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Chapter 5 The Integumentary System

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1 Chapter 5 The Integumentary System

2 Skin (Integument) Consists of three major regions
Epidermis—superficial region Dermis—middle region Hypodermis (superficial fascia)—deepest region Not technically part of skin Mostly adipose tissue Covers the entire body Surface area of about square meters Makes up about 7% of the total body weight Called the integument Easily slides over underlying parts Acts as a shock absorber and insulator Hypodermis thickens when a person gains weight – females, thighs; males, belly

3 Epidermis Keratinized stratified squamous epithelium
Cells of epidermis Keratinocytes—produce fibrous protein keratin Melanocytes 10–25% of cells in lower epidermis Produce pigment melanin Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system Tactile (Merkel) cells—touch receptors Keratin gives the epidermis its protective qualities Melanin is a pigment found in the deepest layers of the epidermis Melanin accumulates in granules called melanosomes Melanosomes are taken up by keratinocytes and move to the sunny side of the nucleus and form a pigment shield to block UV rays Langerhans cells ingest foreign substances and activators for the immune system

4 Layers of the Epidermis: Stratum Basale (Basal Layer)
Deepest epidermal layer firmly attached to the dermis Single row of stem cells Also called stratum germinativum: cells undergo rapid division Journey from basal layer to surface Takes 25–45 days Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes (10-25%) and epidermal dendritic cells.

5 Layers of the Epidermis: Stratum Spinosum (Prickly Layer)
Several layers thick Tension resistant pre-keratin filaments Abundant melanin granules and dendritic cells Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin Lo

6 Layers of the Epidermis: Stratum Granulosum (Granular Layer)
Thin; three to five cell layers in which the cells flatten Keratinization begins Contain two granules Keratohyaline Lamellated Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Keratahyaline – help form keratine in upper layers Lamellated – Contai water resistant glycolipids – slow water loss

7 Layers of the Epidermis: Stratum Lucidum (Clear Layer)
In thick skin Thin, transparent band above the stratum granulosum A few rows of flat, dead keratinocytes

8 Layers of the Epidermis: Stratum Corneum (Horny Layer)
20–30 rows of dead, flat, keratinized membranous sacs Three-quarters of the epidermal thickness Functions Protects from abrasion/penetration Waterproofs Barrier against biological, chemical, and physical assaults Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space.

9 Strong, flexible connective tissue Cells include:
Dermis Strong, flexible connective tissue Cells include: fibroblasts, macrophages, and occasionally mast cells and white blood cells Two layers: Papillary Reticular Second major skin region

10 Layers of the Dermis: Papillary Layer
Areolar connective Dermal papillae contain: Capillary loops Meissner’s corpuscles Free nerve endings Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints Friction ridges Areolar tissu has collagen and elastic fibers and blood vessels Meissners corpuscles – touch receptors On the palms of hands and soles of feet the papillae lie atop larger mounds called dermal ridges which cause the epidermis to form epidermal ridges which help increase friction on the fingers and also generate fingerprints Openings of sweat gland ducts

11 Layers of the Dermis: Reticular Layer
~80% of the thickness of dermis Course, irregularly arranged connective tissue Cutaneous plexus – vascular supply Cleavage (Tension) lines – seperation between bundles of fibers in this layer Important in surgery

12 (b) Figure 5.4b

13 Striae Extreme stretching of skin can cause striae
Stretch marks Short term trauma (burn or overuse friction) can cause separation of the epidermis to dermis layers Blister

14 Three pigments contribute to skin color:
Melanin Yellow to reddish-brown to black, responsible for dark skin colors Produced in melanocytes-transferred to keratinocytes Freckles and pigmented moles Local accumulations of melanin Melanin, carotene, and hemoglobin Synthesis of melanin relies upon en enzyme called tyrosinase Melanin pigment is found only in the deeper layers of the epidermis Darker skinned people produce more and darker melanosomes and their keratinocytes retain the pigment longer Excessive sun eventually causes damage – leathery skin, depression of immune system, can alter DNA and lead to skin cancer – dark complected people get skin cancer less than lighter colored people Some medications(tetracycline, sulfanamides) can cause photosensitivity

