Patho Ch 39 Tissue and Wound Healing

an injury that disrupts the normal structure and function of a tissue or organ

wound 

in what ways are wounds classified?

acute or chronic, partial or full thickness

this wound occurs suddenly or over a brief period of time and is typically caused by physical trauma or medical interventions. typically heals in an organized and timely manner

acute wound 

how long does healing occur with acute wounds?

4-6 weeks

in the instance of an acute wound, upon healing what occurs?

structural and functional integrity are restored

this wound occurs over a relatively long period of time. it does not heal properly and is in a prolonged state of inflammation — it also does not heal in a organized and timely manner. 

chronic wound 

chronic wounds result in some degree of?

structural and functional impairment

a wound in which damage extends through the epidermis while all or a portion of the dermis remains intact

partial thickness wound

partial thickness wounds are primarily replaced by epithelial cells that migrate to the area and replicate by mitosis — this process is known as?

reepithelialization

a wound in which damage extends through the epidermis and the entire thickness of the dermis, with possible extension into subcutaneous tissue, muscle, and bone

• repair is complex and results in considerable scar formation

full thickness wound 

name the four phases of wound healing (tissue repair)

hemostasis, inflammation, proliferation/granulation, remodeling/maturation 

wound healing phases are directed by cells that release what to regulate the healing process?

chemical mediators

cells that release chemical mediators during the healing process include..?

neutrophils, macrophages, lymphocytes, platelets, keratinocytes, fibroblasts, endothelial cells 

chemical mediators include what two things?

growth factors and cytokines

substances secreted by cells that help cells communicate with each other and coordinate the healing process

cytokines

the following are considered to be what? —

1. lifestyle risk factors

2. environmental risk factors

3. nutritional deficits

4. inadequate hydration

5. immobility

6. chronic disease

7. inadequate perfusion to distal extremities

local and systemic factors affecting wound healing

the skin is considered to be what in the body?

the largest organ

how many pounds is the skin? (4-5 kg)

9-11 lbs

how much of the total body weight is skin?

7%

functions of the skin: the skin serves as a?

waterproof barrier and first line of defense

functions of the skin: the skin minimizes?

excessive water loss

functions of the skin: the skin maintains effective?

thermoregulation

functions of the skin: the skin contains what in regards to touch, pain, and temperature?

somatic sense receptors

functions of the skin: when exposed to uv light the skin helps?

metabolize and activate vitamin D

skin in different body areas varies in?

thickness, pigment, distribution

normal thickness of the skin varies from?

1.5-4.0 mm

thickness of the skin varies based on function of specific skin region — so, the skin would be thicker in high friction areas such as the?

soles of the feet

what are the two layers of skin separated by the basement membrane?

epidermis and dermis

visible upper layer of skin composed of multiple layers of keratinocytes

epidermis

these cells flatten as they progress toward the skin surface.

keratinocytes

in the deep epidermis keratinocytes are?

columnar or cuboidal

in the epidermis, more towards the surface of the skin, keratinocytes are?

stratified squamous epithelial cells

cells found in the epidermis in much lower numbers — these cells have specialized functions that contribute to homeostasis and repair of the epidermis

melanocytes, t lymphocytes, dendritic and tactile cells 

the epidermis is ____ and so it contains no ____?

avascular, lymphatic vessels

the epidermis is sustained by nutrients from the blood vessels of the dermis — these nutrients diffuse via the?

basement membrane

as keratinocytes migrate to the skin surface, they synthesize large amounts of what water-insoluble protein?

keratin

when keratinocytes reach the surface of the skin, their cytoplasm has been replaced by keratin

• the cells are dry, scaly, and dead

This process is called?

keratinization

keratinization takes how long to occur?

3-5 weeks

keratinization gives the outer epidermis a tough, horny quality that?

protects the basal layer

layer of skin just below the epidermis that is much thicker

• depth varies with age and anatomical location

dermis

functions of the dermis include providing?

most skin strength and nutrients and oxygen from blood vessels

besides the blood vessels that provide nutrients and oxygen to the dermis and epidermis what is another function of the dermis layer?

stores water and electrolytes

skin appendages present in the dermis includes..?

sweat glands, sebaceous glands, hair follicles, nail roots

skin appendages are present in the dermis but derived from the epidermis. these appendages contain?

keratinocyte stem cells 

skin appendages in the dermis have the potential to?

regenerate

skin appendages play a role in the ?

reepithelialization of partial thickness wounds

the dermis contains ______ for pain, touch, and temperature, as well as ________ muscle cells?

sensory receptors, smooth and skeletal

the dermis is made of two layers: (superficial, deep)

papillary, reticular

the boundary between the epidermis and dermis; a basement membrane zone (DEJ)

dermal-epidermal junction

the DEJ underlies?

