History, anatomy, and phys of integ (lecture1)

what is the largest organ of the body

skin

what % of body weight does skin make up

15-20%

what are the two true layers of the skin

epidermins and dermis

what sits below the dermis

hypodermis or subcutaneous tissue

what is the epidermis composed of

epithelial tissue

what is the dermis composed of

connective tissue

what are the functions of the skin

protection, sensation, mobility and function, endocrine activity, exocrine activity, immunity, and regulation of temperature.

what does the skin protect against

microogranisms, dehydration, UV light, mechanical damage

what is the endocrine activity of the skin

initiates biomechanical processes involved in vitamin D production

what is the exocrine activity of the skin

release of water, urea, ammonia, sebum, sweat, pheromones, and cytokines.

what type of skin is found on the palms and plantar surface

glabrous skin

what is unique about glabrous skin

it is more firmly attached to the dermis so it can withstand more friction and weight bearing.

what is the rest of the skin on the body called

hairy skin

what is unique about hairy skin

it is more mobile but less able to withstand friction.

what is the outer layer of the skin

the epidermis

does the epidermis receive blood supply

no, it is avascular

how long does it take for the epidermis to be completely renewed

28 days

how many layers are there in the epidermis

5. From top to bottom stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

the top layer (stratum corneum) is composed of

dead keratinocytes. It is the thickest layer of the epidermis.

what types of cells make up the epidermis

keratinocytes, melanocytes, langerhan cells, and merkel discs

how does the epidermis get nutrition

through diffusion

langerhan cells help with

immune response

merkel discs function

light touch sensation

what are the two layers of the dermis

papillary and reticular

what is the papillary layer of the dermis composed of

loosen woven fibers of collagen and elastin in a gelatinous ground substance.

what does the papillary layer of the dermis do

resist shear forces

what is the reticular layer of the dermis composed of

dense, irregularly arranged collagen and elastin fibers.

what does the reticular layer of the dermis help with

structural integrity.

what is located in the epidermis

hair follicle, sebaceous glands, sudoridferous (sweat) glands, nails

what are the cell types of the dermis

fibroblasts (collagen and elastin) and WBCs (macrophages and mast cells)

does the dermis recieve blood supply

yes there is capillary vasculature

what are meissners corpuscles

they are located in the papillae and help to discriminate touch

what are pacinian corpuscles

they are located deep in the dermis and hypodermis and help to sense pressure and stretch

what type of tissue is in the hypodermis

some loose connective tissue and a lot of adipose tissue

what is the function of the hypodermis

it is a transit area for larger neurovascular structures

if the subcutaneous tissue is exposed what type of wound is it

full thickness

if only the epidermis is lost what type of wound is it

superficial wound.

what is an example of a superficial wound

sunburn or erosion

what is a partial thickness wound

when there is loss of the epidermis and part of the dermis

all tissues form what when healing

a scar

how do scars from

from the botton up

what happens in the inflammatory response of healing

blot clot and WBCs

what are the 3 phases of wound healing

inflammation, proliferation, maturation and remodeling

how long does the inflammatory phase typically last

5 days

how long does the proliferative phase last

21 days

how long does the maturation and remodeling phase last

11 months to 2 years

what are the goals of the inflammatory phase

hemostatsis, clot formation, vasoconstriction

clinical signs of inflammation phase

wound and periwound have rubor (pink/red in light skin tone, brown / purple in dark skin tone), edema, increased temp, pain

what is the goal of inflammation

to cleanse the area and set the stage for further healing.

who may need facilitation of the inflammatory response using modalities or serial debridement

patients with malnourishment, immune disorders, high dose corticosteroids, or the elderly

what are the four stages of the proliferative stage

angiogenesis, granulation, wound contraction, re-epithelization

what are clinical signs of the proliferative phase

wound has formation of granulation, silver clear covering = new epithelium, contraction

what is angiogensis phase of proliferation

new capillary buds which looks like tiny red dots in the wound.

