Question 308

exposure of platelets to collagen causes them to develop pseudopodia, facilitating adhesion. Platelets thereby participate in haemostasis and formation of the temporary platelet plug.

B) Platelets are non-nucleated fragments of megakaryocytes and therefore cannot develop a multilobed nucleus. Multilobed nuclei are described in mature neutrophils.

C) platelet granules as stores of biologically active substances but does not identify loss of dense granules as the morphological mechanism of collagen-induced adhesion. Pseudopodia are specifically described.

D) Multinucleated giant cells may arise from macrophage lineage in chronic infections such as tuberculosis or leprosy. This is unrelated to platelet adhesion.

E) A biconcave disc is the characteristic morphology of an erythrocyte. Platelets exposed to collagen instead form pseudopodia.

Saxena. Textbook for MRCOG-1. Physiology - Haematology - Platelets, p.70.