Integumentary System: Structure & Function of Skin, Epidermis, Dermis, Hypodermis, Slides of Physiology

Download Integumentary System: Structure & Function of Skin, Epidermis, Dermis, Hypodermis and more Slides Physiology in PDF only on Docsity! The Integumentary System (Skin) aca CNET Skin (Integument) • Consists of three major regions: - Epidermis – outermost superficial region. Is a keratinized, stratified squamous epithelium – Dermis – middle region. Is a dense irregular connective tissue – Hypodermis (superficial fascia) – deepest region contains adipose tissue docsity.com Cells of the Epidermis • Keratinocytes – produce the fibrous protein keratin • Melanocytes – produce the brown pigment melanin • Langerhans’ cells – epidermal macrophages that help activate the immune system • Merkel cells – function as touch receptors in association with sensory nerve endings docsity.com Layers of the Epidermis: Stratum Basale, S. spinosum, S. granulosum, S. Corneum Figure 5.2b docsity.com • Deepest epidermal layer firmly attached to the dermis • Consists of a single row of the youngest keratinocytes • Cells undergo rapid division, hence its alternate name, stratum germinativum Layers of the Epidermis: Stratum Basale (Basal Layer) docsity.com • Thin, transparent band superficial to the stratum granulosum • Consists of a few rows of flat, dead keratinocytes • Present only in thick skin Layers of the Epidermis: Stratum Lucidum (Clear Layer) docsity.com • Outermost layer of keratinized cells • Accounts for three quarters of the epidermal thickness • Functions include: – Waterproofing – Protection from abrasion and penetration – Rendering the body relatively insensitive to biological, chemical, and physical assaults Layers of the Epidermis: Stratum Corneum (Horny Layer) docsity.com Layers of the Epidermis Keratinocytes Desmosomes Stratum corneum Stratum granulosum Stratum spinosum Stratum —_ 7 basale oe he ae ae * is Melanocytes Melanin granules b Langerhans’ cell Sensory nerve ending Cells are dead; represented only by fla membranous sacs filled with keratin. |— Glycolipids in extracellular space. Cells are flattened; organelles — deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. t— Cells contain thick bundles of intermediate filaments made of pre- keratin. Cells are actively mitotic stem cells; |— some newly formed cells become part of the more superficial layers. -— Dermis Figure 5.2b Layers of the Dermis: Papillary Layer • Papillary layer – Areolar connective tissue with collagen and elastic fibers – Its superior surface contains peglike projections called dermal papillae – Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings docsity.com Layers of the Dermis: Reticular Layer • Reticular layer – Accounts for approximately 80% of the thickness of the skin – Collagen fibers in this layer add strength and resiliency to the skin – Elastin fibers provide stretch-recoil properties docsity.com Skin (Hypodermis) Hair shaft Pore _—f Dermal papillae ft (papillary layer of dermis) oi x \b a ae Meissner's corpuscle rol PY “jy EY. ——— Free nerve ending Eidrmia = Reticular layer of dermis Sebaceous (oil) gland Arrector pili muscle Dermis Sensory nerve fiber Eccrine sweat gland Pacinian corpuscle Hypodermis eK (superficial Artery fascia) Vein — Hair follicle receptor t (root hair plexus) docsity.com Adipose tissue Figure 5.1 Functions of the Integumentary System • Protection – chemical, physical, and mechanical barrier • Body temperature regulation is accomplished by: – Dilation (cooling) and constriction (warming) of dermal vessels – Increasing sweat gland secretions to cool the body • Cutaneous sensation – exoreceptors sense touch and pain docsity.com Functions of the Integumentary System • Metabolic functions – synthesis of vitamin D in dermal blood vessels • Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume • Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat docsity.com Hair • Filamentous strands of dead keratinized cells produced by hair follicles • Contains hard keratin which is tougher and more durable than soft keratin of the skin • Made up of the shaft projecting from the skin, and the root embedded in the skin • Consists of a core called the medulla, a cortex, and an outermost cuticle • Pigmented by melanocytes at the base of the hair docsity.com Hair Follicle Connective tissue root sheath Follicle wall Cuticle Medulla Cortex Internal epithelial root sheath External epithelial root sheath Glassy membrane Hair shaft 1 Arrector pili ————~fui Sebaceous AN Hair bulb in follicle Hair shaft 1 Arrector pili ——__“ Sebaceous — gland 1 Hair root —zi i Ls : _ oO Hair shaft iubcle se (cuticle, cortex, medulla) Internal epithelial root sheath External epithelial root sheath Glassy membrane =| — __———__ Medulla Connective tissue root sheath Hair matrix Melanocyte Hair papilla — Subcutaneous adipose tissue Sweat Glands • Different types prevent overheating of the body; secrete cerumen and milk – Eccrine sweat glands – found in palms, soles of the feet, and forehead – Apocrine sweat glands – found in axillary and anogenital areas – Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen – Mammary glands – specialized sweat glands that secrete milk docsity.com