An exoskeleton is a hard, external skeleton that protects an animal and that gives points of attachment for the muscles that provide movement for appendages. This nonliving cuticle is generally made from layers of chitin and protein. The exoskeleton tends to be larger around the head in order to protect the brain. However, in other locations such as joints of the abdomen and legs, it is thinner and more flexible. An arthropod is a segmented animal that has an exoskeleton and jointed appendages. In a process called molting, an arthropod must shed its exoskeleton and secrete a larger one as it grows. The hermit crab pictured here, an arthropod, has an exoskeleton that is a shell, that it sheds as the animal grows.