Human Anatomy & Physiology Chapter 5: Integumentary System PDF

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 5 – The Integumentary System INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands INTEGUMENTARY SYSTEM ANATOMY Consists of:...

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 5 – The Integumentary System INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands SKIN STRUCTURE Skin has distinct regions: Epidermis: superficial region Epithelial tissue Avascular Dermis: deep to (underlies) epidermis Areolar & Dense Irregular connective tissues Vascular Hypodermis: superficial fascia; subcutaneous layer deep to skin Not actually part of skin but shares function Mostly adipose tissue Absorbs shock, insulates body, anchors skin to muscles CELLS OF EPIDERMIS Epidermis is predominantly keratinized stratified squamous epithelial tissue Withstands high degree of wear and tear 4 Main Cell Types: Keratinocytes: produce keratin which give skin its protective properties Millions “slough” off every day Large component of household dust Melanocytes: produce piment called melanin Protects cell nucleus from UV damage Located deep within epidermis Dendritic Cells: star-shaped macrophages Patrol deep epidermis; key activators of immune response Antigen-presenting cells “sound the alarms” Merkel Cells: sensory receptors for touch EPIDERMAL LAYERS Epidermis has very distinctive layers (strata) Thin skin has 4 Thick skin has 5 High wear areas (i.e., palms of hands & soles of feet) From Deep to Superficial: 1. Stratum Basale 2. Stratum Spinosum 3. Stratum Granulosum 4. Stratum Lucidum (thick skin only) 5. Stratum Corneum EPIDERMAL LAYERS 1. Stratum basale (aka stratum germinativum) Deepest (Base) Layer Firmly attached to dermis Single row of actively dividing stem cells Continually renewing epidermal cell population Cells die as they move toward surface “new” external skin every 25 – 45 days 2. Stratum spinosum (prickly layer) Several cell layers thick Web-like system of pre-keratin filaments Resists tension & pulling Cells appear “spiky” or “prickly” Dendritic cells & Melanosomes abundantly scattered throughout EPIDERMAL LAYERS 3. Stratum granulosum (granular layer) 1 – 5 layers of cells But cells flat making layer thin Cell appearances begin to change Cells become flat; nuclei & organelles disintegrate Keratinization begins Cells above this layer die Too far from dermal capillaries 4. Stratum lucidum (clear layer) Found only in thick skin Thin, translucent band of 2 – 3 layers of flat, dead keratinocytes Cells appear identical to next layer EPIDERMAL LAYERS 5. Stratum corneum (horny layer) Outermost epidermal layer 20 – 30 layers of flat, keratinized dead cells Accounts for 75% of epidermal thickness ~18kg (40lbs) of these cells shed/slough off over lifetime While cells are dead, they still: Protect deeper layers from environment Prevent water loss Protect from abrasion & penetration Act as barrier  Keratinocytes Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and tactile Dermis epithelial cells. (a) Dermis Melanin Sensory Tactile granule nerve epithelial ending cell (b) Desmosomes Melanocyte Dendritic cell DERMIS Epidermis Strong, flexible connective tissue Cell contents similar to connective tissue proper (fibroblasts, macrophages, mast cells, WBCs) Semifluid matrix Fibers within bind it together Dermis: Papillary dermis Aka your “hide” (areolar connective tissue) Like that used to make leather Reticular dermis (dense irregular Contains: connective tissue) Nerves Blood/Lymph Vessels Hair Follicles Dermal papillae Sweat & Sebaceous Glands Two Layers: Papillary & Reticular DERMAL LAYERS Papillary Layer: Superficial layer of dermis Loose areolar connective tissue Contains collagen, elastic fibers, blood vessels Dermal papillae: finger-like projections into epidermis Papillae contain: Capillaries Free nerve endings (nociceptors = pain) Touch receptors (Meissner’s corpuscles) Reticular Layer: Dense irregular fibrous connective tissue Elastic fibers = stretch-recoil properties Collagen fibers = strength & resiliency Named for the network (reticulum) of collagen fibers; not reticular fibers 80% of dermal thickness CLINICAL CONNECTION Extreme stretching of skin can cause dermal tears Leave silvery white scars called striae or stretch marks Rapid gains in muscle size or body size i.e., pregnancy, puberty, rapid muscular hypertrophy, obesity Acute, short-term trauma to skin can