blood compositionand function by dr rashmi

1. DR RASHMI MISHRA
BLOOD COMPOSITION AND
FUNCTION /PLASMA PROTEINS

2. INTRODUCTION
 Blood is a fluid connective tissue which transports
substances from one part of the body to another.
 It provides nutrients and hormones to the tissues and
removes their waste products.
 Blood, confined in the cardiovascular system,
constitutes a major part of the extracellular fluid of the
body.

3. COMPOSITION OF BLOOD
 Colour of the blood is opaque red due to the pigment
haemoglobin in the red blood cells (RBCs).
- The arterial blood is bright red and venous blood is
dark red in colour.
 Volume of blood in an average adult is about
5–6 L (8% of the body weight or 80 mL/kg body
weight).
 Viscosity of blood is five times more than that of
water.

4. CONTD..................
 Specific gravity of blood is 1.050–1.060.
-Specific gravity of RBC is greater (1.090) than that of
plasma (1.030).
 pH of blood is about 7.4 (ranges from 7.38 to 7.42),
i.e. it is alkaline in nature.
- In acidosis, pH of blood falls below 7.38 and in
alkalosis, pH is more than 7.42.

5.  Blood is composed of two main components
- cellular elements
-plasma.

6. CELLULAR ELEMENTS OF
BLOOD
 They are about 45% of the total blood volume and
constitute the so-called packed cell volume.
 Blood cells are:
- Erythrocytes or RBCs (5 million/μL)
-Leucocytes or white blood cells (4000–11,000/μL)
- Platelets or thrombocytes (1.5–4 lac/μL).

7. PLASMA
 Plasma is the clear straw coloured fluid (with
dissolved solid substances) portion of the blood minus
its cellular elements.
 It constitutes about 55% of the blood volume (about
5% of body weight).

8. COMPOSITION
 Plasma contains the following constituents:
-Water. Water is the main constituent of plasma forming
91% of it.
-Solids. The solids dissolved in the plasma constitute a
total of 9% of the plasma.

9. PLASMA PROTEINS
 Plasma proteins form 7% of the solids in plasma.
 Their normal value ranges from
6.4 to 8.3 g/dL.
-They include albumin, globulins, fibrinogen and others.

10. ORGANIC MOLECULES
 It constitutes 1% of the solids
- Carbohydrates, mainly glucose (100–120 mg/dL). --
Fats are neutral fats (30–150 mg/dL), --phospholipids
(150–300 mg/dL) and cholesterol (150–240 mg/dL).
- Non-protein nitrogenous substances (28–40 mg/dL)
are ammonia (traces), amino acids, creatine (1–2
mg/dL), creatinine (0.6–1.2 mg/dL), xanthine (traces),
hypoxanthine (traces), urea (20–40 mg/dL) and uric
acid (2–4 mg/dL).
- Hormones, enzymes and antibodies

11. INORGANIC SUBSTANCES
 Inorganic substances which constitute 1% of the solids
in plasma include sodium, calcium, chloride,
bicarbonate (mainly extracellular) phosphates, copper,
potassium, magnesium (mainly intracellular) iron and
iodides

12. FUNCTION OF
BLOOD

13. NUTRITIVE FUNCTION
 Blood carries the nutritive substances like glucose,
amino acids, fatty acids, vitamins, electrolytes and
others from the gut to the tissues where they are
utilized.

14. RESPIRATORY FUNCTIONS
 Blood picks up oxygen from the lungs and delivers it
to the various tissues.. It also carries away CO2 from
the tissues to the lungs from where it is expelled out in
the expired air.

15. EXCRETORY FUNCTION
 Blood transports various metabolic waste products,
such as urea, uric acid and creatinine to excretory
organs (kidney, skin, intestine and lungs) for their
disposal.

16. TRANSPORT FUNCTION
 The various hormones produced by the endocrine
glands, the biological enzymes and antibodies are
transported by the blood to the target tissue to
modulate metabolic process.

