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The Integumentary System

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1 The Integumentary System
5 The Integumentary System Chapter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Structure of the Skin Also called the cutaneous membrane or the integument Covers the entire surface of the body Largest organ in the body Comprised of all 4 tissue types The integumentary system is made up of the skin and several accessory organs


4 Structure of the Skin Regions of the Skin Epidermis
Outer, thinner region Made of stratified squamous epithelium Five layers (strata) Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum

5 Structure of the Skin Stratum Basale Just superior to dermis
Constantly dividing and new cells are pushed to the surface As cells move toward the surface of the epidermis, they die and are sloughed off Cells Langerhans cells – macrophages Melanocytes – produce melanin Skin color Protection from UV radiation Sensory nerves Free nerve endings – pain and temperature sensations Tactile cells (Merkel cells) – touch sensations

6 Structure of the Skin Stratum Lucidum Stratum Corneum
Just deep to stratum corneum Found only in thick skin Provides protection from constant friction Stratum Corneum Tough, uppermost layer of epidermis Cells are keratinized (hardened) Keratin prevents water loss and water gain Serves as a mechanical barrier against microbes

7 Structure of the Skin Dermis Thicker than epidermis
Made of dense, irregular connective tissue Dermal papillae Collagenous fibers prevent skin from being torn Elastic fibers stretch to allow movement of muscles and joints Vascularization of dermis supplies oxygen and nutrients to cells of dermis and epidermis Numerous sensory nerve fibers

8 Structure of the Skin Hypodermis
Subcutaneous layer located below the dermis Composed of loose connective tissue Energy storage Insulation

9 Accessory Structures of the Skin
Hair On all body parts except the palms, soles, lips, nipples, and portions of the external reproductive organs After puberty there is noticeable hair in the axillary and pelvic regions Hirsutism – characterized by excessive body and facial hair in women due to increased production of male sex hormone Alopecia – hair loss Androgenic alopecia – male pattern baldness Alopecia areata – sudden onset of patchy hair loss

10 Accessory Structures of the Skin
Hair follicles Formed from epidermal cells Located in dermis Cells become keratinized as they are pushed out Hair root – portion of hair within follicle Hair shaft – portion of hair that continues beyond the skin Sebaceous (oil) glands Arrector pili muscle – smooth muscle attached to hair follicle

11 Accessory Structures of the Skin
Nails Formed from specialized epithelial cells Nail root – base of the nail Nail body – visible portion of the nail Cuticles – fold of skin that hides the root Epithelial cells become keratinized as they move away from the root

12 Accessory Structures of the Skin
Glands – specialized cells that produce and secrete substances into ducts Sweat glands Sebaceous glands

13 Accessory Structures of the Skin
Sweat (sudoriferous) glands – active under stress Apocrine glands Open into hair follicles in anal region, groin, and armpits Begin to secrete at puberty Mammary glands are modified apocrine glands Eccrine sweat glands Open onto surface of skin Active when body heats up; helps lower body temperature Sweat (perspiration) is mostly water, but also excretes wastes Ceruminous glands – modified sweat glands that produce cerumen (earwax)

14 Accessory Structures of the Skin
Sebaceous glands Most are associated with a hair follicle Secrete an oily substance called sebum Lubricates and waterproofs hair and skin Weakens or kills bacteria on skin surface If sebum collects, whiteheads or blackheads form Acne vulgaris – inflammation of the sebaceous glands

15 Disorders of the Skin Athlete’s foot – fungal infection often involving skin of the toes and soles Impetigo – bacterial infection common in young children Psoriasis – chronic condition where skin develops pink or reddish patches Eczema – inflammation of the skin Dandruff – caused by a dry scalp producing flaking and itching Urticaria (hives) – allergic reaction causing reddish, elevated, and often itchy patches

16 Disorders of the Skin Skin Cancer
Begins with mutation of the skin cell DNA Nonmelanoma cancers – less likely to metastasize Basal cell carcinoma Squamous cell carcinoma Melanoma cancers

