Questions and Answers
The skin is the largest organ of the body by surface area and ______.
weight
The outer, thinner layer of the skin is called the ______.
epidermis
The inner, thicker layer of the skin is known as the ______.
dermis
The epidermis consists of keratinized stratified squamous ______.
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The skin's subcutaneous layer is also called the ______.
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The average thickness of the skin is between ______ and 2 mm.
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Keratinocytes make up about ______% of the cells in the epidermis.
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Lamellar granules produce a water repellent ______ for the skin.
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The subcutaneous layer is also called the ______.
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The subcutaneous layer helps attach the skin to underlying ______.
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The accessory structures of the skin include hair, skin glands, and ______.
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Hair is primarily composed of dead, ______ epidermal cells.
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Sebaceous glands secrete an oily substance called ______.
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Eccrine sweat glands help to cool the body by ______ cooling.
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There are different types of hairs, including lanugo, vellus hairs, and ______ hairs.
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Hair color is determined by the amount and type of ______.
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The cells that produce the pigment ______ protect against damage by ultraviolet radiation.
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The deepest layer of the epidermis is called the ______ or stratum germinativum.
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Stratum lucidum is present only in ______ skin, such as the skin of the fingertips and palms.
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The outer papillary region of the dermis consists of areolar connective tissue containing thin ______ and elastic fibers.
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Keratinization occurs as cells move from the deepest layer to the surface, resulting in the accumulation of protective ______.
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The epidermis typically contains four major layers in ______ skin and five major layers in thick skin.
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The stratum spinosum consists of 8-10 layers of ______.
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Dandruff is an excess of keratinized cells shed from the ______.
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Study Notes
Structure of the Skin
- Skin is the largest organ by surface area and weight, covering about 2 square meters (22 square feet) and weighing 4.5-5 kg (10-11 lbs), approximately 16% of body weight.
- Average skin thickness ranges from 0.5 to 4 mm, thinnest on eyelids and thickest on heels.
- Comprised of two main layers: epidermis (outer, thinner layer of epithelial tissue) and dermis (inner, thicker connective tissue layer).
- Beneath the dermis lies the subcutaneous (hypodermis) layer, connecting skin to underlying tissues.
Cells of the Epidermis
- Consists of four major types of cells:
- Keratinocytes: Comprise about 90% of cells; produce keratin for protection and lamellar granules for water resistance.
- Melanocytes: Produce melanin, providing protection from UV damage.
- Langerhans cells: Immune cells originating from red bone marrow.
- Merkel cells: Sensory cells involved in touch sensation.
Layers of the Epidermis
- Thin skin has four major layers, while thick skin has five.
- Stratum Basale (Stratum Germinativum): Deepest layer where continuous cell division occurs.
- Stratum Spinosum: Composed of 8-10 layers of keratinocytes.
- Stratum Granulosum: Contains keratohyalin and lamellar granules.
- Stratum Lucidum: Present only in thick skin (e.g., fingertips, palms, soles).
- Stratum Corneum: Comprises multiple layers of dead keratinocytes that are continuously shed and replaced; friction can lead to callus formation.
Dermis Structure
- Composed of connective tissue with collagen and elastic fibers, providing strength and elasticity.
- Divided into two layers:
- Papillary Region: Areolar connective tissue with dermal papillae, capillary loops, corpuscles of touch, and free nerve endings.
- Reticular Region: Denser layer with more collagen fibers for strength.
Functions of the Skin
- Regulates body temperature.
- Acts as a barrier against external elements.
- Detects sensations like touch, pain, and temperature.
- Stores blood and synthesizes vitamin D.
- Facilitates excretion and absorption.
Accessory Structures of the Skin
- Includes hair, nails, and skin glands.
- Hairs serve multiple roles: protection, reducing heat loss, and sensing light touch.
Hair Characteristics
- Composed of dead, keratinized epidermal cells; includes a shaft (above skin) and root (below skin).
- Hair follicles contain epithelial and dermal root sheaths.
- Types of hair: lanugo (fine hair), vellus (short, fine hair), and terminal (thick, pigmented hair).
- Hair color is determined by the type and amount of melanin.
- Sebaceous glands associated with hair follicles secrete sebum to prevent dehydration and inhibit bacteria.
Skin Glands
- Sebaceous Glands: Secrete sebum, keeping skin and hair moisturized.
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Sudoriferous (Sweat) Glands: Two types exist:
- Eccrine Sweat Glands: Major component of thermoregulation through evaporation and waste elimination.
- Apocrine Sweat Glands: Located in axillae, groin, and areolae; produce a thicker secretion, often associated with emotional stress.
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Description
Explore the intricate structure of human skin and its cellular components in this quiz. You will learn about melanocytes, Langerhans cells, and Merkel cells, as well as their roles in skin protection and sensation. Test your knowledge on the layers of the epidermis and their functions.
