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Flashcards in Integument System Deck (23):

Intro to the Integument

-Fun facts
-2 layers of integument

-Largest organ (7-8% of body weight)
-Can shed up to 18kg of skin in life

Consists of 2 layers;
1. Epidermis; superficial layer of stratified squamous epithelium
2. Dermis; deeper layer of areolar and dense irregular connective tissues
-hypodermis lies under dermis, mostly adipose connective tissue (not part of skin)

eyelid = 0.1 mm
heel = 4.6 mm


7 Functions of the Integument

1. Protection
2. Prevention of H2O loss (not totally, some interstitual fluids slowly escape and evaporate in air = transepidermal water loss (TEWL)
3. Temp regulation through blood vessels under skin
4. Metabolic Regulation (i.e. syn. of vitamin D)
5. Immune Defense (immune cells derived from WBC called epidermal dendritic cells)
6. Sensory reception (tactile cells = specialised cells that stimulate specific sensory nerve endings)
7. Excretion/Secretion: e.g. toxins released through sweat


The Epidermis - characteristics (including tissue classification)

-Is the most superficial layer
-Avascularised - receives nutrients via diffusion
-Keratinized stratified squamous epithelium
-keratin = water insoluble protein
-Has 4 to 5 layers of distinct cell type (depends if referring to thick or thin skin)


Epidermal Strata: Layers from deep to superficial as they grow

-Stratum basale
-Stratum spinosum
-Stratum granulosum
-Stratum lucidem (found only in thick skin)
-Stratum corneum

*first 3 = living, lucidem & corneum = dead


Stratum Basale

-3 cells its composed of

*Is the ONLY layer that undergoes mitosis
-comprises of one layer of cells adjacent to the dermis (sits on top)
Comprised of 3 cells;
-Keratinocytes: most abundant (are stem cells that divide); produce keratin to waterproof the skin; cuboidal in this layer
-Melanocytes: cells w/ long, branched cytoplasmic processes; produce pigment that absorbs UV light to prevent DNA damage
-Tactile cells: few in no. & scattered among cell - involved in senses as in direct contact with nerves



-Main role respond to UV light
-pigment released & taken up by surround cells which helps protect their DNA


Stratum Spinosum

-Has Epidermal dendritic cells (immune cells that help fight infection in epidermis)
-Keratinocytes start becoming even more specialised & more interconnected by junctions (desmosomes)
-There are many layers withing this stratum


Stratum Granulosum

-Consists of 3 to 5 layers of keratinocytes
-Keratinocytes begin producing karatin - cytoplasm starts to fill and organelles start dying off
-cells become thinner and flatter, membranes thicken and become less permeable.
-stables epidermis by creating a waterproof barrier (& karatin begins interlocking between cells)


Stratum Lucidum

-Found only in thick skin (i.e. palms or soles)
-Is a clear layer
-cells appear pale and featureless
-have indistinct boundaries
-keratinocytes in layer are flattened and filled with protein eleidin (intermediate product in process of keratin maturation)
-cells lack organelles; are dead


Stratum Corneum

*is what you see when you look at your skin - the most superficial layer
-20-30 layers of dead, scaly, interlocking keratinized cells called corneocytes
-dead cells anucleate (no nucleus)

-cells remain at corneum for 2 weeks
-total lifespan of cell approx. 4 weeks


Epidermal Variation: Skin Colour (determined by 3 pigments)

1. Hemoglobin: blood pigment that binds to oxygen
2. Melanin: pigment produced by melanocytes - everyone has same no. (activity and colour of malanin produced differs)
3. Carotene: yellow-orange pigment from food that builds up in skin


3 Skin Markings

-Nevus: Localized overgrowth of melanocytes (are harmless) - i.e. moles
-freckles are similar, but they are just an increase in the activity of melanocytes
-Hemangioma: Proliferation of blood vessels (form benign tumor)
-may disappear in childhood (strawberry) or may persist through adulthood (port wine)
-Friction Ridges: folds of epidermis/dermis on fingers, arms, soles and toes for grasping (i.e. fingerprints)


The Dermis - make up of 2 layers of connective tissue

-Lies deep to the epidermis

2 layers of connective tissue;

-Papillary (superficial)
-Reticular (deeper)
-mainly collagen fibres
-contains blood vessels, glands, hair follicles, nail roots, sensory nerve endings & smooth muscle


Papillary Layer in the Dermis

-Directly below stratum basale cells
-dermal papillae & epidermal ridges interlock (increases SA for binding)
-contain capillaries that supply nutrients to avascular epidermal cells)


Reticular Layer of the Dermis

-Forms the majority of the dermis
-Comprised mainly of dense irregular CT w/ large bundles of collagen fibres, blood vessels, glands, hair follicles & nerves
-fibres interwoven into a meshwork that surrounds structures in dermis


Innervation in Dermis

-Nerve fibres are present in dermis
-Tactile receptors (touch)
-Control blood flow
-Control glandular secretion


Blood supply

Epidermis: Avascular
Dermis: contains blood vessels (which assist in body temp control)
-vasoconstriction: narrowing blood vessels to preserve core body temp
-vasodilation: widening blood vessels to release body temp from core into extremities (causes heat loss)


The Hypodermis (Isn't technically part of Integument System)

-AKA subcutaneous layer
-composed of areolar and adipose connective tissues
-protects underlying structures
-stores energy (fat cells)
-Thermal insulation

*drugs often injected into this layer as it has an extensive vascular network (provides rapid drug absorption)


Integumentary Structures (or Accessories) derived from epidermis

-Nails (protective structures on digits that have densely packed cells that are filled w/ parallel fibres of hard keratin
-composed of nail body (flat keratinised cells), nail bed (live epidermal cells under nail body) and Nail root (region hidden by cuticle)
-Hair: columns of keratinocytes growing from follicles deep in dermis (or hypodermis).
-hair bulb: swelling at bottom of follicle - hair growth
-hair root (connected to arrector pili - involuntary smooth muscle responsible for goose bumps)
-hair shaft


Functions of Hair

-Heat retention
-Facial expression
-Sensory reception
-Visual identification
-Chemical signal dispersal


2 most common types of skin exocrine glands

1. Sweat glands: produce watery solution (merocrine = water soln. at skin surface; apocrin = viscous cloudy secretion at hair surface)
-are coiled, tubular glands
2. Sebaceous Glands: produce oily secretions


2 Rarer types of Exocrine Glands

-Ceruminous glands: produce ear wax
-Mammary Glands: produce milk


Burns - cause and tissue involved

-Caused by exposure to; -
excessive heat

Burns differentiated based on level of dermis & subcutaneous tissue involved;
-Superficial = first degree (no scar)
-Deep = second degree (may scar)
-Full thickness = third and fourth degree (scars - singes off nerve ends)