一、Purpose of teaching




Дата канвертавання27.04.2016
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Phylum platyhelminthes

Experiment 4

Class nematode (geo-nematodes)

一、Purpose of teaching

1. Master the morphological charactristic of the nematodes (roundworm)

2. Recognize the adults and eggs of nematodes (roundworm).

二、Contents of experiments

1. Self-observation: slide specimen and observed under the microscope

Eggs of Ascaris lumbricoides,

Hookworms (Ancylostoma duodenale and Necator americanus.)



Trichuris trichiura,

Enterobius vermicularis,

2. Demonstration: gross specimen and macroscopic observation

⑴ adult of Ascaris lumbricoides,

Hookworms (Ancylostoma duodenale and Necator americanus.)



Trichuris trichiura,

Enterobius vermicularis,

⑵ intestinal obstruction caused by Ascaris lumbricoides,

⑶ intestinal hookworm disease
the worms use their buccal capsule and teeth to burrow through the mucosa, where they vigorously begin feeding upon blood.

三、works:


Drawing the picture of eggs of geonematodes
Ascaris lumbricoides

一、Self-observation



Egg(microscopic observation)

They are unsegmented when deposited, have a thick shell with an outer albuminous,


(1) Fertilized eggs:

Oval to round, 45-75μm by 35-50μm, with a thick, lumpy outer shell (proteinaceous layer) that is contributed by the uterine wall.


(2) Unfertilized eggs:

Elliptical in shape, approdinmately 88-94μm in length by 39-44μm in breadth

They are usually elongate with a relatively thin middle layer of the shell and often with little or no outer mammillated layer and consists of a mass of disorganized, highly refractive granules of various sizes.
二、Demonstration

Adult worm(macroscopic observation)

Adults

1. Shape:cylindrical in shape,tapering gradually at the anterior end and somewhat less an the posterior end. Covered with cuticles.the cuticle has fine circular striations.The sexes are separate, generally males are much smaller than female worms.The posterior end of the female is straight,while that of the male curves ventrally, and there are a pair of copulatory spicules.

2. Size: the largest nematode in human intestine,

Adult females: 20 to 35 cm long, may reach 49 cm; by 3-6 mm in diameter.


adult male: 15 to 30 cm ,by 2-4 mm in diameter.

3. Colour:

They are creamy-white in color, sometimes with a pinkish cast



4. Structure: simple esophagus without a venticulus .

buccal cavity: centrally located among the lips is a small triangular buccal cavity. one dorsal and two ventrolateral lips, the lips bear dentigerous ridges; fine denticles, papillae and cephalic sensors.

The genitalia:

Male:consist of a long single tubule made up of testis, vas defenrens , and ejaculatory duct.

Female: consist of a double tubules made up of uterus, oviduct, ovary.

copulatory spicules

The male curves ventrally,and there are a pair of copulatory spicules at the tail.

5. Pathgenesis specimen

Intestinal obstruction caused by Ascaris lumbricoides


三、Homework :

Drawing the eggs of Ascaris lumbricoides.

Hookworms

(Ancylostoma duodenale and Necator americanus.)

、Self-observation

Egg(microscopic observation)

The eggs are ovoid, measuring 64-75μm by 34-40μm, and containing 1-8 cells or embryos. Their shells are thin and hyaline.

、Demonstration

Adult worm(macroscopic observation)

Adults

Ancylostoma duodenale

Necator americanus

(Adult females: 10 to 13 mm (A. duodenale), 9 to 11 mm (N. americanus); adult males: 8 to 11 mm (A. duodenale), 7 to 9 mm (N. americanus).


A. duodenale is “C” shaped , but N. americanus is “S” shaped in appearance.
There are 2 pairs of ventral teeth in buccal capsule of A. duodenale, and 1 pair of ventral semilunar cutting plates in N. americanus, buccal capsule.

Identification of male and female adult hookworms:

♀: The posterior end is cone-shaped.
♂: The posterior end is elliptic and fan-shaped (umbrella-shaped bursa, with riblike rays).

Hookworm buccal capsules.



(a) Ancylostoma. (b) Necator.


三、Homework :

Drawing the eggs of Ascaris lumbricoides.


Enterobius vermicularis

Morphology
Adults: are small, milk-white.

♀: 8-13 mm, slender, sharp-pointed tail.

♂: smaller than♀, 2-5 mm, with vertrally curved posterior end.
Some cuticle structures are formed such as cephalic alae, lateral alae, striation, lips, and buccal cavity.
Eesophageal bulb and the uteri distended with eggs can be seen under light microscope.

Eggs :are elongated-oval and flattened on one side, 50-60 µm by 20-30 µm, contain a larva.


The stereogram of the egg is unequally triangle shuttle in shape






Trichuris trichiura

Morphology

Adults: whiplike,

♀: 30-50 mm in length; ♂: slightly smaller.
Eggs: lemon-shaped, each with a prominent opercular plug at each end (pole),

50-54 µm by 22-23 µm, containing an uncleaved zygote.




三、Homework :



Drawing the eggs of Trichuris trichiura and Enterobius vermicularis







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