In order from the deepest layer of the epidermis to the most superficial, these layers (strata) are the: Skin overview: Skin layers, of both hairy and hairless skin. The cells in the stratum basale bond to the dermis via intertwining collagen fibers, referred to as the basement membrane. An epithelium containing large amounts of keratin is termed a keratinized or cornified epithelium. These corneocytes are eventually shed into the environment and become part of the dandruff in our hair or the dust around us, which dust mites readily munch on. The stratum basale, also called the stratum germinativum, is the basal (base) layer of the epidermis. Let us also discuss the deepest to the most superficial layer of the epidermis. It contains no blood supply of its own—which is why you can shave your skin and not cause any bleeding despite losing many cells in the process. The dead cells in the exposed stratum corneum layer usually remain for two weeks before they are shed or washed away. From the stratum lucidum, the keratinocytes enter the next layer, called the stratum corneum (the horny layer filled with cornified cells). Carbon Cycle. From the most external to the deepest layers, these are: cornified layer (stratum corneum), translucent layer (stratum lucidum), granular layer (stratum granulosum), spinous layer (stratum spinosum) and basal or germinal layer (stratum basale/germinativum). This death occurs largely as a result of the distance the keratinocytes find themselves from the rich blood supply the cells of the stratum basale lie on top off. The stratum corneum is the top layer of your epidermis (skin). Water from the interstitial fluids slowly penetrates the surface and evaporates into the surrounding air. It is the layer that’s closest to the blood supply lying underneath the epidermis. emilypacific. Under the squamous cells are round cells called basal cells. The epidermis is itself divided into at least four separate parts. Medical Terminology Chapter 4: The Muscular System. epidermis [ep″ĭ-der´mis] (pl. Bodytomy takes a closer look at these layers along with their functions. It consists of a single layer of dividing cells. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Epidermis is formed by 4 or 5 layers of cells (depending on the skin region). The stratum basale is the deepest layer, while the stratum corneum is the outermost layer of epidermis. Mnemonicsused for remembering the layers of the skin (using "stra… hair follicle. Maintenance of this barrier involves coating the surface with the secretions of sebaceous and sweat glands (discussed in a later section). The upward waves are fingerlike extensions of the dermis called dermal papillae and the downward epidermal waves between the papillae are called epidermal ridges. In more superficial layers, this substance forms a complete water resistant layer around the cells that protects the epidermis, but also prevents the diffusion of nutrients and wastes into and out of the cells. It is the process where cells divide, making new epidermal skin cells. Beneath the epidermis is a connective tissue layer, the dermis. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. There are two layers of epidermis, the living basal layer, which is next to the dermis, and the external stratum corneum, or horny layer, which is composed of dead, keratin-filled cells that have migrated outward from the basal layer. 12 terms. This migration is slower in old age and faster in skin that has been injured or stressed. The tonofibrils act as cross braces, strengthening and supporting the cell junctions. The stratum basale (also called the stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. stratum germinativum: The basal layer—sometimes referred to as stratum basale—is the deepest of the five layers of the epidermis. Thick skin, found only on the palms of the hands and soles of the feet, contains all five layers and may be covered by 30 or more layers of keratinized cells. It takes 15–30 days for a cell to move superficially from the stratum basale to the stratum corneum. The deepest layer of the epidermis is composed of living cells while the upper layer is dead. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Mitosis requires an abundant supply of oxygen and nutrients, which these deep cells acquire from the blood vessels in the nearby dermis. On the fingertips, this wavy boundary forms the friction ridges that produce fingerprints. When melanocyte DNA is damaged by ultraviolet radiation, any resulting uncontrolled cell growth can lead to the skin cancer melanoma. Superficial to the stratum spinosum is the stratum granulosum (granular layer). The epidermis is composed of multiple layers of flattened cells that overlie … This single layer of cells is firmly attached to the basal lamina, which separates the epidermis from the loose connective tissue of the adjacent dermis. The corneocytes serve as a hard protective layer against environmental trauma, such as abrasions, light, heat, chemicals, and microorganism. Human skin: This image details the parts of the integumentary system. }). Stratum lucidum(not present in thin skin, only thick, hairless skin of palms & soles) 3. 9 terms. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Once the epidermal cells migrate more than two or three cells away from the dermis, their mitosis ceases. The epidermis is the outermost layer of our skin. The deepest layer of the epidermis is called the stratum basale, sometimes called the stratum germinativum. They divide to form the keratinocytes of the stratum spinosum, which migrate superficially. They are found only in the deepest layer of the epidermis, called the stratum basale. Layers of the Epidermis and their Functions The epidermis, which is the topmost layer, actually has 5 sub-layers. (3) Membrane-coating vesicles release a lipid mixture that spreads out over the cell surface and waterproofs it. 0.07 to 1.4 mm they originate from cells in the stratum granulosum, stratum lucidum ( not present in areas. Tough, outer layer of the skin is usually the thickest redder color and more sensitivity touch! 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