Anatomy and Function of the Integumentary System: Skin, Hair, Nails, and Glands - Prof. Va, Study notes of Physiology

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Chapter 6 Integumentary System  Skin, hair, nails, cutaneous glands  Dermatology: study of integumentary system  most well treated, examined easily, first line of defense, vulnerable Functions  resistance to trauma and infection (keratin and mantle (low pH))  barrier functions: waterproof, protection against UV radiation  vitamin D synthesis: first reaction in process happens in skin  sensation  thermoregulation: regulate internal temp according to the environment  nonverbal communication  transdermal absorption: absorbing patches put on skin  covers almost two square meters  made of epidermis and dermis  epidermis: stratified squamous epithelium keratinized. Dead cell layer on top. No blood vessels, nerve endings.  Dermis: connective tissue.  hypodermis: CT, under dermis  “thick skin”: palms/soles of feet. Sweat glands, no hair. 0.5 mm thickness of epidermis.  “thin skin”: sweat glands, hair, 0.1 mm epidermis Cells of Epidermis  Stem cells (undifferentiated) found in stratum basale  Living keratinocytes actively dividing in stratum spinosum  Dead keratinocytes in stratum corneum o Die off in stratum granulosum  Melanocytes: produce skin pigment (melanin). Only exist in stratum basale.  Tactile (merkel cells): touch receptors  Dendritic cells (langerhans): immune cells of skin Layers of Epidermis  Superficial to deep

1. Stratum corneum: last step of production of Keratin. Help with abrasion. Bacteria protection. Layers constantly flaking off. Generally leave live skin cells too.
2. Stratum lucidum: translucent. Only found in thick skin. Keritinocytes are packed with eledin.
3. Stratum granulosum: appear darker and purple due to accumulation of keratin (keratohyalin granules). Converted into eledin in this layer. Still have cells with nuclei
4. Stratum spinosum: several layers of kerationocytes. Will start to see the production of keratin. Get endridic cell (immune not nervous cell)

5. Stratum basale: stem cells and kerotinocytes. Must constantly replace. Lose nucleus and gain keratin The Dermis  Connective tissue layer beneath the epidermis  Contains: o Reticular fibers o Blood vessels o Sweat glands o Nerve endings/fibers o Hair follicles o Sebaceous glands (oil)  Dermal papillae (dermis contains these) o Like the hills  Epidermal ridges o The valleys  The papillae and ridges create fingerprints  Papillary layers: superficial zone of dermis  Reticular layer: o Deeper and much thicker layer of dermis o Collagen fibers have broken making stretch marks (striae)  Hair follicles and nail roots o Embedded in the dermis o Smooth muscle (piloecrector or arrector muscles) associated with the hair o When muscle is stimulated it pulls on the hair and causes goose bumps Hypodermis  Under the dermis  Subcutaneous tissue  Drugs introduced by injection  Subcutaneous fat (contains more than dermis/epidermis) o Reservoir for energy o Provides insulation o Tends to be thicker in females Skin Color  Three pigments  Melanin o only one produced in the skin o Polymer of tyrosine AA o In order to hook tyrosine together must use enzyme tyrosinase o Black

o Melanocytes in stratum basale and spinosum o Two major forms of melanin:  Eumelanin (brownish/blackish)  Theomelanin (reddish/yellow)  Hemoglobin o Red pigment used in bloods that carries oxygen  Carotene o A yellow pigment comes from veggies in the yellow-orange range o Concentrates the stratum corneum and hypodermis  Skin pigment not based on melanocytes o Amount of melanin o Ratio of melanin to melanocytes o Exposure to the sun to get more melanin  Skin color o Darker skinned people produce more melanin and spread it out o Light skinned people produce less melanin, which surrounds the nucleus o Used as a diagnostic value:  Cyanosis: blueness of skin (code blue= not breathing, respiratory arrest)  Erythema: abnormal redness of skin (cold weather, embarrassment)  Pallor: pale or ashen color (too little blood flow, possible a cut vessel)  Albinism: genetic lack of melanin (defect in tyrosinase (enzyme))  Jaundice: yellowing of skin and sclera (look at whites of eyes of darker people). Excess bilirubin in the skin gets reabsorbed in the blood  Hematoma: bruise. Mass of clotted blood showing through skin  Not problematic unless because of major injury or lack of oxygen Hair and Nails  Hair, nails and cutaneous glands are accessory organ of the skin  Hair and nails are composed of mostly dead, keratinized cells o When you condition cells, the flakey, dead cells lay flat  Pilus: another name for hair (pili is plural version)  Structure of the hair o Hair is divisible into 3 zones along its’ length  Bulb : only where cells divide, living cells  Root : the remainder of the shaft that is under the skin  Shaft : part of hair above epidermis o Medulla: central core, contains soft keratin (only part that does) o Cortex: several layers o Cuticle: like shingles on microscopic level, single layers, part that is “split end”  Figure 6.

