Lecture 4 Skin PDF

Dermis Located between epidermis and hypodermis (subcutaneous layer) Anchors accessory structures (hair follicles, sweat glands) Has 2 layers: superficial papillary layer deep reticular layer Dermis Papillary layer Reticular layer Superficial layer Dee...

Dermis Located between epidermis and hypodermis (subcutaneous layer) Anchors accessory structures (hair follicles, sweat glands) Has 2 layers: superficial papillary layer deep reticular layer Dermis Papillary layer Reticular layer Superficial layer Deep layer Consists of areolar tissue Consists of dense irregular Contains smaller capillaries, CT lymphatics, and nerve fibers Contains larger blood Has dermal papillae vessels, lymphatics, and projecting between nerve fibers epidermal ridges Connected to the hypodermis Characteristics of Dermis Strong, due to collagen fibers Elastic, due to elastic fibers (skin turgor) Decreased Skin Turgor Reduced skin elasticity → sagging and wrinkles Causes: Dehydration hormonal changes exposure to UV aging Dermatitis Inflammation of the papillary layer Caused by infection, radiation, mechanical irritation, or chemicals Characterized by itching or other pains Lines of Cleavage (Langer’s Lines) Collagen and elastic fibers in the dermis: ̶are arranged in parallel bundles ̶resist force in a specific direction Clinical importance: ̶a parallel cut remains shut, heals well ̶a cut across (right angle) pulls open and scars Dermal Blood Supply Arteries: ̶cutaneous plexus:  arterial network along the reticular layer ̶papillary plexus:  capillary network in papillary layer Veins: ̶venous plexus:  receives blood from capillaries Contusion (Bruise) Skin blunt trauma damage to blood vessels blood leaks in dermis “black and blue” color Day 1 Day 4 Bed Sores (Decubitus Ulcers) Due to disturbances of dermal circulation Affect skin at pressure points Prevented by: ̶frequently changing position ̶air mattress Common Sites Dermis & Nerve Supply Nerve fibers in the skin control: blood flow gland secretions sensations Dermis contains a number of receptors: Receptor Sensation Pacinian (Lamellar) corpuscles Pressure and vibration Meissner's (Tactile) corpuscles Light touch Merkel discs Pressure, position, and deep touch Ruffini (Bulbous) corpuscles Skin stretch Free nerve endings Pain and temperature Dermis at a Glance Provides mechanical strength, flexibility and protection 2 layers of CT Highly vascular Contains a variety of sensory receptors Hypodermis = subcutaneous tissue, superficial fascia NOT Underneath the integument PART OF THE Quite elastic SKIN Stabilizes the skin and allows independent movement Structure of the Hypodermis Areolar and adipose tissues Connected to the reticular layer of dermis by connective tissue fibers Clinical Importance of Hypodermis Has few capillaries and no vital organs Site of: ̶subcutaneous injections ̶liposuction Routes of Injection Accessory Structures of the Integumentary System a i H r Glan Na ds i ls  Hair Hair Structure: Sebaceous ̶hair gland Arrector ̶hair follicle pili muscle ̶accessory structures Connective th in tissue sheath l y in Root hair On plexus skin  Hair Regions of the Hair Hair root: Hair shaft lower part of the hair attached to the integument Hair shaft: Hair root upper part of the hair sticks out of the integument Layers in a Hair Hair Structure Hair The cuticle, although The medulla, or core, The cortex contains thick Medulla: of the hair contains a layers of hard keratin, which flexible soft keratin. give the hair its stiffness. thin, is very tough, and it contains hard keratin. central core Follicle Structure Cortex: Sebaceous gland The internal root sheath surrounds Arrector the hair root and the deeper portion middle layer pili muscle of the shaft. The cells of this sheath disintegrate quickly, and this layer does not extend the entire length of the Cuticle hair follicle. The external root sheath extends outer layer from the skin surface to the hair Connective matrix. tissue sheath Root hair The glassy membrane is a plexus thickened, clear layer wrapped in the dense connective tissue sheath of the follicle as a whole. Connective tissue sheath Keratin As hair is produced, it is keratinized: medulla contains flexible soft keratin cortex and cuticle contain stiff hard keratin Hair Follicle Located deep in dermis Factory of hair Wrapped in a dense connective tissue sheath Base is surrounded by sensory nerves (root hair plexus) Layers of the Hair Follicle Follicle Structure The internal root sheath surrounds the hair root and the deeper portion of the shaft. The cells of this sheath disintegrate quickly, and this layer does not extend the entire length of the hair follicle. The external root sheath extends from the skin surface to the hair matrix. The glassy membrane is a thickened, clear layer wrapped in the dense connective tissue sheath of the follicle as a whole. Connective tissue sheath Hair Production by the Follicle Hair papilla: Connective tissue sheath of hair follicle Glassy membrane ̶contains capillaries and nerves External root sheath Hair bulb: Internal root sheath Cuticle of hair ̶surrounds the papilla Cortex of hair Medulla of hair ̶produces: Matrix  hair layers Hair papilla Hair bulb  hair