15 Skin Color Carotene Yellow to orange, most obvious in the palms and soles Hemoglobin Responsible for the pinkish hue of skin Cyanosis – bluish tint to skin from poorly oxygenated blood

16 Skin Color Conditions Erythema – reddened skin due to fever, blushing, inflammation, hypertension Pallor/Blanching – pale skin due to anemia, emotional stress, or low blood pressure Jaundice – liver disorder, bile pigments accumulate in skin Bronzing – metallic skin tone, sign of Addison’s disease Bruises – black and blue marks which are hematomas Addison's disease is a disorder that occurs when the adrenal glands do not produce enough of their hormones. Symptoms: Changes in blood pressure or heart rate; Chronic diarrhea

17 Derivatives of the epidermis
Appendages of the Skin Derivatives of the epidermis Sweat glands Oil glands Hairs and hair follicles Nails

18 Sweat (Sudoriferous) Glands
Two main types Eccrine (merocrine) sweat glands—abundant on palms, soles, and forehead Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes Ducts connect to pores Function in thermoregulation Sweat is a hypotonic filtrate of blood Sweat pH is between 4-6 Under the control of the sympathetic division of the autonomic nervous system-fight or flight system Sweating starts at the forehead and moves south Emotional sweating (cold sweat) – begins in the palms, soles and armpits

19 Sweat Glands Apocrine sweat glands—confined to axillary and anogenital areas Sebum: sweat + fatty substances and proteins Ducts connect to hair follicles Functional from puberty onward (as sexual scent glands?) Specialized apocrine glands Ceruminous glands—in external ear canal; secrete cerumen Mammary glands Approximately 2000 of these Larger than eccrine glands Sebum is quite viscous and a milky or yellowish color This substance is broken down by bacteria and gives us the body odor we have These are activated by sympathetic nerve fibers during pain and stress Activity is increased by sexual activity Cerumen = ear wax

20 Sebaceous (Oil) Glands
Widely distributed Most develop from hair follicles Become active at puberty Sebum Oily holocrine secretion Bactericidal Softens hair and skin Small glands on the body but large on the face, neck and upper chest Sebum secretion is stimulated by the release of androgens – become highly active glands during puberty Are associated with arrector pili muscles – when these contract they force out sebum onto the hair follicles

21 Sebaceous gland conditions
Whitehead – blocked sebaceous gland Blackhead – sebum oxidizes and hardens Acne – inflammatory condition with pimples Boil – a reddened area that eventually harderns Seborrhea – cradle cap Acne is typically caused by staph on the skin infecting gland A boil is a localized infection in the skin that generally starts as a reddened, tender area. Over time, the area becomes firm, hard, and tender. Eventually, the center of the boil softens and becomes filled with infection-fighting white blood cells from the bloodstream to eradicate the infection. This collection of white blood cells, bacteria, and proteins is known as pus Furuncle or carbuncle: This is an abscess in the skin usually caused by the bacterium Staphylococcus aureus. A furuncle can have one or more openings onto the skin and may be associated with a fever orchills. The term furuncle is used to refer to a typical boil that occurs within a hair follicle. The term carbuncleis typically used to represent a larger abscess that involves a group of hair follicles. A carbuncle can form a hardened lump that can be felt in the skin. The condition of having chronic, recurring boils is referred to as furunculosis or carbunculosis. Cystic acne: This is a type of abscess that is formed when oil ducts become clogged and infected. Cystic acne affects deeper skin tissue than the more superficial inflammation from common acne. Cystic acne is most common on the face and typically occurs in the teenage years. Hidradenitis suppurativa: This is a condition in which there are multiple abscesses that form under the armpits and often in the groin area. These areas are a result of local inflammation of the sweat glands. This form of skin infection is difficult to treat with antibiotics alone and typically requires a surgical procedure to remove the involved sweat glands in order to stop the skin inflammation. Pilonidal cyst: This is a unique kind of abscess that occurs in the crease of the buttocks. Pilonidal cysts often begin as tiny areas of infection in the base of the area of skin from which hair grows (the hair follicle). With irritation from direct pressure, over time the inflamed area enlarges to become a firm, painful, and tender nodule that makes it difficult to sit without discomfort. These frequently form after long trips that involve prolonged sitting. Seborrhea – cradle cap – over reaction of the sebaceous glands – yellow patches that slough off the babies head

