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Skin flora, also called skin microbiota, refers to microbiota (communities of microorganisms) that reside on the skin, typically human skin. Many of them are bacteria of which there are around 1,000 species upon human skin from nineteen phyla. [1] [2] Most are found in the superficial layers of the epidermis and the upper parts of hair follicles.
It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbiota and also found in marine sponges. [2] [3] It is a facultative anaerobic bacteria. Although S. epidermidis is not usually pathogenic, patients with compromised immune systems are at risk of developing infection.
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. [1] The epidermis layer provides a barrier to infection from environmental pathogens [2] and regulates the amount of water released from the body into the atmosphere through transepidermal water loss.
For the average adult human, the skin has a surface area of 1.5–2.0 square metres (15–20 sq ft). The thickness of the skin varies considerably over all parts of the body, and between men and women, and young and old. An example is the skin on the forearm, which is on average 1.3 mm in males and 1.26 mm in females. [4]
For example, the expression of N-cadherin is crucial to maintaining separation of precursor neural cells from precursor epithelial cells. [2] Likewise, while the surface ectoderm becomes the epidermis , [ 6 ] the neuroectoderm is induced along the neural pathway by the notochord , which is typically positioned above it.
In reptiles, the stratum corneum is permanent, and is replaced only during times of rapid growth, in a process called ecdysis or moulting. This is conferred by the presence of beta-keratin, which provides a much more rigid skin layer. In the human forearm, about 1300 cells per cm 2 per hour are shed. [10]
An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial ) tissues line the outer surfaces of many internal organs , the corresponding inner surfaces of body cavities , and the inner surfaces of blood vessels .
Examples of bacteria containing intracellular membranes are phototrophs, nitrifying bacteria and methane-oxidising bacteria. Intracellular membranes are also found in bacteria belonging to the poorly studied Planctomycetota group, although these membranes more closely resemble organellar membranes in eukaryotes and are currently of unknown ...