Collection of Blood
Blood present in the body system is called invivo, is in a liquid form. When blood is out from the body is called invitro, and it cloth in a few minutes, as such become solid. If the blood where discard in plain tube, and the tube is left undisturbed for some hours, the clothed blood get shrinks, living a pale yellow fluid called plasma. As shown on the picture below is picture of an anticoagulated blood.
As we can see on the above picture, if it is a clothed blood, the red cells will be surrounded by plasma of which the clothing blood will be in the center. But we see that the blood on the above picture sink to the bottom of the tube, living pale yellow plasma on the top that is an ant coagulated blood. During coagulation process, some blood constituent are use up, and white blood cells and platelet are trapped in the clothed cells.
Such blood sample is not good for hematological investigation, as such is very important to prevent the coagulation of blood that must subjected for hematological investigation. Coagulation prevention are carried out by storing the blood in an anticoagulated container. Example of anticoagulant are; Ethylene Diamine tetracetic acid (EDTA), heparin, sodium oxalate. If the blood is well mix with the anticoagulant, when centrifuge, it give a clear separation, of serum on the top, buffy coat on the center, and the red blood cell under the container as shown on the picture above. The bottom layer the packed cells and is made up of 40 to 49% of the total volume of the blood. Buffy coat is a thin whitish appear on the top of red blood cells before the serum, it account for 1% of the volume, and it contain leucocyte and platelet. Plasma or serum on the top account for 52 to 58% of the total volume. In a healthy individual this three layer are in a normal equilibrium in relation to demand and supply of the body functions. The equilibrium state of this three blood layer is known as homeostasis.
Blood sample for hematological investigation, are collected in three places which are;
Venipuncture (venous Blood)