Integument System: Skin Anatomy
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Questions and Answers

What percentage of body weight does the skin typically account for?

  • 20-25%
  • 5-10%
  • 10-15%
  • 15-20% (correct)

    • Which of the following is NOT a function of the skin?

  • Prevention of dehydration and loss of body fluids
  • Protection of body from invasion of pathogens
  • Production of vitamin C from precursors (correct)
  • Regulation of body temperature

    • What is the origin of the epidermis?

  • Ectodermal (correct)
  • Endodermal
  • Mesodermal
  • Epithelial

    • Which epidermal layer is characterized by a translucent, thin layer of extremely flattened eosinophilic cells?

    <p>Stratum Lucidum</p> Signup and view all the answers

    What is the primary function of Langerhans cells in the skin?

    <p>Presenting antigens to lymphocytes</p> Signup and view all the answers

    What is the outermost layer of the epidermis?

    <p>Stratum Corneum</p> Signup and view all the answers

    What is the primary component of the cytoplasm in Stratum Lucidum cells?

    <p>Keratin filaments</p> Signup and view all the answers

    What is the primary function of Stratum Basale?

    <p>Constant renewal of epidermal cells</p> Signup and view all the answers

    What is the name of the enzyme that catalyzes the first step of melanin synthesis?

    <p>Tyrosinase</p> Signup and view all the answers

    What is the resulting product of tyrosinase activity in melanin synthesis?

    <p>DOPA</p> Signup and view all the answers

    How often is the human epidermis renewed?

    <p>Every 15-30 days</p> Signup and view all the answers

    What is the name of the pigment found in red hair?

    <p>Pheomelanin</p> Signup and view all the answers

    What type of cells are found in Stratum Basale?

    <p>Basophilic columnar cells</p> Signup and view all the answers

    What is the main component of Stratum Corneum cells?

    <p>Fibrillar proteins</p> Signup and view all the answers

    What is the characteristic shape of melanosomes?

    <p>Elliptical</p> Signup and view all the answers

    What is the site of melanin synthesis?

    <p>Melanocytes</p> Signup and view all the answers

    What is the main function of tonofibrils in the stratum spinosum?

    <p>To resist friction by forming strong bonds between cells</p> Signup and view all the answers

    Which type of skin cancer is most commonly derived from cells of the stratum spinosum?

    <p>Squamous cell carcinoma</p> Signup and view all the answers

    What is the primary function of lamellar granules in the stratum granulosum?

    <p>To form a barrier against water loss</p> Signup and view all the answers

    What is the term for the short cellular extensions around tonofibrils that give the appearance of spines or prickles on the cell surface?

    <p>Prickle cells</p> Signup and view all the answers

    What is the term for the process by which the keratin filaments and lipid-rich layer form a barrier to penetration by foreign materials?

    <p>Keratinization</p> Signup and view all the answers

    Which of the following is a risk factor for developing skin cancer?

    <p>Fair skin</p> Signup and view all the answers

    What is the primary cause of skin hypopigmentation in albinism?

    <p>Defect in tyrosinase</p> Signup and view all the answers

    What is the main component of the epidermal barrier against water loss?

    <p>Lamellar granules</p> Signup and view all the answers

    What is the term for the granules present in the cytoplasm of cells in the stratum granulosum?

    <p>Keratohyalin granules</p> Signup and view all the answers

    What is the term for the benign melanocytic nevi that can progress to malignant melanoma?

    <p>Congenital melanocytic nevus</p> Signup and view all the answers

    What is the primary function of Langerhans cells in the skin?

    <p>Antigen presentation</p> Signup and view all the answers

    What is the name of the type of carcinoma that originates from Merkel cells?

    <p>Merkel cell carcinoma</p> Signup and view all the answers

    What is the term for the patches of skin that can be affected in vitiligo?

    <p>Depigmented patches</p> Signup and view all the answers

    What is the term for the immune cells that Langerhans cells present antigens to?

    <p>T lymphocytes</p> Signup and view all the answers

    What is the primary function of Merkel cells in the skin?

    <p>Touch sensation</p> Signup and view all the answers

    What is the relative mortality rate of Merkel cell carcinoma compared to malignant melanoma?

    <p>Twice the mortality rate</p> Signup and view all the answers

    Study Notes

    Integument System (Skin)

    • The skin is the largest organ of the body, accounting for 15-20% of body weight.
    • The skin is composed of two layers: the epidermis (an epithelial layer of ectodermal origin) and the dermis (a layer of mesodermal connective tissue).

