BIOL 4105 Chapter : Amoebas And Cilliates
Document Summary
Amoebas: two forms, trophozoite, feeding and reproducing form, single cell, 1 nucleus with endosome (karyosome)=nucleolus, cyst, environmentally resistant form, transmission. Infective stage for new host: direct life cycle, cyst ingested by new host, no intermediate host, reproduction: binary fission, most amoeba are not parasitic, genuses: entamoeba, endolimax, iodameba found in humans, endolimax, lodameba are commensal. Infective species: entamoeba histolytica (pathogen, e. dispar (commensal, e. coli (commensal, e. hartmanni (commensal, e. gingivalis (commensal) Entamoeba histolytica: distribution: worldwide, morphology: 2 stages, trophozoite, motile, phagocytic, feeds on host cells, reproduces by binary fission, cyst, resistant to the environment. Infective stage: survives weeks in most environments, chlorination will not kill, dry heat or freezing can kill, host niche: large intestine and rectum, transmission: direct. Wide range of presenting symptoms : mild, moderate, or severe diarrhea with abdominal pain, pathogenesis of amebic colitis, attaches to surface of mucosal cells of large intestine, lyses cells and feeds on contents.
