1378968920.48619- Blood.pdf lab
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Zainab Sajid Mohammed
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, Blood
- Blood is a viscous fluid formed of cellular element suspended in plasma.
- The cellular element composed of: Erythrocytes (red blood cells), Leucocytes (white blood
cells), and Platelets.
- Plasma is a viscous, translucent, yellowish fluid composed of water (90%), proteins (7%),
organic salts (1%), and organic compound (2%) such as amino acids, lipids, and vitamins.
- The total blood volume in human is about 5 L (depending on body size).
- Outside the blood vessels, blood undergoes a complex reaction called coagulation or clot
formation, which plays an important role in repairing damaged blood vessels and preventing
blood loss.
- Erythrocytes and blood platelets perform their functions inside the blood vessels,
whereas leukocytes reside temporarily in the blood vessels and then leave the blood
stream through the capillary walls and venules to enter either the connective tissues or
lymphoid tissues.
- The ratio of erythrocytes to the total blood volume is about 43% and is known as
haematocrit.
Blood film showing red blood cells and different types of white blood cells
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, COMPOSITION OF PLASMA
A. Water: constitutes 90% of plasma volume.
B. Solutes: constitutes 10% of plasma. and include plasma proteins and other organic
compounds as well as inorganic salts.
1. Plasma proteins. Plasma contains a rich variety of soluble proteins, 7% by volume.
Important examples include:
a. Albumin. This is the most abundant plasma protein (3.5-5 g/dL of blood) and is
mainly responsible for maintaining the osmotic pressure of blood.
b. Globulins (Alpha, beta, and gamma globulins) are globular proteins dissolved in
the plasma. The gamma globulins include the antibodies, or immunoglobulins,
synthesized by plasma cells.
c. Blood coagulation proteins: such as prothrombin, fibrinogen which is converted
into fibrin during clot formation. Fibrinogen is synthesized and secreted by the
liver.
2. Organic compounds. They include nutrients such as amino acids and glucose,
vitamins, and a variety of regulatory peptides, steroid hormones, and lipids.
3. Inorganic salts. They constitutes 0.9% of plasma volume, include blood electrolytes
such as sodium, potassium, and calcium salts.
Serum: portion of plasma that separates from coagulum after clotting.
When anticoagulants (heparin, citrate, etc) are added, blood samples can be separated by
centrifugation into 3 major fractions:-
The erythrocytes constitute the densest fraction and end up at the bottom of the tube.
- The percentage of packed erythrocytes per unit volume of blood is termed
hematocrit.
- In adults, normal hematocrit values vary from 35 to 50% and are sex
dependent.
Leukocytes are less dense and less numerous (about 1 % of blood volume) and form a
thin white or grayish layer over the erythrocytes (buffy coat).
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