1. Principles of Human Anatomy and Physiology, 11e1 Chapter 5 The Integumentary System Lecture Outline

2. Principles of Human Anatomy and Physiology, 11e2 INTRODUCTION The skin and its accessory structures make up the integumentary system. The integumentary system functions to guard the body’s physical and biochemical integrity, maintain a constant body temperature, and provide sensory information about the surrounding environment.

3. Principles of Human Anatomy and Physiology, 11e3 Chapter 5 The Integumentary System Skin and its accessory structures –structure –function –growth and repair –development –aging –disorders

4. Principles of Human Anatomy and Physiology, 11e4 General Anatomy A large organ composed of all 4 tissue types 22 square feet 1-2 mm thick Weight 10 lbs.

5. Principles of Human Anatomy and Physiology, 11e5 STRUCTURE OF THE SKIN (Figure 5.1) The superficial portion of the skin is the epidermis and is composed of epithelial tissue. The deeper layer of the skin is the dermis and is primarily composed of connective tissue. Deep to the dermis is the subcutaneous layer or hypodermis. (not a part of the skin) –It consists of areolar and adipose tissue. –fat storage, an area for blood vessel passage, and an area of pressure-sensing nerve endings.

6. Principles of Human Anatomy and Physiology, 11e6 Overview of Epidermis Stratified squamous epithelium –avascular (contains no blood vessels) –4 types of cells –5 distinct strata (layers) of cells

7. Principles of Human Anatomy and Physiology, 11e7 Four Principle Cells of the Epidermis – Figure 5.2 keratinocytes (Figure 5.2a) –produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant melanocytes (Figure 5.2b) –produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light Langerhans cells (Figure 5.2c) –derived from bone marrow –participate in immune response Merkel cells (Figure 5.2d) –contact a sensory structure called a tactile (Merkel) disc and function in the sensation of touch

8. Principles of Human Anatomy and Physiology, 11e8 Layers of the Epidermis There are four or five layers of the epidermis, depending upon the degree of friction and mechanical pressure applied to the skin. From deepest to most superficial the layers of the epidermis are (Figures 5.3 a and b). –stratum basale (stratum germinativum) –stratum spinosum –stratum granulosum –stratum lucidum (only in palms and soles) –stratum corneum

9. Principles of Human Anatomy and Physiology, 11e9 Layers (Strata) of the Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

10. Principles of Human Anatomy and Physiology, 11e10 Stratum Basale ( stratum germinativum) Deepest single layer of epidermis –merkel cells, melanocytes, keratinocytes & stem cells that divide repeatedly –keratinocytes have a cytoskeleton of tonofilaments –Cells attached to each other & to basement membrane by desmosomes & hemi- desmosomes When the germinal portion of the epidermis is destroyed, new skin cannot regenerate with a skin graft.

11. Principles of Human Anatomy and Physiology, 11e11 Stratum Spinosum (Figure 5.3b) provides strength and flexibility to the skin –8 to 10 cell layers are held together by desmosomes. –During slide preparation, cells shrink and appear spiny (where attached to other cells by desmosomes.) Melanin is taken in by keratinocytes (by phagocytosis) from nearby melanocytes.

12. Principles of Human Anatomy and Physiology, 11e12 Stratum Granulosum transition between the deeper, metabolically active strata and the dead cells of the more superficial strata 3-5 layers of flat dying cells that show nuclear degeneration –example of apoptosis Contain lamellar granules that release lipid that repels water Contain dark-staining keratohyalin granules –keratohyalin converts tonofilaments into keratin

13. Principles of Human Anatomy and Physiology, 11e13 Stratum Lucidum present only in the fingers tips, palms of the hands, and soles of the feet. Three to five layers of clear, flat, dead cells Contains precursor of keratin

14. Principles of Human Anatomy and Physiology, 11e14 Stratum Corneum 25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids –continuously shed Barrier to light, heat, water, chemicals & bacteria Lamellar granules in this layer make it water-repellent. Constant exposure to friction will cause this layer to increase in depth with the formation of a callus, an abnormal thickening of the epidermis.