 Structure of Hair Follice o Outer connective tissue sheath o Inner epithelial root sheath: right next to outer CT sheath o Dermal papilla: area of dermis that butts up against hair shaft itself. Will have nerve and blood vessels (provide nutrition). Will divide through mitosis. The growth center. o Hair matrix: cells that are dividing, get away from nutrition source and die.  Types of Hair o Three kinds over course of our lives  Lanugo: fine, downy, unpigmented hair that appears on the fetus.. Replaced by vellus?  Vellus: children, woman  Terminal: longer, coarser and usually more heavily pigmented  Eyelashes, pubic hair, hair on head, facial hair.  Will not grow as well as older, appearing thin  Hair color o Due to varying concentration of pigment granules in the cells of the cortex  brown and black hair (eumelanin)  red hair: has eumelanin but higher concentration of pheomelanin  blonde hair: not as much pheomelanin as red, not much eumelanin  grey and white hair: lack of melanin, cortex replaced by absence of melanin or air.  Hair Cycle: consists of three developmental stages o Anagen  The start of a new cell growing in the follicle, pushing out old hair  Formation of the bulge (surround hair and keep there)  After 8 years will pull away and become club hair o Catagen  Degenerative phase o Telogen  1-3 months of resting and shedding o Alopecia: thinning of the hair or baldness. No replacement of terminal hair  Nails o Hyponychium: epidermis of the nail bed under the bed o Eponychium (cuticle): narrow zone of dead skin that commonly… Cutaneous Glands  5 glands  Sudoriferous (sweat) o Merocrine  Eccrine sweat glands

 Most numerous skin glands (palm, sole, forehead)  Simple coiled tubular glands  Myoepithelial cells (water perspiration)  Myo- muscle o Apocrine  Occur in groin, anal region, axilla, areola, bearded area in mature males  Scent glands that respond to stress and sexual stimulation  Develop at puberty  Pheromones  Bromhidrosis: disagreeable body odor produced by bacterial action on fatty acids  Sebaceous o Found all over the body except in thick skin o Sebum: oily section produced by sebaceous glands o Lotions are made of Lanolin: sheep sebum  Ceruminous o Found only in external ear canal o Secretion of cerumen and dead cells that create cerum o Secrete ear wax that protects the ear and helps to kill bacteria  Mammor o Milk producing glands that develop only during pregnancy and lactation o In females it actually produces milk Skin Cancer  Induced by the UV rays of the sun  Most often on the head and neck  Three different types (named from epidermal cells that originate in) o Basal cell carcinoma  Most common type, least dangerous because seldom metastasize  Forms from cells in stratum basale  Starts as a raised shiny bump o Squamous cell carcinoma (stratum squanosum)  Second most common  Arise from keratinocytes from stratum spinosum  Chance of recovery good  Tends to metastasize to lymph nodes  Appear on scalp, start off as scaly smooth bump, also cave in o Malignant melanoma (melanocytes)  Skin cancer that arises from melanocytes: often in a preexisting mole  Metastasizes rapidly; if unresponsive to chemotherapy usually fatal  ABCD Rule for recognizing melanomas

o A symmetry o B order irregularity o C olor: moles tend to have one color (brown to black), melanoma have 2+ color o D iameter: mole smaller in diameter than 6 mm  Burns and Burn Injuries o Leading cause of accidental death o Sunlight/suntan/cooking o Estimating the extent of burns using the rule of Nines  Totals  Body divided into different percentages  Anterior and posterior head and neck 9% (4.5% and 4.5%)  Anterior and posterior upper limbs 18% (4.5% x 4)  Anterior and posterior trunk 36% (18% and 18%)  Perineum 1%  Anterior and posterior lower limb 36% (9% x 4)  No matter what type of burn, tissue dies  Eschar: burn tissue  Debridement: want to remove eschar  people with burns can die from dehydration o Degrees of a Burn  First degree : partial thickness, epidermis  Second degree : partial thickness, all epidermis destroyed and part of dermis  Third degree : full thickness burn: epidermis and all of dermis, sometimes even subcutaneous tissue destroyed. Subcutaneous not very thick so bone, muscle, even organs, may be exposed. Cannot keep hydrated. o Treating  third degree burns require skin grafts due to lack of dermal tissue  eschar (dead tissue in 3rd^ degree burns) must be debrided every 5- days. Good reservoir for infectious bacteria, so must be removed.  graft options:  autograft: skin from another part of a person  isograft: skin from another person (twin)  temporary  homograft (allograft): from unrelated person (cadaver)  heterograft (xenograft): from another species  artificial skin from silicone and collagen o doesn’t always work, but can be grown in labs  inducing stem cells  must suppress immune system: prevent rejection