17. PROTECTIVE FUNCTION
 Blood plays an important role in the defence
mechanism of the body:
- Neutrophils and monocytes engulf the microorganisms
entering the body by phagocytosis.
- Lymphocytes and γ globulins initiate immune
response.
- Eosinophils accomplish detoxification, disintegration
and removal of foreign proteins

18. HOMEOSTATIC FUNCTION
 Blood plays an important role in maintaining the
internal environment of the body (homeostatic
function):
-The water content of blood is freely interchangeable
with the interstitial fluid and helps in maintaining the
water and electrolyte balance of the body.
-Plasma proteins and haemoglobin act as buffers and
help in maintaining the acid–base balance and pH of
the body fluids

19. MAINTENANCE OF BODY
TEMPERATURE
- Specific heat of blood is high, which is useful in
buffering the sudden changes in the body temperature.
- High heat conductivity of blood renders it possible for
distribution of heat from deep organs to the skin and
lungs for dissipation.
- Due to high latent heat of evaporation of blood, a large
amount of heat is lost from the body by evaporation of
water from the lungs and skin.

20. STORAGE FUNCTION
 Blood serves as a ready-made source of substances
stored in it (such as glucose, water, proteins and
electrolytes for use in emergency conditions like
starvation, fluid loss and electrolyte loss).

21. PLASMA
PROTEINS

22. INTRODUCTION
 Plasma proteins form the major solid constituent of the
plasma.
 The total plasma protein concentration is
7.4 g/dL (ranges from 6.4 to 8.3 g/dL).

23. SYNTHESIS OF PLASMA
PROTEINS
 In embryo, the plasma proteins are synthesized by the
mesenchymal cells.
 First, the albumin is produced and then the other
proteins are synthesized.

24. CONTD.......
 In adults, plasma proteins are synthesized as described
below:
- The albumin and fibrinogen are synthesized mostly by
the reticuloendothelial cells of the liver.
- α and β globulins are synthesized by the liver, spleen
and bone marrow.
- γ globulins are synthesized by the B lymphocytes

25. TYPES OF PLASMA PROTEINS
 Albumin (4.8 g/dL),
 Globulins (2.3 g/dL) include:
- α1 globulin
- α2 globulin
- β globulin
- γ globulin
 Fibrinogen (0.3 g/dL).

26. PROPERTIES
Molecular weight Albumin: 69,000,
Globulins: From 90,000 to 1,56,000 and
Fibrinogen: 5,00,000.
Osmotic pressure The plasma proteins exert an oncotic pressure
of about 25 mm Hg.
Specific gravity The specific gravity of plasma proteins is 1.026
Isoelectric point Proteins can ionize either as acids or as bases
owing to the fact that the side chains of their
constituent amino acids contain a selection of
amino group (NH2) and carboxyl groups (–
COOH).
Electrophoretic mobility The proteins act as anions in alkaline solutions
and as cations in acidic solutions. Because of
this property they possess electrophoretic
mobility.

27. Water solubility The protein molecules are soluble in water
because of the presence of polar residues like
NH2 and COOH.
Amphoteric nature Protein molecules are amphoteric in nature
because of the presence of NH2 and COOH
groups
Precipitation by salts Albumin is precipitated by full saturation.
Globulins are precipitated by half saturation.
Among the globulins, there is a fraction which
can be pre cipitated by one-third saturation with
ammonium sulphate and is termed euglobulin.
The rest is called pseudoglobulin.
Fibrinogen is separated by one-fifth saturation
with ammonium sulphate

28.  Albumin
- Plasma levels are 4.8 g/dL (range 3–5 g/dL). -
Molecular weight of prealbumin is 60,000 and of
albumin is 69,000
-Synthesized in liver.
- Half-life is about 10 days.
FEATURES OF INDIVIDUAL FRACTION
OF PLASMA PROTEINS

29. GLOBULINS
- Plasma levels are 2.3 g/dL (range 2 to 3 g/dL).
-Molecular weight varies from 90,000 to 156,000.
-Types include α1, α2, β1, β2 and γ globulins
 Forms of globulins are described below:
- Glycoproteins consist of carbohydrates and protein .
- Lipoproteins consist of α2 globulin and lipids.

