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Most of the barrier functions of the epidermis localize to this layer. [12] clear/translucent layer (stratum lucidum, only in palms and soles) This narrow layer is found only on the palms and soles. The epidermis of these two areas is known as "thick skin" because with this extra layer, the skin has 5 epidermal layers instead of 4.
The epidermis itself is devoid of blood supply and draws its nutrition from its underlying dermis. [5] Its main functions are protection, absorption of nutrients, and homeostasis. In structure, it consists of a keratinized stratified squamous epithelium; four types of cells: keratinocytes, melanocytes, Merkel cells, and Langerhans cells.
The main type of cells that make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, and basale.
The epidermis is the outermost cell layer of the primary plant body. In some older works the cells of the leaf epidermis have been regarded as specialized parenchyma cells, [1] but the established modern preference has long been to classify the epidermis as dermal tissue, [2] whereas parenchyma is classified as ground tissue. [3]
In the epidermis of skin in mammals, reptiles, and birds, the layer of keratin in the outer layer of the stratified squamous epithelial surface is named the stratum corneum. Stratum corneum is made up of squamous cells which are keratinized and dead. These are shed periodically.
The cells here may possess microvilli for maximizing the surface area for absorption, and these microvilli may form a brush border. Other cells may be ciliated to move mucus in the function of mucociliary clearance. Other ciliated cells are found in the fallopian tubes, the uterus and central canal of the spinal cord.
Micrograph of keratinocytes, basal cells and melanocytes in the epidermis Keratinocytes (stained green) in the skin of a mouse. Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. [1]
This circulation net has a big importance, it's the way of direct communication between the specific site of the skin and the lymph cells found inside the lymph node and the systematic tissues. The epidermis antigens are connected with some cells of the skin. Among them there are the APC, antigen presenting cells (Langerhans, dentritic and ...