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Integumentary (Skin)
Question | Answer |
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Integumentary System | The skin and it's accessory structures (derivatives) |
Integument | Means the same as "skin"; Largest organ in the body (7-8% total weight of the body). Two Layers: Epidermis and Dermis |
Epidermis | Most superficial layer; Comprised solely of Keratinized Stratified Squamous Epithelium (keratin is a water-insoluble protein); Is Avascular; Consists of 4-5 layers (strata) of distinct cell types; Up to hundreds of cells thick. |
Dermis | Between epidermis and hypodermis; Mainly comprised of CT (primarily collagen fibers) but does contain blood vessels, glands, hair follicles, nail roots, sensory nerve endings and smooth muscle; Divided into two layers (Papillary layer and Reticular layer) |
Hypodermis (subcutaneous layer) | AKA hypodermis or superficial fascia; Deep to, but not considered part of, the integument; Consists of areolar and adipose connective tissue; Acts as protection of underlying structures, a store of energy and thermal insulation |
Integument Function | Protection (physical and chemical); Prevention of dehydration; Temperature regulation (sweating and vasodilation/constriction); Metabolic regulation (Vit. D); Immune defense (Dendritic cells); Sensory reception; Excretion/Secretion |
Epidermis Strata Layers (from most superficial to deepest) | Stratum Corneum; Stratum Lucidum (found only in thick skin); Stratum Granulosum; Stratum Spinosum; Stratum Basale |
Stratum Corneum | Most superficial layer of epidermis; Thickness varies from a few to 30 layers thick depending on location on the body; Anucleate (a "everything" but keratin for that matter); Comprised solely of dead keratinocytes to be sloughed off by abrasion of skin. |
Stratum Lucidum | Thin, translucent region, 2-3 layers thick; Sole of feet and palms of hands (calluses); Cells devoid of organelles but filled with ELEIDIN which is a transparent, intermediate product of keratin maturation. |
Stratum Granulosum | AKA Granular layer; 3-5 layers of keratinocytes; As they migrate from blood supply organelles begin to degrade and cytoplasm fills with concentrated keratin;Fully ketatinized cells are dead but strong and highly water-insoluble. |
Stratum Spinosum | AKA Spiny layer; Several layers thick; 2 types of cells (Keratinocytes and Epidermal dendritic) |
Integumentary System | The skin and it's accessory structures (derivatives) |
Integument | Means the same as "skin"; Largest organ in the body (7-8% total weight of the body). Two Layers: Epidermis and Dermis |
Epidermis | Most superficial layer; Comprised solely of Keratinized Stratified Squamous Epithelium (keratin is a water-insoluble protein); Is Avascular; Consists of 4-5 layers (strata) of distinct cell types; Up to hundreds of cells thick. |
Dermis | Deeper layer of dense irregular connective tissue |
Hypodermis (subcutaneous layer) | A third layer (not considered part of the integument) lies deep to the dermis. Consists mostly of adipose connective tissue. |
Integument Function | Protection (physical and chemical); Prevention of dehydration; Temperature regulation (sweating and vasodilation/constriction); Metabolic regulation (Vit. D); Immune defense (Dendritic cells); Sensory reception; Excretion/Secretion |
Epidermis Strata Layers (from most superficial to deepest) | Stratum Corneum; Stratum Lucidum (found only in thick skin); Stratum Granulosum; Stratum Spinosum; Stratum Basale |
Stratum Corneum | Most superficial layer of epidermis; Thickness varies from a few to 30 layers thick depending on location on the body; Anucleate (a "everything" but keratin for that matter); Comprised solely of dead keratinocytes to be sloughed off by abrasion of skin. |
Stratum Lucidum | Thin, translucent region, 2-3 layers thick; Sole of feet and palms of hands (calluses); Cells devoid of organelles but filled with ELEIDIN which is a transparent, intermediate product of keratin maturation. |
Stratum Granulosum | AKA Granular layer; 3-5 layers of keratinocytes; As they migrate from blood supply organelles begin to degrade and cytoplasm fills with concentrated keratin;Fully ketatinized cells are dead but strong and highly water-insoluble. |
Stratum Spinosum | AKA Spiny layer; Several layers thick; 2 types of cells (Keratinocytes and Epidermal dendritic) |
Keratinocytes (Stratum Spinosum) | Differentiated daughter cells from the Stratum Basale; Non-dividing (may see a rare mitotic cell); Attach to each other with desmosomes. |
