Introduction of blood: –

Blood is a complex viscous fluid with a pH 7.4. Blood is specialized body fluids in animals that delivers necessary substances such as nutritious and oxygen to the cells and transports metabolites waste products away from the cell.

Blood function:

  • Supply oxygen to tissue
  • Removal of waste Co2 and urea
  • Maintain of body PH and body temperature
  • Immunological function
  • Supply nutrients

It is circumstance tissue of body it is mainly composed 2 parts.

  1. Cells (45%)
  2. Plasma (55%)

The total volume of blood is about 8 to 8.5% of body weight.

There are three types of cells.

  1. Red blood cells
  2. White blood cells
  3. Platelets

Blood is made in the Bone Marrow

All of the cells in the blood, red blood cells, all types of white blood cells, and platelets are made in the bone marrow. This happens primarily in the flat bones in your body such as the skull, the sternum, and the pelvis.

Blood Cell Development

All of the cells differentiate from one group of “master cells” called stem cells. The stem cells can become whatever kind of blood cell the body needs. They come under the influence of factors in their environment to become red cells, white cells, or platelets.

Bone Marrow

This microscopic view of a sample of bone marrow shows mature and immature white cells, the cells that produce platelets and both mature and immature red cells. Notice the variety.

Red Blood Cells 

Most of the cells in the blood are red blood cells. These are highly specialized cells that have been “stripped” of everything, including the nucleus that might get in the way of doing their major job, transporting oxygen.


Red blood cells are filled with a special red colored molecule called hemoglobin. It picks up oxygen in areas where oxygen is abundant and releases oxygen in tissues where the oxygen concentration is lowest.

White Blood Cells

There are five distinctly different kinds of white blood cells neutrophils, monocytes, lymphocytes, eosinophil and basophils. Some have the ability to change with needs and situations in the body. So, for example, there are different monocytes found in different tissues, and different types of lymphocytes with different roles in fighting infections. These cells can leave the bloodstream, sliding out through the vessel walls and attacking invaders at the site of an infection.


Platelets are fragments of a much larger cell, the Megakaryocyte, which stays in the bone marrow after it differentiates and matures from the stem cell.  The platelets leave the bone marrow and circulate throughout the body. When stimulated by substances from damaged tissue, the platelets release substances necessary to help blood clot. This helps initiate the clotting sequence and protect the integrity of the vasculature.


The plasma is the river in which the blood cells travel. It carries not only the blood cells but also nutrients (sugars, amino acids, fats, salts, minerals, etc.), waste products (CO2, lactic acid, urea, etc.), antibodies, clotting proteins (called clotting factors), chemical messengers such as hormones, and proteins that help maintain the body’s fluid balance. When you spin blood in a centrifuge, the red cells go to the bottom of the container, and the white cells and platelets to the middle, leaving the yellowish plasma at the top.

Components of human blood

Component Description Function
Plasma Fluid portion of blood: 90% water; 10% solutes, including proteins (primarily albumins, globulins, fibrinogen, and enzymes), glucose, amino acids, lipids, metabolic compounds, respiratory gases, hormones Transport of soluble nutrients and waste, coagulation
Cellular components

(red blood cells)

Biconcave, enucleated cells containing hemoglobin Transport O2 and CO2

(white blood cells)

Granular Neutrophils, eosinophils, basophils Phagocytosis and immune response
No granular Lymphocytes, monocytes Cellular antibody formation
Platelets Irregular, fragment-like appearance Initiate blood clotting

Plasma: – liquid medium of blood.

Serum: – serum is blood without fibrinogen.

Coagulation: – it is the process by which blood forms clots. It is important part of             hemostasis.

Fibrinogen: – it is soluble plasma glycoprotein, synthesized by the liver that is converted by thrombin into fibrin during blood coagulation.

Clotting process: – Platelets break down thrombin plastid — Pro thrombin –ca+2—thrombin — fibrinogen — fibrin — coagulation — clotting

Blood Group System

The human being has been classified on the basis of their differential blood system and this system is known as blood group system.

Blood group system on RBC: –

  1. ABO
  2. Rh
  3. MNS

Blood group system on WBC

  1. HLA

ISO enzyme pattern

  1. ESD
  2. PGA
  3. EAP

Serum protein

  1. GC
  2. GM
  3. HP

In 1901, Karl Landsteiner reported that blood had TYPES. By matching these types, one could achieve success in blood transfusion. The bases of these types are specific proteins called antigens that are found on the surface of red blood cells and antibodies found in the plasma.

There are four basic types:

  • Type A with A antigens on the red cells and B antibodies in the plasma.
  • Type B with B antigens on the red cells and A antibodies in the plasma.
  • Type AB with both A and B antigens on the red cells and no of type antibodies in the plasma.
  • Type O with no type of antigens on the red cells and both A and B antibodies in the plasma.
Blood Group Antigen Antibody Receiver Donner
A A B A, AB, O A, AB
B B A B, AB, O B, AB

(Universal Recipient)

A, B A, B, AB, O A, B, AB

(Universal Donner)

A, B O A, B, AB, O

Rh factor Blood Grouping System

Many people also have a so-called Rh factor on the red blood cell’s surface. This is also an antigen and those who have it are called Rh+. Those who haven’t are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh-blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problem.