22

23 Hair Functions Distribution
Alerting the body to presence of insects on the skin Guarding the scalp against physical trauma, heat loss, and sunlight Distribution Entire surface except palms, soles, lips, nipples, and portions of external genitalia

24 Dead keratinized cells Contains hard keratin
Hair Dead keratinized cells Contains hard keratin Tougher and more durable Won’t flake off Hair pigments: melanins (yellow, rust brown, black) Gray/white hair: decreased melanin production, increased air bubbles in shaft Main regions of hair are the shaft (where karitinization is complete) and the root (keratinization is still ongoing) If the

25 Hair Structure Shaft - where keratinization is complete
Root – keratinization is ongoing Ribbonlike shaft – hair is kinky Oval shaft – silky and wavy Round – straight and course

26 Hair Structure Three layers of cells Medulla – central core
Large cells and air spaces Cortex Several layers surrounding medulla Cuticle Single layer of cells Hair conditioners smooth rough surfaces of the cuticle and make hair look shiny

27 Hair Follicle Extends from the epidermal surface into dermis
Hair bulb: expanded deep end Hair follicle receptor (root hair plexus) Sensory nerve endings around each hair bulb Stimulated by bending a hair Arrector pili Smooth muscle attached to follicle Responsible for “goose bumps” Deep end of the follicle is located about 4 mm in the skin Bending the hair stimulates the hair plexus

28 Types of Hair Vellus—pale, fine body hair of children and adult females Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)

29 Types of Hair Hair Growth
Active growth phase (weeks to years) followed by regressive stage and resting phase (1–3 months) Growth phase varies (6–10 years in scalp, 3–4 months in eyebrows) Hair growth varies with body region, sex, and age – usually about 2.5 mm per week During regressive phase hair matric cells die and the follicle base and hair bulb shrivels – hair then goes into a resting phase and then the cycle starts again Hair in the scalp will be actively growing for 6-10 years and then become active for a few months – lose on average 90 scalp hairs a day

30 Hair Thinning and Baldness
Alopecia—hair thinning in both sexes after age 40 True (frank) baldness Genetically determined and sex-influenced condition Male pattern baldness is caused by follicular response to DHT DHT – dihydrotestosterone – a metabolite of testosterone – growth cycle becomes so short that hairs never emerge from their follicle before shedding Hair thinning has been treated with minoxidil – a drug used to treat high blood pressure Hair loss can be due to high fever, surgery, severe emotional trauma, and certain drugs

31 Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Nail matrix – Thickened portion of the proximal nail bed responsible for nail growth Lunula – thick nail matrix that appear white Nail folds – proximal and lateral skin folds Proximal fold becomes the cuticle or eponychium Hyponichuim is where dirt and debri accumulate also called the quick Yellow tinged nails make indicate a respiratory or thyroid disorder Thickening of the nails may indicate a fungal infection

32 Tufts Fracture

33 Functions of the Integumentary System
Protection—three types of barriers Chemical Low pH secretions (acid mantle) and defensins retard bacterial activity Physical/mechanical barriers Keratin and glycolipids block most water and water- soluble substances Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs Biological barriers Dendritic cells, macrophages, and DNA Skin has a low pH so it makes an acid barrier Defensins literally punch holes in bacteria Oil of poison ivy is very stable and can last virtually for ever – usually not contagious because the oil seeps in quickly Nitroglycerin and nicotine can penetrate the skin Skin is extremely permeable for 24 hours after drinking alcohol DNA is a great sunscreen because the electrons of DNA absorb UV light and then the transfers the heat to water molecules

