1. The Integumentary System and Body Membranes
Chapter 6
The Integumentary System and Body Membranes

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

3. 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
A membrane is a thin, sheetlike structure that covers and protects the body’s surface, lines body cavities, and covers the inner surfaces of hollow organs, such as the digestive, reproductive, and respiratory passageways.
What are some of the other functions performed by membranes? Some membranes anchor organs to each other or to bones, membranes secrete lubricating fluids that reduce friction during organ movements (beating heart or lung expansion and contraction), membrane lubricants also decrease friction between bones in joints.

4. Types of body membranes
Types of body membranes. A, Epithelial membranes, including cutaneous membrane (skin), serous membranes (parietal and visceral pleura and peritoneum), and mucous membranes. B, Connective tissue membranes, including synovial membranes.

5. Classification of Body Membranes
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
What are the three types of epithelial membranes? cutaneous, serous, and mucous
The cutaneous membrane is the primary organ of the integumentary system. It has a superficial layer of epithelial cells and an underlying layer of supportive connective tissue.
The serous membrane that lines body cavities and covers the surfaces of organs is a single, continuous sheet of tissue.
The name of the serous membrane is determined by its location.
What are some examples of serous membranes? What are their functions? Serous membranes are found only on surfaces within closed cavities. Parietal membranes line the walls of cavities like wallpaper in a room. Visceral membranes cover the surface of organs within body cavities.

6. Classification of Body Membranes
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
Serous membranes secrete a thin, watery fluid that helps to reduce friction and serves as a lubricant when organs rub against one another and against the walls of the cavities that contain them.

7. Classification of Body Membranes
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
Pleurisy is also known as “pleuritis.”
Why might peritonitis sometimes be a serious complication of an infected appendix? An infected appendix that ruptures will allow the contents of the gastrointestinal tract to enter the peritoneal cavity.

8. Classification of Body Membranes
Mucous membranes
Line body surfaces that open directly to the exterior
Produce mucus, a thick secretion that keeps the membranes soft and moist
What are some examples of mucous membranes in the body? Mucous membranes line body surfaces that open directly to the exterior such as those lining the respiratory, digestive, urinary, and reproductive tracts.
What is the mucocutaneous junction? The transitional area that serves as the point of fusion where skin and mucous membranes meet
The epithelial component of a mucous membrane varies depending on location and function.
The esophagus has a tough, abrasion-resistant stratified squamous epithelium.
The lower segment of the digestive tract has a simple, columnar epithelium.

9. Classification of Body Membranes
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
What are some examples of connective tissue membranes, and what are the functions that they serve? Synovial membranes line the spaces between bones and joints; they also line the cushion-like sacs called bursae.
In figure 6-2 the various types of epithelial and connective tissue membranes are shown.
What are the functions performed by each of the membranes in figure 6-2?

10. The Skin Structure—two primary layers called epidermis and dermis
Outermost and thinnest primary layer of skin
Composed of several layers of stratified squamous epithelium
One square inch of skin contains: 500 sweat glands, 1000 nerve endings, yards of blood vessels, 100 oil (sebaceous) glands, 150 sensors for pressure, 75 sensors for heat, and 10 sensors for cold.
What type of membrane is the skin? Cutaneous
Describe the process of cell reproduction performed by the stratum germinativum. Mitosis; then they move toward the surface and specialize in ways that increase their ability to provide protection for the body tissues that lie below them.
What purposes does this process serve? It enables the skin to repair itself if injured.

11. Microscopic view of skin
Microscopic view of skin. The epidermis, shown in longitudinal section, is raised at one corner to reveal the ridges in the dermis.

12. 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
What is keratin and what purpose does it serve? Keratin is a tough, waterproof material that provides cells in the outer layer of the skin with a horny, abrasion-resistant, and protective quality.

13. 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
Pigment—comes from Latin term meaning “paint.”
The higher the concentration of melanin, the deeper the color of skin.
What is the primary function of melanin? Melanin determines skin color.
How is the amount of melanin in the skin determined? Heredity and exposure to sunlight affect amount of melanin.
Cyanosis: change in skin color (bluish tinge in light-skinned individuals) if blood oxygen levels or blood flow is reduced.

14. 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

15. 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
Cells of the dermis are scattered far apart, with many fibers in between.
What types of fibers are in the dermis, and what are their characteristics? Dermis is composed largely of connective tissue with tough, strong fibers (collagen or white fibers) and stretchable and elastic (yellow).

16. Thick and thin skin. A, Thick skin is hairless and has roughly parallel friction ridges. B, Thin skin has hairs and shallow, irregular grooves. (Copyright Kevin Patton, Lion Den Inc, Weldon Spring, MO.)

