Composition Of Blood And Haematology Biology Essay

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Blood composes of erythrocytes; containing globular protein haemoglobin that aids the efficient transport of oxygen, leukocytes; the body's defence cells, providing the body immunity, platelets; involved with blood clotting and blood plasma; transporting dissolved organic nutrients, proteins, salts, respiratory gases and nitrogenous waste products in water. Alteration of blood cell sizes, numbers, shapes and the level of maturity from the normal ranges may suggest blood disorders, caused as a result of disease or nutrient deficiency. Haematologic tests are done to diagnose these blood disorders. The parameters measured to diagnose these disorders were red cell count; 6.25 x 1012 /l, Haemoglobin content; 167g/l, Haematocrit 0.50 l/l.

Normal ranges are kept sensible by using blood samples of healthy individuals of same age, gender and if relevant, same ethnic origin, as the individual whose blood is being tested.

The Wintrobe indices MCV; 80 fl, MCH; 27pg, and MCHC; 333 g/l, were calculated by using the previously mentioned parameters. They are used in the diagnosis of the different kinds of anaemia, and diseases associated with anaemia.

Introduction

Haematology is the sub-division of medicine involved with the study of blood, blood-forming tissues and disorders of blood. There are various hematologic tests which aid haematologists in the detection of abnormalities of blood and blood forming tissues.

Haematologic test parameters are interpreted by always referencing the absolute test results with a standard normal range. Normal ranges are kept sensible by using blood samples of healthy individuals of same age, gender and if relevant, same ethnic origin, as the individual whose blood is being tested. (Bain,BJ.,2004).

Physiological variation is also taken into consideration when comparing with a standard normal range, e.g. special cases as pregnancy changes the normal ranges for an individual. (Bain,BJ.,2004).

Normal human blood is a liquid tissue composed of blood cells and platelets suspended in a liquid called plasma, rich in plasma proteins, hormones and electrolytes dissolved in water. The main function of blood is transportation of respiratory gases, waste products of metabolism, hormones, enzymes, nutrients, plasma proteins and blood cells. Also, maintenance of body temperature, pH control, removal of toxins and regulation of body fluid electrolytes.

Some haematologic tests are:

Haemoglobin (Hb) Content of a Blood Sample

Haemoglobin is the most abundant protein contained within erythrocytes aiding the efficient transport of respiratory gases. It is a globular protein with a 'haem'-group; iron-consisting ring which imparts the red colour of blood. The haemoglobin content is the concentration of haemoglobin in a sample of blood in grams per litre.

A reduction of the Haemoglobin content from normal is known as anaemia and an increase as polycythaemia. The haemoglobin content is used as an indicator of these blood disorders as anaemia and also as a guide for blood transfusions.

The standard normal ranges for haemoglobin content varies extensively in healthy individuals, with age, sex and special physiological variations such as during pregnancy. Therefore haemoglobin content of an individual falling off a certain range does not necessarily mean the individual is ill. Other parameters should also be taken into consideration for the diagnosis.

Red Cell Count (RCC)

Red cell count /erythrocyte count is the number of erythrocytes in a litre of blood. This denotes the oxygen carrying capacity of blood. Erythrocytes contain haemoglobin which aids the distribution of oxygen in erythrocytes. RCC is a used as indicator of blood disorders such as polycythaemia; usually accompanied by an increase or anaemia; a decrease in number of erythrocytes. (Ravel,1995). A microscopic count could be performed using a Neubauer haemocytometer. This is calibrated such that the chambers correlate with an appropriate volume of the fluid added.

Haematocrit (Hct)/ Packed Cell Volume (PCV)

Haematocrit is the proportion of blood volume that is occupied by erythrocytes expressed as a percentage of the whole. Erythrocytes are specialised for the delivery of oxygen into body cells and transport of carbon dioxide to the lungs for excretion. Blood plasma, transports dissolved organic nutrients, proteins, salts, respiratory gases and nitrogenous waste products in water and the buffy coat with leukocytes make up the rest of the blood. Haematocrit and Haemoglobin content tests are major tests in the diagnosis of anaemia and polycythaemia. Haematocrit is extensively used as indicator of dehydration, haemorrhage, and hence the need of a blood transfusions and as a measure of effectiveness of blood transfusions.

Mean Cell Volume (MCV)

Mean Cell Volume is the average size of the erythrocytes usually measured in femtolitres. This affects the Haematocrit greatly. The larger the erythrocytes in a unit volume of blood, the larger will be their cellular mass that and densities, resulting in a larger haematocrit. Vice versa for smaller erythrocytes. The MCV varies along with the variation of the mean cell haemoglobin according to the body's need of folic acid, Iron, Copper, or/and Vitamins B12 and B6. (Ravel,1995).

Mean Cell Haemoglobin (MCH)

Mean Cell Haemoglobin is the average content of haemoglobin in an erythrocyte. MCH is affected by the size and number of erythrocytes when their haemoglobin contents are normal. MCH also varies with the variation of the haemoglobin content in relation to size of erythrocytes. (Ravel,1995).

Mean Cell Haemoglobin Concentration (MCHC)

Mean Cell Haemoglobin Concentration is the average concentration of haemoglobin in erythrocytes per unit volume. Thus it varies according to the haemoglobin content and the volume of erythrocytes. (Ravel,1995).

The MCV, MCH and MCHC are called Wintrobe indices and are calculated by using the parameters RCC, Haemoglobin content and Haematocrit. They are used in the diagnosis of the different kinds of anaemia, and diseases associated with anaemia. (Ravel,1995).

White Cell Count (WCC)

In order to observe leukocytes, they are stained in Leishmann's stain; consisting of methylene azure and eosin dissolved in 100% methyl alcohol. White cell count denotes the numbers of white blood cells in a given volume of blood. The numbers change in response to parasite infection, invasion of foreign particles.

Leukocytes are the body's defence cells; they attack and destroy the parasite or foreign particles, providing the body immunity. The numbers of each type of leukocytes increases according to the invading foreign particle:

Neutrophils:-are attracted to sites of infection and perform phagocytosis of parasites destroying them.

Eosinophils:- same function as neutrophils, and has a role in allergic responses

Basophils:- involved in the control of parasitic infections, allergic and inflammatory responses, and has a role in immediate hypersensitivity reactions

Lymphocytes:-mediates immune responses; humoral immunity; secretes anti-bodies (B-lymphocyte, attack cells with foreign antigens (T-lymphocytes) and natural killer cells attacks foreign cells or tumour cells.

Monocytes:- phagocytosis of parasites, dead and worn-out cells of body. They differentiate to become macrophages.

Leukocytes having different immune responses to different parasites can be used as an indicator in diagnosing different diseases. This is called a differential white cell count.

WCC is widely used for the diagnosis of the blood cancer leukaemia; uncontrolled increase of leukocytes.

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