الفهرس 
Genetic PrinciplesOnly 14 pages are availabe for public view
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Abstract
-147- SUMMARY Haemopoiesis
Haemopoiesis may be medullary or extramedullary. The bone marrow produces each day about 2.1 x 10 red cells, it has also large reserve capacity in response to increased demands Extramedullary haemopoiesis is a term applied to blood formation in organs other than the marrow e.g. the spleen, liver and the lymph nodes, they are the site of myeloid metaplasia in response to increased demand for cells following haeinorrhage or haemolysis (De Grucby, 1972). Erythropoiesis
Erythropoiesis comprises these biological processes of cell differentiation, proliferation, biosynthetic activities and maturation which provide erythrocytes
and hemoglobin (Hb) in appropriate amounts for the respiratory gas transport requirements of the organisms (Douglas 1974). All the blood cells are developed in the bone marrow from one stem cell called colony forming unit which proliferates and differentiates to give different series of bl. cells. Factors that determine erythropoiesis.
(1) Arterial 02 content and tissue 02 tension.
A decrease in 02 content stimulates erythropoiesis
while an increase depresses it.
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(2)Erythropoietin.
The effect of 02 tension on the rate of
erythropoiesis occurs through the erythropoietin produced in response to 02 lack, the kidney is the site of its production or activation
(Talaat, 1973).
(3)Dietary factors
Proteins, iron, vitamin B12, folic acid, cobalt,copper, vitamin c and hormones as thyroxine. Phzsioloa of red blood cells
The adult red blood cell is a non nucleated cell, shaped as flat biconcave disc, it is pliable and flexible. It may be regarded as a frame work of protein in which is contained the Hb and at its outer surface is the red cell membrane. The red ’,tell membrane is semipermeable, it is consisted of bimolecular leaflet of lipids covered exter-nally and internally by a layer of protein changes in its lipid composition influence its flexibility (Cooper et.al., 1975) The bl. group antigens are situated on the surface Hb is conjugated protein consisted of 4 molecules of haem attached to each molecule of globin, Haem is composed of protoporphyrin and ferrous iron it is a red pigment (De Gruchy 1972) Normal human Hb exists in 2 main forms
mainly adult and foetal Hb (HbA & HP) and in small quanti-ties HbA2 is present, they differ in the structure of the.
Hb moeity.
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Function of the red cells
The primary role of the red cell is to transport 02’ a function, made possible by the Hb within the erythrocyte. The amount of 02 delivered to tissues by
oxygenated blood is dependent on Hb content, the rate of bl. flow, and on the affinity of Hb for 02 that can be significantly reduced by certain phosphate compounds as 2,3 DPG, (Kerr, 1970). Red cell breakdown
The normal red cell has a definite life span in the circulation of 120 ± 20 days. As the cell becomes older enzymatic activity is decreased membrane is lost and cell pliability is decreased the red cell is no longer able to traverse the microvascnlature and is phagocytosed by the RE tissues especially the spleen
(Weiss, 1972) The Hb is broken down, the globin is split-ted off from the haem, the globin is reutilised and the haem is broken into iron and Porphyrin. The iron
passes to blood stream to be either reutilised or stored. The prophyrin is broken down to bilirubin.
Anaemia
Anaemia may be defined as a reduction in the concent-ration of Hb in the peripheral blood below the normal for the age and sex of the patient. Following the reduction
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in the 02 carrying capacity of the blood, the body brings to play several compensatory mechanisms to make the most effective use of the available Hb:
(1)An increase in the cardiac output and in the rate of blood dirculation, with a state of hyperkinetic circulation.
(2)The Hb delivers to the tissues more than the usual proportion of its oxygen, this is aided by a shift to the right in the 02 dissociation curve.
(3)The blood volume is kept at normal by expansion of plasma volume to maintain an adequate circulation.
(4)There is some deviation of blood flow from tissues with lesser 02 requirements to those with greater requirements. So the compensatory mechanisns commonly allow the patient to be symptom-free at rest, but exertion causes symptoms by increasing 02 requirements (Oski and Delivoria 1970). Classification of anaemia (Michael Beard 1977)
(A) Aetiological classification
(1)Due to diminished production of normal Reo.c. - Deficiency of iron, vitamin B12, C, folic acid
and thyroxine.