    Skin Functions

    • Protection of the body from invasion of pathogens and prevention of tissue damage by toxic chemicals and ultraviolet light.
    • Prevention of dehydration and loss of body fluids (impermeable to water).
    • Regulation of body temperature (production and excretion of sweat, vascular shunts).
    • Sensation of touch, pain, temperature, pressure, and vibration.
    • Immunological function of Langerhans cells (antigen-presenting cells) presenting antigens to lymphocytes in the immune response.
    • Production of vitamin D from precursors under the effects of steroids and sunlight.

    Epidermis

    • Stratified Squamous Keratinized Epithelium
    • Cells: keratin-producing cells (keratinocytes), melanocytes, Langerhans cells, and Merkel's cells

    Epidermis Layers

    • 5 layers of keratinocytes: Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, and Stratum Corneum

    Stratum Basale

    • One layer of basophilic columnar cells resting on the basement membrane
    • Contains intermediate keratin filaments
    • Desmosomes bind the cells in their lateral and upper surfaces
    • Hemidesmosomes help bind these cells to the basal lamina
    • Responsible for constant renewal of epidermal cells, with a renewal rate of every 15-30 days depending on age and body region

    Stratum Spinosum

    • Thickest epidermal layer
    • Consists of polyhedral or slightly flattened cells having central nuclei with nucleoli and cytoplasm actively synthesizing keratin filaments
    • Keratin filaments form microscopically visible bundles called tonofibrils
    • Desmosomes bind the cells together strongly to resist friction

    Medical Conditions

    • Skin cancer is common in adults, with one-third of all cancers originating in the skin
    • Basal cell carcinomas and squamous cell carcinomas are the most common types of skin cancer
    • Skin cancer shows an increased incidence in fair-skinned individuals residing in regions with high amounts of solar radiation

    Stratum Granulosum

    • 3-5 layers of flattened polygonal cells whose cytoplasm is filled with coarse basophilic granules (keratohyalin granules)
    • Lamellar granules: membrane-coated, small ovoid or rod-like structures containing lamellar disks formed by lipid bilayers
    • Granules fuse with the cell membrane and discharge their contents into the intercellular spaces of the Stratum Spinosum
    • Forms the epidermal barrier against water loss and has a sealing effect, preventing penetration by foreign materials

    Stratum Lucidum

    • More apparent in thick skin
    • Translucent, thin layer of extremely flattened eosinophilic epidermal cells
    • Organelles and nuclei are no longer evident
    • Cytoplasm consists primarily of densely packed keratin filaments embedded in an electron-dense matrix

    Stratum Corneum

    • Consists of 15-20 layers of flattened non-nucleated keratinized cells
    • Cytoplasm is filled with keratin
    • Cells consist of only fibrillar and amorphous proteins and thickened plasma membranes
    • Cells are continuously shed at the surface of the Stratum Corneum

    Melanocytes

    • Produce melanin, which is responsible for skin color
    • Eumelanins are brown or black pigments produced by melanocytes
    • Pheomelanin is a similar pigment found in red hair
    • Melanin synthesis involves the conversion of tyrosine into 3,4-dihydroxyphenylalanine (DOPA) by tyrosinase
    • Melanin accumulates in vesicles until they form mature elliptical granules called melanosomes

    Albinism

    • A congenital disorder producing skin hypopigmentation due to a defect in tyrosinase or some other component of the melanin-producing pathway

    Melanocytic Nevi

    • Melanocytes can normally proliferate in skin to produce moles or benign melanocytic nevi
    • Changes in the size or appearance of moles can be indicative of dysplasia that can progress further to malignant melanoma

    Langerhans Cells

    • Antigen-presenting cells (APCs) that bind, process, and present antigens to T lymphocytes in the immune response
    • Represent 2% to 8% of the epidermal cells
    • Found in the spinous layer
    • Play a crucial role in the skin's adaptive immunity

    Merkel Cells

    • Sensitive mechanoreceptors essential for light touch sensation
    • Found in highly sensitive skin, such as fingertips and at the bases of some hair follicles
    • Originate from the same stem cells as keratinocytes
    • Merkel cell carcinoma is a rare but aggressive and difficult to treat disease

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    Description

    Learn about the skin, the largest organ of the body, its composition, and functions. Understand the epidermis, dermis, and its role in protecting the body from pathogens and tissue damage.

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