cause blisters Fluid-filled pockets separating dermal and epidermal layers Trauma can include burns, friction CLINICAL SIGNIFICANCE Excessive sun exposure can cause: Elastic fibers to clump Skin becomes “leathery” Alterations in skin cell DNA Skin cancer risk ↑ UV light destroys folic acid Necessary for DNA synthesis Photosensitivity = increased reaction to sun Can be caused by: Drugs (e.g., antibiotics, antihistamines) Perfumes/colognes Leads to skin “rashes” SKIN COLOR 1. Melanin Only pigment made in skin 2 Forms: Red-Yellow & Brown-Black Shields DNA of keratinocytes from damaging UV More sun = more protection needed → greater melanin production Differences in pigmentation due to different amounts of & form of melanin produced Freckles & Moles: local accumulations of melanin 2. Carotene Yellow-Orange pigment (palms & soles) Yes…too much β-carotene in food can change skin to take this hue Can be converted to Vit A for vision & epidermal health 3. Hemoglobin Provides pinkish hue to fairer skins Ex: Caucasians have less melanin, so skin more transparent allowing Hb’s hue to show CLINICAL SIGNIFICANCE Cyanosis Alterations in skin color can be good indicators for disease: Cyanosis: blue Pallor Low oxygenation of hemoglobin Pallor: blanching/pale Erythema Anemia, low blood pressure, fear, anger Erythema: redness Fever, hypertension, inflammation, allergy Jaundice: yellow Jaundice Liver disorders CLINICAL CONNECTION: VITILIGO Chronic autoimmune disorder causing patches of skin to lose color Destruction of melanocytes Skin takes on a “milky-white” color Patches usually appear symmetrically on body Patches on both sides, not necessarily same shapes INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands HAIR Made up from keratinized cells Functions: Warn or insects (or foreign bodies) on skin Guard against physical trauma (head) Protect from excessive heat loss Shield skin from sunlight Covers body (to some degree) except: Palms Soles Lips Nipples Portions of external genitalia HAIR FEATURES Hairs extend from the epidermis into the dermis Hair Bulb: expanded area at deep end of hair follicle Hair Matrix: actively dividing area of bulb Hair growth Hair Follicle Receptor: sensory nerve endings encasing bulb Hair is a touch receptor Arrector pili: small band of muscle attached to follicle Causes “goose bumps” and “hair standing” sensations Hair’s pigment caused by melanocytes in follicles Different combinations of melanins give color Red hair has additional pheomelanin pigment Graying caused by decrease in melanin production HAIR TYPES & GROWTH Fetuses/newborns have lanugo Soft, unpigmented hairs Body hair on children & adult females (assigned female at birth) termed vellus hair Pale & fine “peach-fuzzy” Scalp & eyebrows have terminal hairs Coarse & long, pigmented Will begin to grow on axillary, pubic, face & neck during puberty Hair growth largely dictated by hormones & nutrition CLINICAL CONNECTION: ALOPECIA Alopecia: some degree of hair loss Different Types of Alopecia: Alopecia areata: portion of single body part Alopecia totalis: entire portion of single body part Alopecia universalis: entire body Androgenic alopecia: gene/hormone-related Tellugen effluvium: caused by thyroid disorder, stress, diet, etc. Anagen effluvium: caused by chemotherapy Traction alopecia: caused by hair consistently pulled back tight i.e., military, dance, cheer, gymnastics, etc. INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands  Lunule NAILS Nails are just modifications of the epidermis Contain hard keratin Act as protective covers for distal, dorsal Nail root surface of fingers & toes Nail Nail Eponychium matrix Free edge Have a: of nail plate (cuticle) Free Edge: what hangs past distal end of finger/toe Keratinized Nail Plate: sits over distal surface of finger/toe Keratinized Root: proximal to cuticle; embedded in skin Nail Bed rests deeply covering epidermis Phalanx (bone of fingertip) Nail Matrix: portion of nail bed responsible for nail Hyponychium Nail bed growth CLINICAL SIGNIFICANCE Nail appearance can be important Nails usually pinkish color due to underlying Fungal Infection capillaries Koilonychia Discoloration & abnormal shapes can indicate disease Thick, yellow nails = fungal infection Smoking can also turn nails yellow but will also discolor skin around nail Koilonchya: “spoon nail”; nail becomes outwardly concave Indicates possible iron deficiency (can lead to anemia) Beau’s Lines: