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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).
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 .
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
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).
The subcutaneous tissue (from Latin subcutaneous ' beneath the skin '), also called the hypodermis, hypoderm (from Greek ' beneath the skin '), subcutis, or superficial fascia, [2] is the lowermost layer of the integumentary system in vertebrates. [3]
The following outline is provided as an overview of and topical guide to human anatomy: . Human anatomy is the scientific study of the morphology of the adult human.It is subdivided into gross anatomy and microscopic anatomy.
The bones were determined to be up to 47,500 years old. Until now, the oldest Homo sapiens remains from northern central and northwestern Europe were about 40,000 years old.
Sclerotised tubular leg segments house the leg muscles, their nerves and attachments, leaving room for the passage of blood to and from the hemocoel. Hardened plates in the exoskeleton are called sclerites. Sclerites may be simple protective armour, but also may form mechanical components of the exoskeleton, such as in the legs, joints, fins or ...