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Integumentary System - Anatomy & Physiology

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  • What are the main components of the integumentary system?

    The integumentary system consists of skin, hair, nails, sweat glands, and sebaceous (oil) glands.

  • What are the three main layers of the skin?

    The skin has three layers: epidermis (superficial, epithelial, avascular), dermis (underlying connective tissue, vascular), and hypodermis (subcutaneous layer, mostly adipose tissue, not part of skin).

  • What type of tissue makes up the epidermis?

    The epidermis is made mostly of keratinized stratified squamous epithelium.

  • Name the four cell types found in the epidermis.

    1. Keratinocytes (produce keratin)
    2. Melanocytes (produce melanin)
    3. Dendritic (Langerhans) cells (immune cells)
    4. Tactile (Merkel) cells (touch receptors)

  • List the five layers (strata) of the epidermis from deepest to most superficial.

    1. Stratum basale
    2. Stratum spinosum
    3. Stratum granulosum
    4. Stratum lucidum (only in thick skin)
    5. Stratum corneum

  • What is the function of the stratum basale?

    It is the deepest epidermal layer with mitotically active stem cells producing new keratinocytes; also contains melanocytes (~10-25%).

  • Describe the stratum spinosum.

    Several layers thick with keratinocytes connected by desmosomes; contains melanosomes and dendritic cells; cells appear spiky (prickle cells).

  • What happens in the stratum granulosum?

    Cells flatten, nuclei and organelles disintegrate, keratinization begins, and cells accumulate keratohyaline and lamellar granules to form keratin fibers and slow water loss.

  • Where is the stratum lucidum found and what is its characteristic?

    Found only in thick skin (palms, soles); thin, translucent layer of dead keratinocytes above stratum granulosum.

  • What is the stratum corneum composed of and its function?

    20-30 layers of flat, dead, keratinized cells that protect deeper layers, prevent water loss, and act as a barrier against abrasion and pathogens.

  • What are the two layers of the dermis?

    Papillary layer: superficial areolar connective tissue with dermal papillae.
    Reticular layer: deeper dense irregular connective tissue with collagen and elastic fibers.

  • What are dermal papillae and their function?

    Fingerlike projections of the papillary dermis that contain capillaries and sensory receptors; they increase surface area for nutrient exchange and contribute to fingerprints.

  • What are friction ridges and their significance?

    Ridges formed by dermal papillae and epidermal ridges that enhance grip and create unique fingerprint patterns.

  • What are cleavage lines and why are they important?

    Lines in the reticular dermis where collagen fibers run parallel; important for surgeons because incisions made parallel to these lines heal better.

  • What causes flexure lines in the skin?

    Dermal folds near joints where the dermis is tightly secured to underlying structures, causing deep creases visible on hands and fingers.

  • What is the composition and function of hair?

    Hair consists of dead, keratinized cells with hard keratin; functions include protection from trauma, heat loss, sunlight, and sensory input.

  • Name the three parts of the hair shaft.

    Medulla: central core
    Cortex: surrounding layers
    Cuticle: outer overlapping layer of cells

  • What is the hair follicle and its key structures?

    Extends from epidermis to dermis; includes hair bulb (growth area), hair matrix (dividing cells), hair papilla (capillaries), and arrector pili muscle (causes goosebumps).

  • What are the two main types of hair?

    Vellus hair: fine, pale body hair
    Terminal hair: coarse, long hair on scalp, eyebrows, and after puberty in axillary and pubic regions.

  • What are nails and their main parts?

    Scale-like modifications of epidermis with hard keratin; main parts include free edge, nail plate, root, nail bed, nail matrix, eponychium (cuticle), and hyponychium.

  • What are the two main types of sweat glands?

    Eccrine (merocrine) glands: abundant, thermoregulation, secrete watery sweat.
    Apocrine glands: found in axillary and anogenital areas, secrete milky sweat, begin functioning at puberty.

  • What are sebaceous glands and their function?

    Oil glands associated with hair follicles; secrete sebum, an oily holocrine secretion that softens skin and hair and has bactericidal properties.

  • List the main functions of the skin.

    Protection, body temperature regulation, cutaneous sensations, metabolic functions, blood reservoir, and excretion of wastes.

  • What are the three types of barriers the skin provides for protection?

    Chemical barrier (acid mantle, antimicrobial secretions), physical barrier (keratinized cells and glycolipids), and biological barrier (immune cells like dendritic cells and macrophages).

  • How does the skin regulate body temperature?

    By producing sweat (insensible and sensible perspiration) and adjusting blood flow through dermal vessels (vasodilation and vasoconstriction).

  • What role does the skin play in metabolic functions?

    Synthesizes vitamin D for calcium absorption, disarms carcinogens, activates hormones, and produces collagenase to prevent wrinkles.

  • How does the skin act as a blood reservoir?

    It can hold up to 5% of the body's blood volume and constrict vessels to shunt blood to other organs when needed.

  • What wastes are excreted by the skin?

    Limited amounts of nitrogenous wastes such as ammonia, urea, and uric acid, along with salt and water loss through sweating.

  • What are some developmental aspects of the integumentary system?

    Fetal skin develops by 4th month; lanugo and vernix caseosa protect fetus; skin thickens and gland activity increases through adulthood; aging causes thinning, dryness, wrinkles, and hair thinning.