TAILIEUCHUNG - Lecture Human anatomy and physiology - Chapter 5: The integumentary system

Would you be enticed by an ad for a coat that is waterproof, stretchable, washable, and permanent-press, that automatically repairs small cuts, rips, and burns? How about one that’s guaranteed to last a lifetime? Sounds too good to be true, but you already have such a coat-your skin. The skin and its derivatives (sweat and oil glands, hairs, and nails) make up a complex set of organs that serves several functions, mostly protective. Together, these organs form the integumentary system. | 5 The Integumentary System Skin (Integument) Consists of three major regions Epidermis—superficial region Dermis—middle region Hypodermis (superficial fascia)—deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue Figure Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin • Eccrine sweat gland • Arrector pili muscle • Sebaceous (oil) gland • Hair follicle • Hair root Nervous structures • Sensory nerve fiber • Pacinian corpuscle • Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue Epidermis Keratinized stratified squamous epithelium Cells of epidermis Keratinocytes—produce fibrous protein keratin Melanocytes 10–25% of cells in lower epidermis Produce pigment melanin Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system Tactile (Merkel) cells—touch receptors Figure Dermis Stratum corneum Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and epidermal dendritic cells. (a) Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer firmly attached to the dermis Single row of stem cells Also called stratum germinativum: cells undergo rapid division Journey from basal layer to surface Takes 25–45 days Layers of the Epidermis: Stratum Spinosum (Prickly .

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