(M) Nematodes: Adenophorea & Secernentea [A. lumbricoides] (module-based) Flashcards
T. trichiura, T. spiralis, C. philippinensis & A. lumbricoides 165-172
Helminths, either parasitic or free-living, are worms classified under?
METAZOA
phyla
nematodes or roundworms
Nematoda
phyla
hair-snakes or gorgiid worms
Nematomorpha
Phyla
trematodes (flukes), cestodes (tapeworms), turbellaria
Platyhelminthes
Phyla
thorny-headed worms
Acanthocephala
Most of the medically important helminths are under the phylum (2)?
nematoda and platylheminths
TOF. Species of phylum Nematoda have separate sexes while Platyhelminthes are mostly hermaphroditic.
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All platylhelminthes are hermphroditic except for?
blood flukes (schistosoma)
Other species are provided with cup like structures called the
suckers or acetabula (present among flukes and tapeworms)
How many eggs can A. lumbricoides produce?
200,000 per day
Not all these eggs, however, will be able to withstand the adverse conditions in the environment thus, not all of them are able to reach maturity.
The eggs, laid larvae, or the larvae that hatched from the eggs, encounter unfavorable conditions in the environment that may destroy them. These conditions include
familiarize nalng
desiccation, fermentation, overgrown by other organisms such as bacteria and/or fungi, too much water, extreme heat, inability to find or failure to be taken by the appropriate host, death of the host, and man-made barriers for their survival
- considered true roundworms
- free- living and exist everywhere in vast number
- Some species are exclusive parasites of lower form of animals while others are found among humans only
- provided with elongate and cylindrical bodies and with separate sexes
Nematodes
Nematodes
Majority of parasitic nematodes inhabits the?
intestinal tract of a man
Nematodes
TOF. The life history of nematodes may be direct (no intermediate host needed), or indirect (need intermediate host/s).
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Nematodes
Pattern fo development
egg - larva - adult
Nematodes
Majority of roundworms undergoes 4 larval transformations, each of which is characterized by a?
molting process
In most instances, transformation from 3rd to 4th larval form, before becoming adult, takes place in the body of the definitive host. Thus, it takes 4 moltings before maturity.
Nematodes
Autoinfection can also occur with some nematodes like?
Strongyloides stercoralis, and Enterobius vermicularis
Nematodes
Integument system of roundworms consists of non-nucleated cuticula, which is secreted by the?
part of the skin sya
underlying hypodermis
Nematodes
TOF. They are no circular muscle fibers, and they move, mainly, through pseudopodia.
F (body flexion)
Nematodes
TOF. Some intestinal nematodes have structures such as** teeth, plates, hooks, stylets, or spines** for attachment.
T
. Some species can maintain their position in the lumen of the intestine through continuous flexion and relaxation of the longitudinal muscle fibers to counteract the peristalsis of the intestinal tract, which can cause them to be expelled out. The body cavity is called?
pseudocele
no mesothelial lining cells
Sperm cells are discharged through the
cloaca
The esophagus may be classified, based on shape and structure, into five types, namely:
- filariform
- rhabditiform
- spiruroid
- stichsoma
- strongyliform
Long, slender, simple, and muscular, seen among Strongyloidea
Filariform
muscular with three parts: proximal bulb, narrow isthmus, and distal body or corpus, as seen among free-living rhabditoids, parasitic
oxyuroids, and free-living and non-infective strongyloids
Rhabditiform
with muscular anterior and glandular posterior, seen in most of the spiruroidea and filaroidea
Spiruroid
long, slender embedded in a row of emboidal esophageal glandular cells (stichocytes), seen among trichinelloidea
Stichosoma
with short, muscular buccal structure with a waist, seen
among ancylostomatidae
Strongyliform
The excretory system consists of
- excretory gland cells
- lateral canals
- excretory pore
is situated at the mid-ventral portion of the cephalic or cervical region.
excretory pore
is composed of fibers with dorsal, ventral, and lateral longitudinal trunks with transverse commissures, whereby the most important is the circum-esophageal ring (around the esophagus)
nervous system
TOF. Most part of nematodes’ existence is under anaerobic condition thus, they have no respiratory- or circulatory structures, they are in an anaerobic environment, anyway.
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have curved tail end and are, usually, provided with special structures such as copulatory spicule or bursa, which aid during copulation.
Males of most species
TOF. females are smaller than males.