horizontal lines across nails Can indicate severe illnesses Beau’s Lines i.e., uncontrolled diabetes, heart attack, cancer Clubbing “Clubbing”: nails appear convex like clubs Can indicate respiratory and cardiovascular diseases INTEGUMENTARY SYSTEM ANATOMY Consists of: Skin Hair Nails Sweat Glands Sebaceous (oil) Glands SWEAT GLANDS Aka sudoriferous glands On all skin surfaces except nipples & part of external genitalia 2 Types: Eccrine (aka merocrine) Most numerous/abundant Esp. on palms, soles, forehead Ducts empty to pores Sole secretion is sweat for thermoregulation Apocrine (post-puberty) Only in axillary and anogenital areas Larger than eccrine glands Ducts empty into hair follicles Secretes viscous, milky/yellow sweat Also has fatty substances & protein Bacteria break this down → BO SEBACEOUS (OIL) GLANDS Widely distributed (except thick skin) Most develop from follicles & secrete into hair follicles Occasionally secrete through pores Stimulated by hormones (esp. androgens) Therefore relatively inactive until puberty Secrete sebum Oily secretion Bactericidal (bacteria-killing) Softens hair and skin Acne results from infectious inflammation of glands Creates pustules/cysts or pimples Whitehead = blocked gland Blackhead = secretion oxidized in pimple INTEGUMENTARY ANATOMY SUMMARY The integumentary system is comprised of: 1. Skin Epidermis: superficial layer Multilayered epithelial tissues Serves as first interaction with environment 4 or 5 strata thick (Basale, Spinosum, Granulosum, Lucidum, Corneum) Each serves specific function Newest cells at “base” strata; dead cells in most superficial layer(s) Dermis: deep layer Anchors skin to deeper tissues and provides skin with its stretch & give 2. Hair Sensory organ Helps warn us from foreign bodies on skin, thermoregulation, UV (sun) protection Follicles arise from bulbs deep within dermis and extend to epidermis Pigmentation created by combinations of melanins within follicle (just like with skin cells) 3. Nails Just hardened, keratinized modifications of the epidermis to cover & protect epidermis of finger/toe ends Nail beds and nail plates arise from nail matrix found proximal to cuticles 4. Sweat Glands Eccrine glands are most abundant, but Apocrine glands responsible for BO Sweating important for thermoregulation and waste removal 5. Sebaceous Glands Oil glands which produce sebum to kill bacteria and keep skin moisturized SAMPLE QUESTIONS 1. Name the 4 layers of the epidermis which exist in both types of skin (thin and thick) 2. At which layer of the epidermis do the new cells from the base layer begin to die? 3. What condition is denoted by partial or complete loss of hair? 4. A yellowish discoloration of the nail can indicate what? 5. Which type of sweat gland becomes active predominantly after puberty? 6. __________ is caused by infectious inflammation of the sebaceous glands. FUNCTIONS OF THE SKIN Skin is a barrier Main Functions include: Protection Body Temperature Regulation (Thermoregulation) Cutaneous Sensation Metabolism Blood Reservoir Waste Excretion PROTECTION Skin is exposed to all kinds of stuff Microorganisms Abrasions Temperature extremes Harmful chemicals Radiation Has 3 Barriers for Protection Chemical Sweat, sebum, low pH (slightly acidic), melanin, defensins Physical Cells are keratinized Biological Dendritic cells in epidermis, macrophages in dermis, DNA absorbs UV THERMOREGULATION Normal, resting body temperature: 500 mL/d insensible perspiration Unnoticed, evaporates quickly, no beads If body temperature rises: Dermal vessels dilate Sweat production increases to up to 12 L (3 gal) sensible perspiration Very noticeable, will bead, will evaporate (eventually) or drip If body temperature drops, vessels constrict Prevent heat loss CUTANEOUS SENSATION Exteroceptors on skin respond to stimuli outside body (environment) i.e., touch, temperature Meissner’s corpuscles: light touch i.e., caress, brush Pacinian corpuscles: coarse touch i.e., bumps, ridges Free nerve endings sense pain (nociceptors) Often trigger a withdrawal reflex OTHER SKIN FUNCTIONS Metabolic Skin synthesizes vitamin D Via sunlight exposure Necessary for calcium absorption in intestines Also why milk is fortified with vitamin D Blood Reservoir Skin holds up to 5% of total blood volume at any given time When needed, dermal vessels will constrict to shunt blood elsewhere i.e., exercising muscle Excretion Skin can secrete some nitrogenous wastes