Chapter 5 The Integumentary System 2/19/2009

Introduction The organs of the integumentary system include the skin and its accessory structures including hair, nails, and glands, as well as blood vessels, muscles and nerves Dermatology is the medical specialty for the diagnosis and treatment of disorders of the integumentary system. 2/19/2009

Structure of the Skin: Objectives Describe the layers of the epidermis and the cells that compose them. Compare the composition of the papillary and reticular regions of the dermis. Name the tissue types composing the epidermis and dermis. List the major layers of each and describe their functions. Explain the basis for different skin colors. Briefly describe how changes in skin color may be used as clinical signs of certain disease states. 2/19/2009

Structure of the Skin The skin (cutaneous membrane) covers the body and is the largest organ of the body by surface area and weight Its area is about 2 square meters (22 square feet) and weighs 4.5-5kg (10-11 lb), about 16% of body weight It is 0.5 – 4 mm thick, thinnest on the eyelids, thickest on the heels; the average thickness is 1 – 2 mm 2/19/2009

Structure of the Skin It consists of two major layers: outer, thinner layer called the epidermis, consists of epithelial tissue inner, thicker layer called the dermis Beneath the dermis is a subcutaneous (subQ) layer (also called hypodermis) which attaches the skin to the underlying tissues and organs. 2/19/2009

Components of the Integumentary System 2/19/2009

Structure of the Skin The epidermis has a number of important characteristics: the epidermis is composed of keratinized stratified squamous epithelium it contains four major types of cells: see next slide 2/19/2009

Structure of the Skin Keratinocytes (90% of the cells) produce keratin which is a tough fibrous protein that provides protection Melanocytes: which produce the pigment melanin that protects against damage by ultraviolet radiation Langerhans cells: involved in immune responses, arise from red bone marrow Merkel cells: which function in the sensation of touch along with the adjacent tactile discs 2/19/2009

Types of Cells in the Epidermis 2/19/2009

Epidermis The epidermis contains four major layers (thin skin) or five major layers (thick skin) Stratum basale (deepest layer) or stratum germinativum, where continuous cell division occurs which produces all the other layers Stratum spinosum, 8-10 layers of keratinocytes Stratum granulosum, which includes keratohyalin and lamellar granules 2/19/2009

Epidermis Stratum lucidum is present only in thick skin (the skin of the fingertips, palms, and soles) Stratum corneum: composed of many sub layers of flat, dead keratinocytes called or squames that are continuously shed and replaced by cells from deeper strata; constant friction can stimulate formation of a callus. Keratinization, the accumulation of more and more protective keratin, occurs as cells move from the deepest layer to the surface layer 2/19/2009

Layers of the Epidermis 2/19/2009

Dermis The dermis has several important characteristics: is composed of connective tissue collagen and elastic fibers contains two layers papillary region (upper layer immediately beneath epidermis) consists of areolar connective tissue containing thin collagen and elastic fibers, dermal papillae (including capillary loops), corpuscles of touch and free nerve endings 2/19/2009

Dermis reticular region, the deep layer, consists of dense irregular connective tissue containing collagen and elastic fibers adipose cells, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands 2/19/2009

Dermis Lines of cleavage - “tension lines” in the skin indicate the predominant direction of underlying collagen fibers Epidermal ridges reflect contours of the underlying dermal papillae and form the basis for fingerprints (and footprints); their function is to increase firmness of grip by increasing friction. 2/19/2009

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Basis of Skin Color Variations in skin color arise from variations in the amounts of three pigments: melanin, carotene, and hemoglobin Melanin - a yellow-red or brown-black pigment produced by melanocytes (located mostly in the epidermis, where it absorbs UV radiation) The amount of melanin causes the skin’s color to vary from pale yellow to tan to black The number of melanocytes are about the same in all people; differences in skin color is due to the amount of pigment produced 2/19/2009

Basis of Skin Color A benign localized overgrowth of melanocytes is a nevus or mole Albinism is an inherited inability to produce melanin - vitiligo is a condition in which there is a partial or complete loss of melanocytes in patches of skin Carotene - yellow-orange pigment (found in the stratum corneum, dermis, and subcutaneous layer) Hemoglobin - red color (located in erythrocytes flowing through dermal capillaries) 2/19/2009

A, B, C ’ s of Melanoma Asymmetry Borders Color Diameter Elevation 2/19/2009

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Subcutaneous Layer Subcutaneous layer (hypodermis) is not part of the skin but, among its functions, it attaches the skin to the underlying tissues and organs; this layer (and sometimes the dermis) contains lamellated (pacinian) corpuscles which detect external pressure applied to the skin. 2/19/2009

