There are two phases in the life cycle of malarial parasite in man.They are
(1) Pre erythrocytic cycle or Exoerythrocytic cycle (in liver cells) and
(2) Erythrocytic cycle or Endo-erythrocytic cycle (inside the red blood corpuscles)
The pre-erythrocytic cycle comprises the asexual reproduction of the parasite in the liver. When an infected female Anopheles mosquito bites a person, thousands of slender, sickle shaped nucleated sporozoites are injected in the blood. The sporozoites first enter the capillary vessels of the skin and then enter the general circulation. These parasites circulate in the blood for about 30 minutes and enter into the pre-erythrocytic cycle in the reticuloendothelial cells of the liver.
The sporozoites penetrate the liver cells and develop into forms known as cryptozoites. A cryptozoite has a compact nucleus and no pigment or vacuoles. Cryptozoites rapidly grow feeding on the liver cells.