nematodes Flashcards
phylum:
class:
phylum: nemathelminthes
class: nematoda
intestina spp: [NAS]
Necator americanus
Anclyostoma duodenale
Strongloides sterocoralis
intestinal-tissue spp: [TD]
Trichinella spiralis
Dracunculus medinensis
The feeding, non-infective first-stage larval form of certain nematodes, characterized by a short buccal cavity and a prominent genital primordium.
rhabditiform larvae
[can feed but cannot infect
have a short mouth area and a developing reproductive system.]
The non-feeding, infective third-stage larval form of nematodes, adapted for host penetration with a long esophagus and a pointed or notched tail.
Filariform Larvae
[do not eat but are ready to infect]
A flared, cuticular expansion at the posterior end of male nematodes, used for grasping the female during mating.
Copulatory Bursa
The oral opening of nematodes, which varies in length and structure and is used for feeding and host attachment.
Buccal Cavity
A form of asexual reproduction where a female produces offspring without fertilization by a male
parthenogenetic
*seen in Strongyloides stercoralis
reproductive strategy where the female gives birth to live larvae instead of laying eggs.
viviparous
*observed in Trichinella spiralis.
A reproductive strategy where the female produces eggs that hatch inside her body, releasing live larvae.
ovoviviparous
*as seen in Dracunculus medinensis.
A term referring to a fertilized female nematode carrying developing eggs or larvae.
gravid
*such as the gravid T. spiralis female that releases live larvae
[means a female worm is carrying fertilized eggs or developing larvae inside her body.]
The process by which a larva forms a protective cyst within host tissue, allowing for long-term survival and transmission.
encystation
*as seen in Trichinella spiralis.
general characteristics of nematodes
● Multicellular roundworms (cylindrical in cross-section).
● Bilaterally symmetrical, with a complete digestive and reproductive system.
● Nematodes are eukaryotes/ eukaryotic cells.
[Multicellular roundworms:
made up of many cells, and their bodies are shaped like tubes (cylindrical).
Bilaterally symmetrical:
If you cut them down the middle, both sides of their body would look the same. They also have a full digestive and reproductive system.
Eukaryotic:
Their cells have a nucleus.]
what are the 3 morphologic forms of nematodes
- Eggs
Female sex cells post-fertilization, varying in size & shape. - Juvenile worms (larvae)
Long, slender, and actively developing. - Adult worms
Mature nematodes, with
separate sexes (Dioecious).
Females are larger than males.
it refers to a species that has separate male and female individuals
Dioecious
[means there are distinct male and female worms, rather than both sexes being in the same body]
when does the nematode reproductive system begins
when fertilized eggs are expelled via stool
briefly explain the maturation process
Eggs → Larvae (juveniles) → Adult worms
○ Developing larvae emerge from fertilized eggs in the right environment. [ environment is suitable (like warm, moist conditions), baby worms (larvae) break out of the fertilized eggs.]
○ Adult worms reside in the intestine, focusing on nutrition & reproduction.
briefly explain how fertilized adult female nematodes lay eggs in the intestine
eggs exit via stool and require warm, moist soil (2-4 weeks) for development.
once mature, the eggs become infectious and restart the cycle
[-cycle starts with fertilized eggs being released in stool then develop in the environment and eventually become infectious.
-person or animal accidentally swallow these infectious eggs
-once inside the intestine, the eggs hatch into larvae.
-larvae mature into adult worms, which reproduce and lay more eggs = restarting the cycle.
Key Point:
The infective stage is usually the egg, not the larvae (for most nematodes). The larvae only develop inside the host after the eggs are swallowed.]
where does the Trichinella & Dracunculus primarily reside in
tissue, not js the intestine
*Some nematodes can exist free-living, independent of a host.
how nematodes can infect humans
- ingestion
Consuming infective eggs or larvae
(e.g., Pinworms, Ascaris ) - inhalation
Eggs inhaled and swallowed.
(e.g., Enterobius) - skin penetration
Infective larvae burrow into the skin
(e.g., Hookworms) - vector-borne transmission
Blood-sucking insects transmit filarial worms
(e.g., Wuchereria Bancrofti)
habitat of adult nematode
- small intestine
ASCARIS LUMRICOIDES
STRONGYLOIDES STERCORALIS
HOOKWORM
TRICHINELLA SPIRALIS - large intestine
TRICHURIS TRICHIURA
ENTEROBIUS VERMICULARIS - lymphatic
WUCHERIA BANCROFTI
BRUGIA MALAYI - subcutaneous
LOA LOA
ONCHOCERCE VOLVULUS
what are the hookworm adult that can be found in the small intestine
[CASHT]
Capillaria philippinensis
Ascaris lumbricoides
Strongyloides stercoralis
Hookworm
Trichinella spiralis
what are the 2 organisms of hookworm and briefly explain its
1.shape
2. buccal capsule (mouth parts)
3. borsa and dorsal ray
4. spicules
Ancylostoma duodenale
Necator americanus.
- both have a curve or hook-like appearance
- A: teeth
N: cutting plates - copulatory bursa in males used for matting. (show subtle structural diff in dorsal ray)
- male reproductive structures also differ in shape and orientation btwn the 2
why does the nematode eggs has thin shell
as it contains developing embryos
- to hold and protect
morphology of hookworms
Ancyclostoma duodenale
Necator americanus
both have
- thin, smooth, colorless shell
- unsegmented or embryonic cleavage
= they are morphologically indistinguishable, report as hookworm ova
*N (60-75um) is bigger than A (55-60um)
common name of
Ancyclostoma duodenale:
Old World Hookworm
*clear spaces btwn segmented ovum and thin clear shell of A duodenale ova
[The egg has a thin, clear outer shell that is smooth.
Inside the shell, the developing embryo (segmented ovum) has a clear space around it = does not completely fill the egg.]
Necator americanus:
New World Hookworm
