Integumentary System Overview PDF

Professor Lindboom-Broberg (LB) Integumentary System Overview Components & Layers Levels of Organization Integumentary System ▪ Skin or integument (covering [Latin]) ▪ Body’s first line of defense against environment ▪ Three major components 1. Cutaneous membrane 2. Accessory structures 3....

Professor Lindboom-Broberg (LB) Integumentary System Overview Components & Layers Levels of Organization Integumentary System ▪ Skin or integument (covering [Latin]) ▪ Body’s first line of defense against environment ▪ Three major components 1. Cutaneous membrane 2. Accessory structures 3. Superficial fascia Integumentary System 1. Cutaneous membrane ▪ Epidermis (epi, above) Keratinized stratified squamous epithelium ▪ Dermis Papillary layer (areolar connective tissue) Reticular layer (dense irregular connective tissue) Integumentary System 2. Accessory structures ▪ Hairs ▪ Nails ▪ Exocrine glands Sebaceous (oil) glands Sweat glands ▪ Sensory receptors and nerve fibers ▪ Arrector pili muscles ▪ Cutaneous plexus (network of blood vessels) Integumentary System Integumentary System 3. Superficial fascia ▪ = Subcutaneous layer ▪ = Hypodermis (hypo, below) ▪ Areolar & adipose tissue ▪ Separates integument from deep fascia  Professor Lindboom-Broberg (LB) Epidermis Layers Cells Skin Color Skin Cancer Epidermis ▪ 4 to 5 layers of cells (strata/stratum) ▪ Primary cell type in epidermis is keratinocyte ▪ Deeper layers of epidermis form epidermal ridges Adjacent to dermal papillae Increase surface area for better attachment Epidermis 1. Stratum basale Basal layer Attached to basement membrane by hemidesmosomes Most cells here are basal cells, stem cells that divide to replace more superficial keratinocytes Melanocytes also reside here – Produce melanin for skin tone Epidermis 2. Stratum spinosum “Spiny layer” Composed of 8–10 layers of keratinocytes bound together by desmosomes Begin keratin production – Water repellant protein Contains dendritic (Langerhans) cells – Part of immune response Only look spiny on histology Epidermis 3. Stratum granulosum (“grainy layer”) Composed of 3–5 layers of keratinocytes – Continue producing keratin – Grow thinner and flatter – Cell membranes thicken and become less permeable Last layer of living keratinocytes Epidermis 4. Stratum lucidum (“clear layer”) Found only in thick skin Separates stratum corneum from underlying layers Flattened, densely packed dead cells filled with keratin Epidermis 5. ​Stratum corneum (cornu, horn) Outermost, protective region with 15–30 layers of keratinized cells (filled with keratin) Dead cells still tightly connected by desmosomes Water resistant, not waterproof – Lose water through insensible perspiration (unable to see or feel) and sensible perspiration (sweat) Epidermis ▪ Thin skin ▪ Thick skin ▪ Covers most of body surface ▪ Found on palms of hands and ▪ Four strata soles of feet Does not contain Stratum ▪ Five strata Lucidum Contains Stratum Lucidum  Professor Lindboom-Broberg (LB) Skin Color Skin Color ▪ Melanin ▪ Brown, yellow-brown, or black pigment ▪ Produced by melanocytes in stratum basale Darker = greater melanin production ▪ Protects skin cell DNA Increases production with UV exposure Skin Color ▪ Blood (hemoglobin) ▪ Red pigment found in red blood cells ▪ Blood flows to through the dermis More blood = red Less blood = pale – Sustained reduction of blood flow decreases available oxygen – From surface view, skin has bluish color (cyanosis) – Most apparent in very thin skin (lips, beneath nails) Skin Color ▪ Jaundice (jaune = yellow [French]) ▪ Yellowing of the whites of the