Chapter 06 Lecture Outline

See separate PowerPoint slides for all figures and tables pre- inserted into PowerPoint without notes.

• Integumentary system – Covers body and consists of skin and accessory tissues (nails, hair, sweat glands, sebaceous glands) – Integument = skin o Cutaneous membrane – Barrier to the outside world – Visual indicator of our physiology and health – Dermatology, study of skin

2 6.1 Composition and Functions of the Integument • The integument – Body’s largest organ – Composed of all tissues types functioning in concert o Surface covered by an epithelium o Underlying CT ˗ Provides strength and resilience ˗ Contains smooth muscle associated with hair follicles o Nervous tissue ˗ Senses touch, pressure, temperature, and pain – Protects internal body structures – 7 to 8% of body weight – Thickness depends on body location

3 6.1 Composition and Functions of the Integument • Layers of the integument ̶ Epidermis o Stratified squamous epithelium ̶ Dermis o Upper Areolar CT o Primarily dense irregular connective tissue o Subcutaneous layer (hypodermis) ˗ Below the dermis ˗ Not part of integumentary system

4 Layers of the Integument

Figure 6.1 5 6.1a Epidermis

• Epithelium of the integument – Epidermis – Keratinized, stratified squamous epithelium – Specific layers, or strata – Layers from deep to superficial 1. Stratum basale 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum 5. Stratum corneum – 1st three layers composed of living keratinocytes – Corneum and lucidum composed of dead cells

6 6.1a Epidermis • Stratum basale – Deepest epidermal layer – Stratum germinativum or basal layer – Attached to underlying basement membrane – Three cell types 1. Keratinocytes 1. Most abundant cell type 2. Stem cells divide to regenerate new cells 3. Synthesizes keratin: protein that strengthens epidermis and makes it waterproof 2. Melanocytes 1. Produces melanin in response to UV light; pigment accumulates around nucleus of keratinocytes 3. Tactile cells 1. Merkel cells 2. Respond to touch or compression

7 6.1a Epidermis • Stratum spinosum – Spiny layer: Several layers of polygonal keratinocytes – Begin to develop into specialized, non-dividing keratinocytes; Some in deepest level still dividing cells – Epidermal dendritic cells (Langerhans cells): initiate immune response • Stratum granulosum – Granular layer: 3 to 5 layers of keratinocytes – Process begins called keratinization o Keratinocytes fill with keratin o Causes nucleus and organelles to disintegrate o Fully keratinized cell dead but structurally sound o Process not complete until in more superficial layers 8 6.1a Epidermis • Stratum lucidum – Clear layer • Cells filled with a translucent protein, eleidin o Intermediate product in keratin maturation o Helps protect from UV light – Found only on thick skin on palms and soles • Stratum corneum – Hornlike layer: Most superficial layer – 20 to 30 layers of dead, interlocking keratinized cells o Cells are anucleate (without a nucleus) and tightly packed – Cornified epithelium contains large amount of keratin

9 6.1a Epidermis

Stratum corneum (continued) ̶ Migration of keratinocytes o Originate from stem cells in stratum basale o Migrate through strata to stratum corneum over two weeks o Undergoing structural changes ̶ Remain in stratum corneum another two weeks ̶ Shed ̶ Stratum corneum has dry, thickened surface o Unsuitable for microorganism growth o Secretions help protect

10 Epidermal Strata

Figure 6.2 11 6.1a Epidermis • Variations in the epidermis – In thickness, color, and skin markings • Thick versus thin skin – Thick skin o Palms of hands, soles of feet o Occurs in all five layers of epidermal strata o Houses sweat glands o No hair follicles or sebaceous glands – Thin skin o Covers most of body o Lacks a stratum lucidum o Sweat glands, hair follicles, and sebaceous glands

12 Thick Skin and Thin Skin

Figure 6.3 13 6.1a Epidermis

• Skin color ̶ Normal color from hemoglobin, melanin, carotene ̶ Hemoglobin o Oxygen-binding protein in red blood cells o Bright red color upon binding oxygen (erythema) o Gives blood vessels in dermis a reddish tint o Seen most easily in fair skinned individuals o More visible if blood vessels dilate

14 6.1a Epidermis

• Melanin – Pigment produced and stored in melanocytes – In black, brown, tan, yellow-brown shades – Transferred to keratinocytes in stratum basale – Amount in skin varies o According to heredity and light exposure o UV light stimulates melanin production o Sunscreens protect against UVA and UVB – All people with same number of melanocytes – Darker-skinned individuals produce more and darker colored melanin

