Question

Tooth extraction in a person causes death due to excessive bleeding. This is because of

• A. Absence of prothrombin
• B. Presence of plasma factor that causes haemorrhage
• C. Presence of plasma factor that prevents blood clotting
• D. Absence of plasma factor required for haemorrhage

Answer 1

Answer: (A)

Absence of prothrombin

Prothrombin is a glycoprotein occurring in blood plasma and is an essential component of the blood-clotting mechanism. Prothrombin is transformed into thrombin by a clotting factor known as factor X or prothrombinase; thrombin then acts to transform fibrinogen, also present in plasma, into fibrin, which, in combination with platelets from the blood, forms a clot (coagulation). Under normal circumstances, prothrombin is changed into thrombin only when an injury occurs to the tissues or circulatory system or both; therefore, fibrin and blood clots are not formed except in response to bleeding. Hypoprothrombinemia, a deficiency in prothrombin, is characterized by a tendency to prolonged bleeding. It is usually associated with a lack of vitamin K, which is necessary for the synthesis of prothrombin in the liver cells.