34 Functions of the Integumentary System
Body temperature regulation ~500 ml/day of routine insensible perspiration (at normal body temperature) At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body Cutaneous sensations Temperature, touch, and pain Meissner’s corpuscles Pancinian corpuscles On a hot day sweat loss can be up to 12L (3 gallons) in one day Meissner’s corpuscles – sense the feel of our clothes against our skin Panician corpuscles – bumps involving deep contact

35 Functions of the Integumentary System
Metabolic functions Synthesis of vitamin D precursor and collagenase Chemical conversion of carcinogens and some hormones Blood reservoir—up to 5% of body’s blood volume Excretion—nitrogenous wastes and salt in sweat Sunlight converts cholesterol to Vitamin D precursors Keratinocyte enzymes can convert carcinogens to non-lethal chemicals and back again Can also convert cortisone into hydrocortisone a powerful anti-inflamatory

36 Skin Cancer Most skin tumors are benign (do not metastasize)
Risk factors Overexposure to UV radiation Frequent irritation of the skin Some skin lotions contain enzymes in liposomes that can fix damaged DNA Some skin creams repair damaged dna before the cells become cancerous Warts are potentially caused by viruses – freezing irritates the skin which in turn stimulates the immune response to attack the virus

37 Skin Cancer Three major types: Basal cell carcinoma
Least malignant, most common Squamous cell carcinoma Second most common Melanoma Most dangerous ABCD rule Basal cell accounts 80% of skin cancers - Stratum basale cells proliferate and slowly invade dermis and hypodermis – occurs mostly in the face as dome shaped nodules that develp into a an ulcer – slow growing – full recovery in 99% of cases Squamous cell - Involves keratinocytes of stratum spinosum – forms a reddened papule that is usually on the scalp or ears and hands – grows rapidly and can metastisize if not removed. Chance of complete cure is good if caught early. Melanoma – cancer of the melanocytes – highly metastatic – resistant to chemotherapy – 2-3% of skin cancers – usually starts as a brown patch that metastisizes to surrounding lymph and blood tissues – chance of survival is poor if the lesion is over 4 mm thick – usual treatment is wide surgical removal

38 Characteristics (ABCD rule)
Melanoma Characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser)

39 Figure 5.8a

40 Figure 5.8b

41 Figure 5.8c

42 (tissue damage, denatured protein, cell death)
Burns Heat, electricity, radiation, certain chemicals Burn (tissue damage, denatured protein, cell death) Immediate threat: Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock IV fluids are the immediate treatment

43 Used to estimate the volume of fluid loss from burns
Rule of Nines Used to estimate the volume of fluid loss from burns Fluid loss can be estimated by the percentage of body surface burnt Burn victims need additional nutritional supplementation to replace proteins lost often given through a g-tube Secondary concerns are infection Burned skin is sterile for approx. 24 hours – this is complicated by the fact that the immune system becomes difficient one to two days after a severe burn

44 Partial-Thickness Burns
First degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear

45 Full-Thickness Burns Third degree Entire thickness of skin damaged
Gray-white, cherry red, or black No initial edema or pain (nerve endings destroyed) Initial treatment – cutdown or fasiotomy Skin grafting usually necessary

46 Severity of Burns Critical if:
>25% of the body has second-degree burns >10% of the body has third-degree burns Face, hands, or feet bear third-degree burns

47 Burn Treatment Silvadene – burn cream antibiotic (sulfanamide)
Fasciotomy – split skin to prevent swelling skin from tearing Flood area with antiobiotics Debride eschar Skin graft – taking skin from own person or donor (high rejection) Amniotic sac treatment – living bandage Silvadene turns black when exposed to air


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