15 Production of Melanin by Melanocytes

Figure 6.4 16 6.1a Epidermis

• Jaundice – Yellowing of the skin due to bilirubin in blood (can be compromised liver function) • Cyanosis – Bluish tint due to decreased oxygen levels – smokers • Carotene – Yellow-orange pigment from yellow-orange vegetables – Converted to vitamin A by body – Plays important role in o Vision, Reducing free radicals, Immune function

17 6.1a Epidermis

• Pallor – Paleness due to decreased blood flow • Albinism ̶ Inherited recessive condition ̶ Enzyme for melanin nonfunctional ̶ Melanocytes unable to produce melanin ̶ Individuals have white hair, pale skin pink irises

18 6.1a Epidermis Skin markings • Nevus – Mole: Harmless localized overgrowth of melanocytes – Rarely becomes malignant but should be monitored for changes suggesting malignancy (ABCD) • Freckles – Yellowish or brown spots – Represent localized areas of increased melanocyte activity – Degree of pigmentation based on sun exposure and heredity

19 6.1a Epidermis Skin markings (continued) • Hemangioma – Skin discoloration due to benign blood vessel tumor – Capillary hemangiomas o Bright red to deep purple nodules o Usually present at birth and disappear in childhood o Strawberry-colored birthmarks – Cavernous hemangiomas o Larger dermal blood vessels o May last a lifetime o Port-wine stains

20 6.1a Epidermis

Skin markings (continued) • Friction ridges – Small conical pegs in thin skin – Complex arches and whorls on finger, palms, soles, and toes – Large folds and valleys of dermis and epidermis – Increase friction on contact – Each individual with a unique pattern of friction ridges – Personal identification

21 Friction Ridges of Thick Skin

Figure 6.5 22 • What are the layers of the epidermis, What did you starting from the surface of the skin? learn? • Which type of skin lacks a stratum lucidum and is found covering most of the body?

• Describe the different types of cells found in each stratum of the epidermis?

• In which stratum are the keratinocytes alive?

• What form of UV ray is dangerous and often cancer causing?

• What color is seen in jaundice?

• Blood vessels, sweat glands, sebaceous glands, hair follicles, nail roots, sensory nerve endings, arrector pili – Two layers • Papillary layer of the dermis – Areolar connective tissues – Projections of epidermis interdigitate with dermal papillae, epidermal ridges • Reticular layer of the dermis – Dense irregular connective tissue – Large bundles of collagen fibers project o Fibers interwoven into meshwork surrounding structures

24 Layers of the Dermis

Figure 6.6 25 6.1b Dermis • Collagen and elastic fibers oriented in parallel bundles at specific locations due to applied stress during routine movement – Bundles function to resist stress: lines of cleavage (tension lines) – Important consideration for surgery o Incisions parallel to cleavage line are more likely to heal quickly o Incisions perpendicular to cleavage lines are more likely to open due to cut elastic fibers • Fibers contribute to skin characteristics – Collagen fibers impart tensile strength – Elastic fibers allow stretch and recoil – If skin stretched beyond its capabilities o Some collagen fibers torn o Stretch marks, striae – Flexibility and thickness of dermis o Diminished by UV light and aging – Causes sagging or wrinkled skin

26 Lines of Cleavage

Figure 6.7 27 6.1c Subcutaneous Layer

• Subcutaneous layer – Hypodermis, superficial fascia – Not part of integument – Areolar and adipose CT – Subcutaneous fat in areas of more adipose tissue – CT fibers interwoven with fibers of reticular dermis – Pads and protects body – Acts as energy reservoir – Provides thermal insulation

28 6.1c Subcutaneous Layer

• Subcutaneous layer (continued) – Drug injection site o Extensive vascular network promotes rapid absorption – Sexes have different layer thickness and distribution o Thicker in women ˗ Accumulates primarily in breasts, buttocks, hips, and thighs o Thinner in men ˗ Accumulates primarily in neck, upper arms, abdomen, lower back, buttocks

29 Integument Layers and the Subcutaneous Layer (Table 6.1)

30 • The dermal papillae are a part of what layer of the skin? What did you learn? • Should a surgeon generally cut perpendicular or parallel to cleavage lines?

• What two types of tissue form the subcutaneous layer?

• What type of tissue is found in the two layers of the dermis?

