The basic event in the formation of a blood clot is the change of:
Thrombin to prothrombin.
Fibrinogen to fibrin.
Vitamin K to prothrombin.
Fibrin to fibrinogen.
The Correct Answer is B
This is because fibrinogen is a soluble protein in the blood plasma that is converted to insoluble fibrin strands by the enzyme thrombin during blood clotting. Fibrin forms a mesh-like network that traps platelets and other blood cells to form a clot.
Choice A is wrong because thrombin is not converted to prothrombin, but rather prothrombin is converted to thrombin by another enzyme called prothrombinase.
Choice C is wrong because vitamin K is not converted to prothrombin, but rather vitamin K is required for the synthesis of prothrombin and other clotting factors in the liver.
Choice D is wrong because fibrin is not converted to fibrinogen, but rather fibrinogen is converted to fibrin as explained above.
Normal ranges of fibrinogen in the blood are 200 to 400 mg/dL.
Normal ranges of prothrombin time (a measure of how long it takes blood to clot) are 11 to
13.5 seconds.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Capillary walls consist of a single layer of epithelial cells, and they exchange substances in the blood for substances in the tissue fluid surrounding body cells.
This single layer of cells is called the endothelium and it forms the barrier between the blood and the interstitial fluid.
The endothelium can be either continuous or fenestrated, depending on the tissue type and function.
The capillaries are very thin and allow red blood cells to flow through them single file.
The capillaries also have a layer of a glycoprotein called the glycocalyx that covers their luminal surface.
Choice B. False is wrong because it contradicts the definition and structure of capillaries.
Capillaries are not made of multiple layers of cells, nor do they prevent the exchange of substances between the blood and the tissue fluid.
Correct Answer is B
Explanation
Innate defenses counter specific disease-causing agents, whereas adaptive defenses include mechanical and chemical barriers.
Choice A is wrong because it confuses the two types of defenses.
Innate defenses are nonspecific and include physical barriers such as the skin, molecules that are toxic to invaders, and phagocytic cells that ingest invaders.
Adaptive defenses are specific and are activated by the innate immune system.
They involve the production of antibodies and specialized cells that recognize and eliminate specific pathogens.
Normal ranges are not applicable in this question as it is about the definitions of innate and adaptive defenses.
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