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المرحلة 2
أستاذ المادة افراح حاتم عمران ألبو موسى
3/30/2011 8:43:08 AM
Malaria parasites
They belong to the genus Plasmodium, which belong to the superclass Sporozoa. The genus have many species affecting man are:
P. malariae, the cause of quartean malaria.
P. vivax, the cause of benign tertian malaria.
P. ovale, the cause of tertian malaria.
P. falciparum, the cause of malignant tertian malaria.
The genus Plasmodium have two stages in life cycle:
1- Schizogony (Asexual cycle), occur in vertebrate host like human and birds.
2- Sporogony (Sexual cycle), occur in female mosquitoes, the genus Anopheles of mosquito transport the malaria to the human, while the genus Culex to the birds.
1- Schizogony occur in human after the sporozoites (the infective stage to human) inoculated by the infected Anopheles remain in the blood about half an hour. From the blood they enter the paranchyma cells of the liver. These called exoerythrocyte cycle because it occur outside RBCs, in this cycle sporozoite undergo asexual division by multiple fission or segmentation to produce schizont, and then the nucleus divided into small parts each one surrounded by a cytoplasm to form a merozoite, then the large number of merozoites dystroyed the liver cells and re-infection of liver cells except P. falciparum doesn t reinfected other liver cells.
Other cycles in schizogony erythrocyte cycle, which began when merozoites enter to RBCs, the shape of parasite in this stage as a thin circle of cytoplasm and neuclic material (chromatin) aggregate in one end to form a ring stage. thus, these stage enlarged and form a trophozoite, and merozoites develop into sexually different cells, the male and female gametocyte. The gametocytes continue their development in the mosquito vector.
2- Sporogony, represent the second stage of life cycle of parasite, which occur in female Anopheles when absorbe the blood of infected human.
In the midgut of the mosquito the gametocytes become male and female gametes. The male gametes (microgametes) arise by a process of exflagellation. The union of a microgametes and macrogametes (female gametes) leads to the formation of zygote. Within 4-6 hours of its formation the zygote is transformed into motile organism (ookinete), it penetrates the wall of the gut and become transformed into a circular body, the oocyst, inside it sporozoites develop from germinal cells, known a sporoblasts. The sporozoites emerge from the oocysts and migrate to the cells of salivary gland and enter the host tissues (human) during the act of feeding of mosquito.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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