Chapter 5 Integumentary System Lecture Outline Kenneth W. Blank PhD CIP 859-358-2503 Ken.firstname.lastname@example.org Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Integument Introduction Same as the skin Largest organ in the body (7-8% total weight of the body) Comprised of two layers Epidermis ? superficial layer of stratified squamous epithelium Dermis ? deeper layer of dense irregular connective tissue A third layer (not considered part of the integument) lies deep to the dermis. It is called the hypodermis and consists mostly of adipose connective tissue Layers of the Integument Integument Function Protection Prevention of H2O loss Temperature regulation Metabolic regulation Immune defense Sensory reception Excretion/Secretion EPIDERMIS Most superficial layer Comprised solely of keratinized stratified squamous epithelium (keratin is a water-insoluble protein) Avascular Consists of 4-5 layers (strata) of distinct cell types Epidermal Strata From deepest to most superficial: Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (found only in thick skin) Stratum corneum Stratum Basale Only layer that is mitotically active Single layer of cells directly adjacent to the dermis populated by three cell types: Keratinocytes ? most abundant and produce a water-insoluble protein (keratin) that is strong and prevents the skin from dissolving in an aqueous environment Stratum Basale Melanocytes Have long branching cytoplasmic processes that are distributed throughout this cell layer Produce a black/brown/yellow-brown pigment that can absorb energy from the ultraviolet spectrum of light thus preventing damage to DNA of cells in this layer and possibly preventing a form of skin cancer Tactile cells ? sensitive to touch Cells of the Stratum Basale Stratum Spinosum Daughter cells from the stratum basale Differentiate into non-dividing (may see a rare mitotic cell), highly specialized keratinocyte Several layers thick Epidermal dendritic cells may be present in this layer. These cells are phagocytitic and engulf invading pathogens Cells of the Stratum Spinosum Stratum Granulosum 3-5 layers of keratinocytes Organelles begin to degrade and cytoplasm fills with concentrated keratin filaments Fully ketatinized cells are dead but strong and highly water-insoluble Cells of the Stratum Granulosum Stratum Lucidum Thin, translucent region, 2-3 layers thick Present only in thick skin such as sole of feet and palms of hands Cells devoid of organelles but filled with eleidin which is a transparent, intermediate product of keratin maturation Stratum Corneum Most superficial layer of epidermis Thickness varies from a few to 30 layers thick depending on location on the body Comprised solely of dead keratinocytes to be sloughed off by abrasion of skin (ever wonder what most of those floating particles were when the sun shined into a room?) Cells of the Stratum Corneum Variations in Epidermis -- Skin Color -- Color of skin determined by three pigments: Melanin ? brown pigment produced by melanocytes, predominant in people more exposed to UV light Hemoglobin ? reddish skin color in light complexioned individuals Carotene ? a yellow-orange pigment Melanocytes Abnormal Skin Colors DERMIS Lies deep to epidermis Mainly comprised of connective tissue (primarily collagen fibers) but does contain blood vessels, glands, hair follicles, nail roots, sensory nerve endings and smooth muscle Dermis divided into two layers: Papillary layer -- superficial Reticular layer -- deep Layers of the Dermis Papillary Layer of Dermis Directly adjacent to stratum basale cells of epidermis Dermal papillae and epidermal ridges interlock with each other to increase the surface area exposure between the epidermis and the dermis Dermal papillae contain capillaries that supply nutrients to avascular epidermal cells Reticular Layer of Dermis The majority of the dermis Comprised mainly of dense irregular connective tissue possessing large bundles of collagen fibers with blood vessels, glands, hair follicles and nerves Collagen bundles help connect dermis to underlying hypodermis Lines of Cleavage These lines in the deep dermis mark the 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 are present in 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 ? narrowing of blood vessels thus preserving core body heat Vasodilation ? widening of blood vessels thus loosing body heat and lowering body temperature Subcutaneous Layer (Hypodermis) 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 Subcutaneous Layer (Hypodermis) Epidermal Derivatives There are three major structures that are derived from epidermal tissue: Nails Hair Sweat and Sebaceous Glands Structure of Hair Function of Hair Protection Heat Retention Facial Expression Sensory Reception Visual Identification Chemical Signal Dispersal Sweat Glands
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