3 Skeletal Systems

There are three different types of skeletal systems: hydrostatic skeletons, exoskeletons, and endoskeletons. Hydrostatic skeletons are found mainly in soft-bodied invertebrates. Examples of these are as follows: squids, jellyfish, slugs, and earthworms. Basically, water is being pushed against the body which acts as a “skeleton.” The central cavity is surrounded by circular muscles and longitudinal muscles which go against the circular muscles. As circular muscles contract, longitudinal muscles react. Exoskeletons are a firm casing of the body. An example of what an exoskeleton is would be chitin surrounding the arthropods. Arthropods and the cell walls of fungi have chitin which acts as the skeleton. Chitin, a nonliving tissue, resists bending
and is the framework. A negative attribute to this is the fact that having an exoskeleton limits the size of such organisms. When individuals do indeed start to increase size, they are forced to molt (which is the shedding away of the exoskeleton as another begins to produce). Molting leaves each organism defenseless and in more danger and has a risk of not surviving. Endoskeletons are found in vertebrates and echinoderms. The skeletons of these organisms are found inside the body and are made up of cartilage and/or bone. Bone and cartilage are actual living tissue. Chitin is not living tissue.