Integument System Flashcards
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;
- Epidermis; superficial layer of stratified squamous epithelium
- 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
- Protection
- Prevention of H2O loss (not totally, some interstitual fluids slowly escape and evaporate in air = transepidermal water loss (TEWL)
- Temp regulation through blood vessels under skin
- Metabolic Regulation (i.e. syn. of vitamin D)
- Immune Defense (immune cells derived from WBC called epidermal dendritic cells)
- Sensory reception (tactile cells = specialised cells that stimulate specific sensory nerve endings)
- 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
Melanocytes
- 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)
- Hemoglobin: blood pigment that binds to oxygen
- Melanin: pigment produced by melanocytes - everyone has same no. (activity and colour of malanin produced differs)
- 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
- Functions;
- 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
FUNCTIONS:
-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
- Protection
- Heat retention
- Facial expression
- Sensory reception
- Visual identification
- Chemical signal dispersal
2 most common types of skin exocrine glands
- Sweat glands: produce watery solution (merocrine = water soln. at skin surface; apocrin = viscous cloudy secretion at hair surface)
- are coiled, tubular glands
- 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 fire/steam chemicals radiation electricity
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)