15. Principles of Human Anatomy and Physiology, 11e15 Keratinization and Growth of the Epidermis Stem cells divide to produce keratinocytes As keratinocytes are pushed up towards the surface, they fill with keratin –Keratinization is replacement of cell contents with the protein keratin; occurs as cells move to the skin surface over 2-4 weeks. Epidermal growth factor (EGF) and other hormone-like proteins play a role in epidermal growth. Table 5.1 presents a summary of the features of the epidermal strata.

16. Principles of Human Anatomy and Physiology, 11e16 Dermis (Figure 5.1) Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Contains hair follicles, glands, nerves & blood vessels Two major regions of dermis –papillary region –reticular region

17. Principles of Human Anatomy and Physiology, 11e17 Dermis - Papillary Region Top 20% of dermis areolar connective tissue containing fine elastic fibers, corpuscles of touch (Meissner’s corpuscles), adipose cells, hair follicles, sebaceous glands, sudoriferous glands –The collagen and elastic fibers provide strength, extensibility (ability to stretch), and elasticity (ability to return to original shape after stretching) to skin. Finger like projections are called dermal papillae –anchors epidermis to dermis –contains capillaries that feed epidermis –contains Meissner’s corpuscles (touch) & free nerve endings for sensations of heat, cold, pain, tickle, and itch

18. Principles of Human Anatomy and Physiology, 11e18 Dermis - Reticular Region Dense irregular connective tissue Contains interlacing collagen and elastic fibers Packed with oil glands, sweat gland ducts, fat & hair follicles Provides strength, extensibility & elasticity to skin –stretch marks are dermal tears from extreme stretching Epidermal ridges form in fetus as epidermis conforms to dermal papillae –fingerprints are left by sweat glands open on ridges –increase grip of hand

19. Principles of Human Anatomy and Physiology, 11e19 Dermis -- Structure Epidermal ridges increase friction for better grasping ability and provide the basis for fingerprints and footprints. The ridges typically reflect contours of the underlying dermis. Lines of cleavage in the skin indicate the predominant direction of the underlying collagen fibers. Knowledge of these lines is especially important to plastic surgeons. Table 5.2 presents a comparison of the structural features of the papillary and reticular regions of the dermis.

20. Principles of Human Anatomy and Physiology, 11e20 Basis of Skin Color The color of skin and mucous membranes can provide clues for diagnosing certain problems, such as –Jaundice yellowish color to skin and whites of eyes buildup of yellow bilirubin in blood from liver disease –Cyanosis bluish color to nail beds and skin hemoglobin depleted of oxygen looks purple-blue –Erythema redness of skin due to enlargement of capillaries in dermis during inflammation, infection, allergy or burns

21. Principles of Human Anatomy and Physiology, 11e21 Skin Color Pigments Melanin produced in epidermis by melanocytes –melanocytes convert tyrosine to melanin UV in sunlight increases melanin production –same number of melanocytes in everyone, but differing amounts of pigment produced –results vary from yellow to tan to black color Clinical observations –freckles or liver spots = melanocytes in a patch –albinism = inherited lack of tyrosinase; no pigment –vitiligo = autoimmune loss of melanocytes in areas of the skin produces white patches The wide variety of colors in skin is due to three pigments - melanin, carotene, and hemoglobin (in blood in capillaries) - in the dermis.

22. Principles of Human Anatomy and Physiology, 11e22 Skin Color Pigments Carotene in dermis –yellow-orange pigment (precursor of vitamin A) –found in stratum corneum & dermis Hemoglobin –red, oxygen-carrying pigment in blood cells –if other pigments are not present, epidermis is translucent so pinkness will be evident

23. Principles of Human Anatomy and Physiology, 11e23 Accessory Structures of Skin develop from the embryonic epidermis Cells sink inward during development to form: –hair –oil glands –sweat glands –nails

24. Principles of Human Anatomy and Physiology, 11e24 HAIR Hairs, or pili, are present on most skin surfaces except the palms, palmar surfaces of the digits, soles, and plantar surfaces of the digits. Hair consists of –a shaft above the surface (Figure 5.4a) –a root that penetrates the dermis and subcutaneous layer (Figure 5.4c,d) –the cuticle (Figure 5.4b), and –a hair follicle (Figure 5.4c,d). New hairs develop from cell division of the matrix in the bulb.

