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Questions and Answers
Where are sweat glands typically located?
Where are sweat glands typically located?
What is the function of the duct in sweat glands?
What is the function of the duct in sweat glands?
What is the nail bed composed of?
What is the nail bed composed of?
What is the main component of the nail substance?
What is the main component of the nail substance?
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What is the function of the germinal matrix?
What is the function of the germinal matrix?
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What is the lunule?
What is the lunule?
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What is the sterile matrix?
What is the sterile matrix?
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What type of cells are present in large sweat glands?
What type of cells are present in large sweat glands?
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What is the function of melanin in the skin?
What is the function of melanin in the skin?
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Which of the following cells is responsible for forming melanin?
Which of the following cells is responsible for forming melanin?
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What is the name of the layer of the dermis that is dense and just below the epidermis?
What is the name of the layer of the dermis that is dense and just below the epidermis?
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What is the function of the arrector pili muscles?
What is the function of the arrector pili muscles?
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What is the innermost layer of the hair follicle that surrounds the hair root?
What is the innermost layer of the hair follicle that surrounds the hair root?
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What is the outermost layer of the hair that is covered by a thin membrane?
What is the outermost layer of the hair that is covered by a thin membrane?
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What is the function of the sebaceous gland in relation to the hair follicle?
What is the function of the sebaceous gland in relation to the hair follicle?
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What is the structure that is formed by a downgrowth of epidermal cells into the dermis or subcutaneous tissue?
What is the structure that is formed by a downgrowth of epidermal cells into the dermis or subcutaneous tissue?
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What is the name of the receptor that is sensitive to light pressure?
What is the name of the receptor that is sensitive to light pressure?
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What is the part of the hair that is anchored in the thickness of the skin?
What is the part of the hair that is anchored in the thickness of the skin?
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What is the main function of the lipid in the stratum corneum?
What is the main function of the lipid in the stratum corneum?
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What is the term for the shedding of keratinized cells from the surface of the epidermis?
What is the term for the shedding of keratinized cells from the surface of the epidermis?
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What is the name of the protein found in the granules of the stratum granulosum?
What is the name of the protein found in the granules of the stratum granulosum?
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What is the term for the process of continual cell division in the deepest layers of the epidermis?
What is the term for the process of continual cell division in the deepest layers of the epidermis?
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What is the name of the layer of the epidermis that is composed of a single layer of columnar cells?
What is the name of the layer of the epidermis that is composed of a single layer of columnar cells?
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What is the function of the papillae in the epidermis?
What is the function of the papillae in the epidermis?
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What is the term for the unique pattern of ridges on the surface of the epidermis?
What is the term for the unique pattern of ridges on the surface of the epidermis?
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What is the name of the cells responsible for producing melanin?
What is the name of the cells responsible for producing melanin?
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What is the term for the layer of the epidermis that is made up of flattened scale-like elements containing keratin filaments?
What is the term for the layer of the epidermis that is made up of flattened scale-like elements containing keratin filaments?
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What is the result of trauma causing separation of the dermis and epidermis?
What is the result of trauma causing separation of the dermis and epidermis?
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Study Notes
Structure of the Skin
- The skin is the largest organ in the body and contains glands, hair, and nails.
- It consists of two main layers: the epidermis and the dermis.
- The epidermis is the most superficial layer, composed of stratified keratinized squamous epithelium.
- The dermis is a tough and elastic connective tissue containing collagen fibers and elastic fibers.
The Epidermis
- The epidermis is thickest on the palms of the hands and soles of the feet.
- It has no blood vessels or nerve endings, but is bathed in interstitial fluid from the dermis.
- The epidermis has several layers of cells, extending from the deepest germinative layer to the most superficial stratum corneum.
Layers of the Epidermis
- Basal Layer/Germinal Layer: The deepest layer, made up of a single layer of columnar cells that rest on a basal lamina.
- Stratum Spinosum: Several layers of polygonal keratinocytes that constitute the Malpighian layer.
- Stratum Granulosum: Few layers of flattened cells characterized by the presence of deeply staining granules in their cytoplasm.
- Stratum Lucidum: A homogeneous layer superficial to the stratum granulosum.
- Stratum Corneum: An acellular layer made up of flattened scale-like elements containing keratin filaments embedded in protein.
Pigmentation of the Skin
- The number of melanocytes is constant, and differences in skin color depend on the amount of melanin secreted.
- Melanin protects the skin from harmful sunlight, and exposure to sunlight promotes melanin synthesis.
- The epidermis is translucent, allowing the color of blood to show, especially in light-skinned individuals.
Melanocytes
- Melanocytes are responsible for producing the pigment melanin.
- They have processes that transfer melanin granules to surrounding non-melanin-producing cells.
- Each melanocyte has dendritic processes.
The Dermis
- The dermis is a tough and elastic connective tissue containing collagen fibers and elastic fibers.
- It rests on the superficial fascia, which attaches it to deeper structures.
- The dermis has two main layers: the papillary layer and the reticular layer.
- Fibroblasts, macrophages, and mast cells are the main cells found in the dermis.
Blood and Lymph Supply
- Blood vessels do not penetrate the epidermis.
- Arterioles form a fine network with capillary branches supplying sweat glands, sebaceous glands, hair follicles, and the dermis.
- Veins from the dermal papillae drain into a venous plexus lying on deep fascia.
Nerve Supply
- Sensory receptors for touch, temperature, pressure, and pain are widely distributed in the dermis.
- Different types of sensory receptors are activated by various stimuli:
- Meissner's corpuscle: light pressure
- Pacinian corpuscle: deep pressure
- Free nerve endings: pain
Appendages of the Skin
- Hair and Hair Follicle: Each hair consists of a visible part (shaft) and an embedded part (root).
- The root has an expanded lower end (bulb) and is surrounded by a tubular sheath (hair follicle).
- The surface of the hair is covered by a thin membrane (cuticle).
- The cortex is acellular and made up of keratin.
Sweat Glands
- The wall of the tube making up the gland consists of an inner epithelial lining, basal lamina, and supporting layers of connective tissue.
- In large sweat glands, flattened contractile myoepithelial cells are present between the epithelial cells and their basal lamina.
- Sweat glands are innervated by cholinergic nerves.
Nails
- Nails are present on fingers and toes.
- The main part of the nail is the body, which has a free distal edge.
- The proximal part of the nail is implanted into a groove on the skin and is known as the root or radix.
- The nail represents a modified part of the zone of keratinization of the epidermis.
- The nail substance consists of several layers of dead, cornified cells filled with keratin.
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Description
Learn about the role of melanocytes and melanin in skin pigmentation, and how they protect the skin from harmful sunlight.
