MODULE 2 UNIT 1 Flashcards
one of the three major groups of parasites that are of medical importance to man
Protozoa
performs all the functions of life, i.e., reproduction, respiration, excretion, etc.
single cell unit
carried on by specialized cells
higher organisms
They have remarkable range in size and form, some visible to the naked eye, while others require magnification up to a thousand fold before they can be seen. INTRODUCTION
Protozoa
Some are spherical or ovoidal, while others have bizarre contours.
Protozoa
are found in all moist habitats
Protozoa
Protozoa are common in
sea, in soil and in fresh water.
“first animal”
‘protos’ and ‘zoon’
they often possess animal-like behaviors, such as motility at some stage of their life cycle
“one-celled animals”
three phyla of protozoa of medical interest in humans
• Phylum Sarcomastigophora • Phylum Ciliophora •Phylum Apicomplexa
includes subphylum Sarcodina, and, subphylum Mastigophora
Phylum Sarcomastigophora
T or F: Although, protozoa exhibit marked diversity in size, shape, and other characteristics, there are fundamental characteristics common to the entire group.
TRUE
The structure of a protozoan cell is composed of
(1) cytoplasmic body, and (2) a nucleus
The various life functions are carried out by specialized intracellular structures known as
organelles
consists of a thin outer ectoplasm and a voluminous inner endoplasm
cytoplasm
very complex in electron microscope
cytoplasm
appears more transparent, less granular, and more homogeneous
Ectoplasm
It is covered with plasma membrane that is like those found in all cells.
Ectoplasm
functions of cytoplasm
movement, respiration, procurement of food, discharge of metabolic wastes, and protection
The locomotory organelles of protozoa arise from the
ectoplasm
are temporary extensions of the ectoplasm and are found in amoebas under the subphylum Sarcodina
Pseudopodia
are long, slender, whiplike structures seen in subphylum Mastigophora
Flagella
subphylum Mastigophora are also called
flagellates
T or F: They may have one or more than one flagellum, and these may be inserted into the cell at different angles.
TRUE
structurally similar to flagella but shorter and covering the entire surface of the body
Cilia
seen in phylum Ciliophora (locomotory structure)
Cilia
do not exhibit an obvious mode of mobility but can glide nonetheless
Protozoa in phylum Apicomplexa
is a lateral expansion of the plasma membrane with a flagellar rim extending out like a fin along the outer edge of the body of certain flagellates
Undulating membrane
Food may be taken in at any place in the [?] or ingested at a particular point.
cytoplasm
function for feeding by phagocytosis
Pseudopodia in amoebas
a ciliate; food passes directly into a specialized “cell mouth” structure which is located near the anterior end of the body
Balantidium coli
specialized “cell mouth” structure which is located near the anterior end of the body
cytostome
excretion of undigested particles are discharged at the general surface or through a specialized “ cell anus”
cytopyge
Certain protozoa at times enter an inactive cystic state, in which they secrete a membranous
cyst wall
It is necessary for the protection and survival outside the body and against the acidic digestive juices of the gastrointestinal tract.
cyst wall
consists of a moderately dense granular protoplasm that immediately surrounds the nucleus
endoplasm
functions of endoplasm
metabolism and nutrition, and storage of food
endoplasm contains which organelles?
mitochondria, Golgi apparatus, microbodies, and endoplasmic reticulum
endoplasm may also contain:
contractile vacuoles, food vacuoles, food reserves, and foreign bodies
acts as osmoregulators
contractile vacuoles
hypertonic to their environment; they imbibe water continuously by osmosis
Freshwater protozoa
collects excess water in their cytoplasm and pumps them out of the cell
contractile vacuoles
these species maintain a reserve food supply such as glycogen vacuole and chromatoidal bodies
immature amoebic cysts
represents the main storage form of glucose
Glycogen vacuole
n wet mount preparation, they are demonstrated by staining a brown color with iodine solution.
Glycogen vacuole
are dense structures which are made up of crystalline RNA and RNA-binding proteins
Chromatoidal bodies (or bars)
has chromatoid bodies with blunt, rounded ends in an unstained concentrated wet mount of stool
Cyst of Entamoeba histolytica/dispar
may show food vacuoles or inclusions such such as red blood cells , bacteria, or other ingested materials
Endoplasm of some protozoa
ingestes erythrocytes (arrow), under differential interference contrast (DIC) microscopy
Trophozoite of Entamoeba histolytica
contains the chromosomes that are essential for life, reproduction, and genetic composition of the organism
nucleus
It is bounded externally by a well-defined nuclear membrane similar to that of most eukaryotic cells.
