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Questions and Answers
What is the heaviest organ in the human body?
What is the primary function of the Stratum Germinativum layer of the epidermis?
Which type of skin covers the majority of the human body?
Which of the following cells is responsible for producing pigment in the epidermis?
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What is the characteristic of the Stratum Corneum layer of the epidermis?
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What is the primary function of the Hypodermis layer of the skin?
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What is the characteristic of the dermis layer of the skin?
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How often is the human epidermis renewed?
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What is the primary function of the lamellar granules in the stratum granulosum?
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Which of the following characteristics is NOT a feature of the cells in the stratum spinosum?
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What is the main component of the cytoplasm in the stratum corneum?
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Which of the following factors does NOT contribute to the color of the skin?
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What is the purpose of the epidermal barrier formed by the lipid-rich material in the stratum granulosum?
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What is the primary function of melanocytes in the epidermis?
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Which of the following layers is NOT present in thin skin?
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What is the characteristic of the cells in the stratum corneum?
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Study Notes
Skin Overview
- Skin is the heaviest and largest organ in the human body, making up 15-20% of total body weight.
- There are two types of skin: thick skin (found on palms and soles) and thin skin (found on the rest of the body).
Layers of the Skin
- The skin consists of two distinct regions: epidermis (outer) and dermis (inner).
- Epidermis:
- Thin
- Derived from ectoderm
- Non-vascular but rich in sensory nerve endings
- Dermis:
- Thick
- Derived from mesoderm
- Characterized by connective tissue, vascular, and nerves
Hypodermis
- Beneath the dermis lies the hypodermis, a loose connective tissue that may contain pads of adipocytes.
- Hypodermis binds skin loosely to the underlying tissues.
Epidermal Cells
- Keratinocytes: most abundant cells in the epidermis
- Non-keratinocytes:
- Melanocytes: pigment-producing cells
- Langerhans cells: antigen-presenting cells
- Merkel cells: tactile epithelial cells
Stratum Corneum (Horny Layer)
- Composed of 5 layers of keratinocytes
- Keratinocytes in the stratum basale contain intermediate filaments composed of keratins
- Function: renewal of keratinocytes
Other Epidermal Layers
- Stratum Spinosum (prickle cell layer):
- Cells have short cellular extensions around the tonofibrils
- Appearances of many short spines or prickles at the cell surfaces
- Stratum Granulosum (granular layer):
- Cells have keratohyaline granules and lamellar granules
- Contains lipids that produce sheets that envelop the cells
- Stratum Lucidum (clear zone):
- Only seen in thick skin
- Cells have flattened nuclei and are degenerating
- Cytoplasm consists almost only of densely packed keratin filaments
Melanocytes
- Depend on the interaction of three factors:
- Melanin: yellow to brown to black pigment produced by melanocytes
- Carotene: orange-yellow pigment found in some vegetables
- Hemoglobin: red coloring from blood cells in dermis capillaries
- Melanocytes:
- Specialized cells of the epidermis found among the cells of stratum basale and in the hair follicles
- Synthesize melanin from tyrosine and store it in vesicles called melanosomes
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Description
Learn about the human skin, its composition, and its different layers. Understand the characteristics of thick and thin skin, as well as the epidermis and dermis regions.