the basal layer of keratinocytes

the DEJ separates the epidermis from the dermis and: ..?

binds the layers together, minimizes slippage and separation

the DEJ acts as a barrier against what coming into the body?

chemicals and pathogens

the DEJ acts as a barrier against what leaving the body?

water and electrolytes

the DEJ provides a framework on which regenerating cells can?

migrate and restore tissue

combination of substances essential for tissue growth and wound healing; a ground substance (ECM)

• most dermal cells attach to this and spread over it to proliferate and survive

extracellular matrix 

the ECM is primarily secreted by?

fibroblasts

the ECM provides a framework that promotes structural integrity of the body. part of this involves helping the body withstand?

compressive forces 

the ECM framework promotes structural integrity of the body by acting as a scaffold for?

cell adhesion and migration

ECM adds what to the skin?

strength, elasticity, and compressibility 

the ECM provides a medium for rapid diffusion of various substances between blood and tissue cells including..?

nutrients, metabolites, chemical mediators, hormones

three classes of substances make up the ECM including?

fibrous structural proteins, adhesive glycoproteins, polysaccharide chains

fibrous structural proteins of the ECM — the most abundant protein in the human body and in the ECM

• about 16 types

collagen

the extracellular matrix is composed of three types of collagen including types?

1,3,5

cross-linking collagen chains provide?

strength and stability

hydration in the dermis is maintained by?

collagen’s water-binding capabilities

elastin is the primary structural component of elastic fibers in connective tissues like the?

skin, lungs, blood vessels

molecules synthesized by fibroblasts and smooth muscle cells of blood vessels

• loosely arranged in all directions

• can coil and recoil like a spring

elastin

elastic fibers calcify with age causing?

elasticity of skin to deteriorate

elastic fibers are absent from?

scar and fibrotic tissue

adhesive glycoproteins of the ECM:

polysaccharides that are highly polar and attract water to the ECM; influx of water determines dermal volume and compressibility 

• glycosaminoglycans

GAGs

adhesive glycoproteins of the ECM:

a type of GAG abundant in the ECM; produced in large amounts during wound healing

hyaluronic acid

communication is essential for cells to respond to?

internal and external environmental changes

a prominent family of receptors involved in the cell-cell and cell-ECM communication network

integrins

what else is also essential components in cell-cell and cell-ECM communication?

cytokines and growth factor

cytokines and growth factors enable epidermal cells to influence what in cell-cell and cell-ECM communication?

location and structure of ECM

cytokine and growth factors enable the ECM to influence what in cell-cell and cell-ECM communication?

keratinocyte growth, mitosis, proliferation, and apoptosis

uncomplicated wound healing occurs in three ways including?

primary, secondary, tertiary intention

type of intention of uncomplicated wound healing depends on several factors including?

type of injury, extent of tissue loss, types of cells involved

type of wound healing intention is also dependent on the presence of what factors?

infection, necrosis, or secondary tissue breakdown

healing process is similar in all three intention but varies in what three ways?

amount of granulation tissue, length of healing, amount of scar formation

healing by this intention usually occurs after surgical closure of a wound and may also occur in some nonsurgical wounds — this intention is?

primary

primary intention may also occur in some nonsurgical wounds WITH?

minimal tissue loss and edges that can be approximated or closed

primary intention may also occur in some nonsurgical wounds WITHOUT?

infection or contamination

primary intention closure can be achieved in several ways including?

suture, staple, butterfly closure, fibrin glue

two principal events in primary closure include?

repair and regeneration

formation of new ECM to replace lost ECM

repair

reepithelialization can be referred to as the second principal event in primary closure and is also known as?

regeneration

tissue damage is minimal during primary intention which means what is needed to fill dead space?

little granulation

since tissue damage is minimal in primary intention mitosis and regeneration of epidermal cells is?

rapid

during primary intention epithelium migrates over suture line resulting in?

minimal scarring, restoration of normal tissue

the primary intention process is complete in?

5-21 days

healing by this intention (spontaneous closure) occurs when a full thickness wound heals without a closure attempt

secondary intention

in secondary intention wounds are left open to heal for specific reasons including if?

large amount of exudate is present, wound is infected, necrotic, or contaminated

in secondary intention wounds are left open to heal for specific reasons — this would occur if the size or margins of the injury prevent what?

approximation of wound edges

in secondary intention, what is generated during healing?

large amount of granulation tissue

in secondary intention, what is the primary mechanism interacting with the ECM?

wound contraction by myofibroblasts 

in secondary intention, more CT is needed to fill the wound than in primary intention meaning…?

healing is longer, scar is larger

risk for infection is greater in primary or secondary intention?

secondary

healing by (delayed primary closure) occurs when wound closure is delayed

• this intention is a combination of the other two 

tertiary intention

in tertiary, scarring is _____? than in primary intention but ____? than in secondary intention

greater, less