Structure and Life Cycle of Entamoeba Histolytica (With Diagram)

In this article we will discuss about structure and life cycle of entamoeba histolytica (with diagram).

Structure of Entamoeba Histolytica

A pathogenic parasite called Entamoeba histolytica lives in the intestines of many primates, including humans. It resides in the large intestine’s mucous and submucous layers. It frequently causes severe ulcers and abscesses and primarily feeds on the tissues of the intestinal wall.

It may enter the bloodstream in chronic cases and reach the liver, lungs, brain, and other organs. Amoebic dysentery or amoebiasis is a serious and frequently fatal disease that is caused by it. There are two distinct forms of E. histolytica: the minuta or precystic form and the magna Trophozoite form.

Entamoeba Histolytica Diagram

Entamoeba Histolytica Diagram

Trophozoites

Trophozoite or Magna is the adult trophic form of Entamoeba. It lives in the anterior part of the large intestine, or the human colon. Its structure is similar to that of an amoeba, but it lives in a parasitic mode. It has a plasma lemma covering its body, and its cytoplasm is divided into ectoplasm and endoplasm. Ectoplasm has formed a single large, broad, and blunt pseudopodium. Endoplasm is made up of a single spherical nucleus and food vacuoles. Nucleus has peripheral crown of chromatin blocks and a centrally located nucleolus.

The trophozoites multiply in the host’s intestinal wall through repeated binary fission. Some of the daughter entamoebae mature into adults, while others do not. These are known as Minuta forms because they are significantly smaller than normal trophozoites.

Minuta Form

It is a smaller, spherical stage that is not pathogenic. It is normally found in the lumen of the intestine and is rarely found in tissues. It goes through encystations and aids in the transmission of parasites from one host to another.

Life Cycle of Entamoeba Histolytica

Entamoeba histolytica is monogenetic, i.e., its life cycle is completed on one host only; the man.

Encystment

Entamoeba only stays in the intestinal lumen in the precystic forms. The parasites go through encystment, but before that, they round up, get rid of food vacuoles, and store a lot of food in the form of glycogen and dark, rod-like chromatoid granules. Each parasite surrounds itself with a thin, rounded, robust, colourless, and transparent cyst wall.

Entamoeba histolytica produces cysts of various sizes. At this stage, each cyst is mononucleate and has clear cytoplasm. Entamoeba histolytica cysts are distinguished by the presence of chromatoid bodies. They can be found singly or in groups of two or more, or both. Each cyst becomes tetra nucleate after the cysts’ nuclei divide twice. The cyst is currently capable of infecting a new host. Encysted forms pass out with the faecal matter of the host.

Transfer to new host

If the environment is favourable, the infectious cysts can survive outside of the human intestine for a long time. Fresh human hosts are infected by ingesting contaminated food and beverages that contain infectious cysts.

Life cycle of Entamoeba histolytica

Excystment

Metacystic trophozites feed on the contents of the intestine and grow in size to form the next generation of trophozites. The trophozoites remain in the intestine lumen for a specific period of time before attacking the intestine wall and restarting the life cycle. Entamoeba histolytica causes amoebic dysentery, liver, lung, and brain abscesses, and non-dysenteric infections.