17 Disorders of the Skin Basal cell carcinoma
Most common type of skin cancer Ultraviolet (UV) radiation causes epidermal basal cells to form a tumor Signs are varied Open sore that will not heal Recurring reddish patch Smooth, circular growth with a raised edge Shiny bump Pale mark 95% of patients are easily cured by removal

18 Disorders of the Skin Squamous cell carcinoma
Five times less common than basal cell carcinoma More likely to spread than basal cell carcinoma About 1% of cases result in death Triggered by excessive UV exposure Signs are the same as those for basal cell carcinoma, but may also resemble a wart or scaly growth that bleeds and scabs

19 Disorders of the Skin Melanoma More likely to be malignant
Starts in the melanocytes Has the appearance of an unusual mole Warning signs Asymmetry Irregular borders Uneven color Diameter greater than 6mm Most common in fair-skinned persons

20 Disorders of the Skin Wound Healing Causes an inflammatory response
Steps in wound healing A blood clot forms White blood cells and fibroblasts move to the injured area Fibroblasts pull the margins of the wound together and promote tissue regeneration The basal layer of the epidermis produces new cells Proliferating fibroblasts form a scar

21 Disorders of the Skin

22 Disorders of the Skin Burns Usually caused by heat
Burn severity affected by: Extent of the burned area “Rule of nines” is a technique used to estimate the extent of a burn Lund-Browder chart is used for children


24 Disorders of the Skin Depth of the burn First degree burn
Only epidermis affected Redness and pain No blisters or swelling occurs Second degree burn Extends through entire epidermis and part of the dermis Redness, pain, and blistering Third degree burn Destroys entire thickness of the skin Surface of wound is leathery and may be brown, tan, black, white, or red Patient feels no pain Fourth degree burn – involve tissues down to the bone

25 Disorders of the Skin Burns are considered a critical injury if:
Second-degree burns cover 25% or more of the patient’s body Third-degree burns cover 10% or more of the patient’s body Any portion of the body has a fourth-degree burn Third-degree burns occur on the face, hands, or feet Major concerns associated with severe burns: Fluid loss Heat loss Bacterial infection

26 Effects of Aging Rate of cell mitosis decreases
Dermis becomes thinner and the dermal papillae flatten Adipose tissue in the hypodermis decreases Collagen decreases Elastic fibers in upper layer of dermis are lost and those in the lower layer become thicker, less elastic, and disorganized Wrinkles form because of: Loose epidermis Fewer fibers Less padding in hypodermis

27 Limited homeostatic adjustment to heat because of:
Effects of Aging Limited homeostatic adjustment to heat because of: Less vasculature (fewer blood vessels) Fewer sweat glands Number of hair follicles decreases Reduced number of sebaceous glands Number of melanocytes decrease

28 Homeostasis Functions of the Skin Protection
Safeguards from physical trauma Protection from UV radiation Help prevent bacterial invasion Sebum is acidic, which retards growth of bacteria Langerhans cells phagocytize pathogens and alert the immune system to the presence of pathogens

29 Homeostasis Regulation of water loss Vitamin D production
Keratinized cells prevent water from entering the body Water is excreted through perspiration Vitamin D production Useful to digestive and skeletal systems Small amounts of UV radiation are needed Vitamin D leaves the skin and enters the liver and kidneys

30 Homeostasis Gathers sensory information
Sensory receptors in the epidermis and dermis are specialized for touch, pressure, pain, hot, and cold Receptors supply the central nervous system with information about the external environment

31 Homeostasis Helps regulate body temperature
If body temperature rises, blood vessels in the skin dilate and sweat glands become active If the outer temperature is cool, blood vessels constrict Arrector pili muscles contract, but insulating effect is absent in humans Hyperthermia - body temperature above normal Hypothermia – body temperature below normal

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