5A. - 5E. Flashcards
The most important feature that separates amoebas from the other groups of unicellular Protozoa is the [?].
means by which they move
Amoebas are equipped with the ability to extend their cytoplasm in the form of [?], which allows them to move within their environment.
pseudopods
With one exception, there are two morphologic forms in the amoebic life cycle – [?], the form that feeds, multiplies, and possesses pseudopods, and [?] – the nonfeeding stage that is characterized by a thick protective cell wall designed to protect the parasite from the harsh outside environment when deemed necessary.
trophozoites
cysts
It is important to note here that the [?] of trophozoites are basically identical to those of their corresponding cysts.
nuclear characteristics
The [?] of all the intestinal amoeba are similar.
life cycles
The most common means whereby amoebas are transferred to humans is through [?] in contaminated food or water.
ingestion of the infective cyst
In most cases, [?] are easily destroyed by the gastric juices of the stomach.
trophozoites
are also susceptible to the environment outside the host.
Trophozoites
are not usually transmitted to humans.
trophozoites
is the morphologic conversion from the cyst form into the trophozoite form, which occurs in the ileocecal area of the intestine.
Excystation
is the conversion of trophozoites into cyst form.
Encystation
It usually occurs in the intestine when the environment becomes unacceptable for continued trophozoite multiplication.
Encystation
are equipped with a protective cell wall.
cysts
allows cysts to remain viable in the outside environment for a long period of time.
cell wall
The ingestion of the [?] completes the typical intestinal amebic life cycle.
infective cysts
General morphologic characteristics of a typical amoeba:
✓ Relatively [?]
✓ Typically lack [?]
✓ Multiply by [?]
✓ Undergo encystation EXCEPT: [?]
small
contractile vacuoles
binary fission
E. gingivalis
➢ The presence of commensal amoeba in the stool of an individual is significant for two reasons:
- They may be mistaken for the pathogenic E. histolytica
- They are an indication of fecal contamination of food or water
➢ Accurate diagnosis of the [?], is therefore, crucial.
commensal amoeba
➢ Among the numerous free-living amoeba of soil and water habitats, certain species belonging to two genera –[?]– are facultative parasites of man.
Acanthamoeba and Naegleria
➢ Habitat: Stagnant water, brackish and ocean sediments, thermal pools, swimming pools, polluted soil, sewage disposal systems
Acanthamoeba and Naegleria
➢ Usually inhabits the Central Nervous System once it enters a human host
Acanthamoeba and Naegleria
The species of amoeba that are commonly found in human fecal specimens are [?].
E. histolytica, E. dispar, E. hartmanni, E. coli, E. polecki, E. nana, and I. butschlii
E. histolytica, E. dispar, E. hartmanni, E. coli, E. polecki, E. nana, and I. butschlii
They are mainly differentiated on the basis of structure and size, thus, proper determination of the organism size is essential identifying the amoebas.
Sarcodina (Amoeba)
The appearance of key nuclear characteristics, such as the number of nuclei present and the positioning of the nuclear structures is crucial to differentiate the amoebas correctly.
Sarcodina (Amoeba)
The presence of other amebic structures and characteristics such as cytoplasmic inclusions and motility also aids in the identification.
Sarcodina (Amoeba)
It is important to note that only one of the intestinal amoebas, [?], may produce characteristic symptoms, and is universally considered to be a pathogen.
E. histolytica
The flagellates belong to the phylum Protozoa and are members of the subphylum [?].
Mastigophora
The flagellates can be categorized into two groups, [?].
intestinal and atrial
Members of this class lack chromatophores and thus depend on previously manufactured plant and animal foods.
Mastigophora (Flagellates)
Their nutrition is holozoic or parasitic, and their form may be simple or quite complex, but as a rule, they have a single nucleus and a neuromotor apparatus.
Mastigophora (Flagellates)
The neuromotor consists of a blepharoplast, which constitutes the kinetoplast (energizing component), and an axoneme, with or without a free flagellum.
Mastigophora (Flagellates)
The axial structure of the flagellum is a continuation of the [?], which is composed of one or more fibrils.
axoneme
Some species of flagellate protozoa have a rudimentary mouth, the [?].
cytostome
Reproduction is essentially asexual and is by longitudinal binary fission.
In majority of the family groups, the life cycle is simple, but in trypanosomes, the organisms are [?].
dimorphic or polymorphic
Most are free-living or parasitic
Mastigophora (Flagellates)
Possess whip-like locomotory organelle called flagella
Mastigophora (Flagellates)
Motor component: flagella and axonemes
Mastigophora (Flagellates)
Neuromotor apparatus: kinetoplast which contains of blepharoplast and parabasal body
Mastigophora (Flagellates)
Mode of Reproduction: longitudinal binary fission
Mastigophora (Flagellates)
▪ Exist only as trophozoites; NO CYSTIC STAGE
Genus Trichomonas
▪ Trophozoite stage is the infective stage and pathogenic stage
Genus Trichomonas
▪ Multiplication is through longitudinal binary fission
Genus Trichomonas
▪ Motility: Fast jerky tumbling movement
Genus Trichomonas
➢ Nucleus: single, spherical or subspherical in the mid-line near the anterior pole
Genus Trichomonas
➢ Cytoplasm: highly vacuolated
Genus Trichomonas
➢ Rounded anterior and pointed posterior end (Pyriform in shape)
Genus Trichomonas
– rod-like structure arising from or near the anterior end and extends through the entire body, protruding as a rather sharp spike through the posterior end of the cytoplasm; functions for anchorage
Axostyle
– small, located on one side of the anterior end
Cytostome
– located between the nucleus and the anterior margin of the organism
Blepharoplast
– 4 free flagella and 1 which runs along the undulating membrane
Flagella
The parasitic flagellate Protozoa is earlier classifications were placed in the class or superclass [?] together with all species of one-celled animals that bear one to several long, delicate, thread-like extensions of the cytoplasm, which are termed flagella.