eyes, skin, and mucous membranes ▪ Due to high level of bilirubin Liver converts hemoglobin → bilirubin Bilirubin is mixed to form bile Inability to process heme or blockage causes bilirubin to overflow into the blood and tissues Skin Color ▪ Bruising ▪ Discoloration of the skin due to broken blood vessel underneath the skin ▪ Many colors! Red = O2 bound hemoglobin Blue = Hemoglobin without O2 Purple = mix of red + blue Green, Yellow, Brown = Hemoglobin break down & processing  Skin Color ▪ Carotene ▪ Orange-yellow pigment ▪ Dietary Red, orange, yellow, and green vegetables ▪ α/β-Carotene becomes Vitamin A ▪ Xanthophylls provide color & photosynthesis Responsible for fall leaf colors Grune, T. (2010) β-Carotene is an important vitamin A source for humans. The Journal of Nutrtion. 140(2): 2268S-2285S. Skin Color ▪ Papa Smurf?? ▪ Paul Karason ▪ Took colloidal silver to treat dermatitis on his face, topically & orally This was NOT medically advised Self-medicated ▪ Today Show (2008) ▪ Skin discoloration side effect Silver stored in the skin Epidermal Cancers Epidermal Cancer ▪ Basal cell carcinoma ▪ Most common form of skin cancer ▪ Originates in stratum basale due to mutations caused by overexposure to UV radiation ▪ Virtually no metastasis and most people survive ▪ Malignant melanoma ▪ Extremely dangerous ▪ Cancerous melanocytes grow rapidly and metastasize through lymphatic system ▪ Squamous Cell Carcinoma ▪ Specific to squamous cells, not only cutaneous ▪ Commonly from UV exposure  Professor Lindboom-Broberg (LB) Dermis & Hypodermis Layers Tissues Internal Structures Dermis ▪ Dermis overview ▪ Between the epidermis and hypodermis ▪ Contains two layers 1. Papillary Layer 2. Reticular Layer Dermis 1. Papillary layer ▪ Named for dermal papillae in this region ▪ Deep to epidermal ridges ▪ Composed of areolar tissue ▪ Contains capillaries, lymphatic vessels, and sensory neurons Dermis 2. Reticular layer ▪ Interwoven meshwork of dense irregular connective tissue ▪ Contains… Blood vessels Lymphatic vessels Nerve fibers Accessory organs – Hair follicles – Sweat glands – Oil glands Hypodermis ▪ Subcutaneous layer (superficial fascia) ▪ Separates skin from deeper structures ▪ Dominated by adipose tissue Important energy storage site Includes areolar tissue  Professor Lindboom-Broberg (LB) Fingerprints, Sensory Perception, & Burns Fingerprints ▪ Deeper layers of epidermis form epidermal ridges ▪ Superficial layer of the dermis form dermal papillae ▪ On thick skin, stratum lucidum adds another layer ▪ Creates ridges on the epidermal surface Fingerprints! (Toeprints too) Fingerprints ▪ Fingerprints ▪ Semi-unique pattern on surface of fingertips and toes ▪ Formation Interaction between epidermal ridges & dermal papillae – Based on environment and external pressures in utero – Formed by 6-months in utero ▪ Sweat glands ducts open on ridges When you touch something, small amounts of sweat are left behind ▪ 1 in 64 billion chance of having the same prints as someone else NOT full proof!  Fingerprints ▪ Fingerprints ▪ Pattern of epidermal ridges on surface of fingertips ▪ Pattern that does not change during lifetime ▪ No fingerprints Burns – 2nd degree or worse Adermatoglyphia: SMARCAD1 gene mutation – Unknown process – Lack of fingerprint formation Hoy, A.Q. (15 Sept 2017). Fingerprint Source Identity Lacks Scientific Basis for Legal Certainty. Retrieved from, https://www.aaas.org/news/fingerprint-source- identity-lacks-scientific-basis-legal-certainty  Professor Lindboom-Broberg (LB) Sensory Perception  Professor Lindboom-Broberg (LB) Burns Burns ▪ Result from exposure to