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A skeleton is the structural frame that supports the body of most animals.There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal frame to which the organs and soft tissues attach; and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids.
Leonardo da Vinci made notes for a planned anatomical treatise in which he intended to compare the hands of various animals including bears. [4] Pierre Belon, a French naturalist born in 1517, conducted research and held discussions on dolphin embryos as well as the comparisons between the skeletons of birds to the skeletons of humans. His ...
Discarded exoskeleton of dragonfly nymph Exoskeleton of cicada attached to a Tridax procumbens (colloquially known as the tridax daisy)An exoskeleton (from Greek έξω éxō "outer" [1] and σκελετός skeletós "skeleton" [2] [3]) is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs ...
Two recent hypotheses about the evolution of biomineralization in arthropods and other groups of animals propose that it provides tougher defensive armor, [55] and that it allows animals to grow larger and stronger by providing more rigid skeletons; [56] and in either case a mineral-organic composite exoskeleton is cheaper to build than an all ...
A true endoskeleton is derived from mesodermal tissue. In three phyla of animals, Chordata, Echinodermata and Porifera (), endoskeletons of various complexity are found.An endoskeleton may function purely for structural support (as in the case of Porifera), but often also serves as an attachment site for muscles and a mechanism for transmitting muscular forces as in chordates and echinoderms ...
The three small bones in the middle ear of mammals including humans, the malleus, incus, and stapes, are today used to transmit sound from the eardrum to the inner ear. The malleus and incus develop in the embryo from structures that form jaw bones (the quadrate and the articular) in lizards, and in fossils of lizard-like ancestors of mammals.
The arthropod exoskeleton is divided into different functional units, each comprising a series of grouped segments; such a group is called a tagma, and the tagmata are adapted to different functions in a given arthropod body. For example, tagmata of insects include the head, which is a fused capsule, the thorax as nearly a fixed capsule, and ...
The composition of these structures, and the mechanisms involved in building them, are highly diverse. For example, some corals can incorporate both calcite and aragonite polymorphs into their skeletons. Some species, like corals and byrozoans, can incorporate other minerals to form complex protein matrices that perform specific functions. [2] [3]