OS 1- Wound healing (quiz2)

Chemical

unphysiologic pH or tonicity, disrupt protein integrity, cause ischemia or thrombosi

Physical

incision or crushing, extremes of temperature or irradiation, desiccation, obstruction of arterial inflow and venous outflow

Physical or Chemical insults

Traumatic Injuries can be caused by

Wound Repair - Epithelialization

A process wherein injured epithelium has a genetically programmed regenerative ability that allows it to re-establish its integrity through proliferation, migration, and contact inhibition

1. Inflammatory 2. Fibroplastic 3. Remodeling

3 Basic Stages of Wound Healing

1) Stages of Wound Healing: 1.Inflammatory

2) • Vascular

• Cellular

(1)

Begins at the moment tissue injury occurs

• Lasts 3 to 5 days

• Has 2 Phases:

(2)

1. Rubor (Redness) - erythema

2. Tumor (Swelling) - edema

3. Calor (Warmth)

4. Dolor (Pain)

5. Functio Laesa (Loss of Function

Cardinal Signs of Inflammation*

1. Stages of Wound Healing: Inflammatory

2.fibrin

(1)

• aka Lag Phase - no significant gain in wound strength occurs

(2)

- principal material holding the wound together during this stage

Fibrin forms a mesh 🕸️ → Blood clot creates a lattice (net) across the wound.

Fibroblasts arrive 🧫 → They produce:

Ground substance (fills spaces)

Tropocollagen (collagen precursor)

Fibroblasts release fibronectin 🔗 → Acts like glue, helping cells attach and migrate.

More fibroplasia 🌱 → More fibroblasts and new cells grow into the wound.

Fibrin is removed ✂️ → Fibrinolysis breaks down the fibrin mesh because it's no longer needed.

Collagen forms 💪 → Tropocollagen cross-links to become strong collagen fibers.

Stages of Wound Healing: 2. Fibroplastic

Stages of Wound Healing: Remodeling

continues indefinitely

• Wound Maturation

• Previously laid collagen are destroyed and are replaced by new collagen fibers, which are oriented to better resist tensile forces on the wound

• Wound strength increases slowly and never reaches more than 80-85% of the strength of uninjured tissue

Stages of Wound Healing: Remodeling

Collagen fibers are laid in a more efficient orientation = fewer needed

• Excess is removed, which allows the scar to soften

• Less wound metabolism = Less wound vascularity = Less erythema

• Elastin found in normal skin and ligaments is not replaced during wound healing = loss of flexibility in the scarred area

Wound Contraction

-edges of the wound migrate toward each other

-diminishes the size of the wound

-may cause problems for patients with 3rd degree burns and patients with sharply curved lacerations

Foreign Materials

Necrotic Tissue

Ischemia

Tension

Factors that impair wound healing

Foreign Materials

-is everything the host organism's immune system views as "non-self"-includes bacteria, dirt, and suture material- causes 3 basic problems:

1. Bacteria can proliferate and cause infection

2. Non-bacterial foreign materials act as a haven for bacteria 3. Often antigenic and can stimulate a chronic inflammatory reaction that decreases fibroplasia

Necrotic Tissue

- causes 2 problems:

1. Its presence serves as barrier to the ingrowth of reparative cells

2. Serves as protected niche for bacteria -includes blood that collects in a wound (hematoma) = serves as an excellent nutrient source for bacteria

Ischemia

- decreased blood supply to a wound interferes with wound repair by:

1. Leading further tissue necrosis

2. Lessening the delivery of antibodies, WBC and antibiotics to the wound = increasing chances of infection 3. Decreasing delivery of O2 and nutrients for proper healing

1. tight or incorrectly located sutures

2. improperly designed flaps

3. excessive external pressure on a wound

4. internal pressure on a wound (hematoma)

5. systemic hypotension

6. peripheral vascular disease

7. anemia

Ischemia- may be caused by:

Tension

- anything tending to hold wound edges apart

• if sutures are used to pull tissues together forcefully, the tissue encompassed by the sutures will be strangulated, producing ischemia

• if sutures are removed too early , the wound will reopen and heal with excessive scar formation and contraction • if sutures are left in too long , the wound will still tend to spread open during remodelling stage

• and the tract into the epithelium will epithelialize, leaving permanent, disfiguring marks

Primary Intention

-edges of the wound in which there is no tissue loss are placed and stabilized in essentially the same anatomic position they held before injury and are allowed to heal-minimal scar tissue*

-term used to designate wounds in which the edges are closely reapproximated

-more rapid healing, with lower risk of infection, with less scar formation

-i.e. well repaired lacerations or incisions, well-reduced bone fractures

Secondary Intention

-a gap is left between the edges of an incision or laceration or between bone or nerve ends after repair

-tissue loss has occurred in a wound that prevents approximation of wound edges

-requires a large amount of epithelial migration, collagen deposition, contraction and remodeling

-healing is slower, produces more scar tissue compared to primary intention-i.e. extraction sockets, poorly reduced fractures, deep ulcers, large avulsive injuries of any soft tissues

Tertiary Intention

- refer to the healing of wounds through the use of soft tissue grafts to cover large wounds and bridge the gap between wound edges

WBC enters the socket to remove bacteria and begin breakdown of debris (i.e. bone fragments)

Fibroplasia begins with ingrowth of fibroblasts and capillaries

Epithelium migrates down the socket wall until it reaches a level at which it contacts the epithelium from the other side or if it encounters the bed of granulation tissue

Osteoclasts accumulate along the crestal bone

Healing of Extraction Sockets

-large amount of granulation tissue is present inside the socket

-osteoid deposition has begun along the alveolar bone lining in the socket

-in smaller sockets, the epithelium may have become fully intact

Healing of Extraction Sockets

• 2nd week

-process from 2nd week continues

-epithelialization of most sockets complete

-cortical bone continues to be resorbed

-new trabecular bone is laid down across the socket

Healing of Extraction Sockets

• 3rd and 4th week

-cortical bone lining a socket is fully resorbed (loss of distinct Lamina Dura on radiograph)

-as bone fills the socket, the epithelium move toward the crest and eventually becomes level with adjacent crestal gingiva

-only visible remnant : rim of fibrous (scar) tissue that remains on the edentulous ridge

Healing of Extraction Sockets

• 4 to 6 months

Bone Healing

Same as the events that occur in normal wound healing of soft tissue injuries

• Osteogenic cells (osteoblasts) are derived from :

• 1. periosteum

• 2. endosteum and

• 3. circulating pluripotential mesenchymal cells, that lay down osteoid that calcify

• Osteoclasts are derived from monocyte precursor cells, function to resorb necrotic bone and bone that needs to be remodeled

1. Vascularity

2. Immobility

Bone Healing

• 2 factors are important in bone healing:

(1) - blood with normal oxygen content (if compromised, cartilage is formed instead of bone)

(2)- mobility compromises vascularity and favors formation of cartilage or fibrous tissue instead of bone