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The thickness of the epidermis varies from 31.2μm for the penis to 596.6μm for the sole of the foot with most being roughly 90μm. Thickness does not vary between the sexes but becomes thinner with age. [5] The human epidermis is an example of epithelium, particularly a stratified squamous epithelium.
The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbours many nerve endings that provide the sense of touch and heat.
The mechanical stress of heavy structural strain causes this stratum lucidum phase in these regions which require additional protection in order to grasp objects, resist abrasion or impact, and avoid injury. In general, the stratum corneum contains 15 to 20 layers of corneocytes. The stratum corneum has a thickness between 10 and 40 μm.
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 ...
Below the epidermis lies the dermis, which is approximately one millimeter thick, 100 times the thickness of the stratum corneum. The dermis contains small vessels that distribute drugs into the systemic circulation and to regulate temperature, a system known as the skin's microcirculation. [2] [3]
The ability of the skin to heal even after considerable damage has occurred is due to the presence of stem cells in the dermis and cells in the stratum basale of the epidermis, all of which can generate new tissue. When an injury extends through the epidermis into the dermis, bleeding occurs and the inflammatory response begins.
The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. [10] The superficial papillary dermis interdigitates with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. [ 10 ]
Within the healed epidermis they will be replaced by keratinocytes originating from the epidermis. [29] [30] At the opposite, epidermal keratinocytes, can contribute to de novo hair follicle formation during the healing of large wounds. [31] Functional keratinocytes are needed for tympanic perforation healing. [32]