Integumentary System PDF

INTEGUMENTARY SYSTEM Objectives Know the layers of the skin and the functions of each layer Know the accessory structures of the skin and the functions of each Describe the changes that occur in the integumentary system during the aging process D...

INTEGUMENTARY SYSTEM Objectives Know the layers of the skin and the functions of each layer Know the accessory structures of the skin and the functions of each Describe the changes that occur in the integumentary system during the aging process Discuss several common diseases, disorders, and injuries that affect the integumentary system Feel the rain on your skin. INTEGUMENT 16% 1.5 m2 largest What does it do? What does it do? Skin Senses Hair root plexus – movement of hair Free nerve endings – pain and temperature Meissner’s corpuscle – light touch; low-frequency vibration Merkel cell – continuous light touch and pressure Pacinian corpuscle – lamellated; Fast/high-frequency vibration + deep pressure Ruffini endings – steady deep pressure and stretch THE SKIN Cutaneous membrane Epidermis Multiple Layers Dermis of the skin Hypodermis* EPIDERMIS Stratified squamous, keratinizing Avascular Has 4 principal cell types Composed of several layers (BS GLC) Thin skin – 4 layers Thick skin – 5 layers  Two Types of Skin based on the epidermis  KERATINOCYTES MELANOCYTES - Produce keratin - Produce melanin - Produce lamellar - 8% of cells granules - 90% of cells LANGERHANS MERKEL CELL - Immune response - Detect touch sensation against microbial skin - Deepest layer of the invaders! epidermis - Recognition of - Least numerous microbes and eat it - In contact with - (+) Birbeck granules tactile disc/Merkel disc  1: Stratum Basale “Stratum germinativum” Single row of cuboidal/columnar keratinocytes Large nuclei Many ribosomes Attached to the basement membrane Constantly dividing (germinating) Most adequately nourished  Cells found in this layer Basal cells Cuboidal Multipotent stem cell Merkel cell Melanocyte 2: Stratum Spinosum Spiny with protruding cellular processes Intermediate filaments of keratin Inserts into desmosomes 8-10 layers of keratinocytes Start of keratin synthesis Special cell: Langerhans 3: Stratum Granulosum Grainy 3-5 layers of flat keratinocytes undergoing apoptosis Produce more keratin IF and keratohyalin granules (profillagrin, loricrin w/c binds and crosslinks keratin IF) Lamellar granules present (acts as water repellant) 4: Stratum Lucidum 4-6 layers of dead and flattened cells with lots of keratin Found ONLY in thick skin Translucent (Eleidin) From keratohyalin Clear protein allowing light to pass through 5: Stratum Corneum 25-30 layers of flattened dead keratinocytes No longer contain nuclei (corneocytes) Keratinized/cornified Periodically shed in about 4-6 weeks  BS GLC Review the layers! DERMIS Connective tissue Vascularized Houses nerves, lymph vessels, hair follicles, and sweat glands 2 layers Papillary Reticular Papillary Dermis Loose areolar connective tissue Dermal papilla Finger-like projections Contain fibroblasts, small blood vessels, lymphatic capillaries, nerve fibers, and touch receptors (Meissner) Responsible for your fingerprints! Reticular Dermis Dense irregular connective tissue Tight meshwork of elastin and collagen Deepest skin layer Well vascularized with rich sensory and sympathetic nerve supply Has lamellar/Pacinian corpuscles and Ruffini endings HYPODERMIS NOT technically a skin layer Subcutaneous layer or superficial fascia Loose areolar connective tissue Well vascularized Contains adipose Skin Pigments  MELANIN Produced by melanocytes Transferred to keratinocytes via melanosomes 2 forms: Eumelanin (brown to black) – more effective at absorbing UV light; more predominant Pheomelanin (yellow to red)  Protects DNA of epidermal cells from UV damage UV exposure  ↑ Melanin Too much sun exposure  destruction of cell structure  wrinkling Severe: skin cancer HEMOGLOBIN Light skinned individuals appear to have a pinkish undertone Found in blood depending on oxygen content CAROTENE Precursor of vitamin A Found in egg yolks, carrots Can result in skin turning orange Carotenemia Accessory Structures HAIR Dead, keratinized cells Hair follicle Origin at the dermis Hair shaft Exposed part anchored to the follicle HAIR Hair root Below the surface Hair bulb Mitotically active basal cells hair matrix Surrounds hair papilla Hair Shaft Medulla Central core Moderately keratinized transparent cells (weaker, less rigid) Cortex Surrounds medulla Compressed keratinized cells Cuticle Outermost Very hard, keratinized cells Hair Follicle Inner root sheath Surround root of growing hair Extends up to the hair shaft Outer root sheath Extension of the epidermis Encloses hair root Glassy membrane Thick, clear connective tissue Covers hair root connecting to the dermis What does it do?  Hair grows 0.3 mm/day 50-100 strands lost and replaced per day Hair Color Influenced by the amount and type of melanin in the keratinized cells Aging  ↓ Melanin production  Gray/White hair OIL GLANDS Sebaceous glands Simple, branched acinar glands Found all over the body Associated with hair follicles OIL GLANDS Excretes sebum Lipids Lubrication Antibacterial Prevent water loss Stimulated by pubertal hormones  NAILS Tightly packed, hard, dead, Clear, solid covering over the keratinized cells dorsum of the distal finger Nail body On nail bed and is the visible portion Pink due to blood underneath Nail root Matrix of proliferating cells from the stratum basale  Nail fold Overlaps the nail on the sides Anchors the nail Eponychium Nail cuticle Nail fold meeting proximal end of nail body  Lunula Thickened region of the epithelium Crescent shape Hyponychium Thickened region of the stratum corneum  SWEAT GLANDS Sudoriferous glands Produce sweat for thermoregulation From epidermal projections into the dermis Merocrine glands Secretion by exocytosis through duct ECCRINE Simple, coiled, tubular gland More common than apocrine Thermoregulatory sweating Produces hypotonic sweat Water & ions (Na+, Cl-) Urea, uric acid, ammonia Amino acids Glucose Lactic acid Dermicidin (antimicrobial) APOCRINE Simple, coiled, tubular gland with LARGER ducts In hairy areas Release sweat by pinching off a portion of the cell (apocrine) Milky/yellowish color + lipids +proteins Stinky!!! Skin Problems  SKIN CANCER Cancer Abnormal cells that grow For skin cancer, d/t overexposure uncontrollably and chaotically to UV radiation Basal Cell Carcinoma Affects the basal cells Most common cancer in the US Predisposing factors: UV exposure Radiation Arsenic Open wounds Frequently affected: Head, neck, arms, back Responsive to treatment when caught early Squamous Cell Carcinoma Affects keratinocytes Commonly affects: Scalp Ears Hands 2nd most common cancer More aggressive!!! Tx: Surgery, Radiation  Melanoma Affects melanocytes Develops from a mole MOST FATAL Highly metastatic Tx: Surgery, immunotherapy SCARS and LESIONS BEDSORES Decubitus ulcer Caused by constant, long-term unrelieved pressure on bony prominences MC in elderly with debilitating conditions Turn patient every 2h!  STRETCH MARKS Stretching of dermis beyond limits of elasticity No adverse health effect Mostly a cosmetic issue  CALLUSES Due to constant Can be softened abrasive forces on and removed skin Increased thickness of the skin to protect it QUESTIONS?