9 Stratum basale (deepest layer) Skin and Body Membranes: Layers of EpidermisStratum basale (deepest layer)Cells undergoing mitosisLies next to dermisContains two cell types: keratinocytes & melanocytesStratum spinosum (spiny layer)Keratinocytes mature, filling cells with keratin proteinPhagocytic white blood cells – Langerhans cellsStratum granulosum (granular layer)3-5 rows of flattened keratinocytes (produce keratin)
10 Stratum lucidum (clear layer) Skin and Body Membranes: Layers of EpidermisStratum lucidum (clear layer)Occurs only in thick, glaborous (hairless) skinStratum corneum (outermost layer)Shingle-like dead cells filled with keratin5-50 cell layers thick, depending upon locationThe stratum corneum is thickest in the soles of the feet.It’s thinnest in the eyelids.
12 Skin and Body Membranes: Epidermis MelaninThe pigment, melanin, is produced by melanocytes in the stratum basale.Color is yellow to brown to blackMelanocytes have cellular extensions, called dendrites that weave between the cells of the stratum basale and spinsoum. The keratinocytes absorb melanin from the dendrites, and skin is evenly colored…usually.Amount of melanin produced depends upon genetics and exposure to sunlight
13 Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4
15 Most superficial dermal layer Skin and Body Membranes: DermisPapillary layerMost superficial dermal layerCapillaries which provide nutrients to the avascular epidermis through diffusionSense receptors: pain receptors (free nerve endings) & touch receptors (Meissner’s corpuscles)Projections called dermal papillae
16 Skin and Body Membranes: Dermis, papillary layer As the epidermis layers superficially to the dermis, the pattern of dermal papillae is amplified. Your fingerprints, handprints, and footprints are the pattern of your dermal papillae!
17 Reticular layer Thicker than papillary layer Skin and Body Membranes: DermisReticular layerThicker than papillary layerBlood vessels (arterioles, venules) help maintain body temperature homeostasisSweat and oil glandsDeep pressure receptors – Pacinian corpusclesConnective tissue fibers: Collagen & Elastin
18 Skin and Body Membranes: Integumentary System, Anatomy
19 Why do surgeons make incisions along these lines? Skin and Body Membranes: Dermis, reticular layerSeparation of bundles of collagen fibers form lines of cleavage in the skin. (Langer’s cleavage lines)Why do surgeons make incisions along these lines?
21 Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4
22 Appendages of the Skin: Skin and Body Membranes: Integumentary System, AnatomyAppendages of the Skin:Hair & Nails
23 Hair Produced by hair bulb matrix Skin and Body Membranes: Skin appendages, hairHairProduced by hair bulb matrixConsists of hard keratinized epithelial cellsMelanocytes provide pigment for hair colorComposed of a root & shaftFigure 4.7c
25 Root the part of hair enclosed in the follicle. Skin and Body Membranes: Skin appendages, hairRoot the part of hair enclosed in the follicle.Shaft the part of hair projecting from the surface of the scalp or skin
26 Shaft Central medulla Cortex surrounds medulla Skin and Body Membranes: Skin appendages, hairFigure 4.7bShaftCentral medullaCortex surrounds medullaCuticle on outside of cortex (heavily keratinized)
28 Flat shaft = curly/kinky hair Oval shaft = wavy hair Skin and Body Membranes: Skin appendages, hairThe shape of the hair shaft determines the macroscopic appearance of the hair.Flat shaft = curly/kinky hairOval shaft = wavy hairRound shaft = straight hair
29 Associated Hair Structures Skin and Body Membranes: Skin appendages, hairAssociated Hair StructuresHair follicleDermal and epidermal sheath surround hair rootArrector pili muscleSmooth muscle that surrounds hair follicles and contracts when cold or frightenedSebaceous glandSweat gland
30 Skin and Body Membranes: Integumentary System, Anatomy Figure 4.4
31 Nails Heavily keratinized, scale-like modifications of the epidermis. Skin and Body Membranes: Skin appendages, nailsNailsHeavily keratinized, scale-like modifications of the epidermis.Only two layers of epidermis extend beneath the nail bed: stratum basale & stratum spinosumLack of pigment makes them colorless
32 Nail Structures Free edge Body Root of nail Skin and Body Membranes: Skin appendages, nailsNail StructuresSlide 4.22Free edgeBodyRoot of nailNail folds -skin folds that border nailCuticle -thick proximal nail foldLunula –white crescentFigure 4.9