chapter 6 the integumentary system and body...

Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc.

Chapter 6 The Integumentary System and Body

Membranes

Mosby items and derived items © 2010, 2006, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. 2

Objectives

• Classify, compare the structure of, and give examples of each type of body membrane

• Describe the structure and function of the epidermis and dermis

• List and briefly describe each accessory organ of the skin

• List and discuss the three primary functions of the integumentary system

• List and describe major skin disorders and infections • Classify burns and describe how to estimate the extent

of a burn injury


Classification of Body Membranes

• Classification of body membranes – Epithelial membranes—composed of

epithelial tissue and an underlying layer of connective tissue

– Connective tissue membranes—composed exclusively of various types of connective tissue



• Epithelial membranes – Cutaneous membrane—the skin – Serous membranes—simple squamous

epithelium on a connective tissue basement membrane

• Parietal—line walls of body cavities • Visceral—cover organs found in body cavities



• Examples – Pleura—parietal and visceral layers line

walls of thoracic cavity and cover the lungs – Peritoneum—parietal and visceral layers

line walls of abdominal cavity and cover the organs in that cavity



• Diseases – Pleurisy—inflammation of the serous

membranes that line the chest cavity and cover the lungs

– Peritonitis—inflammation of the serous membranes in the abdominal cavity that line the walls and cover the abdominal organs



• Mucous membranes – Line body surfaces that open directly to the

exterior – Produce mucus, a thick secretion that

keeps the membranes soft and moist



• Connective tissue membranes – Do not contain epithelial components – Produce a lubricant called synovial fluid – Examples

• The synovial membranes in the spaces between joints and in the lining of the bursal sacs


The Skin

• Structure—two primary layers called epidermis and dermis – Epidermis

• Outermost and thinnest primary layer of skin • Composed of several layers of stratified

squamous epithelium


The Skin

• Structure – Epidermis

• Stratum germinativum—innermost (deepest) layer of cells that continually reproduce; new cells move toward the surface

– Sometimes called the pigment layer – Pigment cells called melanocytes, which produce the brown

pigment melanin • As cells approach the surface, they are filled with a tough,

waterproof protein called keratin and eventually flake off • Stratum corneum—outermost layer of keratin-filled cells


The Skin

• Structure – Epidermis

• Skin color changes – Pink flush indicates increased blood volume or increased

blood oxygen – Cyanosis—bluish gray color indicates decreased blood

oxygen level – Vitiligo—patchy light skin areas resulting from acquired

loss of epidermal melanocytes (Figure 6-4) – Increased skin pigmentation caused by hormonal changes

in pregnant women – Freckles—small, flat macules—common normal skin

pigment variation


The Skin

• Dermal-epidermal junction—specialized area of contact between the epidermis and dermis; sometimes described as “spot welds” – Provide support for epidermis – Weakened or destroyed junctions can

cause blisters


The Skin

• Structure – Dermis

• Deeper and thicker of the two primary skin layers and composed largely of connective tissue

• Upper area of dermis characterized by parallel rows of peglike dermal papillae

• Thick skin has parallel friction ridges and no hairs • Thin skin has irregular, shallow grooves and hair • Deeper area of dermis is filled with network of tough

collagenous and stretchable elastic fibers


The Skin


• Number of elastic fibers decreases with age and contributes to wrinkle formation

– Striae—“stretch marks”; elongated marks caused by overstretching of skin


The Skin


• Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels

– Birthmarks—malformation of dermal blood vessels » Strawberry hemangioma » Port-wine stain » Stork bite


The Skin

• Appendages of the skin – Hair

• Soft hair of fetus and newborn called lanugo • Hair growth requires epidermal tubelike

structure called hair follicle • Hair growth begins from hair papilla


The Skin

• Appendages of the skin – Hair

• Hair root lies hidden in follicle; visible part of hair called shaft

• Alopecia (Figure 6-8)—hair loss • Arrector pili—specialized smooth muscle that

produces “goose pimples” and causes hair to stand up straight


The Skin

• Appendages of the skin – Receptors

• Specialized nerve endings—make it possible for skin to act as a sense organ

– Meissner (tactile) corpuscle—capable of detecting light touch

– Lamellar (Pacini) corpuscle—capable of detecting pressure


The Skin

• Nails – Produced by epidermal cells over terminal ends of

fingers and toes – Visible part called nail body – Root lies in a groove and is hidden by cuticle – Crescent-shaped area nearest root called lunula – Nail bed may change color with change in blood

flow


The Skin

• Nails – Normal variations in nail structure

• Longitudinal ridges in light-skinned individuals • Pigmented bands in dark-skinned individuals

