Chapter 5. The Integumentary System. The largest organ in the body (~18 sq. feet)

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1 Chapter 5 The Integumentary System The largest organ in the body (~18 sq. feet)

2 Cool facts about the skin There are approximately 19,000,000 skin cells on every square inch of your body Millions of skin cells are rubbed off daily You have over 2 million sweat glands All sweat gland tubules in the body would stretch into 6 miles of tubes Amount of sweat can vary from 100 to 8,000 ml/day Fastest growing hair is the beard

3 Functions of the skin Protection barrier between the internal and external environment Water Proofing and prevents water loss Regulates body temperature Sensation nerve endings that react to heat, cold, touch, pressure, vibration, and tissue injury

4 More functions. Excretion Through perspiration Production of Vitamin D Insulation and Cushion Contributes to skin color - Melanin

5 Skin Layers Superficial to Deep Epidermis Stratified squamous Contains no blood vessels Dermis Dense Irregular CT Contains blood vessels Hypodermis Adipose Contains blood vessels

6 Epidermis Characteristics Outermost layer of the skin Several strata (layers) Thinnest on the eyelids (0.05 mm ) thickest on the palms and soles (1.5 mm) Avascular (no blood supply) Stratified squamous

7 Strata of Epidermis (superficial to deep)

8 Come Let s Get Sun Burned

9 Stratum Corneum rows dead plate-like envelopes filled with keratin that have migrated up underlying layers Cells are worn/sloughed off daily (desquamation) Total new epidermis every days Flattened and hardened cells Contain Keratin (Keratinocytes or K-Cytes) Keeps skin elastic and protects underlying cells from drying out Barrier against microbe invasion

10 Stratum Lucidum 3 5 rows of dead K-cytes As K-cytes are pushed up they get bigger and flatter and adhere together, and then eventually become dehydrated and die Found in thick skin areas palms, soles and elbows Not found in thin skin areas eyelids

11 Stratum Granulosum 3 5 rows Aka: granular layer have lost their nuclei and are characterized by dark clumps (grains) of cytoplasmic material. Begins the process of keratinization

12 Stratum Spinosum 8 10 rows of actively dividing K-cytes Spiny or prickly appearance Cells interlock to support the skin

13 Stratum Basale Aka: basal cell layer Deepest layer One cell thick, rests on the basement membrane Dividing continuously As new cells form older ones are pushed up towards the skin Nutrients received from dermis below

14 Four Types of cells found in Epidermis Cell type Where found Function Keratinocytes All 5 layers Produce keratin Strength Waterproofing Melanocytes S. Basale Produce melanin (same # in all people skin color determined by amount of melanin produced) Merkel cells (tactile cells) S. Basale Involved with touch reception Langerhans Cells S. Basale Immune cells that eat bacteria and foreign debris

15 Dermis Composed of 2 regions Papillary region Reticular layer Vascular Has many blood vessels Sensory nerves

16 Papillary region Dense Irregular CT Contains Dermal Papilla projections into papillary region that extend into and anchor the epidermis Form fingerprints and footprints Contain capillaries that nourish the epidermis Contains Meissner s Corpuscles (sensory touch receptors)

17 Reticular Layer Dense Irregular CT Collagen fibers strength and flexibility Elastic fibers stretchable (maintain skin tension) Contains Pacinian Corpuscles sensory receptors for deep pressure

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19 Hypodermis AKA: subcutaneous tissue Loose CT Adipose Areolar Storage of energy Vascular Contains lymph vessels Insulation Protective padding Excessive adipose = obesity

20 Accessory Structures of the Skin Hair, nails, and glands Originates in the Epidermis Extends into the dermis

21 Hair Everywhere except palms, soles, lips, nipples, portions of external reproductive organs Stronger hair in the scalp region Puberty: Axillary and pelvic hair growth in both sexes Beard growth in males Hirsutism-excess male sex hormone in females

22 Hair Growth Hair grows from hair follicles Follicle cells divide continuously pushed up and away from nutrients Keratinized and die eventually Life-span Eyelash 3-4 months Scalp 3-4 years

23 Hair Follicle and Associated Parts Hair follicle: Root-portion within the follicle Shaft-portion beyond the follicle Sebaceous glands (oil glands) 1 or more per hair Arrector pili (smooth muscle) Attached to follicle Contraction causes goose-bumps

24 Hair Follicle and Associated Parts (Fig 5.1 and 5.2)

25 Nails Nail root-special epithelial cells from which nails growth Nail body-visible part of the nail Cuticle-skin fold that hides the nail root Lunula- whitish half moon Thicker layer of rapidly producing cells Nail bed-area of dermis on which nail grows

26 Nail Growth Nails grow over the nail bed Keratinization About 1mm growth per week Pink color because of vascular dermis below

27 Nail Anatomy (Fig 5.3)

28 Sweat Glands AKA: Sudoriferous glands Two types Apocrine Eccrine

29 Sweat Glands Apocrine Eccrine

30 Sweat Glands Apocrine Larger Duct leads to hair follicle Deeper in dermis More abundant in the axillary region Thicker/viscous sweat Eccrine Duct lead directly to surface of skin watery sweat Found all over body Ceruminous glands modified sweat gland found in ear (secrete earwax or cerumen)

31 Sebaceous Glands Associated with a hair follicle Secrete Sebum Oily (lipid) substance Flows into the follicle then out to the skin surface Lubricates hair and skin Waterproofs Weakens and kills bacteria

32 Mammary Glands Modified apocrine glands secrete milk after childbirth

33 Skin Disorders Athlete s Foot Fungal infection that involves soles and toes of feet Impetigo Infectious disease caused by a bacterial infection that results in pustules that crust over. Psoriasis chronic condition causing skin to develop reddish patches covered by silvery scales. Due to over active cell division.