what is the goal of angiogenesis phase of proliferation

provide nutrition to the wound, and remove waste products and cellular debris

what is the most important cell of granulation

fibroblasts which produce large amounts of matrix materials (collagen, proteoglycans, and elastin) which migrate along the matirx.

how does granulation of the proliferative phase appear

pink, red, beefy, granular

what is the goal of granulation

to provide the ground work to allow migration of epithelial cells

what is wound contraction

when the wound edges approximate as a result of actin-rich myofibroblasts assisted by fibronecting.

what is the driving force of wound contraction

myofibroblasts

do partial thickness or full thickness wounds require more granulation

full thickness wounds

which wounds contract the fastest

linear wounds

which wounds take the longest to contract

circular wounds

what happens in re-epithelialization

epithelial cells at the wound margin detach, multiply, and migrate

what is migration of epithelial cells dependent on

a friendly environment where the wound is moist, free of debris, has adequate nutrients, there is an absence of infection, and there is adequate immune function.

how long can the maturation / remodeling phase last

upwards of 24 months

what happens during maturation

there is a change in the matrix, stronger collagen is laid down, collagen fiber reorient, and the amount of water and GAGs decrease.

what is the tensile strength of a wound at 1 month post injury

around 40%

what is the tensile strength of a wound at 1 year post injury

around 80%

when is scar mobility essential

1-21 days after wound closure to allow collagen to respond to stress

does a close wound ever fully heal

not really. Can take 2+ years.

what is wound healing by primary intention

with clean, low inflammation, closely approximated wounds requiring minimal contraction and granulation

what are examples of primary intention of wound healing

paper cuts, small cutaneous wounds, surgical incisions

what is healing by secondary intention

when the wound edges cannot be approximated, therefore requiring a granulation tissue matrix. It needs considerable contraction and re-epithelialization.

what are examples of secondary intention wounds

abrasions or uclers

what is healing by tertiary intention

a combination of primary and secondary intent. A delayed primary inclosure that is typically used with contaminated wounds.

what is an example of tertiary intention of healing

surgical closure of surgical wounds and lacerations after cleansing.

dehiscence

the opening of a surgical wound closed by primary intention

why does dehiscence occur

there is insufficient scar formation due to insufficient collagen production or tensile strength.

what are the risk factors for dehiscence

malnutrition, diabetes, steroids, smoking

abscess

localized, encapsulated collection of puss / purulent drainage

fistula

sinus tract that connects two epithelial surfaces or spaces

hypertrophic scar

raised scar that appears red, raised, and fibrous that stays within the margin.

why does hypertrophic scar form

the maturation and remodeling balance is off, there is an overproduction of immature collagen, prolonged inflammatory phase

what is a keloid scar

a raised scar that extends beyond the margins of the original scar

what are factors that affect wound healing

wound characteristics, local factors, systemic factors

acute mechanism of wound

fast, traumatic, external

chronic mechanism of wound

internal and harder to heal

why are wounds harder to heal over bony prominences

skin is thinner and there is less blood supply

what dimensions of a wound are harder to heal

those deeper and circular

what edges are hard to heal

rolled, undermined, peri wound

what are local factors that effect wound healing

circulation, mechanical stress, sensation, edema

what are systemic factors that effect wound healing

age, nutrition, comorbidities, medications, lifestyle behaviors

what is essential in wound healing

nutrition

why is hydration important for nutrition of the wound

it is foundational to the cellular process

why is protein important to the nutrition of the wound

for tissue repair and regenerationation. Helps with oncotic pressure and prevention of edema.

why are carbohydrates important to the nutrition of the wound

for cellular metabolism and to spare the use of protein for energy

why are fats important to the nutrition of the wound

for cell membranes

what comorbidities effect wound healing

obesity, infection, autoimmune disease, cardiac disease, arterial disease, immunosuppressed

what medications effect wound healing

anti-inflammatory steroids, NSAID, anticoagulants, anti-rejection meds, chemo