17. The Skin Structure Dermis
Number of elastic fibers decreases with age and contributes to wrinkle formation
Striae—“stretch marks”; elongated marks caused by overstretching of skin
The dermis contains a specialized network of nerves and nerve endings to process sensory information such as pain, pressure, touch, and temperature.
What results from the elastic fibers in the dermis decreasing with age? Why would this happen? The number of elastic fibers decreases with age and wrinkles develop as the skin loses elasticity, sags, and becomes less soft and pliant.

18. The Skin Structure Dermis
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
Are there any parts of the body that are hairless? If so, which? The lips, palms of the hands, and soles of the feet are hairless.
What is lanugo? Lanugo is the downy, soft hair of a newborn.

19. Strawberry hemangioma
Strawberry hemangioma. (From Habif TP: Clinical dermatology, ed 4, St Louis, 2004, Mosby.)

20. 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

21. Hair shaft and follicle
Hair shaft and follicle. Scanning electron micrograph showing shafts of hair extending from their follicles. (Copyright © by David Scharf, 1986, 1993.)

22. 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
What is the arrector pili? What function does it perform and why? The arrector pili is a tiny, smooth (involuntary) muscle attached to the base of a dermal papilla above and the side of a hair follicle below. When it contracts, it simultaneously pulls on its two points of attachment to create goose pimples or goose flesh.
What parts of the hair are in the dermis? What parts are in the epidermis? See Figure 6-2.

23. Alopecia areata. (From Goldstein B, editor: Practical dermatology, ed 2, St Louis, 1997, Mosby.)

24. 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
Receptors are widely distributed over the skin.

25. 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
How are nails formed?
What purposes might the nails serve? See Figure 6-9 and Figure 6-10

26. Structure of nails. A, Fingernail viewed from above
Structure of nails. A, Fingernail viewed from above. B, Sagittal section of fingernail and associated structures.

27. 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
What might cause the nail bed to change colors? Decrease in blood oxygen level

28. Normal variations in nail structure
Normal variations in nail structure. A, Longitudinal ridges in light-skinned people are common. B, Pigmented bands are a normal finding in dark-skinned individuals. (A, From Habif TP: Clinical dermatology: a color guide to diagnosis and therapy, ed 3, St Louis, 1996, Mosby., B, From Habif TP: Clinical dermatology, ed 4, St Louis, 2004, Mosby.)
Abnormal nail structure. A, Onycholysis. Separation of nail from the nail bed begins at the free edge. B, Nail pitting. A common finding in persons with psoriasis. (A, From Habif TP: Clinical dermatology, ed 2, St Louis, 1990, Mosby., B, From Habif TP: Clinical dermatology: a color guide to diagnosis and therapy, ed 3, St Louis, 1996.)

29. The Skin
Skin glands—two main types
Sweat, or sudoriferous
Sebaceous

30. 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
A single square inch of skin on the palms contains about 3000 eccrine sweat glands.
What is the difference between eccrine and apocrine glands? Eccrine sweat glands are more numerous and widespread over the body. They produce a transparent, thin, watery liquid. Apocrine glands are found primarily in the axilla and genital areas. They secrete a thicker, milky secretion that produces odor when skin bacteria decompose the secretion. Apocrine glands become active at puberty.

31. 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
Apocrine glands enlarge and begin to function at puberty.
What causes the odor sometimes associated with secretions of the apocrine glands?

32. 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
Sebum secretion decreases in late adulthood, contributing to increased wrinkling and cracking of the skin.
Why would sebum be referred to as “nature’s skin cream”? It prevents drying and cracking of the skin.

33. Acne. (From Callen JP et al: Color atlas of dermatology, ed 2, Philadelphia, 2000, Saunders.)

34. 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
How does the skin protect the body against the potential hazards listed in this slide? Intact skin prevents damage from external forces; waterproof skin products are best treatment for skin maintenance.
What are the defensive properties of keratin? Keratin is waterproof, which prevents fluid from entering or leaving through the skin
What are the defensive properties of melanin? Protects body against ultraviolet rays of the sun

35. Bruising. Color changes caused by the deoxygenation, clotting, and breakdown of blood are easily seen in light-skinned individuals. (From McCance K, Huether S: Pathophysiology, ed 5, St Louis, 2006, Mosby.)

36. Skin graft. Illustration shows a skin graft covering a severe burn to the hand. Multiple slits allow the grafted piece of skin to stretch over a larger area than would otherwise be possible. (From Wong DL: Whaley & Wong’s nursing care of infants and children, ed 5, St Louis, 1995, Mosby.)

