Practical Physiology: A New Approach Sameer Mohommed Khan
INDEX
×
Chapter Notes

Save Clear


1Hematology
  • 1. Introduction to Hematology
  • 2. Compound Microscope
  • 3. Collection of Blood Sample
  • 4. Hemocytometry
  • 5. Estimation of Hemoglobin
  • 6. Total Erythrocyte Count
  • 7. Total Leukocyte Count
  • 8. Differential Leukocyte Count
  • 9. Determination of Hematocrit/Packed Cell Volume
  • 10. Red Blood Cell Indices
  • 11. Erythrocyte Sedimentation Rate
  • 12. Determination of Blood Groups
  • 13. Estimation of Bleeding Time and Clotting Time
  • 14. Estimation of Platelet Count
  • 15. Absolute Eosinophil Count
  • 16. Reticulocyte Count
  • 17. Determination of Osmotic Fragility2

Introduction to HematologyChapter 1

 
DEFINITION
Hematology is defined as branch of science concerned with the study of blood, blood forming tissues and the disorders associated with them. The word hematology is derived from Greek word “Haima” meaning blood and “logos“ meaning study. It includes:
  1. Analysis of the concentration, structure and functions of the cells and their precursors in the bone marrow.
  2. Analysis of chemical constituents of plasma or serum intimately linked with blood cell structure and functions.
  3. Study of functions of the platelets and proteins involved in coagulation of blood.
  4. The hematology laboratory deals with routine determination of total number of cells in circulation, hemoglobin concentration and differential count of leukocytes based on the study of the stained blood smear.
 
COMPOSITION OF BLOOD
Total blood volume: 5–6 liters (8% of body weight).
Specific gravity: 1050–1060
Viscosity: 4–5 times that of water
pH: 7.4±0.05, alkaline
Blood is very different from other body tissues. Blood is made of a solid and a liquid portion. The liquid portion is called plasma. The solid portion is comprised of cells (Fig. 1.1).
 
Cellular Component
The cellular elements of blood represent 45% of the total blood volume and consist of red blood cells (RBC or erythrocytes), white blood cells (WBC or leukocyte) and platelets (thrombocytes).
  1. RBC: Normal count—5 million/cu mm of blood. These are medium-sized cells ranging from 
7 to 8µm in diameter. These constitute the highest number of formed elements in circulation. The main function of RBC is transport of gases across the tissues and the lungs.
  2. WBC: Normal count—4000–11000/cu mm of blood. These are largest of all the cells with size ranging from 8 to 20 µm. These play an important role in the defence mechanism of the body.
    4
    zoom view
    Figure 1.1: Components of blood
  3. Platelets: Normal count—1.5–4.5 lakhs/cu mm of blood. These are the smallest cells with a size of 2–4µm. These have an important role in the process of hemostasis.
    The development of blood cells is called as hemopoiesis that takes place in the bone marrow.
 
Liquid Component
  1. Plasma: Plasma is a clear straw-colored fluid portion of the blood and represents about 55% 
of the total blood volume and 5% of the body weight. It contains 91% water and 9% solids 
(1% inorganic and 8% organic molecules, respectively). Plasma plays an important role in transportation of nutrients, hormones and chemicals within the body through the blood vessels.
  2. Serum: Plasma consists of soluble protein called fibrinogen. During the process of coagulation fibrinogen is removed from plasma as fibrin and the clear fluid left behind is called serum. Therefore, to obtain plasma for diagnostic tests blood should not be allowed to clot. The serum contains most of the chemicals present in the plasma except for fibrinogen and some clotting factors (2, 5 and 8). It has higher serotonin content because of breakdown of platelets during clotting.
 
FUNCTIONS OF BLOOD
  1. Transportation of gases: It transports oxygen from the lungs to the tissues and carbon dioxide from tissues to the lungs.
  2. Supply of nutrients: Blood transports various food materials like glucose, amino acids, fatty acids, vitamins, electrolytes and trace materials from the GIT to various tissues for further utilization and storage.
  3. 5Excretion of metabolic wastes: Blood performs the excretory function by getting rid of metabolic wastes like urea, uric acid and creatinine through the kidney, skin and intestine.
  4. Homeostatic function of blood: Blood maintains the body homeostasis by playing a role in the maintenance of body fluids in terms of volume, composition, pH and temperature which is regulated to normal physiological limits with respect to minor changes in the blood.
  5. Regulation of body temperature: As the major component of blood is water it plays a role in regulating the body temperature by exhibiting the properties of high specific heat, high conductivity and high latent heat of evaporation.
  6. Chemical for communication: It acts as a chemical of communication as it transports various hormones, antibodies and many other chemicals within the body.
 
HEMATOLOGICAL TESTS
The hematological tests are done as a part of the routine tests and include estimation of hemoglobin, total RBC count, total WBC count, ESR, PCV and the differential leucocyte count. These are mainly performed to detect the presence of disease and also to know the extent and the patient's ability to fight diseases.
Here from the first year point of view you are expected to acquire knowledge about the formed elements of blood, their enumeration and their characteristics, to perform and analyse these tests accurately.
You are also expected to learn and remember the formation, structure and functions of blood cells, the basic principle of determination, use and care of the various instruments used, calculation, interpretation and representation of the results.
For the ease of understanding the practical, every practical has to be studied systematically in the following order:
Name of the practical:
_______________________________________________________
Name of the method:
_______________________________________________________
Principle of the experiment:
_______________________________________________________
Requirements:
_______________________________________________________
Precautions to be followed:
_______________________________________________________
Procedure:
_______________________________________________________
Observation:
_______________________________________________________
Calculation:
_______________________________________________________
Results:
_______________________________________________________
Clinical Importance:
_______________________________________________________
 
QUESTIONS
  1. Define hematology?
  2. Enumerate the functions of blood?
  3. Mention the composition of blood?