A&P UNIT 1 Chpt 5.ppt - The Integumentary System Mark W...

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The Integumentary System Mark W. Burke, PhD Anatomy & Physiology Lecture 5 Chapter 5
Skin (Integument) Consists of two distinct regions Epidermis —superficial region Epithelial tissue Dermis —underlies epidermis Mostly fibrous connective tissue Hypodermis (superficial fascia) Subcutaneous layer deep to skin Not part of skin but shares some functions Mostly adipose tissue that absorbs shock & insulates Anchors skin to underlying structures – mostly muscles
Figure 5.1 Skin structure. Hair shaft Epidermis Papillary layer Dermis Reticular layer Hypodermis (subcutaneous tissue; not part of skin) Dermal papillae Subpapillary plexus Sweat pore Cutaneous plexus Adipose tissue Nervous structures Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root
Epidermis Keratinized stratified squamous epithelium Four or five distinct layers Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum Four cell types Keratinocytes Melanocytes Dendritic (langerhans) cells Tactile (merkel) cells
Cells of the Epidermis Keratinocytes Most numerous, arranged in layers or strata Produce protective keratin protein and lamellar granules which release waterproofing substance Melanocytes Produce pigment melanin protein for protection from ultraviolet light Langerhans cells Immune response Merkel cells Function with Merkel disc of dermis for touch
Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer Also called stratum germinativum Firmly attached to dermis Single row of stem cells Actively mitotic Produces two daughter cells One cell journeys from basal layer to surface Takes 25–45 days Dies as moves toward surface One cell remains in stratum basale as stem cell Melanocytes compose 10 – 25% of this layer
Layers of the Epidermis: Stratum Spinosum (Prickly Layer) Several layers thick Cells contain web-like system of intermediate prekeratin filaments attached to desmosomes Abundant melanosomes and dendritic cells
Layers of the Epidermis: Stratum Granulosum (Granular Layer) Thin - four to six cell layers Cell appearance changes Cells flatten Nuclei and organelles disintegrate Keratinization begins Cells accumulate keratohyaline granules Help form keratin in upper layers Cell accumulate lamellar granules Their water-resistant glycolipid slows water loss Cells above this layer die Too far from dermal capillaries
Layers of the Epidermis: Stratum Lucidum (Clear Layer) Only in thick skin Thin, translucent band superficial to the stratum granulosum A few rows of flat, dead keratinocytes
Layers of the Epidermis: Stratum Corneum (Horny Layer) 20–30 rows of dead, flat,

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