24 Questions
Describe the shape of the cyst in the early stage.
Spherical
What structures are found in the early cyst?
- Mass of glycogen
- 1-4 chromatoid bodies or chromidial bars
How many nuclei does the cyst have in its mature form?
Four
What makes the cyst wall highly resistant to gastric juice and unfavorable environmental conditions?
Highly refractile membrane
What is the vegetative or growing stage of the parasite called?
Trophozoite
What are the finger-like projections formed by sudden jerky movements of ectoplasm called?
Pseudopodia
What is the stage called where trophozoites undergo encystment in the intestinal lumen?
Precystic Stage
What is the newly developed trophozoite called after the rupture of the cyst?
Metacystic trophozoites
What is the process by which reproduction occurs in Ameba?
Reproduction occurs by fission and budding.
Describe the characteristics of the Trophozoite stage in Ameba.
Trophozoite is irregular in shape, large, actively motile, and contains various components like nucleus, food vacuoles, and erythrocytes.
What happens during the precystic stage of Ameba?
Trophozoites undergo encystment in the intestinal lumen, extruding food vacuoles, and forming a cyst with a glycogen vacuole and two chromatid bars.
What is the fate of Metacystic trophozoites in Ameba?
Metacystic trophozoites do not colonize in the small intestine but are carried to the cecum.
Describe the appearance of the ulcers caused by amebiasis in the colon.
The ulcers are multiple and confined to the colon, initially appearing as raised nodules with pouting edges. They later break down discharging brownish necrotic material.
What happens to the cyst wall during excystation and where does this process occur?
During excystation, the cyst wall is damaged by trypsin in the alkaline medium of the cecum or lower part of the ileum.
Explain the significance of the glycogen mass and chromidial bars in the early cyst stage.
In the early cyst stage, the glycogen mass and chromidial bars disappear as the cyst matures. They are structures that are present initially but vanish as mitotic divisions occur.
How does the mature cyst of the amebic parasite become infective, and how long can it remain viable under suitable conditions?
The mature cyst becomes infective by undergoing two successive mitotic divisions to form four nuclei. It can remain viable under moist conditions for about 10 days.
What are the diagnostic features of the Trophozoite stage in Ameba?
Presence of phagocytosed red cells, irregular shape, actively motile
Explain the process of encystment in Ameba and its significance.
Trophozoites extrude food vacuoles, form a retractile cyst wall, and become round or oval. Encystment occurs in the intestinal lumen and helps in survival outside the host's body.
Describe the formation and characteristics of Pseudopodia in Ameba.
Pseudopodia are finger-like projections formed by sudden jerky movements of ectoplasm in one direction, followed by the streaming in of the whole endoplasm.
What is the function of the large glycogen vacuole and chromatid bars in the early cyst stage of Ameba?
The glycogen vacuole provides energy reserves, while chromatid bars play a role in DNA replication and cell division.
What are the two structures found in the early cyst stage of the amebic parasite?
Glycogen mass and chromidial bars
Describe the appearance of a typical amebic ulcer in the colon.
Flask-shaped with narrow mouth and neck, and a large rounded base.
What is the fate of Metacystic trophozoites in Ameba?
Metacystic trophozoites become quadrinucleate amebas.
How does the mature cyst of the amebic parasite become infective, and for how long can it remain viable?
The mature cyst becomes infective by undergoing two successive mitotic divisions to form four nuclei, and it can remain viable for about 10 days under moist conditions.
Study Notes
Early Cyst Stage
- In the early stage, the cyst is spherical in shape.
- The early cyst contains two structures: a large glycogen vacuole and chromatid bars.
- The glycogen mass and chromidial bars play a significant role in the early cyst stage, providing energy and aiding in the protection of the cyst.
Mature Cyst Stage
- The mature cyst has four nuclei.
- The cyst wall is highly resistant to gastric juice and unfavorable environmental conditions due to the presence of a chitin-rich layer.
Life Cycle of Ameba
- The vegetative or growing stage of the parasite is called the Trophozoite stage.
- The Trophozoite stage is characterized by the formation of pseudopodia, which are finger-like projections formed by sudden jerky movements of ectoplasm.
- The process of reproduction occurs in Ameba through binary fission.
- During the precystic stage, Trophozoites undergo encystment in the intestinal lumen.
- After the rupture of the cyst, the newly developed trophozoite is called the Excysted Trophozoite.
Pathogenesis
- The ulcers caused by amebiasis in the colon are flask-shaped and have a characteristic appearance.
- The Metacystic trophozoites are able to penetrate the intestinal mucosa and cause tissue damage.
Excystation
- During excystation, the cyst wall is broken down, and this process occurs in the small intestine.
- The glycoprotein layer of the cyst wall is broken down, allowing the Excysted Trophozoite to emerge.
Diagnostic Features
- The diagnostic features of the Trophozoite stage in Ameba include the presence of pseudopodia and the ability to engulf red blood cells.
- The process of encystment is significant as it allows the parasite to survive outside the host and transmit infection.
Pseudopodia
- Pseudopodia are finger-like projections formed by sudden jerky movements of ectoplasm.
- The function of pseudopodia is to aid in the movement and feeding of the Trophozoite.
Infection
- The mature cyst becomes infective when it is ingested through contaminated food or water.
- The mature cyst can remain viable for weeks to months under suitable conditions.
This quiz covers the characteristics of ameba and trophozoite, including their shapes, reproduction methods, and presence in tissues. Topics include fission, budding, endoplasm content, and more.
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