Introduction to Hematology - What Is Hematology? 

What Is Hematology?

What Is Blood?

                                        

• Blood is sometimes considered to be a fluid connective tissue because of the mesenchymal origin of its cells and a low ratio of cells to liquid intercellular substance, the blood plasma.


• In human adults about 5 liters of blood contributes 7-8 % to the bodyweight of the individual.


• The contribution of red blood cells (erythrocytes) to the total volume of the blood (hematocrit) is about 43%.


• Erythrocytes are the dominant (99%) but not the only type of cells in the blood.


• We also find leukocytes and, also, blood platelets. Erythrocytes, leukocytes, and blood platelets are also being referred to as the formed elements of the blood.


• Erythrocytes and blood platelets perform their functions exclusively in the bloodstream.


• In contrast, leukocytes reside only temporarily in the blood.


• Leukocytes can leave the bloodstream through the walls of capillaries and venules and enter either connective or lymphoid tissues.


Approximately 8% of an adult's body weight is made up of blood.


• Females have around 4-5 liters, while males have around 5-6 liters. This difference is mainly due to the differences in body size between men and women.


• It has a pH of 7.35-7.45.

• Whole blood is about 4.5-5.5 times as viscous as water, indicating that it is more resistant to flow than water.


• This viscosity is vital to the function of blood because if blood flows too easily or with too much resistance, it can strain the heart and lead to severe cardiovascular problems.

• Blood in the arteries is a brighter red than blood in the veins because of the higher levels of oxygen found in the arteries.


• An artificial substitute for human blood has not been found.

Plasma proteins

There are three major categories of plasma proteins, and each type of proteins has its specific properties and functions in addition to their overall collective role:


1. Albumins, which are the smallest and most abundant plasma proteins.


2. Globulins, which can be subdivided into three classes from smallest to largest in molecular weight into alpha, beta, and gamma globulins.


3. Fibrinogen, which is a soluble precursor of a sticky protein called fibrin, which forms the framework of a blood clot.


4. Amino acids These are formed from the breakdown of tissue proteins or the digestion of digested proteins.


5. Nitrogenous waste Being toxic end-products of the breakdown of substances in the body, these are usually cleared from the bloodstream and are excreted by the kidneys at a rate that balances their production.


6. Nutrients Those absorbed by the digestive tract are transported in the blood plasma. These include glucose, amino acids, fats, cholesterol, phospholipids, vitamins, and minerals.


7. Gases Some oxygen and carbon dioxide are transported by plasma. Plasma also contains a substantial amount of dissolved nitrogen.


8. Electrolytes The most abundant of these are sodium ions, which account for more of the blood's osmolarity than any other solute.

Functions of the blood

1. Nutritive: The blood transports nutrients from the gut to all parts of the body for use or storage.


2. Respiratory: the blood carries the oxygen to the tissue and removes carbon dioxide and other waste products from the tissues to be excreted by the lung, kidney, liver, and skin.


3. The blood regulates the temperature of the body because it is constantly in motion


4. Transportive: The blood transports gases and hormones.


5. Excretory: To excrete the waste products of metabolism, for example, urea, and uric acid.


6. Protection: versus invading microorganisms