Accessory Structures of the Skin: Objectives Compare the structure and locations of sweat (sudoriferous), oil (sebaceous), ceruminous, and mammary glands. Also compare the composition and functions of their secretions. Compare and contrast eccrine and apocrine glands. List the functions of hair. Describe the cause of acne and its treatments. 2/19/2009

Accessory Structures of the Skin include hair, skin glands, and nails Hairs (pili) have a number of important functions: protection reduction of heat loss sensing light touch Sebaceous (oil) glands are connected to hair follicles 2/19/2009

Skin Glands Sebaceous glands secrete an oily substance called sebum which prevents dehydration of hair and skin, and inhibits growth of certain bacteria Sudoriferous (sweat) glands – 2 types: Eccrine sweat glands Apocrine sweat glands 2/19/2009

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Acne Inflammation of sebaceous glands Usually begins at puberty when sebaceous glands grow and increase production Androgens play the greatest role Due to colonization of glands by bacteria that grow and thrive in lipid-rich sebum May cause a cyst of sac of connective tissue cells that can destroy and displace normal tissue with a scar Treatment c/o benzoyl peroxide or tretinoin, antibiotics (tetracycline or erythromycin) and isotretinoin (accutane). 2/19/2009

Ceruminous and Mammary Glands Modified sudoriferous (apocrine) sweat glands located in the ear canal and breast, respectively Along with nearby sebaceous glands, ceruminous glands are involved in producing a waxy secretion called cerumen (earwax) which provides a sticky barrier that prevents entry of foreign bodies into the ear canal. Mammary glands produce milk 2/19/2009

Types of Skin: Objectives Compare and contrast structural and functional differences of thick and thin skin. 2/19/2009

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Functions of the Skin: Objectives Describe how skin contributes to: regulation of body temperature blood reservoir protection cutaneous sensations excretion and absorption synthesis of vitamin D 2/19/2009

Functions of the Skin regulation of body temperature: liberating sweat on its surface and adjusting flow of blood in the dermis. blood reservoir: 8-10% of total blood flow in a resting adult Protection: keratin barrier, lipids serve as barrier and resist dehydration, acid pH, pigment blocks UV, immunologic barrier 2/19/2009

Functions of the Skin cutaneous sensations: touch, pressure, vibration, and tickling; pain excretion and absorption: small role in excretion of wastes – ammonia and urea; absorption of water soluble substances is negligible, but some lipid soluble materials such as drugs and vitamins K, E, D, and A; steroids synthesis of vitamin D: requires UV activation then converted to calcitriol in the kidneys 2/19/2009

Skin Wound Healing: Objectives Explain epidermal and deep wound healing. 2/19/2009

Epidermal Wound Healing: superficial 2/19/2009

Deep wound healing: four phases Inflammatory Migratory Proliferative Maturation Fibrosis – scar Hypertrophic scar - keloid 2/19/2009

Deep Wound Healing 2/19/2009

Aging and the Integumentary System Effects begins in late 40’s: Wrinkling, loss of collagen and elastic tissue decrease of skin’s immune responsiveness: Langerhans cells decrease and macrophages less effective dehydration and cracking of the skin: decreased size of sebaceous glands decreased sweat production decreased numbers of functional melanocytes resulting in gray hair and atypical skin pigmentation loss of subcutaneous fat a general decrease in skin thickness an increased susceptibility to pathological conditions: skin heals poorly, increased risk skin cancer and pressure sores develop more readily growth of hair and nails decreases; nails may also become more brittle with age. 2/19/2009

Burns Tissue damage from excessive heat, electricity, radioactivity, or corrosive chemicals that destroys (denatures) proteins in the exposed cells is called a burn. Generally, the systemic effects of a burn are a greater threat to life than are the local effects. Depending on the depth of damage, skin burns are classified as first-degree and second-degree (partial-thickness) and third-degree (full-thickness) (Figure 5.9) The seriousness of a burn is determined by its depth, extent, and area involved, as well as the person’s age and general health. When the burn area exceeds 70%, over half of the victims die. A method for determining the extent of a burn is the rule of nines method (Figure 5.10). 2/19/2009

Burns The injury of skin tissues results in severe systemic effects: Large loss of water, plasma, and plasma proteins may result in shock Risks of bacterial infections markedly increased Reduced circulation of blood results Decreased urine output Markedly diminished immune responses 2/19/2009

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End of Chapter 5 Copyright 2009 John Wiley & Sons, Inc End of Chapter 5 Copyright 2009 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein. 2/19/2009