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The Integumentary System

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Presentation on theme: "The Integumentary System"— Presentation transcript:

1 The Integumentary System
CHAPTER 5 The Integumentary System

2 INTRODUCTION Integument = skin & accessory structures Functions:
Guards body’s physical & biochemical integrity Maintains constant body temperature Provides sensory information about surrounding environment

3 STRUCTURE OF THE SKIN Cutaneous membrane
Superficial portion = epidermis composed of epithelial tissue Deeper layer of skin = dermis primarily connective tissue Deep to dermis = subcutaneous layer (hypodermis) not a part of skin areolar & adipose tissue fat storage area for blood vessel passage area of pressure-sensitive nerve endings

4 Principle Cells In Epidermis
Keratinocytes (90% of epidermal cells) keratin: protect skin & underlying tissue from heat, microbes, & chemicals lamellar granules: produce waterproof sealant Melanocytes (8% of epidermal cells) produce melanin contributes to skin color absorbs damaging ultraviolet (UV) light sensitive to UV light

5 Principle Cells In Epidermis
Langerhans cells (small % of epidermal cells) derived from bone marrow  immune response extremely sensitive to UV light Merkel cells (least numerous cells) contact flattened sensory neuron (Merkel disc) function in sensation of touch

6 Layers of the Epidermis
Four or five layers, depending upon degree of friction & mechanical pressure applied to skin From deepest to most superficial, the layers of the epidermis are: stratum basale (stratum germinativum) stratum spinosum stratum granulosum stratum lucidum (only in palms and soles) stratum corneum

7 Stratum Basale Also called stratum germinativum
Deepest layer of epidermis Single layer of cuboidal or columnar keratinocytes Merkel cells, melanocytes, & Langerhans cells Tonofilaments eventually will form keratin in superficial layers Desmosomes & hemi-desmosomes attach cells to each other & to basement membrane Rapidly dividing layer When destroyed, new skin cannot regenerate without a skin graft

8 Stratum Spinosum Superficial to stratum basale
8-10 layers of keratinocytes Tonofilaments & desmosomes provide strength & flexibility Langerhans cells & melanocytes also found in this layer

9 Stratum Granulosum 3-5 layers of flat apoptotic keratinocytes Tonofilaments more apparent Lamellar granules release lipid that repels water Keratohyalin converts tonofilaments into keratin Keratinocytes die **Transition between the metabolically active strata & dead superficial layer**

10 Stratum Lucidum 3-5 layers of clear, dead, flattened keratinocytes Present ONLY in fingertips, palms & soles  ‘thick skin’ Large amounts of keratin Thickened plasma membranes

11 Stratum Corneum 25 to 30 layers of flattened, dead keratinocytes
Continuously shed & replaced Barrier to light, heat, water, chemicals & bacteria Lamellar granules repel water Callus = abnormal thickening of stratum corneum from constant exposure to friction

12 Keratinization & Epidermal Growth
Stem cells in stratum basale divide to produce keratinocytes Keratinocytes slowly pushed towards surface  accumulate each step keratinization occurs as cells move to skin surface (deep to superfic) about 4 weeks from beginning to end Epidermal growth factor (EGF) and other hormone-like proteins regulate epidermal growth Psoriasis Premature shedding of keratinocytes (7-10d) Treated with UV light & topical ointment

13 Dermis Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells Contains hair follicles, glands, nerves & blood vessels Two major regions: papillary region reticular region

14 Dermis - Papillary Region
Top 20% of dermis Mostly areolar CT contains fine elastic fibers Dermal papillae = finger-like projections anchors epidermis to dermis capillary loops feed epidermis contains Meissner’s corpuscles & free nerve endings touch sensations (Meissner’s) heat, cold, pain, tickle, and itch

15 Dermis - Reticular Region
Attached to subcutaneous (sub-Q) layer Dense irregular connective tissue interlacing collagen bundles coarse elastic fibers Some adipose, oil glands, sweat glands, & hair follicles Provides strength, extensibility & elasticity to skin stretch marks = dermal tears from extreme stretching (striae) Epidermal ridges form in fetus as epidermis conforms to dermal papillae  fingerprints genetically determined increase grip of hand

16 Skin Pigments Melanin produced in epidermis by melanocytes
tyrosinase converts tyrosine to melanin UV light increases melanin production differences in skin color determined by **AMOUNT** of pigment present Clinical observations freckles or liver spots = accumulation of melanocytes mole = benign overgrowth of melanocytes albinism = inherited lack of tyrosinase; no pigment vitiligo = autoimmune loss of melanocytes in areas of skin produces white patches Three pigments in dermis yield variety of skin colors range from yellow to red & tan to black