Epidermal Dendritic | Phagocytitic and engulf invading pathogens |
Stratum Basale | The only layer that is mitotically active;Single layer of cuboid cells directly adjacent to the dermis. 3 cell types (Keratinocytes, Melanocytes, Tactile Cells) |
Keratinocytes (Stratum Basale) | Most abundant; Produce keratina water-insoluble protein that is strong and prevents the skin from dissolving in an aqueous environment |
Melanocytes (Stratum Basale) | Have long branching cytoplasmic processes that are distributed throughout this cell layer; Produce melanosomes; Absorbs energy from the UV light thus preventing damage to DNA of cells in this layer, possibly preventing a form of skin cancer |
Melanosomes | Black/brown pigment produced by the melanocytes of the Stratum Basale |
Tactile Cells (Stratum Basale) | Sensitive to touch and contained in the Basement Membrane of the Stratum Basale |
Papillary Layer of the Dermis | Superficial layer; Directly adjacent to stratum basale; Dermal papillae & epidermal ridges interlock to increase surface area exposure between the epidermis and dermis; Dermal papillae contain capillaries that supply nutrients to avascular epidermal cells |
Reticular Layer | The majority and deepest of the dermis; Mainly dense irregular connective tissue, blood vessels, glands, hair follicles and nerves; Collagen bundles help connect dermis to underlying hypodermis |
Lines of Cleavage | Determined by orientation of collagen bundles; Important to know for surgical procedures since incisions made at right angles to these lines of cleavage will heal very slowly |
Innervation | Nerve fibers dispersed throughout the dermis; Nerves function as tactile (touch) receptors, control blood flow and glandular secretion |
Blood Supply | Unlike the avascular epidermis, the dermis contains blood vessels; These blood vessels have important role in controlling body temperature (Vasoconstriction and Vasodilation) |
Vasoconstriction | Narrowing of blood vessels thus preserving core body heat |
Vasodilation | Widening of blood vessels thus loosing body heat and lowering body temperature |
Epidermal Derivatives | Nails, Hair, Sweat and Sebaceous Glands |
Nail Matrix | Actively growing part of the nail |
Lunula | Whitish semilunar proximal area of the nail body; White because the thickened underlying stratum basale obscures the capillary bed |
Hair | Keratinized cells growing from a hair follicle that extends deep into the dermis or hypodermis; Three zones along the length of a hair (Hair bulb, Hair root, Hair shaft) |
Hair Bulb | A swelling at the dermal base |
Hair Matrix | Dividing epithelial cells that generate daughter cells resulting in growth or lengthening of the hair |
Hair Papilla | Consists of a small amount of connective tissue, nerves and blood vessels that support the dividing epithelial cells within the hair matrix |
Arrector Pili Muscle | Attached to the hair shaft; Involuntary smooth muscle; Responds to emotional states such as fear or rage or exposure to cold temperatures; “goose bumps” |
Function of Hair | Protection; Heat Retention; Facial Expression; Sensory Reception; Visual Identification; Criminal Signal Dispersal |
Integumentary Exocrine Glands | Sweat (sudoriferous) glands; Sebaceous glands; Ceruminous; Mammary |
Sweat (sudoriferous) Glands | Produce a watery solution |
Sebaceous Glands | Produce an oily secretion that coats hair shafts and the surface of the epidermis |
Ceruminous | External ear |
Mammary | Breasts |
Two Types of Sweat Glands | Merocrine sweat glands; Apocrine sweat glands |
Sweat Duct | Carries sweat to pore |
Merocrine Sweat Gland | Simple coiled tubular glands; release secretion directly onto surface of skin (pore is the opening); Most numerous; Found mostly on palms of hands, soles of feet and forehead; Secretion is under nervous system control; Secretion is clear and is 99% H2O |
Function of Merocrine Sweat Gland | Thermoregulation; Excretion; Protection |
Apocrine Sweat Gland | Simple coiled tubular glands that release their secretion into the hair follicles at the armpits (axillae), around the nipple (areola), in the groin (pubic) and anus (anal); Secretion is viscous, cloudy and composed of proteins and lipidsBacterial bypro |
Sebaceous Gland | Secrete an oily or waxy substance (sebum) usually into hair follicles; Sebum is thought to keep hair and skin from becoming dry, brittle and cracked; Secretions increase at puberty |
Ceruminous Gland | Secrete cerumin (Earwax) |
Mammary Gland | Modified apocrine glands; Present in both males and females; Secrete milk |