– Abnormal variations in nail structure • Onycholysis—separation of nail from nail bed • Pitting—common in psoriasis


The Skin

• Skin glands—two main types – Sweat, or sudoriferous – Sebaceous


The Skin

• Skin glands – Sweat, or sudoriferous, glands

• Eccrine sweat gland – Most numerous, important, and widespread of the

sweat glands – Produce perspiration or sweat, which flows out

through pores on skin surface – Function throughout life and assist in body heat

regulation


The Skin

• Skin glands – Sweat or sudoriferous glands

• Apocrine sweat glands – Found primarily in axilla and around genitalia – Secrete a thicker, milky secretion quite different from

eccrine perspiration – Breakdown of secretion by skin bacteria produces

odor


The Skin

• Skin glands – Sebaceous glands

– Secrete oil or sebum for hair and skin – Secretion increases during adolescence – Amount of secretion regulated by sex hormones – Sebum in sebaceous gland ducts may darken to

form a blackhead – Acne vulgaris—inflammation of sebaceous gland

ducts


Functions of the Skin

• Protection—first line of defense – Against infection by microbes – Against ultraviolet rays from sun – Against harmful chemicals – Against cuts and tears – Bruising can cause discoloration as blood

released from damaged vessels breaks down – Skin grafts may be needed to replace skin

destroyed by disease or trauma



• Temperature regulation – Skin can release almost 3000 calories of

body heat per day – Mechanisms of temperature regulation

• Regulation of sweat secretion • Regulation of flow of blood close to the body

surface



• Sense organ activity – Receptors serve as receivers for the body,

keeping it informed of changes in its environment

– Skin can detect sensations of light touch, pressure, pain, heat, and color


Disorders of the Skin (Dermatoses)

• Skin lesions—any measurable variation from the normal structure – Elevated lesions—cast a shadow outside their

edges • Papule—small, firm raised lesion • Plaque—large raised lesion • Vesicle—blister • Pustule—pus-filled lesion • Crust—scab • Wheal (hive)—raised, firm lesion with a light center


Disorders of the Skin (Dermatoses)

– Flat lesions—do not cast a shadow • Macule—flat, discolored region

– Depressed lesions cast a shadow within their edges

• Excoriation—missing epidermis, as in a scratch • Ulcer—craterlike lesion • Fissure—deep crack or break

– Some lesions are produced by scrapes and cuts—the skin can repair itself


Burns

• Treatment and recovery or survival depend on total area involved and severity or depth of the burn

• Classification of burns – First-degree (partial-thickness) burns—only

surface layers of epidermis involved – Second-degree (partial-thickness) burns—

involve deep epidermal layers; always cause injury to upper layers of the dermis


Burns

• Classification of burns – Third-degree (full-thickness) burns—

characterized by complete destruction of the epidermis and dermis

• May involve underlying muscle and bone (fourth degree)

• Lesion is insensitive to pain because of destruction of nerve endings immediately after injury—intense pain is experienced soon thereafter


Burns

• Estimating body surface area using the “rule of nines” in adults – Body divided into 11 areas of 9% each – Additional 1% of body surface area around

genitals


Skin Infections

• Impetigo—highly contagious staphylococcal or streptococcal infection

• Tinea—fungal infection (mycosis) of the skin; several forms occur

• Warts—benign neoplasm caused by papillomavirus

• Boils—furuncles; staphylococcal infection in hair follicles

• Scabies—parasitic infection


Vascular and Inflammatory Skin Disorders

• Decubitus ulcers (bedsores) develop when pressure slows down blood flow to local areas of the skin

• Urticaria or hives—red lesions caused by fluid loss from blood vessels

• Scleroderma—disorder of vessels and connective tissue characterized by hardening of the skin; two types: localized and systemic


Vascular and Inflammatory Skin Disorders

• Psoriasis—chronic inflammatory condition accompanied by scaly plaques

• Eczema—common inflammatory condition characterized by papules, vesicles, and crusts; not a disease itself but a symptom of an underlying condition


Skin Cancer

• Three common types – Squamous cell carcinoma—the most

common type, characterized by hard, raised tumors

– Basal cell carcinoma—characterized by papules with a central crater; rarely spreads

– Melanoma—malignancy in a nevus (mole); the most serious type


Skin Cancer

• The most important causative factor in common skin cancers is exposure to sunlight

• Kaposi sarcoma, characterized by purple lesions, is associated with AIDS and other immune deficiencies

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