• Protection – Protects body from injury and trauma – Protects from harmful chemicals, toxins, microbes, temperature extremes – Protects deeper tissue from solar radiation • Prevention of water loss/gain – Epidermis is water resistant, not waterproof – Water lost by sweat, transpiration o Fluids penetrate through epidermis and evaporate in air – Dehydration a danger with severe burns o Water escapes without skin barrier – Skin also prevents water gain o Water resistance prevents absorption

32 6.1d Functions of the Integument

• Metabolic regulation

– Vitamin D3 (cholecalciferol): increases absorption of calcium and phosphate to regulate blood levels – Upon UV exposure, synthesized from a steroid precursor by keratinocytes

– D3 released into blood and transported to liver and converted to calcidiol – Transported to kidney and converted to calcitriol o Active form of vitamin D o Considered a hormone

33 6.1d Functions of the Integument • Secretion – Waste products secreted onto skin surface during sweating (Urea, salts, water) o Role in electrolyte homeostasis – Sebum of sebaceous glands lubricates skin surface and hair o Helps make integument water resistant • Absorption – Selectively permeable o Some materials pass through, others blocked – Transdermal administration o Some oil-soluble drugs delivered by adhesive patch o Slowly penetrate epidermis, absorbed into blood vessels

34 6.1d Functions of the Integument • Immune function – Epidermal dendritic cells o In stratum spinosum o Initiate immune response against pathogens o Attack cancer cells • Sensory Reception – Skin has extensive innervation o Distribution of nerve fibers o Monitor stimuli in dermis and epidermis – Touch receptors detect stimuli o Send input to brain

35 6.1d Functions of the Integument

• Temperature regulation – Influenced by capillaries and sweat glands in dermis – Vasoconstriction ̶ Vessels narrow, less blood travels through ̶ Shunting of blood away from periphery of body toward deeper structures ̶ Occurs when body tries to conserve heat ̶ Pale color when cold – Vasodilation ̶ Diameter of vessels increases, more blood travel through ̶ More blood can travel close to surface ̶ Results in reddish/pink skin, flushed face during exercise

36 • What is the active form of What did you vitamin D? learn?

• Where 3 organs play a role in Vitamin D synthesis?

• Vasoconstriction vs Vasodilation

Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education 37 6.2 Integumentary Structures Derived from Epidermis

• Epidermal derivatives ̶ Nails ̶ Hair ̶ Exocrine glands ̶ Formed during embryonic development ̶ Portions of epidermis invaginated into the dermis ̶ Hair and nails composed of dead cells ̶ Exocrine glands composed of living cells

38 6.2a Nails • Structure of nails – Scalelike modifications of stratum corneum – Dorsal edges of fingers and toes – Protect distal tips of digits – Assist in grasping objects – Distal whitish free edge (no underlying capillaries) – Pinkish nail body (underlying capillaries) – Nail root (part embedded in skin) o These three constitute nail plate – Nail bed o Layer of living epidermis covered by nail body

39 6.2a Nails • Structure of nails (continued) – Nail matrix o Actively growing part of nail at proximal end of nail body – Lunula o Whitish semilunar area on proximal end of nail body – Nail folds o Folds of skin overlapping nail – Eponychium (cuticle) o Narrow band of epidermis from margin of nail wall onto nail body – Hyponychium o Thickened stratum corneum over which free nail edge projects

40 Structure of a Fingernail

Figure 6.9 41 Clinical View: Nail Disorders • Nails are indicative of overall health – Brittle nails are prone to vertical splitting and separation of nail plate layers (repeated wetting) – Onchomycosis is a fungal infection – Yellow nail syndrome occurs when growth and thickening slows (chronic bronchitis) – Spoon nails outer surface of nail is concave (iron deficiency, hypothyroidism) – Beau’s lines indicate temporary interference with nail growth (hypocalcemia, chemotherapy) – Nail clubbing common in CHF or lung disease – Nail pitting or separation common in psoriasis

42 skindermatologists.com Mayo Clinic 6.2b Hair

• Hair found almost everywhere on the body except ̶ Hands and palmar surface of fingers ̶ Sides and soles of feet and toes ̶ Lips ̶ Portions of external genitalia • Hair type and distribution ̶ Single hair, pilus, shaped like slender filament ̶ Keratinized cells ̶ Grows from hair follicles

45 6.2b Hair

Hair type and distribution (continued) • Three types of hair – Lanugo: fine, unpigmented, downy hair o Appears in last trimester – Vellus: fine hair o Primary human hair o Found on upper and lower limbs – Terminal hair: coarser, pigmented, longer o On scalp, eyebrows, and eyelashes, men’s beards o During puberty, replaces vellus hair in axillary and pubic regions

