Physiology of Blood

1. BLOOD
By: Sathish Rajamani
Associate Professor

2. INTRODUCTION
• Blood is a connective tissue in fluid form.
• It is considered as the ‘Fluid of Life’, ‘fluid of growth’
and ‘fluid of health’

3. Properties of Blood
• Color: Red, Arteria Blood is Scarlet red and Venous
Blood is Purple red.
• Volume: Average Volume is 5 L in normal adult. In
newborn it is 450 ml. in female it is 4.5L.
• Reaction and pH: Slightly alkaline (ph value is 7.4)
• Viscosity: More Viscous than water
• Specific Gravity:
• Total blood cells – 1.052 to 1.061
• Blood Cells:1.092 – 1.092 to 1.101
• Plasma: 1.022 to 1.026

5. Blood Cells
• There are 3 types of blood cells
• 1. Red Blood Cells or Erythrocytes
• White Blood Cells or Leukocytes
• Platelets or Thrombocytes

6. Hematocrit Volume
• Volume of red blood cells expressed in percentage is called as
Hematocrit Volume, or Packed Cell Volume.
• If a blood is collected in a hematocrit tube along with a
suitable anti coagulant and centrifuged for 30 minutes at a
speed of 3000 revolutions per minute, the red blood cells
settle down at the bottom having a clear plasma at the top.
• Plasma forms 55% and red blood cells forms 45 % of the total
blood.
• In between plasma and red blood cells , there is a thin layer of
White Buffy Coat. This is formed due to the aggregation of
WBC and Platelets.

7. Plasma and Serum
• Plasma is a straw colored clear liquid part of blood. It
contains 91 to 92 % of water and 8 to 9 % of solids.
• Serum is a straw colored fluid that oozes from the
blood clot.
• When the blood is shed or collected in a container, it
clots, in this process, the fibrinogen is converted into
fibrin and the blood cells are trapped in this fibrin
forming the blood clot. After about 45 minutes, serum
oozes out of the blood clot.
• Serum = Plasma minus Fibrinogen

8. FUNCTIONS OF BLOOD
• Nutritive Function
• Respiratory Function
• Excretory Function
• Transport of Hormones & Enzymes
• Regulation of Water Balance
• Regulation of Acid – Base Balance
• Regulation of Body Temperature
• Storage Function
• Defenseive Function