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In humans, they constitute 90% of epidermal skin cells. [1] Basal cells in the basal layer (stratum basale) of the skin are sometimes referred to as basal keratinocytes. [2] Keratinocytes form a barrier against environmental damage by heat, UV radiation, water loss, pathogenic bacteria, fungi, parasites, and viruses.
The skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. [8] The epidermis is divided into several layers, where cells are formed through mitosis at the innermost layers.
The cells of these two layers, together called the Malpighian layer(s) after Marcello Malpighi, divide to form the superficial granular layer (Stratum granulosum) of the epidermis. [20] The cells in the stratum granulosum do not divide, but instead form skin cells called keratinocytes from the granules of keratin.
It emerges and originates from the outer layer of germ cells. The word ectoderm comes from the Greek ektos meaning "outside", and derma meaning "skin". [2] Generally speaking, the ectoderm differentiates to form epithelial and neural tissues (spinal cord, nerves and brain).
Others serve to anchor the epidermis glabrous skin (hairless), and hyper-proliferative epidermis (from a skin disease). [1] They divide to form the keratinocytes of the stratum spinosum, which migrate superficially. [2] Other types of cells found within the stratum basale are melanocytes (pigment-producing cells) and Merkel cells (touch receptors).
The dermis is composed of three major types of cells: [3] fibroblasts, macrophages, and mast cells.. Apart from these cells, the dermis is also composed of matrix components such as collagen (which provides strength), elastin (which provides elasticity), and extrafibrillar matrix, an extracellular gel-like substance primarily composed of glycosaminoglycans (most notably hyaluronan ...
These stem cells develop into both keratinocyte precursors and melanoblasts - and these melanoblasts supply both hair and skin (moving into the basal layer of the epidermis). There is additionally evidence that melanocyte stem cells are present in cutaneous nerves, with nerve signals causing these cells to differentiate into melanocytes for the ...
This complex surrounds cells in the stratum corneum and contributes to the skin's barrier function. Corneodesmosomes (modified desmosomes) facilitate cellular adhesion by linking adjacent cells within this epidermal layer. These complexes are degraded by proteases, eventually permitting cells to be shed at the surface. Desquamation and ...