Inflammation And Wound Healing

INFLAMMATION AND WOUND HEALING

Ms.Happy.BscMIR.2025.

Definition

• Inflammation is dynamic process by which living vascularized tissues reacts to injury.
• Causes
• Physical e.g. trauma, temperature, radiation
• Infection e.g. bacteria, viruses, parasites
• Chemical e.g. acids, organic compounds

Immunological e.g. antigen-antibody

Under normal circumstances inflammation is a protective response, a goal of which is to eliminate the initial cause of injury, however if triggered or directed inappropriately, inflammatory response itself can be harmful and cause tissue and organ destruction.

Cardinal signs of inflammation

• Rubor(redness): dilatation of small blood vessels in damaged area.
• Calor(heat): increased blood flow(hyperemia)
• Tumor(swelling): accumulation of fluid in interstitial space(edema)
• Dolor(pain):distortion of tissue from edema especially pus.

Loss of function: movement hindered

How to name the inflammation

• Using suffix – itis after the name of the organs/site involved
• Eg
• Pancreatitis
• Hepatitis
• Encephalitis
• Meningitis
• Peritonitis
• Myocarditis
• This is not applicable to other organs/sites,eg:-
• Pleurisy- inflammation of the pleura

Pneumonia- inflammation of the lungs

Acute inflammation

• Is a rapid response to injurious stimuli, short acting, minutes to days.
• Pathogenesis of events
• Vascular phase

Tissue injury

Release of chemical for local response (histamine, prostaglandin, bradykinin, leukotriene etc) The immediate response is vasoconstriction, it may last about 3-5 sec, even 5 min depends on severity.

Persistent arteriolar dilatation to increase blood flow in the affected site; leads to heat and redness( erythema)

When the volume of blood increases, it increases intravascular hydrostatic pressure, so fluid from capillaries migrate to the tissue (exudate)

2. Cellular phase

• It is marked by two major events
• Leukocyte (WBC) movement

Plasma or fluid gets discharged from the blood due to increased permeability(migration) The leukocyte in the surface contain integrin protein and endothelial cell of blood capillary consists of selectins( P&E) proteins on their surface.

During the leukocyte rolling on to the endothelial cell, integrin and selectin get activated.

They produce adhesion on the capillary of endothelial cell.

After adhesion, leukocytes move to the extracellular space through the gap in the endothelial cells (emigration)

At the site of injury several mediators get released which attract the leukocytes.( chemotaxis process)

• Phagocytosis
• Engulfment of solid particle or an agent ( cell eating)
• After the engulfment phagocyte release the lysosomes or degrading enzymes.

This process fails to kill bacteria like m.tuberculosis

The steps of the inflammatory response

• can be remembered as the five Rs:
• (1) Recognition of the injurious agent
• (2) Recruitment of leukocytes,
• (3) Removal of the agent,
• (4) Regulation (control) of the response,

(5) Resolution (repair).

SPECIAL TYPES OF INFLAMATION

Catarrhal inflammation- exudative inflammation occurring exclusively on the mucous membranes of respiratory and gastrointestinal tracts and producing watery exudate of serum and mucus.

Hemorrhagic inflammation:-when damage is severe there is rupture of blood vessel where hemorrhage is most striking feature, eg hemorrhagic pneumonia in fatal cases of influenza Suppurative inflammation; production of pus is the main characteristics eg abscess, peritonitis following rupture of appendix

Peritonitis- purulent inflammation

CHRONIC INFLAMMATION

Chronic inflammation is a long term inflammatory response that can last for months or even years.

Its different from acute inflammation, which is the body’s normal response to an injury or infection and resolves over time.

Chronic inflammation occurs when the body continues sending out inflammatory cells and substances, even though there is no infection or injury; persistent immune response.

