(2004). Once formed, these vesicles migrate into melanocyte processes and are transferred to neighboring keratinocytes. specialized cells in the epidermis that produce the dark pigment melanin from the amino acid tyrosine in organelles called melanosomes. Stratum Basale. Stratum basale The stratum basale (basal layer) consists of stem cells that continuously divide by mitosis to give rise to keratinocytes. State the location of these cells. When there is an irregular accumulation of melanocytes in the skin, freckles appear. As new keratinocytes are produced atop the stratum basale, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. However, in these cases the effect on skin color has nothing do with the skin’s pigmentation. [1], They divide to form the keratinocytes of the stratum spinosum, which migrate superficially. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. If you zoom on the cells at the outermost layer of this section of skin, what do you notice about the cells? The dermis might be considered the “core” of the integumentary system (derma- = “skin”), as distinct from the epidermis (epi- = “upon” or “over”) and hypodermis (hypo- = “below”). The accumulated granules give the layer its grainy appearance. s. The stratum lucidum is a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum. The desmosomes interlock with each other and strengthen the bond between the cells. The stratum basale (also called stratum germinativum) is the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The spinosum layer lies just over the stratum basale and is only about five to 10 cells thick. the cells that protect the stratum basale are. Stratum Basale 7d. Melanin comes in different shades of brown and black. Eumelanin exists as black and brown, whereas pheomelanin provides a red color. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. C. source of blood vessels in the epidermis. Two types of cells from the basal layer; keratinocytes and melanocytes. In addition, the papillary layer contains phagocytes, defensive cells that help fight bacteria or other infections that have breached epidermis. The body mass index (BMI) is often used as a measure of fat, although this measure is, in fact, derived from a mathematical formula that compares body weight (mass) to height. What are the basic functions of each of these layers? The thickness of the epidermis varies in different types of skin; it is only .05 mm thick on the eyelids, and is 1.5 mm thick on the palms and the soles of the feet. In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying dermal layer (papillary layer), resulting in the formation of the ridges on your fingers that you recognize as fingerprints. Langerhans cells granstein cells (both are part of the immune system) the merkel cell. As such, these cells are the most mitotically active keratinocyte… The basal cell layer (stratum basale, or stratum germinosum), is a single layer of cells, closest to the dermis. A finger-like projection, or fold, known as the dermal papilla (plural = dermal papillae) is found in the superficial portion of the dermis. The stratum spinosum (prickle cell layer) is composed of the daughter cells of the stratum basale (see Fig. Answer: The epidermis provides protection, the dermis provides support and flexibility, and the hypodermis (fat layer) provides insulation and padding. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma. The cells here (three to five layers thick) become flatter, their cell membranes thicken with a coating of lipids secreted by accumulated lamellar granules, and they generate large amounts of the fibrous proteins keratin, incorporating intermediate filaments of the cytoskeleton with filaggrin derived from proteins secreted by accumulated keratohyalin granules (see Figure \(\PageIndex{3}\)). Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis. b. melanocytes location: found only in the stratum basale but they have processes that extend up into the stratum spinosum function: make a brown pigment called melanin and they transfer it to keratinocytes in the stratum basale and the stratum spinosum. Q. Location: Beneath the stratum granulosum Characteristics: Many layers of cells with centrally located large, oval nuclei and developing fibers of keratin; cells becoming flattened Stratum basale … It is interesting to note that the “spiny” nature of this layer is an artifact of the staining process. Melanosomes are temporary structures that are eventually destroyed by fusion with lysosomes; this fact, along with melanin-filled keratinocytes in the stratum corneum sloughing off, makes tanning impermanent. 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