Ascaris

Examine the cross section of Ascaris (a common intestinal parasite) images on top, right. First look at the outermost layer of the body. This consists of an epidermis and an outer cuticle. You need not be able to identify the internal organs in this cross section.

Keeping in mind where this organism lives, what do you think the function of the cuticle is? Now find the muscle layer located just inside the epidermis. Notice that all the muscle fibers have been cut in cross section. In what direction are the muscle fibers oriented? How does this affect the way a nematode moves?

To help visualize the three dimensional shapes of the structures seen above, click on the 'more images' button for an Ascaris dissection.