Questions & Answers

Smallest blood cells are
(d)None of the above

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Hint: These are also called thrombocytes. They do not have a nucleus and their main function is to stop bleeding. Its normal count is 1.5 lakh to 4.5 lakh per microlitre of blood but in case of dengue fever, its count goes down to 20,000 or even lower.

Complete answer:
The smallest blood cells are platelets. The diameter of platelets is only about 20% of the diameter of red blood cells. Platelets are very small irregularly shaped fragments of cytoplasm which are derived from the fragmentation of megakaryocytes of the bone marrow and then enter the circulation system.

Additional Information: -A blood cell is also known as hemocyte or hematocyte is found mainly in blood. The three main types of blood cells include red blood cells or erythrocytes, white blood cells or leukocytes, and platelets or thrombocytes.
-These three kinds of blood cells together make 45% of the blood tissue by volume with the remaining 55% of the volume composed of plasma, the liquid component of blood.
-Platelets circulate in the blood, involved in hemostasis, and leading to the formation of blood clots by releasing thread-like fibers to form these clots.
- The normal count of platelets is 1.5 to 4.5 lakh per cubic millimeter.
-If the number is too low excessive bleeding can occur or if the number is too high blood clots can form thrombosis which may obstruct blood vessels and may result in a stroke or blockage of blood vessels.
-Platelets release growth factors that stimulate the deposition of the extracellular matrix.
-These factors have been shown to play a significant role in the repair and regeneration of connective tissue.
So, the correct answer is,’ platelets’.

Note: -The average lifespan of a platelet is about 5 to 9 days only and these are natural sources of growth factors.
-A disease-related to platelets is called thrombocytopathy.
-If the number of platelets is low then it is called thrombocytopenia.
-If the function of platelets has decreased the disorder is known as thrombasthenia and also if the number of platelets is higher or increased the disorder is called thrombocytosis.
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