Mastigophora
Some species of flagellate protozoa have a rudimentary mouth, called the [?].
cytostome
Reproduction is through longitudinal binary fission.
Mastigophora (Flagellates)
The only intestinal flagellate to cause disease in humans is [?], while among the trichomonas species, the only specie known to be pathogenic in man is [?].
G. lamblia
T. vaginalis
The flagellate protozoa that live in the blood and tissues of human host all belong to the [?].
order Kinetoplastida, family Trypanosomatidae
This family includes species that have a single flagellum, a nucleus, and a kinetoplast from which the flagellum arises.
order Kinetoplastida, family Trypanosomatidae
The [?] consists of a deeply stained parabasal body and an adjacent dot-like blepharoplast.
kinetoplast
The [?] are connected by one or possibly more delicate fibrils.
blepharoplast and parabasal body
The inner portion of the flagellum extending from the blepharoplast to the surface of the body is [?].
axoneme , or axial filament
Species of this family may exist in two or more of four forms or states, which are named after genera exemplifying these forms:
Leptomonas, Crithidia, and Trypanosoma.
▪ Include the Leishmaniasis and trypanosomes
Mastigophora (Hemoflagellates)
▪ May infect the blood, lymph nodes, muscles, and reticuloendothelial system
Mastigophora (Hemoflagellates)
▪ Multiply in the blood (hemoflagellate) and tissue of humans
Mastigophora (Hemoflagellates)
▪ Mastigophora (Hemoflagellates) Basic Structures:
- Single flagellum, a nucleus, and a kinetoplast
- Blepharoplast and the parabasal body
- Axial filament/axoneme
▪ All species require an arthropod intermediate host
Mastigophora (Hemoflagellates)
▪ Mastigophora (Hemoflagellates) Four stages:
- Amastigote (Leishman-Donovan body) or leishmanial form
- Promastigote or leptomonal form
- Epimastigote or crithidial form
- Trypomastigote or trypanosomal form
Members of the clinically significant group of parasites located in blood and tissue that move by means of flagella, known as the hemoflagellates, belong to the genera [?].
Leishmania and Trypanosoma
There are four morphologic forms of clinical significance associated with these hemoflagellates:
amastigote, promastigote, epimastigote, and trypomastigote.
Although the specific life cycle may vary, all the organisms in these two genera involve some combination of the four morphologic forms.
Mastigophora (Hemoflagellates)
The transmission of all hemoflagellates is via the bite of an arthropod vector.
Mastigophora (Hemoflagellates)
The major difference between the two genera is the primary diagnostic form found in each; for Leishmania it is the [?] and for Trypanosoma it is the [?], with the exception of Trypanosoma cruzi, in which amastigotes may also be found.
amastigote
trypomastigote
Members of this group of Protozoa are classified in the Phylum Ciliophora, Class Kinetofragminophorea, which includes one-celled organisms that are provided with short thread-like extensions of their ectoplasmic membrane (cilia) during some stages of their life.
Ciliophora (Ciliates)
In most, cilia are present during all stages of development; in some, however, cilia are lacking in the
definitive stage
➢ Members of this genus are exclusively parasitic in the digestive tract of invertebrate host.
Genus Balantidium
As in other ciliates, asexual multiplication is accomplished by
transverse binary fission
is the only pathogenic ciliate and is the largest protozoan parasitizing humans.
Balantidium coli
The most important key structure of identification of this protozoa is the presence of
cilia
Some individuals with [?] infections are totally asymptomatic, whereas others have symptoms of severe dysentery similar in amoebiasis caused by E. histolytica.
B. coli
The phylum [?] includes parasitic protozoa that live in the body fluids or tissues of the host.
Apicomplexa
It takes its name from the [?] that is generally present at some stage.
apical complex
Most of the Apicomplexa parasitizing humans belong to the class [?], in which the life cycle is characterized by an alternation of generations, one sexual, and one asexual, occurring in the same host, or requiring an alternation of hosts.
Sporozoa
In the asexual reproductive life cycle of development, multiplication is by [?], while in the sexual cycle, it is by [?], which involves [?].
schizogony
sporogony
fertilization or syngamy
Locomotion of the mature organisms is by [?]; flagella are present only on the [?], of some groups; [?] if present, are used for feeding, not for locomotion.
body flexion, gliding, or undulation of longitudinal ridges
microgametes
pseudopodia
Most of the Apicomplexa parasitzing man has a life cycle that is characterized by an alteration of generations, one sexual, and one asexual, occurring in the same host, or requiring an alternation of hosts. As with all parasites, the proper identification of malaria and babesiosis is crucial to ensure that the patient is adequately treated when necessary. Plasmodium and Babesia spp. have morphologic forms that may look similar. However, because not all species typically show all the morphologic forms in the peripheral blood, coupled with the fact that other morphologic forms look different (e.g., mature schizonts, gametocytes) and whether pigment is produced, allow accurate speciation of the malarial organism and differentiation of malaria from babesiosis. The miscellaneous protozoa (Coccidians) have morphologic similarities (e.g., the oocysts of Isospora and Sarcocystis) and distinct differences. When screening suspected samples, attention to organism size, shape, andstructural details is imperative to identify parasites correctly. Note that most of these coccidians are opportunistic especially among immucompetent individuals. Among all of the coccidian parasites, T. gondii is the most clinically significant implicated in causing neonatal toxoplasmosis.
