E integumentary system

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

The Integumentary System and Body Membranes


ObjectivesObjectives

• 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 MembranesClassification 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe Skin


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

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


The SkinThe 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe 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 SkinThe Skin

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


The SkinThe 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 SkinThe 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 SkinThe 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 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




Functions of the SkinFunctions of the Skin

• 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


Functions of the SkinFunctions of the Skin

• 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




– 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 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



BurnsBurns

• 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



BurnsBurns

• 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 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




• 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 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 CancerSkin 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


Health & Medicine

E integumentary system