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Questions and Answers
What is the primary role of keratinocytes in the epidermis?
Which layer of the epidermis does not contain nuclei or organelles?
What is the significance of keratohyalin granules in keratinocytes?
In which skin areas is the stratum lucidum most pronounced?
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What type of cells are Langerhans cells classified as?
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Which type of sweat gland is characterized by its direct secretion onto the skin surface?
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What percentage of epidermal cells do Merkel cells represent?
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What is the primary function of Merkel cells in the skin?
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Where are apocrine sweat glands primarily located in the body?
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What structure pulls hair upright when a person is cold or frightened?
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What is the primary protective function of the skin?
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Which layer of the skin is primarily responsible for the regeneration of its cells?
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What is the main role of sebaceous glands?
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Which type of skin is characterized by having a thicker epidermis?
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What is the function of free nerve endings in the skin?
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Through which process does the skin help regulate body temperature?
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Which layer of the skin is considered the deepest?
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What common problem is associated with abnormally low body temperature?
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What initiates the secretion of sebaceous glands?
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Which characteristic is true for thick skin?
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What is a primary function of sebum discharged by sebaceous glands?
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Which layer is absent in thick skin?
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In terms of the dermis, which statement is correct about thin skin?
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Where is thick skin primarily located on the body?
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Which option describes a significant feature distinguishing thick skin from thin skin?
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What physiological process is stimulated during emotional distress in relation to skin glands?
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Study Notes
Structure and Functions of Skin
- Skin is the largest organ, comprising skin, hair, glands, and nails.
- Protective function: Acts as the first defense against infection, pathogens, and UV rays.
- Sensory function: Contains free nerve endings for pain, touch, heat, and cold detection.
- Secretory function: Sweat aids in temperature regulation, while sebum keeps skin smooth.
- Heat regulation: Facilitates temperature control through sweating and blood flow adjustments.
- Excretory function: Glands in the skin eliminate water, salt, fatty substances, and urea.
- Synthetic function: Skin synthesizes vitamin D upon UV exposure and produces melanin.
- Water balance: Regulates body water through perspiration.
Skin Layers
- Divided into three primary regions: epidermis, dermis, and hypodermis (subcutaneous).
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Epidermis: Outermost layer, first protective barrier with five strata:
- Stratum basale: Contains germinal cells for regeneration, adjacent to the dermis.
- Stratum spinosum: Characterized by desmosomes, referred to as the prickle-cell layer.
- Stratum granulosum: Keratinocytes accumulate keratin and lipid granules, forming a waterproof barrier.
- Stratum lucidum: Clear layer found in thick skin (palms, soles), composed of densely packed flat cells.
- Stratum corneum: Outermost dead cell layer involved in desquamation and keratinization.
Types of Epidermal Cells
- Keratinocytes: Main cells forming keratin, shed and regenerate every 2-4 weeks.
- Melanocytes: Produce melanin from the amino acid tyrosine, located in the basal layer.
- Langerhans cells: Antigen-presenting immune cells found in the stratum spinosum (3-8% of epidermal cells).
- Merkel cells: Modified epidermal cells acting as touch receptors located in the basal layer.
Dermis Structure
- Two layers:
- Papillary layer: Contains blood vessels supplying the avascular epidermis with nutrients.
- Reticular layer: Houses glands and hair follicles, important for thermoregulation.
Skin Appendages
- Hair and Hair Follicles: Composed of hard keratinized epithelial cells.
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Sweat Glands:
- Eccrine (merocrine): Opens onto skin surface, located throughout the body, aids in cooling.
- Apocrine: Associated with hair follicles in areas like armpits and groin, activates during puberty, produces odor.
- Sebaceous Glands: Holocrine glands discharging sebum for lubrication and bactericidal properties.
- Nails: Protective coverings on the tips of fingers and toes.
Hair Color and Texture
- Hair color is determined by types of melanin:
- Brunette: Eumelanin.
- Blonde: Eumelanin mixed with pheomelanin.
- Red: Predominantly pheomelanin.
- Gray/White: Air in medulla and lack of pigment in cortex.
Types of Skin
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Thick Skin:
- Contains five layers, particularly notable stratum corneum.
- Stratum lucidum is present.
- Typically found on palms and soles; lacks hair and sebaceous glands.
- Thicker dermis.
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Thin Skin:
- Contains four layers, less prominent stratum corneum.
- Absence of stratum lucidum.
- Covers most body surfaces, with hair and sebaceous glands present.
- Thinner dermis.
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Description
This quiz covers the structure and functions of skin and its appendages, including the microscopic details of the epidermis, dermis, and hypodermis. Learn to differentiate between thick and thin skin, along with the roles of sebaceous and sweat glands. Test your knowledge about the largest organ of the body and its protective functions.
