Nematodes 1 Flashcards
2 types of helminths
Nemathelminths
Platyhelminths
2 Platyhelminths
Trematodes
Cestodes
Common name:________
Elongated and cylindrical in shape, with bilateral symmetry
Non-segmented
Rounded anterior end; tapered posterior end
roundworm
Nematode
Color of nematodes
Light cream-white in color
Pinkish= well-nourished
Body wall of nematodes
Cuticle = outermost layer
Hypodermis
Somatic musculature = innermost layer
Covered by tough, elastic protective covering
Metabolically active and periodically undergoes molting
cuticle
4 LAYERS OF THE CUTICLE
Epicuticle
Exocuticle
Mesocuticle
Endocuticle
Epicuticle:
thin, protective barrier that contains______
glycocalyx
with obliquely oriented collagenous, fibrous sublayers that can shift angles of orientation, thus, providing flexibility to the cuticle
Mesocuticle
fibrous layer but orientation of fibers is indistinct
Endocuticle
Structure that separates the cuticle from the underlying hypodermis
Basal Lamina
Thin, cellular structure that secretes the cuticle
Gives rise to the entire layer of the cuticle
Hypodermis
Protrudes into the pseudocoelom (cavity; internal to the nematode) along the mid-dorsal, mid-ventral, and lateral lines
Hypodermis
Hypodermal chords
Lateral cords: excretory canal
Important in the excretion of metabolic products
Dorsal and ventral cords: longitudinal nerve trunks
One or more layers of longitudinally arranged muscle cells
Function: Probing and penetrating motion
somatic musculature
3 Types of somatic musculature
Polymyarian
Holomyarian
Meromyarian
= more than 5 groups of muscle
= 1-2 groups of muscle
= 2-5 groups of muscle
Polymyarian
Holomyarian
Meromyarian
Cavity that contains fluid called hemolymph which bathes the internal organs
Offers protection by acting as a cushion
Acts as a hydrostatic skeleton, providing support and rigidity
Pseudocoelom
T or F
Nematodes have a complete digestive tract?
Yuh
3 parts of GUT
Foregut
Midgut
Hindgut
Digestive tract of nematodes
Gut
Cloaca/ anus
Subterminal vent
Mouth
Nematodes have___ lips
Pharynx:______
Esophagus: may be equipped with muscular enlargement called_____ (most posterior portion of the foregut)
FOREGUT
3
triradiate (3 radiations)
bulbs
Intestine
MIDGUT
HINDGUT
Male:
Female:
cloaca
rectum → anus
where the fecal material and the ejaculatory duct are contained in male
cloaca
2 major nerve centers
Circumesophageal commissure or nerve ring
Rectal commissure
at the anterior portion
Corresponds to the brain (CNS) of the nematode
Ganglia from longitudinal nerves
Circumesophageal commissure or nerve ring
at the posterior end
Ganglia from ventral longitudinal nerve
Rectal commissure
Receptors of the NS
- Mechanoreceptors
- Chemoreceptors
Receptor
Located around the mouth
Mechanoreceptor
Types of mechanoreceptors
lips surrounding the mouth
behind the lips
Labial papilla:
Cephalic papilla:
2 types of chemoreceptors
anteriorly located
posteriorly located
Amphids:
Phasmids:
Class of nematode containing sensory organs at the anterior end
APHASMIDS
Aphasmidea
Ex of aphasmids
Trichinella spiralis
Trichuris trichiura
Capillaria philippinensis
Class of nematode containing sensory organs at the caudal end
PHASMIDS
Phasmidea
Ex of phasmids
Hookworms
Ascaris lumbricoides
Strongyloides stercoralis
Enterobius vermicularis
Filarial worms
T or F
Nematodes are dioecious
TRUE!
