Normal Skin

Abstract

The skin is generally considered to consist of three major layers: epidermis, underlying dermis, and subcutaneous fat. Depending on anatomic site, there are four to five layers of the epidermis. The layer closest to the basement membrane is the stratum basalis (or basal layer), which consists of a single layer of cuboidal cells that have a slightly basophilic cytoplasm and high nucleus to cytoplasm ratio. The stratum spinosum (or spinous layer) is above the stratum basalis and is so-called because of the prominent intercellular connections. The stratum granulosum (or granular layer) consists of flattened cells that contain coarse, basophilic granules. The stratum corneum (keratinous layer) is most superficial and consists of anucleate cells arranged in a basketweave pattern. On acral skin an additional layer called stratum lucidum is also present. The dermis consists of papillary dermis, consisting of a fine network of collagen and elastic fibers located immediately beneath the epidermis, and reticular dermis, which consists of thicker dense collagen bundles and extends to the subcutaneous fat. The thickness of the epidermis and dermis varies depending on the region of the body. Finally, the subcutis is composed of lobules of adipocytes separated by fibrous septae. Within the septae are blood vessels, lymphatics, and nerves.