Skin Structure Epidermis—outer layer Summary of layers from deepest to most superficial o Stratum basale o Stratum spinosum o Stratum granulosum o Stratum lucidum (thick, hairless skin only) o Stratum corneum It is interesting to note that the “spiny” nature of this layer is an artifact of the staining process. Figure 6. Layers of the Dermis. This stained slide shows the two components of the dermis—the papillary layer and the reticular layer. A sudden drop in oxygenation can affect skin color, causing the skin to initially turn ashen (white). Within the papillary layer are fibroblasts, a small number of fat cells (adipocytes), and an abundance of small blood vessels. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat. Individuals with vitiligo experience depigmentation that results in lighter colored patches of skin. Two other cell types are found dispersed among the basal cells in the stratum basale. It has a fifth layer, called the stratum lucidum, located between the stratum corneum and the stratum granulosum (Figure 2). Beneath the dermis lies the hypodermis, which is composed mainly of loose connective and fatty tissues. Eumelanin exists as black and brown, whereas pheomelanin provides a red color. In many animals, there is a pattern of storing excess calories as fat to be used in times when food is not readily available. These two proteins make up the bulk of the keratinocyte mass in the stratum granulosum and give the layer its grainy appearance. The deeper layer of skin is well vascularized (has numerous blood vessels). Most of the skin can be classified as thin skin. It also has numerous sensory, and autonomic and sympathetic nerve fibers ensuring communication to and from the brain. As new cells are formed, the existing cells are pushed superficially away from the stratum basale. Start studying Anatomy Cutaneous membrane. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. The edges of the lips are covered with reddish skin, sometimes called the vermilion border, and abundantly provided with sensitive nerve endings. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. group of membrane tissues that includes mucous, serous, and the cutaneous membranes cutaneous membrane dry membrane with 2 layers: epidermis and dermis a.k.a. Within the papillary layer are fibroblasts, a small number of fat cells (adipocytes), and an abundance of capillary loops. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat. The increased keratinization (also called cornification) of the cells in this layer gives it its name. Dermal papillae increase the strength of the connection between the epidermis and dermis; the greater the folding, the stronger the connections made (Figure 4). epithelial membranes: cutaneous, mucous, and serous: connective tissue membranes: synovial capsules, bursae, and tendons: cutaneous membrane: the skin: ... outer layer of skin: dermis: inner layer of skin: hypodermis (subcutaneous tissue) adipose tissue: tissue of the epidermis: made of stratified squamous epithelium: strata The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. Thus, the amount of melanin present in our skin is dependent on a balance between available sunlight and folic acid destruction, and protection from UV radiation and vitamin D production. In addition, the papillary layer contains phagocytes, defensive cells that help fight bacteria or other infections that have breached the skin. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument. Although you may not typically think of the skin as an organ, it is in fact made of tissues that work together as a single structure to perform unique and critical functions. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. The skin protects the body by providing three types of barriers. Figure 8. Superficial epidermis is composed of keratinized stratified squamous epithelium III. This layer also contains lymphatic capillaries, nerve fibers, and touch receptors called the Meissner corpuscles. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. 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