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Difficulty: HardKingdom Protista: Protozoa and Unicellular Algae

During the infection cycle of the parasitic protozoan responsible for malaria, motile sporozoites are introduced into the human bloodstream via a mosquito bite. Before invading erythrocytes to cause clinical symptoms, which specific primary target organ cells must these sporozoites first invade and multiply within during the exo-erythrocytic schizogony phase?

  1. Hepatocytes of the liverAnswer
  2. B
    Plasmodium falciparum cells in blood plasma
  3. C
    Renal tubule cells of the kidney
  4. D
    Chloroplast-containing epithelial cells

Answer

Hepatocytes of the liver are the primary target cells invaded by Plasmodium sporozoites during exo-erythrocytic schizogony.
Sporozoites injected into the human host by an infected female Anopheles mosquito travel through the bloodstream to the liver. There, they invade hepatocytes and undergo exo-erythrocytic schizogony, producing thousands of merozoites that subsequently rupture from liver cells to infect erythrocytes.

Step-by-Step Solution

1
Identify the infective stage of Plasmodium entering the human host.
Infective sporozoites are injected into human blood capillaries by an infected female Anopheles mosquito.
Sporozoites represent the motile stage produced in the mosquito salivary glands.
2
Trace the initial migration path of sporozoites within human tissues.
Sporozoites quickly leave the vascular circulation and specifically target the liver parenchymal cells (hepatocytes).
Surface circumsporozoite proteins bind specifically to receptors on hepatocytes.
3
Analyze the intracellular developmental stage prior to red blood cell invasion.
Asexual multiplication (exo-erythrocytic schizogony) occurs inside hepatocytes, generating thousands of merozoites.
Merozoites are the specific life-cycle stage adapted to invade human red blood cells.

Key Concept

Plasmodium life cycle and tissue tropism during exo-erythrocytic schizogony
Estimated Time:1m 30s
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Topics

Kingdom Protista: Protozoa and Unicellular Algae

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