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 major constituent of the exoskeleton, or external skeleton, of many arthropods such as insects, spiders, and crustaceans.hitin Hard, tough substance that occurs widely in nature, particularly in the shells (exoskeletons) of arthropods such as crabs, insects and spiders. The walls of hyphae (microscopic tubes of fungi) are composed of slightly different chitin.