25. Principles of Human Anatomy and Physiology, 11e25 Structure of Hair Shaft -- visible –medulla, cortex & cuticle –CS round in straight hair –CS oval in wavy hair Root -- below the surface Follicle surrounds root –external root sheath –internal root sheath –base of follicle is bulb blood vessels germinal cell layer

26. Principles of Human Anatomy and Physiology, 11e26 Structure of Hair Shaft -- visible –medulla, cortex & cuticle –CS round in straight hair –CS oval in wavy hair Root -- below the surface Follicle surrounds root –external root sheath –internal root sheath –base of follicle is bulb blood vessels germinal cell layer

27. Principles of Human Anatomy and Physiology, 11e27 Structure of Hair Shaft -- visible –medulla, cortex & cuticle –CS round in straight hair –CS oval in wavy hair Root -- below the surface Follicle surrounds root –external root sheath –internal root sheath –base of follicle is bulb blood vessels germinal cell layer

28. Principles of Human Anatomy and Physiology, 11e28 Hair Related Structures Arrector pili –smooth muscle in dermis contracts with cold or fear. –forms goosebumps as hair is pulled vertically Hair root plexus –detect hair movement sebaceous (oil) glands

29. Principles of Human Anatomy and Physiology, 11e29 Types of hair Lanugo is a fine, nonpigmented hair that covers the fetus. Vellus hair is a short, fine hair that replaces lanugo Course pigmented hair appears in response to androgens Hair that appears in response to androgens and hair of the head, eyelashes and eyebrows is known as terminal hair.

30. Principles of Human Anatomy and Physiology, 11e30 Hair Growth The hair growth cycle consists of a growing stage and a resting stage. –Growth cycle = growth stage & resting stage Growth stage – lasts for 2 to 6 years – matrix cells at base of hair root producing length Resting stage – lasts for 3 months –matrix cells inactive & follicle atrophies –Old hair falls out as growth stage begins again normal hair loss is 70 to 100 hairs per day Both rate of growth and the replacement cycle can be altered by illness, diet, high fever, surgery, blood loss, severe emotional stress, and gender. Chemotherapeutic agents affect the rapidly dividing matrix hair cells resulting in hair loss.

31. Principles of Human Anatomy and Physiology, 11e31 Functions of Hair P revents heat loss Decreases sunburn Eyelashes help protect eyes Touch receptors (hair root plexus) senses light touch

32. Principles of Human Anatomy and Physiology, 11e32 Glands of the Skin Specialized exocrine glands found in dermis Sebaceous (oil) glands Sudiferous (sweat) glands Ceruminous (wax) glands Mammary (milk) glands

33. Principles of Human Anatomy and Physiology, 11e33 Sebaceous (oil) glands Sebaceous (oil) glands are usually connected to hair follicles; they are absent in the palms and soles (Figure 5.1 ). Secretory portion of gland is located in the dermis –produce sebum contains cholesterol, proteins, fats & salts moistens hairs waterproofs and softens the skin inhibits growth of bacteria & fungi (ringworm) Acne –bacterial inflammation of glands –secretions are stimulated by hormones at puberty

34. Principles of Human Anatomy and Physiology, 11e34 Sudoriferous (sweat) glands Eccrine sweat glands have an extensive distribution most areas of skin –secretory portion is in dermis with duct to surface –ducts terminate at pores at the surface of the epidermis. –regulate body temperature through evaporation (perspiration) –help eliminate wastes such as urea. Apocrine sweat glands are limited in distribution to the skin of the axilla, pubis, and areolae; their duct open into hair follicles. –secretory portion in dermis –duct that opens onto hair follicle –secretions are more viscous Table 5.3 compares eccrine and apocrine sweat glands.

35. Principles of Human Anatomy and Physiology, 11e35 Ceruminous Glands Ceruminous glands are modified sudoriferous glands that produce a waxy substance called cerumen. –found in the external auditory meatus –contains secretions of oil and wax glands –barrier for entrance of foreign bodies An abnormal amount of cerumen in the external auditory meatus or canal can result in impaction and prevent sound waves from reaching the ear drum (Clinical Application).