matrix Subcutaneous adipose tissue  Hair Accessory Structures of Hair Arrector pili muscle: involuntary smooth muscle Sebaceous gland causes hair to stand up Arrector pili muscle produces “goose bumps” Sebaceous glands: secrete sebum (oil) lubricate the hair control bacteria Connective tissue sheath Root hair plexus Location of Hair The human body is covered with hair, EXCEPT: palms soles lips portions of external genitalia:  labia minora Glabrous  penis skin Types of Hairs Vellus hairs: soft, fine cover body surface Terminal hairs: heavy, pigmented head, eyebrows and other body areas after puberty (e.g., pubic – axillary) What is lanugo hair? Hair Color Melanin produced by melanocytes at the hair papilla Determined by genes Functions of Hair Protects and insulates Guards openings against particles and insects Sensitive to very light touch  Integumentary Glands Sebaceous (oil) glands Sweat glands Mammary glands Ceruminous glands Sebaceous Glands Simple branched alveolar glands th in Holocrine glands y i n Onl Secrete sebum skin Lumen Sebaceous follicle Sebaceous gland (hair removed) Wall of hair follicle Basement membrane Epidermis Discharge of sebum Lumen Dermis Breakdown of cell membranes Mitosis and growth Subcutaneous Basal cells layer Sebaceous gland LM × 150 Sebaceous gland ducts Sebum Oily material Contains lipids and other ingredients Lubricates and protects the epidermis Inhibits bacteria Seborrheic dermatitis: ̶ inflammation around hyperactive sebaceous gland Cradle Dandruff Acne Cap Sweat Glands Simple coiled tubular glands Produce sweat 2 types: merocrine (eccrine) apocrine Merocrine Sweat Glands Widely distributed on body surface ̶especially on palms and soles Discharge directly onto skin surface Function: ̶excrete water, salts, and organic compounds ̶cool down the skin ̶flush microorganisms and harmful Apocrine Sweat Glands Axilla, around nipples, and pubic region Misnomer … merocrine gland Discharge onto hair follicles Produce sticky and cloudy secretions acted upon by bacteria intensify its odor Mammary & Ceruminous Glands Mammary glands: compound alveolar glands apocrine glands produce milk Ceruminous glands: simple coiled tubular glands modified apocrine sweat glands produce cerumen (earwax) protect the eardrum Control of Glands Autonomic nervous system controls glands secretion: global control:  works simultaneously over the entire body regional control:  sweating occurs locally e.g., palms Skin & Thermoregulation Main function of sensible perspiration: ̶regulates body temperature ̶works with cardiovascular system Skin plays a major role in controlling body temperature: ̶acts as a radiator ̶removes heat from dermal circulation ̶works by evaporation of sensible perspiration Nails Eponychium Proximal Lunula Nail body Produced in nail nail fold Nail root root: ̶deep epidermal fold near the bone ati e r K n Epidermis Dermis Phalanx Hyponychium Nails & Disease Psoriasis Clubbing Spoon nail (koilonychia) Skin Injuries & Repair Steps of Injury & Repair – Step 1 1 Inflammatory Phase - Bleeding occurs at the site of injury Epidermis - Mast cells in the region trigger an inflammatory response. Dermis Mast cells Steps of Injury & Repair – Step 2 2 Migratory Phase After several hours, - A scab has formed - Cells of the stratum basale migrate along the edges Migrating of the wound. epithelial - Phagocytes remove debris, cells and more of these cells are arriving with the enhanced circulation in Macrophages the area. and fibroblasts - Clotting around the edges of the affected area partially Granulation isolates the region. tissue Steps of Injury & Repair – Step 3 3 Proliferation Phase About a week after the injury, - The scab has been undermined by epidermal cells migrating over the collagen fiber meshwork produced by fibroblast proliferation and activity. - Phagocytic activity Fibroblasts around the site has almost ended, and the fibrin clot is dissolving. Steps of Injury & Repair – Step 4 4 Scarring Phase Normal scar After several weeks, - The scab has been4 shed, and epidermis is complete. - A shallow depression marks the injury site, but fibroblasts in the dermis Scar continue to create scar tissue tissue that will gradually elevate the overlying epidermis. Abnormal Scars Hypertrophic scar Keloid Atrophic scar Stretch marks e.g., healed acne e.g., striae gravidarum Burns & Scalds  Denaturation of cell proteins  Dehydration – protein loss – infection  Degrees: ̶ first degree:  epidermis only ̶ second degree:  epidermis and upper dermis  may include blisters ̶ third degree:  full thickness  ± underlying tissues (fourth degree)  skin grafting is necessary  Dangers of facial burns and burns near joints Rule of Nines To estimate burn damage, surface area is divided into multiples of Effects of Aging Epidermal thinning  numbers of Langerhans cells  vitamin D3 production  glandular activity  blood supply  function of hair follicles  melanocyte activity  of elastic fibers Slower repair rate Integument & Other systems  Thin (4 Summary Epidermis (Epitheliu O layers) m) R Thick (5 layers) Skin Papillary Dermis (CT) Reticular Integumentar y System Sweat Hair Sebaceou Gland s Accessories s Mammar y Nails Cerumino us Differences between thick & thin skin