ExerciseⅢ Observation of Nematode
Experimental objective
1.Master the use and maintenance of microscope.
2.Master the morphological features（egg）of different genius of medical Nematod include Ascaris lumbricoides（round worm），Trichuris trichiura Linnaeus（Whipworm），Enterobius vermicularis Linnaeus（Pinworm）and Ancylostoma duodenale（Hookworm）.
Experimental Principles
To observe the morphological features（egg）of different genius of medical Nematod by the optical microscope.Corresponding book color chart NO.36.
Laboratory equipment
1.Optical microscope.
2.Human parasitology teaching specimen.
Experiment methods and contents
Methods find the parasites at low magnification，and then observe them with high magnification（if necessary）
Contents:
Ascaris lumbricoides（round worm）
1.Adult worm
They are large cylindrical worms，with tapering ends，the anterior end being more pointed than the posterior.They are pale pink or flesh colored when freshly passed in stools，but become white outside the body.The mouth is surrounded by one dorsal and two ventrolateral lips.The posterior end of the female is straight while that of the male curves ventrally.
2.Egg
Two types of eggs are passed by the worms，fertilized and unfertilized.
（1）The fertilized eggs，laid by females，inseminated by mating with a male，are embryonated and develop into the infective eggs.It's round or oval in shape，always bile-stained，golden brown in color.It's surrounded by thick smooth translucent shell.In the middle of the egg is a large unsegmented ovum，containing a mass of coarse lecithin granules.
（2）The unfertilized eggs are laid by uninseminated females.These are nonembryonated and cannot become infective.It's ellipitical in shape，narrow and longer，has a thinner shell with an irregular coating of albumin.Contains a small atrophied ovum with a mass of disorganized highly refractile granules of various size.（Figure 1）
Figure 1 Ascaris lumbricoides
Trichuris
1.Adult worm（Corresponding book color chart NO.37）
Adult worm measures 30-50 mm in length，male being relatively smaller with coiled posterior end.The anterior part of the body is thin and long（two third of the body length）whereas the posterior part is thick and stout，thus appears as a whip.Mouth is simply an opening and does not contain any lips.Anus is located near the tip of tail.Male has single spicule surrounded by a spiny sheath.One fertilized female worm lays 1000-7000 eggs per day.
2.Egg（Corresponding book color chart NO.38）(https://www.daowen.com)
Eggs are barrel shaped，golden-brown in color and measure 50μm×25μm in size，with clear polar plug at each end.Embryonation takes place in environment.（Figure 2）
Figure 2 Trichuris egg
Enterobius vermicularis Linnaeus（Pinworm）
1.Adult worm（Corresponding book color chart NO.39，40）
The adult worm E.vermicularis has separate sexes.Female is bigger（8-12 mm in length）than male（2-5 mm in length）.The posterior end of male is strongly curved and bears a single，simple spicule（70μm in length）and a conspicuous caudal alae supported by papilae.The posterior end of female is extended into a long slender point（pin-like appearance）hence the name pinworm.The adult worms live in the caecal area where from the gravid female worm migrate at night to the perianal area to lay their eggs.
2.Eggs are colorless，plano-convex and measure（50-60）μm×（20-30）μm in size.Infection in man takes place by ingestion of eggs.（Figure 3）
Figure 3 Pinworm
Ancylostoma duodenale（hookworm）
Corresponding book color chart NO.41.42
1.Adult worm
The adult worm：Female adults measure about 9 to 13 mm in length，while males are 5-11 mm long.A.duodenale has two pairs of teeth on the ventral wall of its buccal capsule.
2.Egg
The egg of hookworm is：
（1）Oval or elliptical，measuring 60 mim by 40 mim.
（2）Colorless，not bile stained.
（3）Surrounded by a thin transparent hyaline shell membrane.
（4）When released by the worm in the intestine，the egg contains an unsegmented ovum.
（5）During its passage down the intestine，the ovum develops.When passed in feces，the egg contains a segmented ovum，usually with 4-8 blastomeres.
（6）There is a clear space between the segmented ovum and the egg shell.
Figure 4 hookworm and hookworm egg