heat, friction, radiation, electrical shock, strong chemical agents ▪ Can compromise many essential skin functions ▪ Dehydration ▪ Electrolyte imbalance ▪ Loss of insulation ▪ Infection ▪ Severity depends on: ▪ Depth of penetration Partial Thickness: 1st degree, 2nd degree Full Thickness: 3rd degree ▪ Total area affected Burns ▪ First-degree burn ▪ Extends into epidermis ▪ Example: most sunburns Skin redness results from inflammation ▪ Treatment Cool water Allow time to heal Burns ▪ Second-degree burn ▪ Extends into dermis ▪ Accessory structures not affected ▪ Blistering, pain, and swelling Infection can develop from ruptured blisters Pin prick is painful ▪ Treatment Cool water Sterile dressing Pain meds (as needed) ▪ Healing takes 1–2 weeks Burns ▪ Third-degree burns ▪ Extends into hypodermis ▪ Less painful than second- degree burns Nerves are dead Pin prick is NOT painful ▪ Treatment Debriding / Cleaning Hydration (IV) Antibiotics Skin Graft Burns ▪ Skin grafts ▪ Amount of skin involved Split-thickness graft: Transfer of epidermis and superficial portions of dermis Full-thickness graft: Transfer of epidermis and both layers of dermis ▪ Source of material Autograft: Patient’s own undamaged skin Allograft: Donor tissue (typically frozen skin from a cadaver) Xenograft: Animal skin Burns ▪ Percentage of skin that has been burned ▪ Rule of nines Method of estimating percentage of surface area affected by burns Modified for children (different body proportions)  Professor Lindboom-Broberg (LB) Hair Hair ▪ Hair ▪ Location: Almost everywhere Except palms of hands, sides and soles of feet, sides of fingers and toes, lips, parts of external genitalia ▪ Two types of hair 1. Terminal hairs: Large, coarse, darkly pigmented – Scalp, armpit, pubic region, male facial hair 2. Vellus hairs: Smaller, shorter, delicate – Found on general body surface ▪ Individual hairs produced by a hair follicle Complex structure composed of epithelial and connective tissue that forms a single hair Hair ▪ Hair Follicle ▪ Hair Shaft: Region of the hair beneath the skin surface that is disconnected from follicle wall ▪ Hair Root: Region of hair attached to follicle wall Anchors the hair ▪ Root Hair Plexus: Sensory nerves surrounding the base of the follicle Hair ▪ Hair Follicle ▪ Arrector Pili: Smooth muscle attached to hair follicle Contraction pulls hair erect Increases insulation layer, restricting heat loss ▪ Sebaceous Gland: Produces oil secretions to coat hair and skin surface Hair ▪ Hair Follicle ▪ Hair Bulb: Expanded base of hair follicle where hair growth occurs ▪ Hair Papilla: Connective tissue filled with blood vessels and nerves Surrounded by hair bulb ▪ Hair matrix: Actively dividing basal cells in contact with hair papilla Hair ▪ Hair growth ▪ Hairs grow and shed in a hair growth cycle Active phase – Lasts 2–5 years @ ~0.33 mm/day – Longer for terminal hair than vellus Resting phase – Loses attachment to follicle → club hair → shed – New hair formation begins  Professor Lindboom-Broberg (LB) Exocrine Glands Exocrine Glands of the Skin ▪ Exocrine glands deposit a secretion on the external surface of the body ▪ Sebaceous Glands ▪ Secretion: Sebum (oil) ▪ Sweat (sudoriferous) Glands ▪ Secretion: Sweat Sebaceous Glands ▪ Location Most glands is connected to hair follicles Few are connected to skin surface ▪ Sebum Mixture of triglycerides, cholesterol, proteins, and electrolytes Lubricates skin & hair shaft Antimicrobial ▪ Arrector pili muscle contraction causes sebum release into follicle Sebaceous Glands ▪ Acne ▪ Blocked oil gland in which P. acne bacteria are able to multiply ▪ White head ▪ Blocked oil gland