Serum = plasma -- clotting factors and fibrinogen
•Serum albumin: globulin ratio is normally 1.5:1.0
• The ratio may be reversed in liver disease where albumin
formation is decreased and kidney diseases where
albumin is excreted.
Chemistry of plasma proteins:
Serum albuminMol wt- 69000, made up of single polypeptide chain;
each molecule is ellipsoid in shape.
It’s a mixture of several albumins.
It is synthesized in liver
Serum globulin:
•Mol wt-90,000to1,300,000. It is also mixture of several
globulins—alpha (1 & 2) , beta() and gamma()
• 1 consists of two fraction; one fraction combines with
bilirubin, another with lipids, steroids and glycoprotein.
• 2 globulin consists of 2 macroglobulin, mucoprotiens,
cerulopasmins and hepatoglobulins.
•  globulins are--•Beta lipoprotein which help in the carriage of
lipids, steroid and carotene.
• transferrin help in the transport of iron
• Prothrombin
•  globulins– are antibodies
Fibrinogen–Is globulin in nature, has a special property of
clotting by getting converted into fibrin
Origin of plasma proteins: All the fractions are produced in
liver, but albumin, fibrinogen and prothrombin are produced
only in liver.
Sources of globulin are—
disintegrated blood cell
reticulo-endothelial system
general tissue cells and
lymphoid nodules
The plasma proteins get completely used up and replaced
every fourteen days.
• Albumin synthesis is stimulated by osmotic pressure
changes and hypoproteinemia
• Globulin, by depressed blood protein pool
• Fibrinogen by systemic inflammation
• After depletion of plasma proteins, it comes back to
normal level in about 14 days. Fibrinogen is regenerated
first, followed by globulin and last is albumin.
• Relation of diet to plasma—Whipple’s experiment.
Separation of plasma proteins
•
a.
b.
c.
d.
Can be done by various methods like
Electrophoresis
Immuno electrophoresis
Salting out method
Svedberg’s ultra centrifugation
The most commonly used method is
electrophoresis.
Because the plasma proteins are charged
molecules, from the line of application, the
proteins move either towards negative or
positive pole of an electrical field and at
different velocity.
Electrophoresis
Functions of plasma proteins:
• Essential for blood clotting
• Maintains colloidal osmotic pressure of blood
• Maintains viscosity and blood pressure
• Concerned with erythrocyte sedimentation rate (ESR)
• Acts as buffer
• Acts as a protein reserve
• Helps in co2 carriage by forming carbamino proteins
•Antibodies
• Help transport of certain substances in blood
Viscosity of blood:
• Blood is 5 times more viscous than distilled water
• Viscosity is due to both cells and plasma proteins
• Viscosity is dependent on plasma proteins and
number and volume of corpuscles
• The plasma proteins, mainly globulins contribute for
the viscosity of blood.
• It determines the peripheral resistance of the blood flow
through the blood vessels and helps in maintaining blood
pressure
Regulation of pH of blood
pH of blood has to be maintained around 7.4  0.04.
This is absolutely necessary for maintaining the
enzymatic activity to go on smooth. The plasma
proteins have amino (NH2) and carboxyl terminals
(COOH). These terminals either can accept
hydrogen ion (NH2) or can donate hydrogen ion
(COOH).
When pH of blood falls below 7.4 (acidosis) plasma
proteins accept hydrogen ion and when the pH
blood is above 7.4 (alkalosis), plasma proteins
donate hydrogen ions. By doing so, they try to
maintain the pH of blood within the narrow range
that is obligatory to maintain homeostasis.
Colloidal osmotic pressure
Normal colloidal osmotic pressure is about 25 mm Hg.
About 80% of this is contributed by albumin alone.
Since albumin is in higher concentration and has
low molecular weight, it contributes maximally for
maintenance of colloidal osmotic pressure. The
remaining 20% is due to other plasma proteins.
Maintenance of colloidal osmotic pressure is essential
for maintenance of fluid volume in intra vascular
compartment and interstitial spaces (tissue spaces).
To understand the significance of colloidal osmotic
pressure, we should understand capillary dynamics
or Starling’s hypothesis.
Structural details of capillary
Before we go to details of capillary dynamics,
let us try to understand the structural
details of capillary. The capillary takes
origin from an arteriole.
At the beginning of capillary from an arteriole,
a pre capillary sphincter is present. Like
that at the end of capillary, a post capillary
sphincter is also present.
Capillaries join to form venules. Hence the
capillary has two ends namely an arterial
end and a venous end.