: even in the absence of a male, a female adult nematode can procreate (asexual reproduction)
parthenogenetic
Sexes are separate
There are male and female
Dioecious
______are curved posteriorly
______are flat posteriorly
Males
Females
MALE REPRODUCTIVE ORGAN
_____tubule
______testes its smaller end
Extends into a vas deferens and seminal vesicle
Terminates in an ejaculatory duct opening into the cloaca (combination of hindgut/posterior portion of GIT and ejaculatory duct)
Single
One or two
: guides the spicules when extended
Gubernaculum
Penis of male nematodes
Spicule
T or F
Sperm has a flagella or acrosomes (mmotile)
FALSE!!!
Sperm has no flagella or acrosomes (immotile)
T or F
FEMALE REPRODUCTIVE ORGAN
Usually, didelphic (has left & right ovaries)
Two cylindrical ovaries which expand into uteri
TRUEE
Female reproductive organ
______unite to form a common vagina
Single______ or vulva
Uteri
gonophore
Opening of the reproductive organ to the exterior
Frequently located near the middle of the body
Varies in position between species
Single gonophore or vulva
: being fertilized in the spermatheca
= area where fertilization occurs
Oogonia
Spermatheca
Basic component of the excretory system
Large unicellular gland that empties through an excretory pore
Renettes
Stages of nematodes
Adult: diagnostic stage
Ova: infective stage
Larva: infective stage
Modes of transmission
IISMIA
Ingestion of embryonated eggs
Ingestion of infective larvae
Skin penetration
Mosquito borne
Inhalation
Autoinfection
Ex
Ingestion of embryonated egg
Ascaris lumbricoides
Trichuris trichiura
Enterobius vermicularis
Ex
Ingestion of infective larvae
Capillaria philippinensis
Trichinella spiralis
Parastrongylus cantonensis
Ex
Skin Penetration
Hookworms
Strongyloides stercoralis
Ex
Mosquito-borne
Wuchereria bancrofti
Brugia malayi
Ex
Inhalation
Enterobius vermicularis
Ascaris lumbricoides
Ex
Autoinfection
Capillaria philippinesis
Strongyloides stercoralis
Enterobius vermicularis
: most of the nematodes
Produce egg, and the young hatches after being expelled from the body
Most common form in terms of production
Oviparous
Brings forth live young that have developed inside the body of the adult female nematode
Viviparous
Development of a female (rarely a male) gamete (sex cell) without fertilization
Asexual reproduction
Parthenogenetic
Ex
Small Intestine
CHATS
Capillaria philippinensis
Hookworms
Ascaris lumbricoides
Trichinella spiralis
Strongyloides stercoralis
Large Intestine (Colon)
ET
Enterobius vermicularis (pruritus ani)
Trichuris trichiura (rectal prolapse)
Tissue
FT GD
Filarial worms
Trichinella spiralis
Gnathostoma spinigerum
Dirofilaria immitis
Larva Migrans in Man
DAAA
Dracunculus medinensis
Angiostrongylus cantonensis
Ancylostoma caninum
Ancylostoma brazilense
Larval stages preceding each molt of the 4 molts in the life cycle are generally referred to as
L1, L2, L3, L4
MOLTING
FLRE
Formation of new cuticle
Loosening of the old cuticle
Rupturing of the old cuticle
Escape of the larva
: control the sequence of events of molting
Patients in steroids are prone to hyperinfection or hyperparasitism since steroids promote the molting of the larva
Exsheathing fluid
First stage larva of Strongyloides stercoralis and hookworms
Esophagus has terminal esophageal bulb
Rhabditiform Larva
L3 of Strongyloides stercoralis and hookworms
Long esophagus, no terminal bulb
Usually, infective stage to the definitive host
Filariform Larva
Prelarval form of filarial worms
Microfilaria
Stages of larva
Rhabditiform
Filariform
Mrcrofilaria
Developmental arrest
Lag phase at some stage of development - life cycle is temporarily arrested
Adaptation to withstand adverse environmental conditions while waiting for the host
Hypobiosis
APHASMID (anterior) (CaTT)
Capillaria philippinensis
Trichinella spiralis
Trichuris trichiura