where the oil is covered and has not been oxidized ▪ Black head ▪ Blocked oil gland where the exposed oil has been oxidized Sebaceous Glands ▪ Acne ▪ Blocked oil gland in which P. acne bacteria are able to multiply ▪ Papule ▪ Small, red bump caused by inflamed hair follicle ▪ Pustule ▪ Classic “pimple” ▪ Immune system has begun attacking bacteria ▪ Pus develops from dead white blood cells Sweat Glands ▪ Sweat ▪ Watery secretion ▪ Location: skin surface ▪ Myoepithelial cells (myo-, muscle) ▪ Squeeze gland to discharge secretion ▪ Function to wash epidermal surface ▪ Two types 1. ​Eccrine (Merocrine) sweat glands 2. Apocrine sweat glands Sweat Glands ▪ Eccrine sweat glands ▪ Location: most skin surfaces Not axillae, pubic, or nipples Highest number on palms & soles ▪ Secretion Watery secretions with electrolytes Secreted onto skin surface Merocrine secretion (vesicles) ▪ Function Thermoregulation Excretion Sweat Glands ▪ Apocrine sweat glands ▪ Location: axillae, nipple, and pubic regions Includes mammary glands ▪ Secretion Sticky, cloudy, odorous secretion with complex composition Body odor smell comes from bacteria metabolizing excretions Secreted into hair follicle Merocrine secretion ▪ Strongly influenced by hormones Secretion begins at puberty  Professor Lindboom-Broberg (LB) Nails Nails ▪ Thick sheets of dead, keratinized epidermal cells ▪ Limits distortion of digits under physical stress ▪ Protects exposed dorsal surfaces of tips of fingers and toes Nails  Professor Lindboom-Broberg (LB) Interactions & Changes Integument Changes with Age Integumentary & Endocrine Integument & Digestive / Skeletal ▪ Sunlight ▪ UV radiation hits the skin ▪ Steroid → cholecalciferol (vitamin D3) Stratum spinosum & basale ▪ Liver creates intermediate product ▪ Converted to calcitriol by kidneys ▪ Calcitriol allows calcium and phosphate absorption in small intestine Integument & Digestive / Skeletal ▪ Sources of Vitamin D3 ▪ Naturally from fish, fish oils, and shellfish ▪ From fortified food products Integument & Digestive / Skeletal ▪ Inadequate supply of calcitriol ▪ In children, leads to rickets Flexible, poorly mineralized bones From not enough sunlight or vitamin D3 Bone matrix has insufficient calcium and phosphate Uncommon in United States (vitamin D3 added to milk) ▪ Decreased bone density in elderly Partially from insufficient dietary intake Additionally, skin production of cholecalciferol decreases by 75 percent Increases risk for fractures Slows healing process  Professor Lindboom-Broberg (LB) Integument Injury & Repair Integument Repair ▪ Four phases in skin regeneration 1. Inflammation phase Initial injury causes bleeding and mast cell activation Mast cells stimulate inflammation Produces swelling, redness, heat, and pain Integument Repair ▪ Four phases in skin regeneration 2. Migration phase Several hours later Scab (blood clot) forms at surface Cells of stratum basale divide and migrate along wound edges Macrophages remove debris and pathogens If damage into dermis, granulation tissue is formed – Combination of fibroblasts, blood clot, and capillary network Integument Repair ▪ Four phases in skin regeneration 3. Proliferation phase One week after injury Scab undermined by migrating epidermal cells Phagocytic activity almost complete Blood clot disintegrating Fibroblasts have formed collagen fibers and ground substance Integument Repair ▪ Four phases in skin regeneration 4. Scarring phase Several weeks after injury Scab is shed Epidermis is complete Shallow depression marks injury site Fibroblasts continue to create scar tissue, inflexible, fibrous, noncellular material