Structural details of capillary continued
The walls of the capillary is made up of a single
layer of endothelial cell lining. Smooth muscle
is absent in the wall of capillary.
The diameter of the capillary lumen is about 8
microns.
Pressure that is exerted by a flowing column
blood on the walls of artery is known as blood
pressure. This pressure exerted on the
walls of capillaries is known as
hydrostatic pressure.
Capillary dynamics or Starling’s hypothesis
At the arterial end of capillary the hydrostatic
pressure is around 35 mm Hg. At the
venous end of capillary it is only about 16
mm Hg.
Hydrostatic pressure at the venous end of
capillary is decreased because as blood
flows through the narrow lumen of capillary,
it encounters resistance offered by the
walls of the capillary. This contributes for a
slight fall of pressure.
In addition to this, there will be slight
decrease in blood volume at the venous
end of capillary when compared to the
arterial end.
Capillary dynamics continued
Unlike the hydrostatic pressure which decreases along
the length of capillary, colloidal osmotic pressure
remains around 25 mm Hg throughout the length of
capillary because capillary wall is impermeable to
plasma proteins.
The hydrostatic pressure of the capillary is an outdriving force and the colloidal osmotic pressure
is an in-driving (opposing) force.
The hydrostatic pressure and colloidal osmotic
pressure in the tissue spaces is generally
assumed to be zero.
Pressure acting at the level of capillaries
Pressures acting at the level of capillaries
At the arterial end of the capillary the outdriving force (hydrostatic pressure in the
next diagram shown as HP) is stronger
than the in-driving force (colloidal
osmotic pressure in the next diagram
shown as COP).
There is a net difference of pressure of
about 10 mm Hg and is directed
outwards. Because of this pressure
difference, fluid (only the plasma part
without plasma proteins) goes out from
the intra vascular compartment to
interstitial spaces.
Pressures acting at the level of capillaries
At the venous end of capillary, the hydrostatic
pressure falls down to 16 mm Hg, but the
colloidal osmotic pressure continues to be
around 25 mm Hg.
At the venous end of capillary, there is a net
difference of pressure of about 9 mm Hg
and is directed inward. Because of this, most
of the fluid that has gone out at the arterial
end returns to capillaries from tissue spaces.
Diagram of capillary dynamics with fluid exchange
mechanism
Starlings hypothesis
It states that the net filtration through capillary
membrane is proportional to the hydrostatic pressure
difference across the membrane minus the oncotic
pressure difference
These pressure are called Starling’s forces
Capillary dynamics continued
At the arterial end, due to net outward force of
10 mm Hg, let us assume that about 10 parts
of fluid moves out of intra vascular
compartment into interstitial spaces. At the
venous end, due to net inward force of 9 mm
Hg, about 9 parts of fluid is returned to
capillary from interstitial spaces.
Because of this inequality between the
volume of fluid that has gone out and to
the volume of fluid returned to capillary,
about 1 part of fluid remains in the
interstitial spaces. This fluid is known as
tissue fluid or interstitial fluid.
Capillary dynamics continued
If the tissue fluid is allowed to accumulate, not
only it decreases blood volume and alters
cardio vascular dynamics, it also results in
swelling of that part of the body (edema).
This apart, though generally it is said that no
plasma protein moves out from the intra
vascular compartment into tissue spaces,
there will be leakage of minute quantity of
plasma proteins to tissue spaces. This also
should not be allowed to accumulate in
tissue spaces.
Capillary dynamics continued
The remaining one part of fluid in
tissue spaces with the leaked
proteins will enter the lymphatics
and is now known as lymph. Finally
lymph will drain into the circulatory
system.
So effectively no extra fluid is allowed to
get accumulated in tissue spaces and
thereby edema is prevented
Edema
By definition, fluid accumulation in interstitial
spaces is known as edema. One of the
common causes for edema is decreased
concentration of plasma proteins especially
that of albumin fraction.
•
a.
b.
c.
Some of the common conditions in which
edema occurs are:
Protein malnutrition.
Liver diseases.
Kidney diseases.
THANK YOU
Erythrocyte sedimentation rate: (E S R)
Sedimentation occurs in three phases:
Stage of aggregation
True sedimentation following maximum velocity of fall
Slow sedimentation
ESR depends on -• Differences in densities between RBC and plasma
• Degree of adherence of RBCs to one another
(rouleaux formation)
• resistance that plasma exerts on RBC
Red cells carry a negative charge, so any condition that
increases the positive charge in plasma accelerates
ESR
Normal values: by Westergren’s method
Males—1to 5mm at the end of one hour
Females– 5to10 mm at the end of one hour