34 Disorders Continued Eczema an inflammation of the skin caused by sensitivity to various chemicals Dandruff caused by an over accelerated rate of keratinization in certain areas of the scalp. Urticaria (Hives) is allergenic reaction characterized by the appearance of reddish, elevated patches and often itching.

35 Athletes Foot

36 Impetigo

37 Psoriasis

38 Eczema

39 Dandruff

40 Urticaria

41 Skin Cancer Nonmelanoma Basal Cells and Squamous Cells Less likely to metastasize Usually found at sun exposure spots Melanoma Begins in Melanocytes Example unusual moles More likely to metastasize

42 Wound Healing 1. Puncture wound fill with blood 2. Chemicals released by damaged tissue cause blood to clot. 3. Clotting prevents pathogens and toxins from spreading. 4. Scab develops 5. Fibroblasts Help with tissue regeneration Basal Layer begins to form new cells WBC Fight infection Scar collagen fibers arranged to provide maximum strength, devoid of feeling

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44 Burns Two factors affect burn severity: Depth & Extent First Degree Burns Only Epidermis redness and pain, but no blisters Ex. Moderate Sunburn Second Degree Burns Entire Epidermis & Part of Dermis Blistering can occur Ex. Severe Sunburn

45 Burns Continued Third Degree Burns Full thickness burns, destroys the entire thickness of the skin Fourth Degree Burns - Involves tissue down to the bone.

46 Effects of Aging on Skin Layers Epidermis: Maintains its thickness Decrease in the rate of cell mitosis Is held less tightly to the dermis (looser skin) Dermis: dermal papillae flatten Dermis becomes thinner Hypodermis: Decrease in the adipose tissue of face and hands (older people feel cold)

47 Effects of Aging on Fibers in the Dermis Collagen Fibers Collagenous fibers become coarser, thicker, and farther apart Overall less collagen than before Elastic Fibers Elastic fibers in the upper layer are lost Elastic fibers in the lower dermis become thicker, less elastic, and disorganized

48 Why is there wrinkling of skin with Epidermis is loose Fewer and more disorganized fibers in the dermis Less padding in the hypodermis age?

49 Aging and Homeostasis Limited adjustment to heat due to: less vasculature (fewer blood vessels) Fewer sweat glands Decrease in the number of hair follicles Thinning of hair on scalp and extremities Decreased number of melanocytes (gray hair and paler skin) Some pigment cells get larger-blotches Decrease in the number of sebaceous glands Cracking of skin

50 Roughened skin Aging and Sun Damage Uneven pigmentation Fine lines, wrinkles, and deep furrows Benign skin growth Skin cancer (UV radiation)

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52 Skin and Homeostasis Protection Regulation of water loss Waste elimination (assists Urinary System) Production of Vitamin D Gathering of Sensory Information Body Temperature regulation

53 Skin s Protective Functions Protective covering around the body against physical trauma and pathogens Melanocytes protect against UV radiation Outer keratinized cells prevent bacterial invasion Oily (acidic) secretions from sebaceous glands prevents bacterial growth Langerhans cells phagocytize pathogens and alert immune system

54 Regulation of Water Loss Waterproofing by outer keratinized cells Prevention of excess water entry into the skin by keratinized cells

55 Skin and Waste Elimination Sweat glands allow perspiration Sensible perspiration-can be felt Insensible perspiration-without awareness Perspiration contains Water Small amounts of salt, ammonia, urea, and other wastes

56 Skin and Vitamin D Production Vitamin D production in skin cells with the help of UV Small amount of UV needed Vitamin D (skin) goes to the Liver and Kidneys secrete Calcitrol (hormone) circulates and regulates calcium and phosphorus levels Vitamin D helps prevent rickets (soft/deformed bones)

57 Skin and Sensory Information Sensory receptors in the epidermis and dermis Sense touch, pressure, pain, hot, and cold Greatest number of touch receptors in the fingertips!

58 Skin and Regulation of Body Temperature (97ºF-100ºF) Increase in body temperature: Dilation of blood vessels in the skin Increase in the amount of blood brought to skin Sweat glands become more active Evaporation leads to skin cooling Decrease in body temperature: opposite effect Shivering-due to muscle contractions, heat production Arrector pili muscles contract-goose bumps Frostbite-severe restriction of blood flow, dead skin

59 Hyperthermia- Body Temp. Above Normal Heat Exhaustion: Low BP, excessive sweating (salt loss), high body temperature Heat stroke: high body temperature (110ºF), no sweating Fever: high body temperature due to immune response and bacterial infection

60 Hypothermia-Body Temperature below Normal 90º-95ºF: Uncontrollable shivering Incoherent speech, Lack of coordination Low pulse rate below 80º-85ºF: Hallucinations or unconsciousness Shivering diminishes, rigidity sets in 50% mortality