Integumentary System

1. Integumentary System Skin

2. Integument Important organ; represents 15% of total body weight. Functions: a) protection (mechanical barrier) b) detective organ (receptors) c) antiseptic barrier (chemical barrier) d) thermoregulation e) secretion and absorption f) Vitamin D synthesis

3. Integument Two Layers: a) epidermis (ectodermal) b) dermis (mesodermal) Hypodermis - below dermis, attaches skin to body; not part of the skin.

4. Integument Boundary between epidermis and dermis marked by prominent papillations = dermal papilla. These folds manifest themselves on the surface of the skin, especially in thick skin = finger prints, etc. Palmar and Plantar surfaces

5. Integument Epidermis: most cells from superficial ectoderm (keratinocytes). Pigment cells in basal layer from neural ectoderm (melanocytes). Pigment cells form melanin. Skin color due to: a) carotene - yellow pigment in all cells b) blood vessels in underlying dermis c) melanin pigment in melanocytes at basal layer of epidermis.

6. Integument Epidermal cells undergo keratinization as they move from the basal surface to the free surface; keratin or its intermediate protein replaces cell cytoplasm causing cell death. Cells become progressively flattened as they move to the surface. Langerhans Cell = antigen presenting cell of epidermis, mainly in stratum spinosum. Merkel's Cell - disc - tactile receptor in epidermis.

8. Epidermis Epidermis composed of five layers: a) stratum corneum b) stratum lucidum c) stratum granulosum d) stratum spinosum e) stratum germinativum (basale)

9. Epidermis Stratum Corneum - outermost layer of skin; clear, dead, flat, scale-like cells fused together. Cytoplasm completely replaced by keratin. Cells constantly sloughed off. Stratum Lucidum - thin, clear, translucent layer. Cells flat and closely packed. Cytoplasm contains keratohyalin, a precursor product of keratin. Also contains eleiden, a refractile substance related to keratohyalin. Produces the clear nature of these cells.

11. Epidermis Stratum Granulosum - thin, darkly pigmented layer of cells, 3-5 cell layers thick. Nuclei present in these cells; tonofilaments present and keratohyalin (granules). Cells flatten and die in this layer. Stratum Spinosum - cells polyhedral (cuboidal) with spaces between each. Surfaces of cells with desmosomes. Many tonofibrils. Keratinization begins here. Sometimes included with str. germ. as Stratum Malpighii.

13. Epidermis Stratum Germinativum (basale) - single layer of cuboidal cells; have attachment process on basal surface attaching epidermis (hemidesmosome) to basement membrane (outer dermis). Cells divide and move toward the surface. - melanocytes (derived from neural crest) are below and send cytoplasmic processes up between germinativum cells.

16. Dermis Papillary Dermis - outer layer, reticular fibers on outer surface contribute to lamina anchoring the epidermis. Small fibers and more cells (fibroblasts and macrophages) present. Some fat may be present, pigment cells may occur in areola and anal ring. Reticular Dermis - inner layer; strongly fibroid; relatively acellular. Fibers long and orient in layers = Langer's Lines. Thickest layer; hair follicles, smooth muscle and some fat present.

17. Integument Skin Products: 1) Nails - formed by infolding of skin layers. Nail bed formed by deeper layers of epidermis (s. spinosum and s. basale). Outer epidermal layers, corneum and lucidum, have high sulfur content and form nail proper. Pink color due to underlying blood vessels. Corneum forms epinychium (cuticle) and hyponychium

19. Integument 2) Hair - keratinized threads composed of free shaft and root. Occur over entire body except palmar and plantar surfaces, lips, external genitalia and anal apertures. Hair root embedded in a follicle of mostly epidermis and dermis.

20. Hair Shaft: a) medulla - shrunken, cornified cuboidal cells with air spaces between; absent in blond hair; contains pigment and soft keratin. b) cortex - forms bulk of hair; long cornified cells of hard keratin. Pigment between and within cells. c) hair cuticle - outer cornified cells with no nucleus.

21. Hair Follicle: epidermal components: internal epithelial sheath: modified corneum 1) follicle cuticle - cornified outer layer of cells facing hair shaft cuticle. 2) Huxley's Layer - multiple layers of squamoid cells with tricohyalin. 3) Henle's Layer - 1 cell thick, clear cells (squamous) with hyalin.

22. b) external epith. sheath: modified str. spinosumDermal components = dermal papilla, provides blood vascular supply to hair follicle. Sebaceous Glands and smooth muscle attach to hair follicle. Muscle = Arrector pilae, produces cutis anserina (goose flesh). 3) Sweat Glands - located deep in the dermis and/or hypodermis.

23. Sebaceous Gland Acinar gland opens to short duct into upper hair follicle Differentiate from epithelial stem cells (arrow). Accumulate lipid droplets Droplets fuse, cell bursts (holocrine) Sebum- TGs, waxes, cholesterol, squalene Begin to function at puberty

24. Sweat Glands Simple coiled tubular gland under Autonomic Control Secretory gland in dermis, duct through epidermis to surface Stratified cuboidal epith. Merocrine- hypoosmotic, NaCl, urea, ammonia Apocrine- axial, anal, areolar; larger gland; duct opens to hair follicle. Odor with bacterial degrad.