Endoskeleton

Common card · No. 286647

An endoskeleton (from Ancient Greek ἔνδον (éndon), meaning "inside", and σκελετός (skeletós), meaning "skeleton") is a structural frame (skeleton) — usually composed of mineralized tissue — on the inside of an animal, overlaid by soft tissues. Endoskeletons serve as structural support against gravity and mechanical loads, and provide anchoring attachment sites for skeletal muscles to transmit force and allow movements and locomotion. Vertebrates and the closely related cephalochordates are the predominant animal clade with endoskeletons (made of mostly bone and sometimes cartilage, as well as notochordal glycoprotein and collagen fibers), although invertebrates such as sponges also have evolved a form of "rebar" endoskeletons made of diffuse meshworks of calcite/silica structural elements called spicules, and echinoderms have a dermal calcite endoskeleton known as ossicles. Some coleoid cephalopods (squids and cuttlefish) have an internalized vestigial aragonite/calcite-chitin shell known...

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