Blood Volume| normal blood volume in body

Blood is a connective tissue in fluid form. It is considered
as the ‘fluid of life’ because it carries oxygen from lungs
to all parts of the body and carbon dioxide from all parts
of the body to the lungs. It is known as ‘fluid of growth’
because it carries nutritive substances from the digestive
system and hormones from endocrine gland to all the
tissues. The blood is also called the ‘fluid of health’
because it protects the body against the diseases and
gets rid of the waste products and unwanted substances
by transporting them to the excretory organs like
kidneys.

PROPERTIES OF BLOOD
1. Color: Blood is red in color. Arterial blood is scarlet
red because it contains more oxygen and venous
blood is purple red because of more carbon
dioxide.
Blood
2. Volume: Average volume of blood in a normal adult
is 5 L. In a newborn baby, the volume is 450 ml. It
increases during growth and reaches 5 L at the time
of puberty. In females, it is slightly less and is about
4.5 L. It is about 8% of the body weight in a normal
young healthy adult, weighing about 70 kg.
3. Reaction and pH: Blood is slightly alkaline and its
pH in normal conditions is 7.4.
4. Specific gravity:
Specific gravity of total blood : 1.052 to 1.061
Specific gravity blood cells : 1.092 to 1.101
Specific gravity of plasma : 1.022 to 1.026
5. Viscosity: Blood is five times more viscous than
water. It is mainly due to red blood cells and plasma
proteins.

COMPOSITION OF BLOOD
Blood contains the blood cells which are called formed
elements and the liquid portion known as plasma.

BLOOD CELLS
Three types of cells are present in the blood:
1. Red blood cells or erythrocytes
2. White blood cells or leukocytes
3. Platelets or thrombocytes.
Hematocrit Value
If blood is collected in a hematocrit tube along with a
suitable anticoagulant and centrifuged for 30 minutes
at a speed of 3000 revolutions per minute (rpm), the
red blood cells settle down at the bottom having a clear
plasma at the top. Plasma forms 55% and red blood
cells form 45% of the total blood. Volume of red blood
cells expressed in percentage is called the hematocrit
value or packed cell volume (PCV). In between the
plasma and the red blood cells, there is a thin layer of
white buffy coat. This white buffy coat is formed by the
aggregation of white blood cells and platelets



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