F (opposite)
Among bursate nematodes, the perianal or caudal cuticle is extended into an umbrella-like structure called
bursa
TOF. Sperm cells, oftentimes, are amoeboid instead of flagella type.
T
enumarate sp. female reproductive system may be single
Trichinella spiralis, Trichuris trichiura
female reproductive system may be double
Ascaris, Enterobius, and hookworms
this worms discharge eggs in the intestinal tract and are evacuated with the feces to be deposited in the environment
Oviparous worms
Embryonated eggs of Ascaris lumbricoides or Trichuris trichiura enter the body of man via the
oral route
portal of entry
Eggs of Enterobius vermicularis are
usually inhaled (nasal route) or to a lesser extent, may also be ingested (oral route)
infective larval stages of hookworms or Strongyloides stercoralis enter the body through
skin penetration
The infective stages of filaria worms enter the human body through percutaneous (skin) route via
bites of insect vectors
The type of transmission through non-essential, but advantageous intermediate host is referred as?
parathenesis
transport host (non-essential intermediate host) is called
parathenic host
(3) can pass through the placenta or mammary glands resulting to infection of the unborn baby
Strongyloides stercoralis, Ancylostoma species, and Toxocara species
Infective larval forms of some species
All nematodes are provided with a pair of lateral, tiny, receptors?
amphids or lateral organs
What region is the amphids located?
which are in the cephalic or cervical region
Nematodes without caudal glands have a pair of lateral post-anal glands called
caudal chemoreceptors
Species with caudal chemoreceptors are classified as
Secernentea (Phasmids)
Species without caudal chemoreceptors are classified as
Adenophorea (Aphasmids)
Most Adenophorea are non-parasitic and free-living. Only three are parasitic to man, namely:
Trichuris trichiura, Trichinella spiralis and Capillaria philippinensis.
gross appearance has cosmopolitan distribution but more in warm, moist regions of the world
what am i
Trichuris trichiura
T. trichiura
AKA
whipworm
T. trichiura
Inhabits
- anterior end embedded, the walls of the cecum
- walls of the appendix
- colon
- or lower part of the ileum
T. trichiura
TOF. Incidence is higher among children than adults
T
T. trichiura
diagnosed co- existing with
A. lumbricoides
T. trichiura
TOF. Grossly, the worm has narrower anterior 4/5th than the posterior thus called whip worm.
F (3/5)
T. trichiura
MALE OR FEMALE
35-40mm, tail end more or less straight, genitalia consist of single sacculate ovary, oviduct, and uterus, and vulva at the ventral anterior part of the fleshy tail end.
FEMALE
T. trichiura
MALE OR FEMALE
30-45mm, tail end coiled to 360O, genitalia consist of sacculate testis, vas deferens, and ejaculatory duct that empty into the cloaca, and a lancet- shaped spicule, covered with a sheath, situated at the most terminal part of the posterior region
MALE
T. trichiura
Shape of the egg
football or barrel shaped
T. trichiura
No. of layer, color of the egg, and other morphology
3-layered shell, outermost of which is brown in color, with protruding bipolar mucus plugs and laid unsegmented (without embryo)
T. trichiura
The female worm, anterior part attached to the cecal wall, lays unsegmented (fertilized without embryo) eggs in?
feces and deposited into the soil when the infected person defecates
T. trichiura
deposited in moist, warm, and shaded soil, embryonate for a period of about three weeks
eggs
T. trichiura
infective stage to man
embryonate egg
T. trichiura
This may remain viable for weeks or months in the soil
Embryonate egg
T. trichiura
What can damage the eggs?
Direct sunlight, desiccation, marked changes in oxygen and moisture, and other factors
T. trichiura
Man acquires the infection through ingestion of the
embryonated eggs that contaminate foods, drinks, or fingers
T. trichiura
this stage maybe carried by insects or animals like rat, flies, cockroaches, and humans on their bodies or fingers and mechanically transfer the eggs to the foods or drinks
egg
T. trichiura
Where do ingested eggs hatch in the body?
smoll intestine
T. trichiura
Where does the released larvae enter?
crypts of the lower ileum and colon
Later, the larvae enter the epithelium of the cecum (also at the adjacent sites)
T. trichiura
Maturation takes approximately
3 months
T. trichiura
TOF. The adult worms copulate, and female lays eggs in the cecum.
T
T. trichiura
T. trichiura
What part of the worm is embedded in the walls of the cecum
anterior part