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Integumentary System - Anatomy & Physiology

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  • What are the two major parts of the integumentary system?
    The integumentary system consists of the cutaneous membrane (skin) and accessory structures such as hair, nails, and exocrine glands.
  • What layers compose the cutaneous membrane?
    The cutaneous membrane is composed of two layers: the epidermis (superficial epithelium) and the dermis (deep connective tissue).
  • What is the subcutaneous layer (hypodermis) and its function?
    The hypodermis is a loose connective tissue layer deep to the dermis that separates the skin from underlying organs and stabilizes skin position.
  • List key functions of the integumentary system.
    Functions include protection against impact and microorganisms, excretion of salts and wastes, temperature regulation, melanin production, keratin production, and vitamin D3 synthesis.
  • What type of epithelium composes the epidermis?
    The epidermis is made of keratinized, stratified squamous epithelium and is avascular, relying on diffusion from the dermis.
  • What is the main cell type in the epidermis?
    The main cell type is the keratinocyte, which produces large amounts of the tough, fibrous protein keratin.
  • Difference between thin and thick skin?
    Thin skin covers most of the body with four epidermal layers; thick skin is found on palms and soles and has five layers including the stratum lucidum.
  • Name the five strata of the epidermis from deep to superficial.
    Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), and stratum corneum.
  • What is the role of the stratum basale?
    It is the deepest epidermal layer containing basal stem cells that divide to produce new keratinocytes and contains melanocytes and Merkel cells.
  • What are epidermal ridges and their function?
    Epidermal ridges are folds in the stratum basale that interlock with dermal papillae, increasing surface area for dermis-epidermis attachment.
  • What cells are found in the stratum spinosum and their function?
    Contains 8-10 layers of keratinocytes bound by desmosomes and immune dendritic (Langerhans) cells that defend against microorganisms.
  • What happens in the stratum granulosum?
    Keratinocytes produce keratin and keratohyalin, become thinner and flatter, plasma membranes thicken, and cells begin to die.
  • Describe the stratum lucidum.
    A clear, glassy layer of flat, densely packed keratin-filled cells found only in thick skin, superficial to the stratum granulosum.
  • What characterizes the stratum corneum?
    The outermost layer with 15-30 layers of dead, keratinized cells that provide a tough, water-resistant surface.
  • How long does keratinocyte migration from stratum basale to stratum corneum take?
    Approximately 7 to 10 days to reach the stratum corneum, then cells remain there about 2 weeks before shedding.
  • What are the two main layers of the dermis?
    The papillary layer (superficial, areolar tissue with capillaries and sensory neurons) and the reticular layer (deep, dense irregular connective tissue).
  • What are tension lines in the dermis and their clinical significance?
    Tension lines are parallel collagen and elastic fiber bundles that resist skin forces; incisions parallel to them heal better with less scarring.
  • What is the primary composition and function of the hypodermis?
    Primarily composed of adipose tissue, it stabilizes skin position and is the site for subcutaneous injections.
  • What pigments contribute to skin color?
    Melanin (primary determinant) produced by melanocytes and carotene (orange-yellow pigment from diet) both contribute to skin color.
  • How does melanin protect the skin?
    Melanin absorbs ultraviolet (UV) radiation, protecting DNA from damage and reducing skin cancer risk.
  • Describe the synthesis pathway of vitamin D3 in the skin.
    UV radiation converts 7-dehydrocholesterol in epidermal cells to vitamin D3 (cholecalciferol), which is then converted in the liver and kidneys to active calcitriol.
  • What is the role of calcitriol?
    Calcitriol is a hormone essential for calcium and phosphate absorption in the small intestine, critical for bone maintenance and growth.
  • What are hair follicles and their function?
    Hair follicles are organs in the dermis that produce hairs, which protect the scalp, guard body openings, and provide sensory input.
  • What are the three layers of hair?
    Medulla (central core), cortex (intermediate layer), and cuticle (surface layer), each with variable keratin characteristics.
  • What is the function of sebaceous glands?
    Sebaceous glands secrete sebum, an oily lipid that lubricates hair and skin, inhibits bacterial growth, and conditions the skin.
  • Difference between apocrine and eccrine sweat glands?
    Apocrine glands secrete thick, odorous sweat into hair follicles in specific areas and activate at puberty; eccrine glands secrete watery sweat directly onto skin for cooling.
  • What are nails composed of and their function?
    Nails are made of dead, keratinized epidermal cells that protect finger and toe tips and assist in mechanical tasks.
  • What is the lunula of the nail?
    The lunula is the pale crescent near the nail root where blood vessels are obscured.