Human Anatomy: Integumentary System Latest Update Graded A+

Human Anatomy: Integumentary System Latest Update Graded A+ integumentary layers epidermis dermis hypodermis epidermis keratin stratified squamous epithelial tissue layers (stratum basale, spinosum, granulosum, corneum) stratum basale deepest- attached to dermis includes stem cells that are constantly undergoing mitosis stratum spinosum visible extensions of keratinocytes (attachment points) bundles of intermediate filaments made of pre-keratin stratum granulosum flattened keratinocytes that have keratohylin and lamellated granules keratohylin granules- keratin production lamellated granules- contain glycolipids (waterproofing) stratum lucidum only in thick skin flat dead keratinocytes stratum corneum external layer dead keratinocytes (contain keratin and intermediate filaments) epidermis cell types keratinocytes melanocytes tactile epithelial cells dendritic cells keratinocytes originate in stratum basale (soft) keratin production produce detoxifying agents (antibiotics and enzymes) melanocytes in stratum basale derived from neural crest cells melanin production melanin pigmentation transferred to keratinocytes (superficial side) shields nuclei from UV can be digested by lysosomes tactile epithelial cells in stratum basale act as receptors (respond to touch, have sensory nerve ending) dendritic cells in stratum spinosum star-shaped immune function (receptor-mediated endocytosis, can migrate to lymph nodes) dermis second layer two layers: papillary and reticular innervated and vascularized plexuses (collection/network of vessels): subpapillary (superficial) or dermal (hypodermis and lower dermis) papillary layer areolar connective tissue (elastic and collagen fibers) dermal papillae: finger-like projections that increase surface area between dermis and epidermis epidermal and dermal ridges (create fingerprints) reticular layer dense irregular connective tissue (network of collagen fibers), allows for stretch and recoil features or dense irregular CT: cleavage lines, striae, flexure lines cleavage line areas of less dense collagen bundles longitudinal in limbs and head circular in neck and trunk cut parallel for faster healing striae torn collagen (stretch marks) flexure lines wrinkles fingers, palms, wrists, heels, toes dermal plexus temperature regulation by vasoconstriction (conserve heat) and vasodilation (release heat) hypodermis (aka superficial fascia or subcutaneous layer) composed of loose areolar and loose adipose connective tissue insulation, energy storage, cushioning thickness fluctuates with weight appendages of integument nail hair hair follicles glands nails hard keratin parts: free body, body, root body rests on nail bed (epidermis lacking strateum corneum) root nail matrix- actively growing, thickness comes from lunule nail folds- form eponychium (cuticle) hair dead cells with hard keratin three layers: medulla, cortex, cuticle medulla center large cells, air spaces cortex middle layer layer of flattened cells cuticle external layer single layer of overlapping cells separates hair from other hairs hair color melanin made by melanocytes at follicle base transferred to hair root hair follicle extends to dermis parts: hair bulb, hair follicle wall, arector pili muscles hair bulb expanded area root hair plexus (nerve endings): touch receptors hair papilla (blood supply): capillaries hair matrix:epithelial cells that form hair shaft hair follicle wall two root sheaths: outer connective tissue root sheath and inner epithelial root sheath glassy membrane outer connective tissue root sheath derived from dermis inner epithelial root sheath derived from epidermis internal root sheath formed by matrix cells external root sheath formed by epidermal cells and includes stem cells glassy membrane outer connective tissue root sheath meets inner epithelial root sheath arector pili muscle skeletal muscle contract to make hair stand up glands endocrine or exocrine unicellular or multicellular duct+secretory unit=gland endocrine gland hormones mostly epithelial ductless (released within) exocrine gland ducts (released to outside) ex. sweat glands unicellular gland scattered through epithelial sheets Goblet cells of GI tract (mucin+water=mucus) multicellular gland extend into connective tissue underneath connective tissue fibrous capsule forms lobes duct simple (unbranched) vs. compound (branched) secretory unit tubular (coiled tube) alveolar (grape cluster) glands of integument sebaceous or sodoriferous sebaceous gland alveolar with no lumen [central cavity] Holocrine secretion: cells burst to release sebum most trap dirt, condition hair, and slow water loss in hair follicles sodoriferous (sweat) gland composed of filtrate (water, salts, metabolic waste) three types: eccrine, apocrine, modified sweat glands eccrine sweat glands function whole life cover whole body simple tubular shape open at pore apocrine sweat glands start around puberty axillary and groin area open in hair follicle sweat contains lipids and proteins modified sweat glands ceruminous glands: make ear wax mammary glands