Actions

Biology of the schizont: Difference between revisions

From haematologyetc.co.uk

No edit summary
No edit summary
 
(32 intermediate revisions by the same user not shown)
Line 6: Line 6:
<span style="font-size:90%">>>This page: <u>''Biology of the schizont</u></span>
<span style="font-size:90%">>>This page: <u>''Biology of the schizont</u></span>
----
----


{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''What is the purpose of the schizont stage?'''
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''The schizont pathway'''
|}
|}


The stage begins with the first cycle of '''asexual replication''' forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.
<gallery mode="nolines" widths=300px heights=600px>
File:Blood_stages_schizonts_only.jpg|<span style="font-size:80%">''Basic schizont development (coloured images)''</span>|link={{filepath:Blood_stages_schizonts_only.jpg}}
</gallery>


Following the trophozoites stage, malaria parasites may enter one of two separate pathways:<br>
----
(1) '''Sexual replication:''' male or female '''gametocytes''' are formed, these will be taken up by mosquitoes allowing the invasion of new hosts.</br>
 
(2) '''Asexual replication:''' forms '''schizonts''' which will subsequently forming and release individual merozoites that invade further red cells.
{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''Merozoite release'''
|}
 
<gallery mode="nolines" widths=300px heights=300px>
File:the schizont.jpg|<span style="font-size:80%">''Formation and release of merozoites''</span>|link={{filepath:the schizont.jpg}}
</gallery>




(1) The stage begins with the first cycle of asexual division producing two chromatin masses</br>
(2) This is followed by further cycles of replication </br>
(3) In this case this results in the formation of 8 daughter parasites </br>
(4) The daughter parasites mature and the red cell ruptures to release the “merozoites” </br>
(5) The released merozoites very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).


----


{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''The schizont pathway and the role of merozoites:'''
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''Morphological features and relevance'''
|}
|}


The stage begins with the first cycle of '''asexual replication''' forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.


<gallery mode="nolines" widths=250px>
(1) '''The number of replication cycles differs between species:''' the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax)</br>
File:Blood_stages_schizonts_only.jpg|<span style="font-size:80%">''Basic schiont development''</span>|link={{filepath:Blood_stages_schizonts_only.jpg}}
(2) '''This stage may not always occur in blood:''' schizonts of ''P.falciparum'' adhere within the small vessels so is not seen in blood unless infection is very severe
</br></br>
 
<gallery mode="nolines" widths="200px" heights="220px" >
File:Schizontreal4.jpg|Mature schizont releasing merozoites|link={{filepath:Schizontreal4.jpg}}
</gallery>
</gallery>
<span style="font-size:200%">&#x2192;</span> [[Click for images of schizont morphology|Click for more images of schizont morphology]]


----
----
The stage has specific features that have clinical and diagnostic relevance:
The stage begins with the first cycle of asexual division producing two chromatin masses (1), this is followed by further cycles of replication that in this case result in the formation of 8 daughter parasites (2&3). These daughter parasites mature and are then released into blood as separate “merozoites” (4&5). These very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).
-------------------------------------------------------------------------------------------------------------
Morphological relevence
1. The number of replication cycles differs between species.
Some species undergo more cycles of replication, this means the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax).
2. This stage may not always take place in blood.
In P.falciparum the schizont form adheres within the small vessels so is not seen in blood unless infection is very severe


Morphology of schizonts (link)
{| class="wikitable" style="border-style: solid; border-width: 5px; border-color: #023020; color:black"
|colspan="1" style = "font-size:100%; color:black; background: #afbddb |'''Relevance of schizonts to clinical biology'''
|}
 
 
The release of merozoites from schizonts exposes the body to large amounts of free parasite antigens no longer contained within the erythrocytes - the result is an immune response causing high fever and illness symptoms. In some cases the development of parasites is synchronous so that all schizonts mature and release their merozoites at the same time - although rarely seen now, this pattern of development may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.


-------------------------------------------------------------------------------------------------------------
----
Relevance of schizonts to disease symptoms
Development of parasites may be synchronous so that all schizonts mature and release their merozoites at the same time. The release of merozoites exposes the body to large amounts of free parasite antigens at that point in time. The result is a high fever and illness which may settle afterwards. Although rarely seen now, this may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.

Latest revision as of 14:07, 18 April 2024

Navigation
(click blue highlighted text to return to page)

Malaria main index
>Basic malaria biology
>>This page: Biology of the schizont


The schizont pathway


The stage begins with the first cycle of asexual replication forming a recognisable “schizont” then concludes when the individual “merozoites” are released to infect new erythrocytes.

  • Basic schizont development (coloured images)

    Basic schizont development (coloured images)

Merozoite release
  • Formation and release of merozoites

    Formation and release of merozoites


(1) The stage begins with the first cycle of asexual division producing two chromatin masses
(2) This is followed by further cycles of replication
(3) In this case this results in the formation of 8 daughter parasites
(4) The daughter parasites mature and the red cell ruptures to release the “merozoites”
(5) The released merozoites very rapidly infect new red cells (so rapid that free merozoites will not usually be seen in blood).

Morphological features and relevance


(1) The number of replication cycles differs between species: the typical number of merozoites formed differs between species with as few as 8 (in P.malariae) up to a possible 32 (in P.vivax)
(2) This stage may not always occur in blood: schizonts of P.falciparum adhere within the small vessels so is not seen in blood unless infection is very severe

  • Mature schizont releasing merozoites

    Mature schizont releasing merozoites

→ Click for more images of schizont morphology

Relevance of schizonts to clinical biology


The release of merozoites from schizonts exposes the body to large amounts of free parasite antigens no longer contained within the erythrocytes - the result is an immune response causing high fever and illness symptoms. In some cases the development of parasites is synchronous so that all schizonts mature and release their merozoites at the same time - although rarely seen now, this pattern of development may produce a pattern of remitting fever with a distinct periodicity depending on species: underlying the older descriptive terms tertian or quartan malaria.

Retrieved from ‘https://haematologyetc.co.uk/index.php?title=Biology_of_the_schizont&oldid=5854’