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Integumentary System - Anatomy & Physiology

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  • What are the two major components of the integumentary system?

    The cutaneous membrane (epidermis and dermis) and accessory structures (hairs, nails, glands, sensory receptors, arrector pili muscles).

  • Is the hypodermis part of the skin?

    No, the hypodermis is a deep stabilizing layer beneath the dermis and is not technically part of the skin.

  • What tissues compose the hypodermis?

    Loose connective tissue, mostly adipose and loose areolar tissue.

  • List three general functions of the skin.

    Protection, excretion, temperature regulation, melanin and keratin production, Vitamin D3 synthesis, lipid storage, and sensory detection.

  • What type of epithelium makes up the epidermis?

    Stratified squamous epithelium, which is avascular and relies on diffusion from dermal capillaries.

  • Difference between thin skin and thick skin?

    Thin skin has 4 layers and covers most body surfaces; thick skin has 5 layers (includes stratum lucidum) and covers palms and soles.

  • Order the epidermal layers from deepest to most superficial.

    Stratum basale → Stratum spinosum → Stratum granulosum → Stratum lucidum (only in thick skin) → Stratum corneum.

  • What cells are found in the stratum basale?

    Basal stem cells, Merkel cells (touch receptors), and melanocytes (melanin producers).

  • Function of melanocytes and melanin?

    Melanocytes produce melanin, which protects epidermal and dermal DNA from UV damage by clustering around nuclei in keratinocytes.

  • What are dendritic (Langerhans) cells and where are they found?

    Immune cells in the stratum spinosum that defend against microorganisms and superficial skin cancers.

  • What causes skin color differences among people?

    Differences in the amount of melanin produced, not the number of melanocytes.

  • How does UV radiation affect melanocytes?

    UV exposure increases melanin synthesis and melanosome transfer to keratinocytes, causing tanning.

  • What is cyanosis?

    A bluish tint to the skin caused by reduced blood flow or oxygenation in the dermis.

  • What is basal cell carcinoma?

    The most common skin cancer originating in the stratum basale; it rarely metastasizes.

  • What is malignant melanoma and its key warning signs?

    A dangerous skin cancer from melanocytes; signs include Asymmetry, Border irregularity, Color variation, Diameter >6mm, and Evolving lesions (ABCDE rule).

  • What are the two layers of the dermis and their characteristics?

    Papillary layer: loose areolar connective tissue with capillaries and nerves; Reticular layer: dense irregular connective tissue with collagen and elastic fibers.

  • What is the function of the hypodermis?

    Stabilizes skin to underlying tissues, acts as shock absorber, energy reserve, and insulator.

  • What is the composition and function of hair?

    Hair is dead keratinocytes packed with hard keratin, produced in hair follicles; it provides sensory input via root hair plexus and can be raised by arrector pili muscles.

  • What type of gland are sebaceous glands and what do they secrete?

    Holocrine glands that secrete sebum, an oily lipid that lubricates and waterproofs hair and inhibits bacterial growth.

  • What are the two types of sweat glands and their functions?

    Apocrine glands: active at puberty, secrete nutrient-rich fluid into hair follicles causing body odor; Merocrine glands: widespread, secrete sweat directly to skin for cooling and excretion.

  • Where does nail production occur?

    At the nail root, an epithelial fold hidden under the skin.

  • What are the four phases of skin repair after injury?

    Inflammation, Migration, Proliferation, and Scarring phases.

  • What is a keloid scar?

    A thick, raised scar that grows beyond the original wound boundaries.

  • How does aging affect the skin's immune function?

    Dendritic (Langerhans) cell numbers decrease by about 50%, weakening immune defense.

  • How does aging affect Vitamin D3 production?

    Production drops by approximately 75%, reducing bone strength.

  • What causes seborrheic dermatitis?

    Overactive sebaceous glands causing crusted, greasy skin patches, known as 'cradle cap' in infants.

  • Why do tattoos remain permanent in the skin?

    Because tattoo pigment is injected into the dermis, where cells do not shed like epidermal cells.