17 Skin Pigments Melanin Pheomelanin (yellow to red)
Eumelanin (brown to black) Increased synthesis results in “tan”  protects from further damage (within limits) Carotene in dermis yellow-orange pigment (precursor of vitamin A) found in stratum corneum & dermis Hemoglobin red, oxygen-carrying pigment in blood cells epidermis is translucent so if other pigments not present, pinkness will be evident

18 Skin Color as a Diagnostic Tool
Color of skin and mucous membranes can provide clues for diagnosing certain problems Jaundice yellowish color to skin and whites of eyes buildup of yellow bilirubin in blood from liver disease Cyanosis bluish color in nail beds and skin hemoglobin depleted of oxygen looks purple-blue Erythema redness of skin due to enlargement of capillaries in dermis caused by inflammation, infection, allergy or burns Pallor = paleness of skin resulting from shock or anemia

19 Accessory Structures of Skin
Develop from embryonic epidermis Cells sink inward during development to form: hair oil glands sweat glands nails

20 HAIR (PILI) Present on all skin surfaces except palms, soles, & palmar/plantar surfaces of the digits Eyebrows & lashes protect from foreign particles Sense light touch Anatomy shaft root hair follicle New hairs develop from cell division of matrix in the bulb

21 Structure of Hair Shaft = superficial (visible) portion
Root = below the surface 3 concentric layers medulla 2-3 rows of irregularly. shaped cells cortex elongated cells cuticle single layer of thin, flat cells heavily keratinized **concentric = like a tree trunk

22 Structure of Hair Follicle surrounds root Dermal root sheath
Epithelial root sheath external root sheath internal root sheath Dermal root sheath surrounds follicle Bulb = base of follicle blood vessels (in papilla) germinal cell layer (matrix) arise from str. basale **site of cell division** gives rise to internal root sheath

23 Hair-Related Structures
Arrector pili smooth muscle associated w/ hair contraction causes goosebumps as hair is pulled vertically Hair root plexus surrounds follicle touch-sensitive dendrites detect hair movement

24 Types of Hair Lanugo = fine, non-pigmented hair that covers fetus
Vellus hair = short, fine hair that replaces lanugo Terminal hair hair that appears in response to androgens course and heavily pigmented hair of the head, eyelashes and eyebrows

25 Hair Growth Growth cycle = growth stage & resting stage Growth stage
lasts for 2 to 6 years matrix cells at base of hair root divide  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 Rate of growth & replacement can be altered by illness, diet, blood loss, severe emotional stress, & gender Chemotherapeutic agents affect rapidly dividing matrix cells

26 Hair Color Hair color is due primarily to the amount and type of melanin. Dark hair contains true melanin Blond and red hair contain melanin with iron and sulfur added Graying hair is result of decline in melanin production (decline in tyrosinase enzyme) White hair has air bubbles in the medullary shaft Hormones influence growth and loss of hair XS androgens result in hirsutism

Specialized exocrine glands found in dermis: Sebaceous (oil) glands Sudiferous (sweat) glands Ceruminous (wax) glands Mammary (milk) glands

28 Sebaceous glands Usually connected to hair follicles
Absent in palms and soles Secretory portion of gland is located in the dermis Produce sebum lipid-rich, oily substance moistens hairs waterproofs and softens the skin inhibits growth of bacteria & fungi Acne bacterial inflammation of sebaceous glands caused by increased production of sebum

29 Sudoriferous glands Simple, coiled tubular glands
Eccrine sweat glands (merocrine) = most common secretory portion is deep in dermis excretory duct terminates as pore at surface of epidermis regulate body temp thru evaporation (perspiration) help eliminate wastes such as urea

30 Sudoriferous glands Apocrine sweat glands limited distribution in body
found in armpit & groin regions secretory portion in subcutaneous layer secrete via exocytosis (merocrine manner) excretory duct opens into hair follicle more viscous sweat includes lipids & proteins begin puberty responsible for cold sweats

31 Ceruminous Glands Modified sudoriferous glands in external ear
produce waxy substance called cerumen secretory portion in subcutaneous layer excretory ducts open into ear canal or sebaceous gland secretions = combination of oil & wax glands sticky barrier against foreign substances Impacted cerumen abnormal amount of cerumen in external auditory meatus or canal prevents sound waves from reaching ear drum

Tightly packed, dead keratinized cells Nail body pink, visible portion Free edge extends past distal end of finger Nail root portion buried in fold of skin Lunula crescent-shaped area near proximal end Hyponychium (nail bed) secures nail to fingertip Eponychium (cuticle) stratum corneum layer Nail matrix = growth region of nail

33 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 thin and thick skin.

