A) release of merozoites from RBCs
B) entry of sporozoites into blood capillaries
C) entry of cryptomerozoites into RBCs
D) entry of merozoites into liver cells
Correct Answer: A
Solution :
Erythrocytic cycle of Plasmodium occurs in RBCs and begins when a cryptomerozoit or micro-metacryptomerozoite enters into an RBC. After entering into RBC a merozoite becomes rounded disc like young trophozoite. A large non-contractile vacuole appears in its centre pushing the cytoplasm and nucleus to giving a signet ring appearance to the trophozoite. Soon the vacuole disappears and the trophozoite becomes some what amoeboid. Now the trophozoite starts feeding more actively on cytoplasm of RBC. In \[\frac{1}{2}\] to\[2\frac{1}{2}\] days the young trophozoite grows into an adult occupying almost the entire RBC. Its nucleus undergoes repeated mitotic divisions forming 8-26 daughter nuclei and preparing the trophozoite for schizogony. The daughter nuclei migrate to periphery of erythrocyte, surrounded by cytoplasm to form 8-26 small, oval uninucleate merozoites or schizozoites. On completion of schizogony both schizont and host RBC burst due to pressure of merozoites. The accumulation of haemozoin granules (acquire trophozoite) and probably also some other toxic substances in blood causes the characteristic attack of malarial fever initially after about four erythrocytic cycles and than after each cycle.
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