Many other common diseases are caused by autoimmunity such as juvenile diabetes and low thyroid disease. It has been recently discovered that some persons who suffer with hives or angioedema also have an autoimmune disease. In these cases, autoantibodies have been formed that bind to the Fc-receptor on mast cells.
Lesson Summary. Chitin is a primary component in the exoskeletons of arthropods and crustaceans and is also found in the cell walls of fungi. It's a polysaccharide, and it's excreted by the epidermal cells in arthropods. But, it can't grow with the animal, so shedding becomes necessary.
Chitin is a substance found in the shells, or exoskeleton, of horseshoe crabs, as well as other arthropods, such as lobsters, crabs, shrimp, spiders, beetles, and mosquitoes. Chitin has received a lot of attention from scientists because it is non-toxic and biodegradable.orseshoe crabs belong to the phylum, Arthropoda, along with crabs, insects, and other invertebrates with jointed legs, but their closest living relatives are spiders and scorpions. True crabs have two pairs of antennae and a pair of mandibles, or jaws; horseshoe crabs lack these structures.