30. LIPOPROTEINS
High density lipoproteins (HDL). These are α
lipoproteins which contain 50% protein with large
amount of cholesterol and phospholipids.
– Low density lipoproteins (LDL). These are β
lipoproteins and contain large amount of glycerides.
– Very low density lipoproteins. These are also β
lipoproteins and have higher proportion of fat in the
form of triglycerides or cholesterol
– Chylomicron contains 98% triglycerides. It is
synthesized in the intestine following a meal.

31. CONTD......
 Transferrin is an α2-β globulin having a molecular
weight of 90,000.
-It has the specific property of iron binding and thus
helps in its transport and storage.
- Each molecule of transferrin binds two atoms of ferric
iron.
 Haptoglobin is an α2 globulin having a molecular
weight of 90,000.
- It forms stable complexes with free haemoglobin.

32.  Ceruloplasmin is an α2-β globulin having a molecular
weight of 16,000. It binds with copper and helps in its
transport and storage. Its deficiency causes Wilson’s
disease (hepatolenticular degeneration), in which liver and
brain are damaged due to high levels of free copper.
 Fetuin is a growth promoting protein seen in infants and
newborn.
 Immunoglobulins are γ globulins which play role in
immunity.
 Angiotensinogen is an α2 globulin.
 Haemagglutinins are antibodies against the RBCs
antigens.

33. FIBRINOGEN
- Plasma levels are 0.3 g/dL.
- Molecular weight is 500,000.
- Synthesized in the liver.
- Chemical structure. Protein part of the molecule is
made up of six polypeptide chains (α2, β2, γ2) joined
by disulphide bonds.
- Functions as a clotting protein.

34. PROTHROMBIN
- Plasma levels are 40 mg/dL.
- Molecular weight is 68,000.
-Synthesized in the liver.
- Synthesis is promoted by vitamin K.

35. FUNCTIONS
OF PLASMA
PROTEINS

36. EXERT OSMOTIC PRESSURE
 The protein molecules are unable to pass across the
capillary membrane and consequently exert colloid
osmotic pressure of about 25 mm Hg on the capillary
membrane.
 About 70–80% of the osmotic pressure is contributed
by the albumin fraction. The colloid osmotic pressure
plays an important role in exchange of water between
the blood and tissue fluid.

37. CONTRIBUTION TO BLOOD
VISCOSITY
 Fibrinogen and globulins are significant contributors
to blood viscosity because of their asymmetrical shape.
 The blood viscosity plays an important role in the
maintenance of blood pressure by providing resistance
to flow of blood in blood vessels

38. ROLE IN COAGULATION OF
BLOOD
 The fibrinogen, prothrombin and other coagulation
proteins present in the plasma play an important role in
the coagulation of blood.

39. ROLE IN DEFENCE MECHANISM
OF THE BODY
 The γ globulins are antibodies which play an important
role in the immune system meant for defence of the
body against the microorganisms.

40. ROLE IN MAINTAINING ACID–BASE
BALANCE OF THE BODY.
 Plasma proteins act as buffers and contribute for about
15% of the buffering capacity of blood. Because of
their amphoteric nature, plasma proteins can combine
with acids and bases as explained below:
- In acidic pH, the NH2 group of the proteins acts as base
and accepts proton and is converted to NH4.
- In alkaline pH, the COOH group of the proteins acts as
acid and can donate a proton and thus becomes COO−.
- At normal pH of blood, proteins act as acids and
combine with cations (mainly sodium).