Pancytopenia ”aplastic anaemia.
(2)Due to excessive blood destruction ”haemolytic anaemia Hereditary red cell defects.
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Cardiovascular system.
Dyspnea and palpitation on exertion, soft mid systolic haemic murmur that disappears on correction of the anaemia.
Central nervous system.
Giddiness, faintness, headache, lack of concentr-
ation.
Renal system.
Slight proteinuria and impairement of the concentr-ating power of the kidney are not uncommon in severe anaemia.
Gastro-intestinal system.
Anorexia, nausea, and constipation may occur splenomegaly and slight to moderate hepatomegaly are common. The principles in the diagnesis of anaemia
from the detection of signs of anaemia, its
presence and degree can be established only by Hb estimation.
The cause of anaemia is determined from
(a)The history: Rapid onset (acute bleeding or haemolysis or acute leukemia).
(b)Complete physical examination
Skin: pallor, petechiae and ecchymosis
Nails: koilonychia and brittleness Conjunctiva pallor and icterus
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Abdomen: Hepatomegaly, aplenomegaly
Bones: tenderness especially of sternum:. (o) The blood examination
Hb estimation, blood film examination, white cell count,. PCV, reticulocyte count and ESR. (d) When necessary further special investigations. Management of an anaemic patient
The principles of management are:-
(1)Treatment of the disorder causing anaemia.
(2)Administration of specific haematinics when indicated.
(3)treatment of symptoms.
1) Treatment of the disorder causing anaemia
a)Arrest of blood loss as it is the commonest cause of anaemia.
b)Correction of a dietary deficiency as anorexia, bad habits.
c)Treatment of an underlying systemic disorder as infection, renal failure, malignancy.
d)Removal of a toxic chemical agent or drys.
2) The administration of haematinics
Iron can be administred orally e.g. ferrous sulphate gluconate or succinate.
Vit B12 and folic acid in case of megaloblas-tic anaemia.
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3) Symptomatic and supportive treatment
Well balanced diet, blood transfusion is the most important supportive measure in treatment of anaemia Polycythaemia
An increase in the number of red cells per c.mm blood above the normal for the age and sex of the patient.
Erythrocytosis means an increase in the red cells secondary to some underlying disorder and erythraemia is a term used to describe idiopathic polycythaemia vera.
Secondary polycythaemia
A polycythaemia resulting from some known primary disorders, the increase in the red cell values relates to one of the following:-
1)Compensation for generalised hypoxia: accompanied living in high altitudes, congenital heart diseases chronic pulmonary diseases.
2)Abnormalities of 02 transport.
3)Renal diseases with inappropriate erythropoietin.
The clinical pictures are those of the causative. disorder together with cyanosis of varying degrees and headache, tinnitus and vomiting. Polycythaenria verat-
It is a disease of unknown cause characterised
by hyperplasia of all the cellular elementsof the bone marrow, with resultant sustained elevation of the
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erythrocyte count and the Hb. and to a lesser extent leucocytosis and thrombocytosis. It may be regarded as a neoplastic disease of the erythropoietic tissue.
The clinical manifestations include headache, diz-ziness ringing in the ears or visual disturbances they are associated with hypertension. The increased PCV and viscosity tends to slow the blood flow rate that predisposes to thrombosis, Pruritis may be atroublesome, the spleen is palpable in 75% of patients and less com-
monly the liver may be enlarged the major causes of death are thrombosis, haemorthage,,congestive heart failure and leukaemia. Treatment
1)Venesection for rapid relief of symptoms
2)Radioactive phosphorous P32
3)Myelosuppressive dr4gs e.g. chlorambucil
4)Symptomatic measures. Relative polycythaemia
In relative polycythaemia, the total number of red cells in the body is not increased, but the raised cell values are due to haemoconcentration resulting from a decrease in the total plasma volume or sometimes its redistribution. (Harrit 1973).