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Osteoderms represent hard tissue components of the integument, making them easy to identify in fossil examination. [2] This dermal armor is found prominently in many lizards. Some early amphibians have this armor, but it is lost in modern species with the exception a ventral plate, called the gastralia .
The skin (integument) is a composite organ, made up of at least two major layers of tissue: the epidermis and the dermis. [2] The epidermis is the outermost layer, providing the initial barrier to the external environment. It is separated from the dermis by the basement membrane (basal lamina and reticular lamina).
To better understand the structure of avian skin, avian skin has been broken down into three different functional components: hydraulic skeleto-muscular apparatus of the feathers This functional component consists of the only of the structural features of the feather tracts, namely the cutis , and connective tissue layer fascia superficialis.
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 ...
For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium. [22] The Fitzpatrick scale [23] [24] is a numerical classification schema for human skin colour developed in 1975 as a way to classify the typical response of different types of skin to ultraviolet (UV) light:
The word skin originally only referred to dressed and tanned animal hide and the usual word for human skin was hide. Skin is a borrowing from Old Norse skinn "animal hide, fur", ultimately from the Proto-Indo-European root *sek-, meaning "to cut" (probably a reference to the fact that in those times animal hide was commonly cut off to be used as garment).
Endochondral ossification is responsible for development of most bones including long and short bones, [4] the bones of the axial (ribs and vertebrae) and the appendicular skeleton (e.g. upper and lower limbs), [5] the bones of the skull base (including the ethmoid and sphenoid bones) [6] and the medial end of the clavicle. [7]
Arthropods are covered with a tough, resilient integument, cuticle or exoskeleton of chitin. Generally the exoskeleton will have thickened areas in which the chitin is reinforced or stiffened by materials such as minerals or hardened proteins. This happens in parts of the body where there is a need for rigidity or elasticity.