nucleus
two types of nucleus among the protozoa
a. Vesicular nucleus; b. Compact nucleus
is found in most protozoa
Vesicular nucleus
characterized by an irregular distribution of chromatin materials that clear areas are apparent in the nucleoplasm
Vesicular nucleus
The chromatin granules may line the inner side of the nuclear membrane forming the
peripheral chromatin or linin
network of fibrils
radiating towards the periphery of the nucleus
linin network of fibrils
Inside the nucleus is a single mass or aggregate of dense chromatin
karyosome (AKA endosome),
may be located centrally or eccentrically
karyosome (AKA endosome),
may be surrounded by chromatin particles that appear to be arranged in an achromatic network
karyosome (AKA endosome),
found in a few protozoa only, primarily in ciliates
Compact nucleus
chromatin granules are dense so that there are no clear areas of nucleoplasm observed in light microscopy, although present
Compact nucleus
ingestes erythrocytes stained with trichrome
Trophozoite of Entamoeba histolytica
The ingested erythrocytes appear as
dark inclusions
central nuclei
typical small, centrally located karyosome
peripheral nuclei
thin, uniform peripheral chromatin
The space between the karyosome and the nuclear membrane is traversed by a fine thread of linin network having a specific arrangement
“spokes wheel”
two developmental stages commonly encountered in protozoa
(1) trophozoite; (2) cyst
are the motile forms
Trophozoites
are the nonmotile forms; resting
Cysts
They are the vegetative stage, i.e, they have reproductive powers, and the feeding stage, some feeding on host cells
Trophozoites
responsible for the pathogenic effects in the host
Trophozoites
they are delicate and do not survive long outside the host
Trophozoites
They are bounded by tough cell wall so they show considerable resistance in unfavorable environment.
Cysts
closely associated with transfer from host to host and constitutes the infective stage of most of the protozoa
Cysts
In apicomplexans, the cystic form is an
oocyst
The protozoa possess the property of being transformed from the active trophozoite stage to an inactive cyst stage, losing its:
power of motility, growth and reproduction, and enclosing itself in a tough wall
Conditions favoring encystment, in most cases, involve some adverse environmental events such as:
• nutritional deficiency • desiccation • pH or temperature changes • increased tonicity • decreased oxygen concentration • overpopulation
When the condition becomes favorable again, the organism leaves the [?] and continues its life cycle in the [?]
cyst stage; trophozoite stage
Mechanisms for excystation may include:
• absorption of water with consequent swelling of the cyst • secretion of lytic enzymes by the protozoan • action of host digestive enzymes on the cyst wall
T or F: Note, however, that both processes, encystation and excystation, occur only within the host.
TRUE
Trophozoites that are passed in feces during diarrhea, in unfavorable condition outside the host, do NOT encyst but [?], thus must be examined or preserved within a short time after passage.
disintegrate
Cysts are passed in [?] stool.
semi-formed or formed
[?] to another susceptible host is required so that they can continue their life cycle and grow as trophozoite stage.
Transference
Protozoan reproduction may be either [?], or alternate the two types in their life cycles.
asexual or sexual
Most often asexual reproduction is by
binary fission
one individual divides into two of more or less equal parts
binary fission
The plane of fission in amoebas
random
The plane of fission in flagellates
longitudinal
The plane of fission in ciliates
transverse
occurs in Apicomplexa, as in the malaria parasite in the genus Plasmodium
Multiple fission
the nucleus and other essential organelles divide repeatedly followed by cytokinesis (cytoplasmic division)
Multiple fission
a large number of daughter cells are produced almost simultaneously
Multiple fission
A type of multiple fission is
schizogony
Cells undergoing schizogony are called
schizonts or meronts
When the multiplication is completed, the schizont ruptures and liberates daughter cells called merozoites, to initiate another phase of
merogony or gametogony
schizogony producing more asexually reproducing merozoites
merogony
gametocyte formation
gametogony
Another type of multiple fission often recognized is
sporogony
Another type of multiple fission often recognized is
sporogony
products of sporogony are
sporozoites in resistant oocysts
sexually differentiated cells, called gametes unite permanently and a complete fusion of the nuclear material takes place
Syngamy
gametes
female macrogamete, and male microgamete
The resulting product of Syngamy
zygote
Cells that produce macrogametes and microgametes are the gametocytes or gamonts formed by
gametogony
only the nuclei unite, is found only among ciliates
Conjugation
Later on, the two organisms separate, each being rejuvenated during the process, although probably not essential for perpetuation of the species.
Conjugation
two major methods of transmission of protozoal infection:
through ingestion of the infective stage of the protozoa or via an arthropod vector
few transmission of protozoal infection involve
sexual contact
T or F: The mode of transmission is non-specific for each species.
FALSE = specific
T or F: Protozoa, similar to worms, multiply in their hosts, so disease can result from infection initiated by only a few organisms.
FALSE = in contrast
Pathologic changes are due to [?] by the parasite itself or its products.
invasion and destruction of cells or tissues
T or F: Tissue damage primary to immune response, or immunopathology, may occur.
FALSE = secondary
Generalized systemic symptoms are common. Give examples.
fever, and signs like splenomegaly and lymphadenopathy
The early stage of infection may be asymptomatic or it may be severe, leading to death or into a chronic latent stage, with relapses at times before eventual recovery.
FALSE = subclinical
The diagnosis of some diseases, may be strongly suspected on clinical grounds from characteristic signs and symptoms. Give examples.
malaria or leishmaniasis
clinical impressions should always be confirmed by [?] that identified the parasite in the specimen
laboratory diagnosis