34 FUNCTIONS OF SKIN Thermoregulation Blood reservoir
Liberation of sweat lowers body temperature Adjusts blood flow in dermis Constriction of vessels = warming effect Dilation of vessels = cooling effect During exercise moderate exercise: more blood brought to surface to lower temperature extreme exercise: blood shunted to muscles & body temperature rises Blood reservoir extensive network of blood vessels 8-10% total blood flow in adult

35 FUNCTIONS OF SKIN Protection Cutaneous sensations
physical, chemical & biological barriers keratin & tight cell junctions prevent bacterial invasion lipids retard evaporation pigment protects somewhat against UV light Langerhans cells alert immune system to presence of microbes, etc. Cutaneous sensations touch pressure vibration tickle

36 FUNCTIONS OF SKIN Synthesis of Vitamin D Excretion/Absorption
UV light activates precursor molecule in skin enzymes in liver & kidneys modify activated molecule to produce active form of vitamin D necessary for absorption of calcium in the GI tract Excretion/Absorption 400 mL of water/day 200 mL/day as sweat (for sedentary person) excrete NH3, urea, salts via sweat minimal absorption of fat-soluble vitamins

37 Transdermal Drug Administration
Method of drug absorption across epidermis & into blood vessels of dermis drug contained in adhesive skin patch drug absorption most rapid in areas of thin (scrotum, face and scalp) Examples: nitroglycerin (prevention of chest pain from coronary artery disease) scopolamine (motion sickness) estradiol (estrogen replacement therapy) nicotine (stop smoking alternative)

38 Epidermal Wound Healing
Superficial wounds (abrasions/minor burns) Basal cells around wound lose contact w/ basement membrane enlarge & migrate across wound (Figure 5.9a) contact inhibition stops migration Epidermal growth factor stimulates basal stem cells to divide & replace ones that have moved into wound

39 Deep Wound Healing Injury to dermis & subcutaneous layers
Scar tissue forms  some loss of normal function Healing occurs in 4 phases Inflammatory phase Blood clot forms  unites wound edges Inflammation eliminates microbes & foreign materials Migratory phase Clot becomes scab Epithelial cells migrate beneath scab to bridge wound Fibroblasts synthesize scar tissue Damaged vessels begin to regenerate Wound tissue = granulation tissue

40 Deep Wound Healing Healing phase, c’td. Proliferative phase
Extensive epithelial growth under scab Fibroblasts deposit collagen Continued blood vessel growth Maturation phase Scab falls off Organization of collagen fibers Decreased # of fibroblasts Blood vessels back to normal Scar formation (fibrosis) hypertrophic scar remains within the boundaries of the original wound keloid scar extends into previously normal tissue

41 Phases of Deep Wound Healing

Ectoderm Covers surface of embryo Origin of epidermis including hair, nail & skin glands @ 9-12 weeks: hair follicles develop @ 10 weeks: nails develop @ 4 months: skin glands begin to develop @ 4 weeks = single (basal) layer @ 7 weeks: basal layer divides & forms periderm (superficial) layer @ 5 months: vernix caseosa forms Mixture of sloughed periderm & hairs Protects skin of fetus Facilitates birth of fetus

Mesoderm Origin of dermis Gives rise to mesenchyme (embryonic C.T.) @ 11 weeks: differentiate into fibroblasts Development of dermal papillae Capillary loops Corpuscles of touch Free nerve endings


45 Age-Related Structural Changes
Most age-related changes occur in dermis Collagen fibers decrease in number & stiffen Elastic fibers lose elasticity & thicken Fibroblasts decrease in number decreased production of collagen & elastic fibers wrinkles Decrease in number of melanocytes (gray hair, blotching) Decrease in Langerhans cells (decreased immune responsiveness) Reduced number and less-efficient phagocytes Dermal blood vessels thicken decreased nutrient availability loss of subcutaneous fat

Anti-aging treatments Microdermabrasion Chemical peel Laser resurfacing Botuliism toxin injection, and non surgical face lifts. Sun screens & sun blocks help to minimize photo-damage from UV exposure

47 Photodamage Ultraviolet light (UVA and UVB) both damage the skin
Acute overexposure causes sunburn DNA damage in epidermal cells can lead to skin cancer UVA produces oxygen free radicals that damage collagen and elastic fibers and lead to wrinkling of the skin

48 Skin Cancer 1 million cases diagnosed per year
3 common forms of skin cancer basal cell carcinoma (metastasis rare) squamous cell carcinoma (may metastasize) malignant melanomas (rapid metastasis) can result in death within months of diagnosis key to treatment is early detection ‘ABCD’ acronym risks factors: skin color, sun exposure, family history, age & immunological status

49 Burns Tissue damage from excessive heat, electricity, radioactivity, or corrosive chemicals that destroys (denatures) proteins in exposed cells Systemic effects of a burn are greater threat to life than are local effects Systemic effects: water/plasma loss, shock, infection Local effects: damage to tissue directly in contact with damaging agent Seriousness determined by depth, extent, and area involved When burn area exceeds 70%, over half of victims die


51 Types of Burns First-degree only epidermis (sunburn)
mild pain & redness but no blisters 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 & subcutaneous layers loss of function regeneration slow; grafting may be required

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