46 6.2b Hair Hair structure and follicles • 3 zones along length of a hair – Hair bulb o Swelling at base where hair originates in dermis o Surrounds hair papilla, composed of CT o Only region containing living epithelial cells – Root o Zone of hair from bulb to skin surface – Shaft o Portion of hair beyond skin surface

47 6.2b Hair • Hair components – Hair matrix o Structure at base of the hair bulb o Epithelial cells divide here o Produce new cells, gradually pushed toward surface – Medulla o Remnant of matrix o Flexible, soft keratin – Cortex o Flattened cells closer to outer hair surface o Relatively hard – Cuticle o Single cell layer around cortex

48 6.2b Hair

• Hair components (continued) ̶ Hair follicle o Oblique tube surrounding hair root o Extends into dermis and sometimes subcutaneous layer o Outer CT root sheath originating in dermis o Inner epithelial tissue root sheath originating from epidermis ̶ Arrector pili o Thin ribbons of smooth muscle o Extend from hair follicle to dermal papillae o Elevates hair with contraction, “goosebumps”

49 Hair

Figure 6.10 50 6.2b Hair Functions of hair • Protection – Protects scalp from sunburn and injury – Hair within nostrils traps particles – Hair within ears protects from foreign matter – Eyelashes protect eyes – Eyebrows keep sweat out of eyes • Facial expression – Hairs of eyebrows enhance facial expression • Heat retention – Prevents loss of heat from scalp

51 6.2b Hair

Functions of hair (continued) • Sensory reception – Tactile receptors detect light touch • Visual identification – Helps identify age or sex, specific individuals • Chemical signal dispersal – Disperse pheromones o Chemical signals involved in attracting sexual partners o Secreted by specific sweat glands onto hairs in axillary and pubic regions

52 6.2b Hair

• Hair color – Synthesis of melanin in matrix adjacent to hair papillae – Variations reflect genetic, environmental, and hormonal factors – Lightens with age as pigment production decreases – Gray hair results from gradual reduction in melanin – White hair occurs due to complete stoppage of melanin production

53 6.2b Hair • Hair growth and replacement ̶ Three phases of hair growth cycle 1. Anagen—active phase • Living cells in hair bulb rapidly growing, dividing, and transforming into hair. • Longest phase, 18 months to 7 years, depending on genetics 2. Catagen—brief regression period ̶ Cell division ceases ̶ Follicle undergoes involution ̶ Lasts 3 to 4 weeks 3. Telogen—resting phase ̶ Hair is shed ̶ Lasts 3 to 4 months ̶ Then, hair bulb cells begin to regrow

54 6.2b Hair

• Hair loss – Normally 10 to 100 hairs lost per day o More than that could mean a health problem o Temporary loss could be from drugs, dietary factors, radiation, high fever, stress – Thinning of hair, alopecia o Due to aging – Diffuse hair loss o Hair shed from all parts of scalp o Primarily in women o Due to hormones, drugs, iron deficiency

55 6.2b Hair • Hair loss (continued) – Male pattern baldness o Loss of hair first from only crown region of scalp o Combination of genetic and hormonal factors o Baldness allele dominant in males and recessive in females o Expressed only in presence of high testosterone • Hair growth – Hirsutism o Excessive male pattern hairiness o Typically on face, chest, back o Excess androgens o Caused by medical condition or medication

56 6.2c Exocrine Glands of the Skin

• Skin houses many types of exocrine glands • Two most common types ̶ Sweat glands ̶ Sebaceous glands

57 6.2c Exocrine Glands of the Skin

• Sweat glands ̶ Two groups o Merocrine o Apocrine ̶ Sweat gland duct transports secretions to surface ̶ Gland duct opens on epidermal surface, sweat pore ̶ Myoepithelial cells o Contract to squeeze gland o Discharge secretions in response to sympathetic stimulation

58 6.2c Exocrine Glands of the Skin • Merocrine sweat glands ̶ Most numerous and widely distributed ̶ Discharge secretions onto skin surface o Provide a means for loss of water and electrolytes o May help eliminate ingested drugs o Dilute harmful chemicals o Antibacterial/antifungal activity ̶ Secrete sweat o Composed of 99% water and 1% other chemicals o Includes: electrolytes, metabolites, and waste products – Major function, thermoregulation o Regulation of body temperature by fluid evaporation

