BackThe Epidermis: Layers quiz #1
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BackWhat are the five layers of the epidermis in order from deepest to most superficial, and which layer is only found in thick skin?
The five layers of the epidermis from deepest to most superficial are: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), and stratum corneum. What is the main difference between thin skin and thick skin regarding the layers of the epidermis?
Thin skin lacks the stratum lucidum, while thick skin contains all five layers, including the stratum lucidum. What types of cells are found in the stratum basale, and what are their functions?
The stratum basale contains stem cells (which divide to produce new cells), keratinocytes (produce keratin), melanocytes (produce melanin for UV protection), and tactile epithelial cells (Merkel cells, involved in touch sensation). How do keratinocytes change as they move from the stratum basale to the stratum corneum?
Keratinocytes originate in the stratum basale, divide and move upward, flatten and accumulate keratin, lose their nuclei and organelles, die, and eventually become part of the dead, keratin-filled, waterproof stratum corneum that is regularly shed. What is the primary function of the stratum corneum?
The stratum corneum acts as a waterproof, protective barrier against environmental damage and prevents water loss, while its dead keratinocytes are regularly shed. Which layer of the epidermis is known as the 'spiny layer,' and what unique cell type is found there?
The stratum spinosum is known as the 'spiny layer' and contains dendritic (Langerhans) cells, which are immune cells that help protect against infection. What is the significance of the granules found in the stratum granulosum?
The granules in the stratum granulosum (keratohyalin and lamellar granules) help harden keratinocytes and create a waterproof barrier by releasing glycolipids. Why do cells in the stratum granulosum stop dividing and begin to die?
Cells in the stratum granulosum stop dividing and begin to die because they are far from the underlying blood supply, limiting their access to nutrients and causing their nuclei and organelles to disintegrate. What is the role of the stratum lucidum, and where is it found?
The stratum lucidum is a thin, clear layer of dead, densely packed keratinocytes that provides extra protection and is found only in thick skin, such as the palms of the hands and soles of the feet. How does the process of keratinization contribute to the protective function of the epidermis?
Keratinization fills keratinocytes with tough, water-resistant keratin, making the epidermis a strong, protective, and waterproof barrier. What happens to the keratinocytes in the stratum corneum, and how often are they replaced?
Keratinocytes in the stratum corneum are dead, fully keratinized, and are regularly shed from the skin surface; they are replaced by new cells pushed up from deeper layers. Which epidermal layer contains the most actively dividing cells, and why?
The stratum basale contains the most actively dividing cells because it is closest to the nutrient-rich dermis, allowing stem cells to proliferate and replace lost cells. What is the function of melanocytes in the epidermis, and in which layer are they primarily found?
Melanocytes produce melanin, which protects the skin from UV radiation, and are primarily found in the stratum basale. Which layer of the skin lacks blood vessels?
The epidermis lacks blood vessels. What is the name of the avascular layer of the skin?
The avascular layer of the skin is called the epidermis. Which skin layer receives nutrients by diffusion from the underlying vascular tissue rather than directly from blood vessels?
The epidermis receives nutrients by diffusion from the underlying vascular dermis because it lacks its own blood vessels.
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