Wound Healing Flashcards by Emily Moseley

Define Parenchyma

Organ specific cells related to function

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Define Stroma

‘Background’ tissue - provides the structure, mechanical and nutritional support to the organ

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Name some functions of epithelia

Protection

Containment of body fluids

Absorption

Secretion

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Name some functions of connective tissue

Mechanical reinforcement

Immune surveillance

Diffusion of nutrients and waste

Cells are not in close contact - embedded in the ECM

Vascularised

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Name some functions of muscle

Specialised for gross movement through cellular contraction

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Name some functions of nervous tissue

Responsible for rapid, long-distance signalling

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Name 2 areas where connective tissue does not have to be vsacularised

Cartilage

Cornea

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What 3 things make up the ECM?

Not the only 3 things in the ECM; lymphocytes, adipose and other cells found there also

Fibrous components - collagen and elastin

GAGs - to support collagen

Proteoglycans - GAGs attached to a core protein

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What determines the properties of a connective tissue?

The composition of the ECM

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Name the 2 types of connective tissue?

Loose connective tissue

Dense irregular connective tissue

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Which type of connective tissue contain numerous cells, has a lose fiber arrangement in a viscous matrix?

Give some examples

Loose connective tissue

Haematopoietic/lymphatic tissue

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What type of connective tissue has a dense woven network of collagen and fibres in a viscous matrix?

Give some examples

Dense irregular connective tissue

Joint capsules
Tendons and ligaments

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Define ‘wound’

Injury or trauma to tissues that results in a disruption of the function and structure of a tissue

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Name the 4 stages of wound healing

Haemostasis

Inflammation

Proliferation

Remodelling

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What happens during the haemostasis stage of wound healing?

How long does this stage last?

Wound closed by clotting (coagulation cascade)

Platelets and fibrin adhere to site

Formation of a thrombus

<24 hours

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What 3 cell types are present in the inflammatory stage of wound healing?

What do they do?

How long does this stage last?

Platelets - control bleeding

Macrophages - prevent infection

Neutrophils - inflammation

0-4 days

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What happens during the proliferative phase of wound healing?

How long does this stage last?

Angiogenesis

Epithelialisation

Contraction

Fibrous tissue formation

1-14 days

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What happens during the remodelling phase of wound healing?

How long does this stage last?

Maturation of cells

Collagen remodelling and realignment

Day 21 - years

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Name the 2 types of tissue repair

Regeneration

Scar formation

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Define tissue repair

The restoration of the structure and function of a tissue

What 3 molecules are present in the regeneration of tissue?

Platelet-derived growth factor (PDGF)

Vascular endothelial growth factor (VEGF)

Transforming growth factor-beta (TGF-B)

TGF-B does what at a wound site?

How is it activated?

Lays down new collagen
-by converting fibroblasts into myofibroblasts

Activated by macrophages

Give a brief description of labile tissues with some examples

Continuously proliferating to replace dead/sloughed off cells

Skin, GI tract, salivary gland tissues

Give a brief description of stable tissues with some examples

Cells that normally exist in a non-dividing state, but can enter the cell cycle in response to injury

Normally not full regeneration, just compensatory growth

Parenchymal liver cells, kidney, pancreas

Give a brief description of permanent tissues with some examples

Non-dividing cells that lead to scar formation if damaged Cardiac and skeletal tissue

What are growth factors?

Proteins that stimulate proliferation, migration, and differentiation of cells Stimulate the entry of cells into the cell cycle

Which cells produce growth factors?

Macrophages Lymphocytes As part of the inflammatory process

What is the role of the ECM in regeneration?

Stores and presents growth factors Acts as a scaffold for migrating cells to adhere to

What happens in scar formation?

Replacement of damaged parenchymal cells with connective tissue Incomplete restoration of architecture and function

Where does scar formation occur?

Severe/chronic injuries that result in damage to parenchymal cells and connective tissue Permanent non-dividing tissues

Which growth factor stimulates angiogenesis?

VEGF

How does angiogenesis occur?

Sprouting of new vessels from existing ones Involves endothelial cell proliferation an migration

Describe the formation of granulation tissue

Migration and proliferation of fibroblasts to the site of injury Deposition of ECM proteins produced by these cells Derived from growth factors - TGF-B

What is involved in the degradation of collagens and other ECM components during the remodelling phase of wound healing?

Matrix metalloproteinases (MMPs)

Depending on the nature and size of the wound, the healing of skin wounds occurs by:

First intention (primary union) Second intention (secondary union)

When does wound healing by first intention occur?

Healing of a clean, uninfected surgical incision Epithelial regeneration is the principle mechanism of repair

Outline the 6 stages of wound healing

1. Incisional space fills with fibrin-clotted blood 2. Neutrophils migrate from the incision margin to the fibrin clot 3. Epithelial cells migrate and proliferate along the dermis 4. Neutrophils have been replaced macrophages. Angiogenesis in full swing. Granulation tissue begins to invade space 5. Collagen accumulation, fibroblast proliferation 6. Remodelling continues to increase wound tensile strength

When does wound healing occur by second intention?

Large wounds at sites of abscess formation, ulceration, infarction Scar formation is followed by wound contraction - mediated by the action of myofibroblasts

Give some differences between second intention and first intention healing

Second intention: A larger clot or scab Intense inflammation Larger defects that require more granulation tissue Wound contraction

List the 6 stages of fracture healing

Haematoma Granulation tissue Callus formation Woven bone Lamellar bone Remodelling

Describe the haematoma stage of fracture healing

Bleeding from ruptured vessels Inflammatory reaction - phagocytes move to area

Describe the granulation tissue stage of fracture healing

Granulation tissue replaces the haematoma Cell proliferation occurs in response to growth factors/cytokines

Describe the callus stage of fracture healing

Formation of callus (irregular swelling at bone ends) Initially made from fibrocellular material and cartilage

Describe the woven bone stage of fracture healing

Osteoprogenitor cells proliferate and form woven bone

Describe the lamellar bone stage of fracture healing

Woven bone is replaced by mature lamellar bone

Describe the remodelling stage of fracture healing

Osteoclasts and osteoblasts remodel lamellar bone into a form related to function in response to stresses Excessive callus is resorbed

What 6 local factors could affect tissue repair?

Infection Mechanical factors Foreign bodies Size of wound Location of wound Type of wound

What 6 systemic factors could affect tissue repair?

Nutritional status Metabolic status Circulatory status Hormones Age Collagen disorder

Name the 3 complications of tissue repair

Inadequate formation - dehiscence Excessive formation - keloid scars (excessive collagen), proud flesh (excessive granulation tissue) Formation of contracture - fibrosis of connective tissue that prevents normal mobility of the tissue. Myofibroblasts play a role. Severe burns