59 6.2c Exocrine Glands of the Skin

• Apocrine sweat glands – Discharge secretions into hair follicles located axillae, around nipples, in pubic and anal region – Produce viscous cloudy secretions o Contain proteins and lipids o Produce odor when acted on by bacteria – Start producing secretions during puberty

60 6.2c Exocrine Glands of the Skin • Sebaceous glands – Holocrine glands – Produce oily secretion, sebum o Lubricant for skin and hair o Bactericidal o Discharges into a hair follicle – Secretion stimulated by hormones, especially androgens • Activated during puberty – Acne: Plugged sebaceous ducts

61 6.2c Exocrine Glands of the Skin Other integumentary glands • Ceruminous glands – Modified apocrine sweat glands – Located only in external ear canal – Secretions of waterproof earwax, cerumen o Traps foreign material o Lubricates acoustic meatus and eardrum • Mammary glands – Modified apocrine sweat glands of breast – Only function in pregnant and lactating females – Produce milk

62 Exocrine Glands of the Skin

Figure 6.11a 63 What did you • What are the three learn? components of the nail plate?

• What are the three portions of a hair?

• What do sebaceous glands secrete? Where is this material secreted?

Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education 64 6.3 Repair and Regeneration of the Integumentary System

• Tissue is repaired in one of two ways: regeneration or fibrosis • Regeneration ̶ Replacement of damaged or dead cells with same cell type ̶ Restores organ function • Fibrosis ̶ Gap filled with scar tissue ̶ Collagen produced by fibroblasts ̶ Functional activities not restored

65 6.3 Repair and Regeneration of the Integumentary System • Stages of wound healing 1) Cut blood vessels bleed into wound 2) Blood clot forms and leukocytes clean wound – Clot is a temporary barrier for pathogens 3) Blood vessels re-grow and granulation tissue forms – Vascular CT initially forms in wound 4) Epithelium regenerates and CT fibrosis occurs • Dependent on extent of injury – Longer time needed for wider and deeper surfaces – With severe damage less likely to return to original condition o Hair follicles, exocrine glands, nerves, and arrector pili muscle cells not repaired

66 Stages in Wound Healing

Figure 6.12 67 Clinical View: Psoriasis

• Chronic autoimmune skin disease • Keratinocytes attacked by T-lymphocytes • Causes rapid overgrowth of new skin cells • Patches of whitish, scaly skin on epidermal surface • Symptoms: severe itching, pain, skin cracking • Treatments ̶ Corticosteroids, UV light therapy, medications that interfere with skin cell production

68 Clinical View: Burns

• Major cause of accidental death • Caused by heat, radiation, chemicals, sunlight, electrical shock • Threat to life from fluid loss, infection, effects of burned tissue – First degree burns o Involve only epidermis o Slight redness and pain o Immerse burned area in cool water – Second degree burns o Involve epidermis and part of dermis o Skin blistered and painful o Slight scarring

69 Clinical View: Burns (continued)

– Third-degree burns o Involve epidermis, dermis, and subcutaneous layer o Require hospitalization o Treatment for dehydration and infection o Require additional caloric intake o Severe scarring o May need debridement and skin graft – Burn severity can be measured by rule of nines o Estimates surface area of burns

70 Clinical View: Burns (continued)

• Treatments for burns ̶ Manage fluid loss ̶ Relieve swelling ̶ Manage pain ̶ Remove dead tissue ̶ Control infection ̶ Increase calorie intake

71 What did you learn? • What is the term for the process of scar tissue formation?

• Skin changes with aging – Reduced number and activity of stem cells o Skin repair processes slows o Thin skin less likely to protect from trauma – Fewer collagen fibers – Elastic fibers lose elasticity – Crease lines form (wrinkles) – Immune response decreased due to fewer dendritic cells – Hair follicles produce thinner hair or none at all

73 6.4b Aging of the Integument

• Skin changes with aging (continued) • UV radiation – Damages DNA in epidermal cells o Accelerates aging o Predominant factor in skin cancer • Skin cancer – Basal cell carcinoma arises from stratum basale – Squamous cell carcinoma arises from stratum spinosum – Malignant melanoma arises from melanocytes

74 Clinical View: Botox and Wrinkles

• Botox is a treatment for wrinkles caused by facial muscle expression • Clostridium botulinum toxin • Blocks nerve impulses to facial expression muscles • Decreases or eliminates wrinkles • Botox injected into specific facial muscles • Temporary effect only • Muscles regain function and procedure must be repeated