36. Principles of Human Anatomy and Physiology, 11e36 TYPES OF SKIN Thin skin –covers all parts of the body except for the palms and palmar surfaces of the digits and toes. –lacks epidermal ridges –has a sparser distribution of sensory receptors than thick skin. Thick skin (0.6 to 4.5 mm) –covers the palms, palmar surfaces of the digits, and soles –features a stratum lucidum and thick epidermal ridges –lacks hair follicles, arrector pili muscles, and sebaceous glands, and has more sweat glands than thin skin. Table 5.4 summarizes the fractures of thin and thick skin.

37. Principles of Human Anatomy and Physiology, 11e37 FUNCTIONS OF SKIN -- thermoregulation Perspiration & its evaporation –lowers body temperature –flow of blood in the dermis is adjusted Exercise –in moderate exercise, more blood brought to surface helps lower temperature –with extreme exercise, blood is shunted to muscles and body temperature rises Shivering and constriction of surface vessels –raise internal body temperature as needed

38. Principles of Human Anatomy and Physiology, 11e38 FUNCTIONS OF SKIN blood reservoir –extensive network of blood vessels protection - physical, chemical and biological barriers –tight cell junctions prevent bacterial invasion –lipids released retard evaporation –pigment protects somewhat against UV light –Langerhans cells alert immune system cutaneous sensations –touch, pressure, vibration, tickle, heat, cold, and pain arise in the skin

39. Principles of Human Anatomy and Physiology, 11e39 FUNCTIONS OF SKIN Synthesis of Vitamin D –activation of a precursor molecule in the skin by UV light –enzymes in the liver and kidneys modify the activated molecule to produce calcitriol, the most active form of vitamin D. –necessary vitamin for absorption of calcium from food in the gastrointestinal tract excretion –400 mL of water/day, small amounts salt, CO2, ammonia and urea

40. Principles of Human Anatomy and Physiology, 11e40 DEVELOPMENT OF THE INTEGUMENTARY SYSTEM Epidermis develops from ectodermal germ layer –Hair, nails, and skin glands are epidermal derivatives (Figure 5.7). –The connective tissue and blood vessels associated with the gland develop from mesoderm. Dermis develops from mesenchymal mesodermal germ layer cells

41. Principles of Human Anatomy and Physiology, 11e41 Skin Cancer 1 million cases diagnosed per year 3 common forms of skin cancer –basal cell carcinoma (rarely metastasize) –squamous cell carcinoma (may metastasize) –malignant melanomas (metastasize rapidly) most common cancer in young women arise from melanocytes ----life threatening key to treatment is early detection watch for changes in symmetry, border, color and size risks factors include-- skin color, sun exposure, family history, age and immunological status

42. Principles of Human Anatomy and Physiology, 11e42 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. 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.

43. Principles of Human Anatomy and Physiology, 11e43 Burns Destruction of proteins of the skin –chemicals, electricity, heat Problems that result –shock due to water, plasma and plasma protein loss –circulatory & kidney problems from loss of plasma –bacterial infection Two methods for determining the extent of a burn are the rule of nines and the Lund-Bowder method (Figure 5.10).

44. Principles of Human Anatomy and Physiology, 11e44 Burns

45. Principles of Human Anatomy and Physiology, 11e45 Types of Burns First-degree –only epidermis (sunburn) Second-degree burn –destroys entire epidermis & part of dermis –fluid-filled blisters separate epidermis & dermis –epidermal derivatives are not damaged –heals without grafting in 3 to 4 weeks & may scar Third-degree or full-thickness –destroy epidermis, dermis & epidermal derivatives –damaged area is numb due to loss of sensory nerves

46. Principles of Human Anatomy and Physiology, 11e46 Pressure Sores Pressure ulcers, also known as decubitus ulcers –caused by a constant deficiency of blood to tissues overlying a bony projection that has been subjected to prolonged pressure –typically occur between bony projection and hard object such as a bed, cast, or splint –the deficiency of blood flow results in tissue ulceration. Preventable with proper care