37. Functions 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
How is heat lost through the skin? By regulation of the blood flow through capillaries in the skin; dilation will cause heat loss.
Blood supply to the skin far exceeds the amount needed by the skin.

38. Functions 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
How do receptors respond to environmental changes? There are receptors for light touch (Meissner corpuscles), pressure (Pacini corpuscles), pain, heat and cold.

39. 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

40. 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
Skin lesions can be benign or malignant or might not indicate a disorder at all.
What are some examples of benign lesions and malignant lesions? See Table 6-1, Figure 6-15
What are some examples of lesions that do not indicate a disorder?

41. Skin repair. A minor skin injury is followed by blood clotting and self-repair of the damaged epidermis and dermis. Thickened fibrous tissue produced during dermal repair may cause formation of a scar.

42. 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
In what ways can the skin be burned? Burns can occur from a fire, contact of the skin with a hot surface, exposure to ultraviolet light. Burns can also occur when skin contacts an electric current or harmful chemical.

43. Classification of burns by depth of injury
Classification of burns by depth of injury. First- and second-degree burns are classified as partial-thickness burns and third- and fourth-degree burns as full-thickness burns.

44. 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
The classification system used to describe the severity of burns is based on the number of tissue layers involved.
The most severe burns destroy not only layers of skin and subcutaneous tissue but underlying tissues as well.
What are some examples of how one might receive first-, second-, and third-degree burns? What are the symptoms, and what tissues are damaged? See Figure 6-16, Figure 6-17, A, Figure 6-17, B

45. Partial- and full-thickness burns
Partial- and full-thickness burns. A, Second-degree (partial-thickness) burn showing a scald injury in a young child. B, Fourth-degree (full-thickness) high-voltage electrical burn resulting in underlying muscle and bone damage. (From Copstead-Kirkhorn L, Banasik J: Pathophysiology, ed 2, St Louis, 1999, Saunders.)

46. 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
What are the 11 body areas defined by the “rule of nines”? See Figure 6-18
What percentage of the body is injured if a person has burns to the face and both arms? 27%

47. The rule of nines. Dividing the body into 11 areas of 9% each helps in estimating the amount of skin surface burned in an adult. (Barbara Cousins.)

48. 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
Skin infections are common because the skin is the body’s first line of defense against microbes.
Can skin infections be life threatening? Provide an example. Yes, infections with staphylococcal or streptococcal bacteria that begin in the skin and become systemic.
Give examples of skin infections that are caused by a virus, a fungus, and an itch mite.

49. Skin infections. A, Impetigo. B, Tinea (ringworm). C, Furuncle (boil)
Skin infections. A, Impetigo. B, Tinea (ringworm). C, Furuncle (boil). D, Scabies. (A, From Emond RTD, Welsby PD, Rowland HAK: Colour atlas of infectious diseases, ed 3, London, 1995, Mosby., D, Courtesy Jaime A. Tschen, MD, Department of Dermatology, Baylor College of Medicine, Houston, TX.)

50. 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
Skin disorders can be caused by a lack of blood flow, allergic reactions, inflammatory reactions, or autoimmune diseases that attack the skin.

51. 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

52. Vascular and inflammatory skin disorders. A, Decubitus ulcer. B, Hives
Vascular and inflammatory skin disorders. A, Decubitus ulcer. B, Hives. C, Psoriasis. D, Contact dermatitis. (A, From Potter P, Perry A: Fundamentals of nursing, ed 7, St Louis, 2009, Mosby., D, From Kumar V, Abbas A, Fausto N: Robbins and Cotran pathologic basis of disease, ed 7, Philadelphia, 2005, Saunders.)

53. 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
What are the warning signs of malignant melanoma? Asymmetrical, irregular, or indistinct in shape, unevenly colored, larger than 6 mm
What does ABCD stand for in evaluation of a mole? Asymmetry, Border, Color, Diameter

54. 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
Adults who have had more than two blistering sunburns before the age of 20 years have a much greater risk for development of melanoma than someone who has had no such burns.

55. Examples of skin cancer lesions. A, Squamous cell carcinoma
Examples of skin cancer lesions. A, Squamous cell carcinoma. B, Basal cell carcinoma. C, Malignant melanoma. D, Kaposi sarcoma. (A, From Goldman L, Ausiello D: Cecil textbook of medicine, ed 23, Philadelphia, 2008, Saunders., B, From Noble J: Textbook of primary care medicine, ed 3, Philadelphia, 2001, Mosby., C, From Townsend C, Beauchamp RD, Evers BM, Mattox K: Sabiston textbook of surgery, ed 18, Philadelphia, 2008, Saunders., D, From Rakel R: Textbook of family medicine, ed 7, Philadelphia, 2007, Saunders.)