Page 309 - The Veterinary Laboratory and Field Manual 3rd Edition

chapter 5

Haematology

Susan C. Cork and Roy Halliwell

5.1 Introduction blood volume and the appearance
and characteristics of blood cells
Haematology is the study of blood. A number of
organs are involved in the production and recy- Red blood cells are also known as erythrocytes.
cling of red and white blood cells in the body, In most domestic animals, erythrocytes account
these organs form the haematopoietic system. for about 30–40% of the total blood volume. The
In this chapter, we will outline the principles of remaining components of the blood include the
haematology and explain some of the terminol- white blood cells, plasma proteins and water.
ogy used. The collection of blood samples and The total blood volume is generally considered
the techniques used to assess them are also out- to be 10% of the body weight of the animal, for
lined in this chapter. A more detailed description example a 300 kg cow has about 30 l of blood
of white cell function is given in Chapter 6. whereas a 25 kg dog has about 2.5 l of blood.
A healthy animal will develop signs of shock
if it loses > 25% of its blood volume but it is
the haematopoietic system: usually safe to take up to 10% of the blood vol-
terminology ume from a donor animal for the purposes of
blood transfusion, that is, 3 l from a 300 kg cow,
Haematopoiesis (haemopoiesis) is the formation 5 l from a 500 kg horse and so on.
of red and white blood cells. The haematopoi- Mature red blood cells in mammals do not
etic system is widely distributed in the body and have a nucleus and are shaped like biconcave
includes organs, such as the liver, which have discs in many species. However, in deer and
additional functions. The main role(s) of the camelids (camels, lamas and so on) the red cells
organs involved in blood cell production and are elliptical or sickle shaped. In birds, reptiles
recycling are summarized in Table 5.1. In cases and fish mature red blood cells are nucleated and
of anaemia or in disorders of the white blood are oval to round in shape.
cells it is important to evaluate the function of White blood cells, also known as leukocytes,
the whole haematopoietic system in order to are an important component of the immune
identify the source of the problem. system in animals, although they only occupy a
very small percentage of the blood volume. The
number of white blood cells and their composi-
tion will change in response to immune triggers,
such as infection and inflammation. The relative

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