L16: Intestinal nematodes Flashcards
Name general characteristics of nematodes
long, cylindrical, unsegmented bilately, symsttry, covered by cuticle
Describe the face of nematodes
- pseudocoelomates with body cavity
- no suckers/hooks/respiratory/circulatory
- male smaller than female
- nematode infection impact human/animal health a lot very important
What is the body wall made of
outer cuticle, hypodermis, somatic musculature
Go in depth about quantites of body wall
- cutile
*covers whole body and lines cavity, recturm, vagina and pore
*has metabolically active enzymes
*smooth with spines, ridges for locomotion
*molted and reformed 4 times in life - hypodermis to secrete cuticle
- somatic musculature with longi muscles arranged in > 1 rows with different shapes
has 2 muscle regions
contactical with myofibrils and non contracile to hold organelles
What are the layer of cutiicl
It consists of 4 basic layers
i. Epicuticle
ii. Exocuticle
iii. Mesocuticle
iv. Endocuticle
What is the digestive tract of nematodes made of
have compelte digestive tract
foregut: for digestion, mouth, phyraniz, esophogous
midgut: intestine, sight of absoroption with microvilli and digestion
hingut: in females it has recturm and anus in males it has reprodutive parts
What does the nervous system of nemotodes consit of
circumesophageal commissure – also called the nerve ring, surrounds the esophagus
Rectal commissure – encircles the rectum
Longitudinal nerve trunks from the nerve ring extends the length of the nematode and peripheral nerves
branch from here to supply sensory organs
What is the exretory system of nematodes
1 or 2 renettes
digestive tract is the principal excretory organ, so this is only osmoregulatory
no flame cells
Desrcibe reproctuve system of nematodes
seperate sexes => diosecious
tubular organs lysin in pseudocoelom
Detail the male reproductive system of nematodes
posterio end is curved
structures exten to cloacoa
single testis
1 or more copulatory spicules to keepvulva open
spicule guide
Detail male reproductive system of female
didelphic with 2 ovaries and 2 uteri
single vagina and vulva
Life cycle of Nematodes
Sexual reproduction occurs within an infected definitive host
* Typically includes 6 stages – egg, 4 juvenile larval stages and adult
* Infectious stages for humans and animals are either the egg or larva
* Eggs only hatch under specific, favorable external conditions to protect the larva
* Larval stages are separated by rounds of molting
Molting nematodes general characteristics
nematodes go trough 4 rounds of molting or excheatment
during the process it forms a new cuticle, loosens the old one, reaptures to break out of the old one and escapes the larva
controlled by exsheating fluid
host and site specific
Enterobius vermicularis
def host: humans
int host: none
causes enteribasis
worldwide, common in temperate places
kids, overcrowded
most common in N.aermica
whip shape, females have pointed tail = pinworm
Life Cycle of Enterobius vermicularis
- Gravid adult female worms deposit eggs on perianal folds
- Infection occurs via autoinfection (transferring eggs to the mouth with
hands after scratching the perianal area) OR retroinfection by L3
larvae
that hatch from perianally located eggs and migrate back up the host’s
GIT OR cross-infection (exposure to eggs in the environment e.g.,
contaminated surfaces, clothes, bed linens, infected persons etc.) OR
inhalation of airborne eggs - Following ingestion of infective eggs, larvae hatch in the small intestine
- The adults establish themselves in the colon, usually in the cecum
- Gravid females migrate nocturnally outside the anus and oviposit while
crawling on the perianal skin. Females lay up to 15,000 eggs daily
Larvae inside the eggs develop (become infective) in 4-6 hours under optimal
conditions. Eggs can remain viable for up to 20 days in a moist environment