Takes some load off kidneys Sweating also causes water and salt loss SKIN CANCERS & BURNS Skin can develop 1000+ different conditions & ailments Many internal conditions display symptoms on skin i.e., liver decline, heart disease, allergies, anemia, stress, fatigue, nausea, etc. Most skin conditions are caused by infection Less common, but more damaging: Skin Cancer Burns SKIN CANCER Most skin tumors are benign (non-cancerous) and do not spread (metastasize) Skin cancer risk increases with: Overexposure to UV radiation Prolonged sun exposure, tanning, (some) tanning beds Frequent skin irritation Some lotions contain enzymes to help repair damaged DNA Nothing is “foolproof” MAJOR TYPES OF SKIN CANCER 1. Basal Cell Carcinoma Most common, least malignant Stratum basale (base layer) epidermal cells proliferate and slowly invade deeper skin layers 99% cured with simple excision (removal) 2. Squamous Cell Carcinoma 2nd most common Not very malignant but can metastasize Good prognosis if treated by radiation and/or excised early Involves keratinocytes of stratum spinosum Usually appears as red papule or “splotch” on scalp, ears, lower lip, hands MAJOR TYPES OF SKIN CANCER 3. Melanoma Highly malignant & highly metastatic Resistant to chemotherapy Requires excision & immunotherapy Cancer of melanocytes Early Detection is key; ABCD Rule A. Asymmetry: two sides of pigment do not match B. Border irregularity: indentations on borders (not uniform) C. Color: contains several different pigments D. Diameter: >6 mm (pencil eraser) wide BURNS Tissue damage (protein denaturation) via: Heat Chemicals Electricity Radiation Chemicals Damaged/Lysed cells lose intracellular fluid Intracellular contents now “out” Can lead to dehydration & electrolyte imbalance Severe enough or uncorrected → renal failure or shock Burns evaluated by Rule of Nines Body divided into 11 sections (each ~9% body surface except genitals, 1%) Estimate volume of fluid loss BURN CLASSIFICATION First-Degree Based on severity 1. First-Degree Epidermal damage only Localized redness, edema (swelling), pain 2. Second-Degree Second-Degree Epidermis and upper (superficial) dermis damaged Blistering 1st & 2nd degree “partial-thickness burns” 3. Third-Degree Entire thickness of skin damaged Third-Degree “full-thickness burn” Skin turns gray-white, cherry red, or black No edema No pain – nerve endings destroyed Skin grafting necessary BURNS Burns labeled “critical” if: >25% of body has 2nd degree burns >10% of body has 3rd degree burns Face, hands, or feet have 3rd degree burns Treatment: Debridement (removal) of burned skin Antibiotics Temporary coverings Skin grafts SKIN DEVELOPMENT From infancy to adulthood: Skin thickens More subcutaneous fat forms Sweat and sebaceous gland activity increases → acne “Optimal” skin appearance in 20s & 30s After age 30, cumulative effects of environmental assault start to show Epidermal replacement slows & sebaceous gland activity decreases → dry skin Subcutaneous fat & elasticity decrease → cold intolerance & wrinkles Decreased melanocytes & dendritic cells → increased skin cancer risk Signs of “aging” can be delayed by: UV protection (sunblock) Good nutrition Good hydration Good hygiene (and good skincare routine) SKIN FUNCTIONS SUMMARY The skin is our first line of defense and first interaction with our environments It provides a barrier of protection from foreign substances & radiation Helps keep us warm/cold Absorbs sunlight to make necessary vitamin D Holds a blood reservoir that not only helps us thermoregulate and the skin regenerate itself but can also be redirected as needed Helps us excrete some wastes thereby taking some load off other internal organs Therefore, skin health is important Burns destroy skin cells and can lead to dehydration and impaired kidney function Large amounts of UV exposure can lead to cancers which may metastasize and affect other organs Skin naturally degrades with age making it important to take proper measures to maintain skin health throughout the lifespan SAMPLE QUESTIONS 1. How much of our body’s total blood volume does the skin hold at any given time? 2. Sweat, sebum, and skin’s mild acidity are examples of what kind of barrier that the skin provides? 3. The Rule of Nines for assessing the amount of the body burned is used to estimate what? 4. Which type of skin cancer is most aggressive and highly metastatic?  COPYRIGHT © Pearson Edited by Charles Smith, PhD CSCS 2024