Questions and Answers
What is the approximate percentage of body weight accounted for by the skin?
15-20%
What is the function of the skin in terms of body temperature regulation?
Producing and excreting sweat, and vascular shunts
What is the function of Langerhans cells in the skin?
Presenting antigens to lymphocytes in immune responses
What is the origin of the epidermis?
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What is the function of melanocytes in the skin?
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How often is the human epidermis renewed?
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What is the type of epithelium that makes up the epidermis?
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What is the function of the skin in terms of preventing dehydration?
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What is the primary component of the cytoplasm in the Stratum Lucidum?
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What is the function of tyrosinase in melanin synthesis?
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What is the name of the pigment found in red hair?
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What is the primary cause of albinism?
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What is the name of the layer of the epidermis that consists of 15-20 layers of flattened non-nucleated keratinized cells?
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What is the name of the granules that contribute to the matrix of keratin in the Stratum Corneum?
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What is the result of melanocyte loss in vitiligo?
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What is the name of the enzyme that converts tyrosine into DOPA in melanin synthesis?
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What is the function of Langerhans cells in the skin?
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What type of cancer is associated with Merkel cells?
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What is the name of the structure that accumulates melanin pigment in melanin synthesis?
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What are the two main pigments that contribute to the color of the skin?
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What is the function of Merkel cells in the skin?
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What is the main function of the keratin filaments in the Stratum Spinosum?
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What is the percentage of epidermal cells that are Langerhans cells?
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What is the origin of Merkel cells?
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What percentage of all cancers in adults originate in the skin?
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What is the comparison of mortality rates between Merkel cell carcinoma and malignant melanoma?
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What is the name of the granules found in the cytoplasm of cells in the Stratum Granulosum?
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What is the function of the lipid-rich layer produced by the Stratum Granulosum?
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What type of cells are the Stratum Spinosum cells sometimes referred to as?
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Which type of skin cancer is more common in fair-skinned individuals residing in regions with high amounts of solar radiation?
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What is the shape of the lamellar granules seen on EM in the Stratum Granulosum?
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What is the main function of the Stratum Granulosum?
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Study Notes
Introduction to the Integument System (Skin)
- The skin is the largest organ of the body, accounting for 15-20% of body weight.
- The skin consists of two main layers: Epidermis and Dermis.
Epidermis
- The Epidermis is a stratified squamous keratinized epithelium.
- It consists of 5 layers of keratinocytes:
- Stratum Basale (one layer of basophilic columnar cells)
- Stratum Spinosum (thickest epidermal layer, consisting of polyhedral cells)
- Stratum Granulosum (3-5 layers of flattened polygonal cells)
- Stratum Lucidum (thin, translucent layer of extremely flattened eosinophilic cells)
- Stratum Corneum (15-20 layers of flattened, non-nucleated keratinized cells)
Functions of the Skin
- Protection of the body from pathogens and toxic chemicals
- Prevention of dehydration and loss of body fluids
- Regulation of body temperature
- Sensation of touch, pain, temperature, pressure, and vibration
- Immunological function of Langerhans cells
- Production of vitamin D from precursors under the effects of steroids and sunlight
Medical Conditions
- Skin cancer (most commonly basal cell carcinoma and squamous cell carcinoma)
- Increased incidence of skin cancer in fair-skinned individuals residing in regions with high amounts of solar radiation
Melanocytes
- Produce melanin, which determines skin color
- Melanin synthesis involves tyrosinase, which converts tyrosine into DOPA
- Melanin is linked to a matrix of structural proteins and accumulates in melanosomes
- Albinism: a congenital disorder producing skin hypopigmentation due to a defect in tyrosinase or another component of the melanin-producing pathway
Langerhans Cells and Merkel Cells
- Langerhans cells: antigen-presenting cells that bind, process, and present antigens to T lymphocytes, triggering an immune response
- Merkel cells: sensitive mechanoreceptors essential for light touch sensation, originating from the same stem cells as keratinocytes
Skin Conditions
- Melanocytic nevi (moles) can progress to malignant melanoma
- Congenital melanocytic nevus
- Vitiligo: an acquired condition involving skin depigmentation due to the loss or decreased activity of melanocytes
- Merkel cell carcinoma: an aggressive and difficult-to-treat cancer
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