FINAL - Phylum Nematoda Flashcards
Nematodes are commonly called __________
roundworms
2 classes of parasitic nematode
(1) Secernentea (Phasmidia)
2) Adenophora (Aphasmidia
Phasmids
small sensory organs, located posteriorly on body surface of secernenteans
Most human-infecting nematodes belong to this class:
Secernentea
Nematodes characteristics:
elongated, sharply tapered at both ends, uniformly cylindrical (round), bilaterally symmetrical, and possess a pseudocoelom within which all organ systems are found
Tube with in a tube:
Outer tube: the body wall and underlying muscles
inner tube: the complete digestive system with an anterior mouth and a posterior anus
They are _______ with _________:
dioecious
sexual dimorphism
The body wall comprises of the:
cuticle, epidermis and muscles
Cuticle
forms the outermost covering of the body
Metabolically active
Cuticle surface characteristics
surface may be smooth or non-smooth
structures like bristles, microvilli, spines, warts may be present
Cuticle consists of 4 regions:
epicuticle
exocuticle
mesocuticle
endocuticle
Hypodermis
lies beneath the basal lamina and secretes the cuticle
Muscle types present/absent
Circular muscle is absent
Only longitudinal muscle is present
Digestive System
Complete digestive tract with mouth, gut & anus
3 major regions of the gut:
fore-, mid-, and hindgut
Foregut
begins at the mouth, circular opening and surrounded by lips
Buccal cavity lies between the mouth and esophagus
Has muscles
Midgut
aka intestine
simple tube-like
made of 1 layer of cells
With out muscles
Junction between fore-& midgut
esophagus-intestinal valve
________ serves as the primary means of excretion of ____________, in addition to its function in nutrient ________________
Intestine
waste products
digestion and absorption
Hindgut
lies posteriorly. The anus opens to the outside mid-ventrally
Excretory System:
Excretion is via renette cells
renette cells
unicellular glands that eliminate foreign substances through an excretory pore
Male testis:
1 testicle sometimes 2
May be short & uncoiled or long and thread-like
Sperm’s pathway:
Testis –> Vas deferens or sperm duct –> seminal vesicle (sperm is stored) –> ejaculatory duct –> cloaca with 2 pouches containing copulatory spicules
Females
Didelphic - 2 ovaries (most common)
Monodelphic and polydelphic less common
Egg’s pathway:
Ovary –> oviduct –> uterus –> vagina –> vulva
Sperm movement
Sperms lack cilia or flagella and move by using pseudopodia
Eggs have a shell composed of 3 or 4 layers:
1) vitelline layer
2) chitinous layer
3) lipid layer
4) proteinous layer (in ascaris and trichuris)
4 molting stages of larva when hatching form egg:
(1) formation of new cuticle
(2) loosening of the old cuticle
(3) breakage of the old cuticle
(4) escape of the larva
Hypobiosis
a lag phase at some stage of development occurs which is an adaptation to withstand unfavorable environmental conditions
Larval forms
1st stage: L1
2nd: L2
3rd: L3
4th: L4
