Question

1) a person suffering from dengue has negligible blood clotting why? 2) we measure blood presure wth artery but not with vein? 3)in old person some bluish vessels are seeing under the skin? 4) we measure the pulse over the radial artery in the wrist?

Answer 1

1) because the dengue virus specifically reduces the number of platelets in blood which are responsible for blood clotting. it is similar in the case of malaria.
2) blood pressure is measured by the artery because presssure exerted on the vein is very less as compared to the artery which carries blood from heart to all parts of the body.also veins have valves to prevent backflow which results in negligible pressure whereas arteries carry blood away from the heart at maximum rate and hence pressure is really high.
3) an old person's skin is loose enoght to give away the structures of the veins also this cannot only be seen in old people everyone has few veins showing because veins are not deep seated as arteries.