A&P Chapter 5 - Lecture notes 6 PDF

Preview

Summary

Biol 2401 with Prof. Vasefi...

Description

Integumentary System: composed of skin & accessory structures: hair, nail, & glands Two major parts of the Integumentary System 1. Cutaneous Membrane (skin) a. Epidermis (superficial layer) (epithelial cell) b. Dermis (connective tissue) i. Papillary and Reticular layer 2. Accessory Structures (hair, glands, and nails) Five Functions of Skin:  protective: physical barrier against pathogen invasion o protects from abrasion, heat & some toxic chemicals o lipids in epidermis retard dehydration o protects from UV radiation (melanin) 





cutaneous sensation: b/c of sensory receptors in skin & hair follicles o tactile sensations: touch, pressure, vibration o thermal sensation: warmth & coolness o pain thermoregulation: 2 mechanisms o sweat secretion: evaporative cooling o adjustment of blood flow to dermal capillaries  dilation of capillaries increases blood flow & heat loss when hot  constriction of capillaries decreases blood flows & heat loss when cold excretion & absorption: o evaporation of water across skin, additional water loss via sweat o small amounts of salts (CO2, ammonia, & urea) excreted along w/t water by skin o some lipid soluble substances can be absorbed through skin

synthesis of vitamin D: o precursor molecule of vitamin D activated by exposure to UV radiation in skin o PM then modified in liver & kidneys to produce calcitriol (form of vitamin D) Hypodermis- separates integument from the deep fascia; areolar and adipose tissue  Not a part of integument  Connects dermis to underlying organs Skin: cutaneous membrane/integument  subcutaneous layer —> hypodermis, connective tissue (adipose), not really skin, underneath Apoptosis: genetically programmed process of cell death Keratinocytes- most abundant epithelial cells; forms several lavers (strata) and contains keratin Dermal Strength and Elasticity  given by collagen and elastic fibers  collagen fibers- strong and resist stretching; but can be bent  elastic fibers- permit stretching and recoil 

Thick Skin Located in hands and feet only 5 layers in epidermis No hair Many sensory receptors Has epidermal ridges

Thin Skin Located everywhere else 4 layers in epidermis Has hair Few receptors No epidermal ridges

Epidermis: superficial layer of skin, keratinized stratified squamous epithelium  Most superficial layers: dead dehydrated cells containing keratin (fibrous protein)  Layers of Epidermis: 4 or 5, from deep to superficial o Stratum Basale: 1 layer of keratinocytes; deepest layer of the epidermis  contains many stem cells that grow new keratinocytes; living cells o Stratum Spinosum: 8-10 layers of cuboidal keratinocytes, bound by desosomes  living cells -keratinocytes start making keratin here,  this is where living cells get pushed up to o stratum granulosum: 3-5 layers of flattened keratinocytes  younger keratinocytes make keratin and produce lamellar granules made of keratohyalin (nonpolar & hydrophobic) which causes cell dehydration & water proofs skin  cells stop dividing  older keratinocytes begin to dehydrate and die via apoptosis o stratum lucidum: 3-5 layers of dead, flattened keratinocytes  provide extra protection only for skin that is constantly abraded by contact o stratum corneum: 25-30 layers of dead, flattened, keratinocytes, thickest layer   

superficial layers shed & replaced by new layers from below protects underlying layers from mechanical abrasion & pathogens keratinization- formation superficial layers of cells, filled with keratin

Dermis: has embedded blood vessels, nerves, glands & hair follicles  Two Types o papillary: superficial, thin compared to reticular region, made of aerolar connective  dermal papillae projects into epidermis, supplying it w/t blood vessels & nerves reticular: deeper layer, thick compared to papillary region  made of dense irregular connective tissue; many collagen & elastic fibers for extra agility & elasticity Epidermal Ridges: increase surface area of epidermis for better grip  reflect center of underlying dermal papillae  forms in Stratum Basale  unique genetically determined epidermal ridge pattern for individuals Cleavage lines- pattern of fiber bundles in skin o

Skin Glands: exocrine glands made of epithelial tissue 4 types of Skin Glands: sebaceous, sudoriferous, ceruminous, mammary glands  Sebaceous Gland: oil glands, release oil into hair follicle o sebum (triglycerides & cholesterol) which prevents dehydration & inhibits bacterial growth  Sudoriferous Gland: sweat glands, release sweat to surface via pore or into hair follicle o regulate body temp. (homeostasis) Ceruminous Gland: modified sweat glands located in external ear, produce waxy secretion o cerumen (earwax)- combined secretions of ceruminous & sebaceous glands in ear  Mammary Gland: active only in females, produce milk Pigments Responsible for Skin Color: melanin, hemoglobin, carotenes  Melanin: group of related compounds, most important pigmentary protein o By melanocytes in epidermis 

migrates to keratinocytes in form of granules accumulates above nucleus to shield nucleolus from UV radiation in sunlight Dark-skin —> melanocytes produce more melanin, but roughly same density of melanocytes Hemoglobin: within red blood cells or capillaries of dermis o shows through if little melanin o red-colored o protein produced by body Carotene: dietary pigment that accumulates in stratum corneum & subcutaneous adipose tissue o orange colored o o o





Hair: distribution of hair differs across body surface  structure: columns of dead keratinized cells held together by extracellular proteins  root penetrates epidermis & dermis  growth for 2 to 5 years Hair Follicle: deep narrow w pit that hair is rooted in consists of  epithelial root sheath: epidermal tissue around hair itself  dermal root sheath: dermal tissue around outside of hair follicle Papilla of Hair: supplies hair follicle w/t blood vessels Arrector Pili: smooth muscle associated w/t follicle, pulls hair upright Root Hair Plexus: neurons sensitive to tactile stimuli Hair bulb- hair production begins at the base of a hair follicle Medulla- core of hair Hair Matrix: layer of epithelial stem cells that make hair  matrix cells come from stratum basale  responsible for growth of existing hair & production of new hair

Hair Color: depends on amount & type of melanin —> keratinocyte cells  melanocytes occur in hair matrix  based on differences in structure and melanocytes  melanin transferred to keratinocytes  white/gray hair results from decrease in melanin production with aging Types of Hair: A. Lanugo  Fine and unpigmented hair  Most shed before birth  3 month of embryonic development B. Vellus hair  “peach fuzz”  Located over much of the body surface C. Terminal hairs  Heavy and more pigmented Nails: made of densely packed keratinocytes  nail matrix responsible for nail growth  protect the exposed dorsal surfaces nail body- visible portion of the nail lateral nail groove- depression on rear side of the nail hynonychium- thickened stratum corneum  dead, compressed cells packed with keratin Four phases in Skin Regeneration: 1. Inflammatory Phase  Bleeding, swelling, redness, and pain occur 2. Migratory Phase  Blood clot (scab) forms on the surface  Consists of insoluble network of fibrin  Granulation tissue- combination of blood clot, fibroblasrs, and an extensive capillary network at the base of a wound 3. Proliferation  Epidermal cells migrating over the collagen fiber meshwork 4. Scarring Phase  Fibroblast in dermis continue to create scar tissue Keloid- thick raised area of scar tissue...