Prothrombin is a glycoprotein in the liver with the help of vitamin K and present in the blood plasma in the normal concentration 15 to 20mg. per 100ml. of plasma. Normally there in a large excess of prothrombin in plasma over the amount required for effecting coagulation of blood. Therefore, a reduction of prothrombin to a large extent is required before a prolongation of the coagulation time is noticed. Prothrombin has a molecular weight of 62700 and reveals the presence of 18 amino-acids after quantitative analysis. When purified prothrombin is placed in 25% sodium citrate solution, an autocatalytic transformation of it to thrombin occurs. The prothrombin activators like ca-ions, thromboplastin, Factors V, VII, VIII, PTC, PTA and platelets derivatives are regarded as catalysts.
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- DEFECTS IN COAGULATION FACTORS A study of the normal blood coagulation process reveals a two-stage reaction in which four main concepts about the chemistry of blood coagulation are integrated in proper order. The first stage of the reaction, in which the prothrombin of plasma is activated to thrombin represents a co-ordination of the first two concepts, viz., (1) prothrombin activation and (2) inhibition of prothrombin activation. The second stage of the reaction in which thrombin interacts with plasma fibrinogen...
- DEFECTS IN PLATELETS Platelets are derived from megakaryocytes of bone marrow. These are oval and thin, non-nucleated discs 2 to 3 microns in diameter. Normal count – 250,000 – 500,000 per c.mm. of blood. Agglutination of platelets is favoured by substances exuded by injured tissue, and inhibited in vitro, by anticoagulants like citrate or oxalate, or in vivo, by heparin and dicoumarol. Their number is increased by the acute blood loss, trauma, partial asphyxia and splenectomy. The platelets...
- Defects in the Intra-Vascular Factors The arteries, veins and capillaries, all posses the property of contractility on injury. In small vessels with minute ruptures, local vasoconstriction together with the deposition of platelets from flowing blood on the vessel wound may successfully seal off the gaps without the help of blood coagulation. But, when a large vessel is ruptured, these two physical processes are unable to seal off the gap in the blood vessel without the help of coagulation of blood....
- ANEMIAS DUE TO BLOOD LOSS ACUTE HAEMORRHAGE Severe anemia following acute blood loss may occur after post-traumatic haemorrhage, ruptured duodenal ulcer, ectopic pregnancy and in haemophilia. The blood volume is first replaced by plasma, and there is a lowering of haemoglobin, marked increase in the platelets and leucocytes. In acute blood loss the R.B.C. and HB estimations give misleading informations regarding blood loss until the dilution of the blood by the tissue fluids has restored the blood volume 12 to...