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Skin plays an important immunity role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discoloured and depigmented.
In the hollow within bones are many other cell types of the bone marrow. Components that are essential for osteoblast bone formation include mesenchymal stem cells (osteoblast precursor) and blood vessels that supply oxygen and nutrients for bone formation. Bone is a highly vascular tissue, and active formation of blood vessel cells, also from ...
Osteocytes are mechanosensor cells that control the activity of osteoblasts and osteoclasts [16] within a basic multicellular unit (BMU), a temporary anatomic structure where bone remodeling occurs. [17] Osteocytes generate an inhibitory signal that is passed through their cell processes to osteoblasts for recruitment to enable bone formation. [18]
In structure, it consists of a keratinized stratified squamous epithelium; four types of cells: keratinocytes, melanocytes, Merkel cells, and Langerhans cells. The predominant cell keratinocyte , which produces keratin , a fibrous protein that aids in skin protection, is responsible for the formation of the epidermal water barrier by making and ...
Osteoblasts, the bone-forming cells, secrete the organic components of bone matrix [osteoid] and then initiates its mineralization. As osteoblasts become surrounded by the bone matrix, they differentiate into osteocytes , which reside in the lacunae and maintain bone tissue.
The matrix is hardened by the binding of inorganic mineral salt, calcium phosphate, in a chemical arrangement known as bone mineral, a form of calcium apatite. [8] [9] It is the mineralization that gives bones rigidity. Bone is actively constructed and remodeled throughout life by special bone cells known as osteoblasts and osteoclasts.
As the cells continue to elongate, a group of cells immediately above the notochord change their shape, forming a wedge in the ectodermal region. These special cells are called medial hinge cells (MHPs). As the ectoderm continues to elongate, the ectodermal cells of the neural plate fold inward.
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).