Which component forms an adhesive bridge between platelets and vascular subendothelial structures in the clotting process?

Choice A rationale:

Adequate platelet production does not explain the prolonged bleeding times in von Willebrand disease. These patients often have normal platelet counts, but their platelets do not function properly due to the absence or dysfunction of von Willebrand factor.

Choice B rationale:

Deficiency in intrinsic clotting system factor is not the primary cause of prolonged bleeding times in von Willebrand disease. The deficiency or dysfunction of von Willebrand factor, a protein that helps platelets adhere to the blood vessel walls and clot properly, is the key issue in this disorder.

Choice C rationale:

Impairment of the thrombin fibrinogen reaction does not directly relate to von Willebrand disease. This disorder primarily involves platelet dysfunction and variable factor VIII deficiencies, leading to prolonged bleeding times.

Choice D rationale:

Variable factor VIII deficiencies and platelet dysfunction are characteristic of von Willebrand disease. Factor VIII helps with blood clotting, and its deficiency, along with impaired platelet function, contributes to the prolonged bleeding times in patients with von Willebrand disease.

Choice B rationale:

A decrease in plasma renin levels is not a known cause of primary hypertension. Primary hypertension often has no identifiable cause, and it is a diagnosis of exclusion.

Choice C rationale:

Too much plaque in the blood vessels describes atherosclerosis, which is a risk factor for hypertension but not the direct cause of primary hypertension. Plaque buildup narrows arteries and increases resistance, contributing to elevated blood pressure.

Choice D rationale:

Kidney disease can cause secondary hypertension but is not the most common cause of primary hypertension. Primary hypertension, also known as essential hypertension, is the most common form, and its exact cause remains unknown in many cases.