41. ROLE AS RESERVE PROTEINS
 Plasma proteins serve as reserve proteins and are
utilized by the body tissues during conditions like:
 Fasting, Inadequate protein intake and Excessive
catabolism of body proteins.

42. ROLE IN SUSPENSION STABILITY
OF RBCS.
 Suspension stability refers to the property of RBCs by
virtue of which they remain uniformly suspended in
the blood.
 Globulins and fibrinogen accelerate this property

43. FIBRINOLYTIC FUNCTION
 The enzymes of the fibrinolytic system digest the
intravascular clot (thrombus) and thus save from the
disastrous effects of thrombosis.

44. ROLE IN GENETIC
INFORMATION
 Many plasma proteins exhibit polymorphism.
Polymorphism is a Mendelian trait that exists in the
population with differing prevalence.

45. TRANSPORT FUNCTION
 Plasma proteins combine easily with many substances
and play an essential role in their transport as
explained below:
- Carbon dioxide is transported by the plasma proteins in
the form of carbamino compound. Thyroxine is
transported by an α globulin called thyroxinebinding
protein.

46. CONTD.....
 Cortisol is transported by transcortin which is a
mucoprotein.
 Vitamin A, D and E are transported by the high and
low density lipoproteins (HDL and LDL).
 Vitamin B12 is bound to transcobalamin for transport.
 Bilirubin is associated with albumin and also with
fractions of the α globulin.
 Drugs of various types are transported after combining
with the albumin.

47. CONTD......
 Calcium of the plasma is partly (50%) bound to the
proteins for transport.
 Copper is bound to ceruloplasmin (α2 globulin) for
transport.
 Free haemoglobin in the vessels is bound by
haptoglobin and carried to reticuloendothelial system.

48. ABNORMALITIE
S OF PLASMA
PROTEIN

49. HYPOPROTEINAEMIA
 Hypoproteinaemia refers to generalized decrease in the
levels of plasma proteins.

50. CAUSES OF
HYPOPROTEINAEMIA
1. Dietary deficiency and starvation are associated with
hypoproteinaemia.
2. Malabsorption syndrome due to intestinal diseases
such as sprue is associated with hypoproteinaemia.
3. Liver diseases like hepatitis and cirrhosis cause
hypoproteinaemia due to reduced synthesis of proteins
in the liver.

51. 4.Renal diseases like nephrotic syndrome cause
hypoproteinaemia due to more loss of proteins in
the urine.
5.Haemorrhage and extensive burns are associated
with acute hypoproteinaemia.
6.Hereditary analbuminaemia is an inborn defect in
the genetic level where there is no synthesis of
albumin.
7.Congenital afibrinogenaemia is a rare condition
characterized by defective blood clotting

52. EFFECTS OF
HYPOPROTEINAEMIA
 Low levels of plasma proteins are associated with a
decrease in the plasma osmotic pressure which causes
water retention and oedema of the body tissue

53. HYPERPROTEINAEMIA
 Hyperproteinaemia, i.e. increase in the plasma protein levels,
is seen in following conditions:
-Acute inflammatory conditions are associated with increased
synthesis of the so-called acute phase proteins which include
C-reactive proteins, α antitrypsin, haptoglobin, fibrinogen
and ceruloplasmin. .

54. -Chronic inflammation and malignancies are also associated
with raised levels of C-reactive proteins.
Multiple myeloma is associated with increased levels of the
so-called Bence Jones proteins and myeloma globulin due
to their abnormal formation in the bone marrow.

55. REVERSAL OF NORMAL A/G
RATIO
 The normal albumin: globulin (A/G) ratio (1.7:1) is
reversed in the following conditions:
 When the albumin synthesis is decreased as occurs in
liver diseases (globulin levels being normal because
many globulins are synthesized by the B
lymphocytes).
 When the globulin levels are increased (as
occurs in most of the conditions) associated with
hyperproteinaemia.