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Questions and Answers
What is the primary function of keratinocytes in the epidermis?
What is the primary function of keratinocytes in the epidermis?
Which layer of the epidermis contains keratohyaline granules?
Which layer of the epidermis contains keratohyaline granules?
How are the cells in the stratum spinosum characterized?
How are the cells in the stratum spinosum characterized?
What happens to keratinocytes during the keratinization process?
What happens to keratinocytes during the keratinization process?
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Which type of cell is responsible for the detection of sensory stimuli in the epidermis?
Which type of cell is responsible for the detection of sensory stimuli in the epidermis?
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What is the primary role of Langerhans cells in the epidermis?
What is the primary role of Langerhans cells in the epidermis?
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What distinguishes the stratum germinativum from other layers of the epidermis?
What distinguishes the stratum germinativum from other layers of the epidermis?
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What characterizes the cytoplasm of cells in the stratum granulosum?
What characterizes the cytoplasm of cells in the stratum granulosum?
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What is the main function of melanocytes in the epidermis?
What is the main function of melanocytes in the epidermis?
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Which layer of the skin contains 20-30 layers of flattened cells adhering through remnants of desmosomes?
Which layer of the skin contains 20-30 layers of flattened cells adhering through remnants of desmosomes?
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What distinguishes the cytocrine secretion mode of melanocytes?
What distinguishes the cytocrine secretion mode of melanocytes?
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Which statement correctly describes Langerhans cells?
Which statement correctly describes Langerhans cells?
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What effect does exposure to sunlight have on melanocytes?
What effect does exposure to sunlight have on melanocytes?
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Which condition is characterized by a lack of pigmentation due to the failure of melanocytes to produce melanin?
Which condition is characterized by a lack of pigmentation due to the failure of melanocytes to produce melanin?
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What features are typical of Merkel cells?
What features are typical of Merkel cells?
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What characterizes the stratum lucidum layer of the epidermis?
What characterizes the stratum lucidum layer of the epidermis?
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Study Notes
The Integumentary System
- The integumentary system encompasses the skin and its appendages: hair, nails, sweat glands, sebaceous glands, and mammary glands.
Skin Layers
- The skin is composed of two layers:
- Epidermis: The superficial layer, derived from ectoderm, is avascular but rich in sensory nerve endings, particularly for pain.
- Dermis: The deeper, vascular connective tissue layer, derived from mesoderm.
Epidermis
- The epidermis is a keratinized stratified squamous epithelium.
- It contains four types of cells:
- Keratinocytes: The most abundant cell type in the epidermis.
- Melanocytes: Contribute to skin pigmentation.
- Langerhans cells: Immune cells involved in antigen presentation.
- Merkel cells: Sensory cells associated with touch.
Keratinocytes
- Keratinization is a process that takes 15-30 days.
- Superficial epithelial cells are shed and replaced by cells from stem cells in the basal layer.
- As cells move upwards, they accumulate keratin filaments (cytokeratin filaments), lose their nucleus and organelles, and eventually die.
Layers of the Epidermis
-
Stratum Germinativum (Stratum Basale):
- Single layer of low columnar cells with large, oval nuclei.
- Deeply basophilic cytoplasm due to abundant polysomes.
- Cells are attached by desmosomes and hemidesmosomes.
- Frequent mitotic figures.
- Function: Renewal of keratinocytes.
-
Stratum Spinosum (Prickle Cell Layer):
- 5-10 layers of polyhedral cells with multiple spinous processes.
- Spinous processes interdigitate with similar processes of adjacent cells via desmosomes.
- Function: Resisting friction and pressure.
-
Stratum Granulosum (Granular layer):
- 3-5 layers of diamond-shaped cells with flattened nuclei.
- Deeply basophilic cytoplasm containing:
- Keratohyaline granules (non-membrane-bounded granules that pack keratin filaments together).
- Membrane-bounded lamellated granules (increase in number in stratum granulosum, discharge their contents into intercellular spaces).
- Function: Waterproof barrier of the skin.
-
Stratum Lucidum (Clear Zone):
- 2-3 layers of flattened, pale cells.
- Nuclei and organelles are degenerating.
- Cytoplasm densely packed with keratin filaments.
-
Stratum Corneum (Horny Layer):
- 20-30 layers of flat, eosinophilic horny scales.
- Nuclei and organelles are degenerated.
- Cytoplasm densely packed with keratin filaments.
- Cells adhere to each other by remnants of desmosomes
Non-Keratinocytes:
Melanocytes
- Responsible for skin pigmentation.
- Located in the epidermis, primarily in the stratum basale, and also in hair follicles.
- Branching cells containing melanosomes.
- Melanin formation: Protects against UV radiation.
- Cytocrine secretion: Melanosomes are transferred from the melanocyte to neighboring epidermal cells.
Langerhans Cells
-
Originate from blood monocytes (mononuclear phagocytic system).
-
LM:
- Branching cells with multiple cytoplasmic processes.
- Folded and irregular nuclei.
- Pale cytoplasm.
- Located between cells of stratum spinosum.
-
EM:
- Numerous lysosomes.
- No keratin or desmosomes between Langerhans cells and keratinocytes.
-
Function: Act as antigen-presenting cells to T lymphocytes, involved in the cutaneous contact hypersensitivity reaction.
Merkel Cells
- Large cells with short processes.
- Located in the basal layer of the epidermis.
- Attached to keratinocytes via desmosomes.
- Function: Sensory cells associated with touch.
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Description
Explore the intricacies of the integumentary system, focusing on the skin's structure and its various appendages. Learn about the distinct layers of skin, including the epidermis and dermis, as well as the different cell types that play vital roles in skin function and health.