Two major characteristic features of chronic inflammation

• Ongoing tissue destruction
• Attempt to repaire by fibrosis( with or without cell regeneration)
• May develop soon after an acute reaction

May be insidious in onset

causes

• Persistent infection
• Some organisms may be difficult to be eradicated.
• M. tuberculosis- tuberculosis
• M. leprae-leprosy
• T. pallidum- syphilis
• Fungi

parasites

ii. Persistent indigestible material.

• Endogenous- necrotic bone, necrotic adipose tissue, calcium and uric acid deposits.
• Exogenous- silica, asbestos fibers, suture materials.
• iii. Immune mediated reactions

Autoimmune reactions (Rheumatoid arthritis, Systemic lupus erythromatosus(SLE), Hashimoto’s thyroiditis, Chronic autoimmune gastritis) Organ transplant rejections

Unregulated immune responses ( inflammatory bowel disease e.g. ulcerative colitis)

iv. Hypersensitivity reactions; inappropriate immune response to generally harmless antigen.

• bronchial asthma
• hypersensitivity pneumonitis
• Following acute inflammation; persistent abscess.
• Predominant cell type in
• — acute inflammation; neutrophil

–chronic inflammation; macrophage

Macrophages are a type of wbc of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances.

MACROPHAGE IN CHRONIC INFL.

• Continuous recruitment from blood
• -blood is most important source of macrophage
• -Mediated by: TGF &PDGF
• Proliferation of macrophage at the site of inflammation.

Immobilization of macrophage at the site of inflammation.

• mediated by migration inhibition factor (MIF) secreted by activated T. lymphocytes.

Diseases involving chronic inflammation.

• Autoimmune diseases (e.g. lupus, rheumatoid arthritis)
• Cardiovascular diseases (e.g. heart disease, high blood pressure)
• Several cancers
• Gastrointestinal diseases (e.g., Crohn’s disease, inflammatory bowel disease)

Lung diseases (e.g., asthma, chronic obstructive pulmonary disease)

Management

• Eating an anti-inflammatory diet rich in fruits, vegetables and health fats.
• Regular exercise
• Managing stress
• Avoid smoking and excessive alc consumption.

Taking medications as described by a healthcare professional.

WOUND HEALING

Wound healing is a complex, dynamic process that involves a series of overlapping phases to restore the integrity of damaged tissues. The main phases includes

• hemostasis; this is the immediate response to injury. It involves blood clotting to stop bleeding. Platelets aggregate at the injury site and release factors that initiate the clotting cascade.

Inflammation And Wound Healing

• inflammation; this phase begins shortly after the injury. It’s characterized by the recruitment of immune cells(like neutrophils and macrophages) to the wound site.

These cells clear debris, fight infection and release growth factors that promote healing.

• proliferation; this phase involves the formation of new tissue, key processes include:-

Angiogenesis : formation of new blood vessels to supply oxygen and nutrients to the healing tissue

Fibroplasia: production of collagen by fibroblasts to form the extracellular matrix, providing structural support.

Epithelization: migration and proliferation of epithelial cells to cover the wound surface.

Inflammation And Wound Healing

• Remodeling: this is the final phase, where the newly formed tissues matures and strengthens. Collagen fibers reorganize and the wound contracts. The goal is to restore the tissue’s original structure and function.

Pathological issues in wound healing

Infection: infections can impede healing and lead to further tissue damage.

Ischemia: reduced blood supply can impair the delivery of oxygen and nutrients, hindering healing.

Excessive scarring: overproduction of collagen can lead to hypertrophic scars and keloids.

Delayed healing: factors like diabetes, malnutrition and certain medications can slow down the healing process

Key players

Platelets: clear debris and fight infection in the early stages.

Macrophages: remove debris, release growth factors and regulate the inflammatory response.

• Fibroblasts: produce collagen and other components of the extracellular matrix.
• Endothelial cells: form new blood vessels.

Epithelial cells: cover the wound surface.

Bone healing involves several stages

Inflammation: Starts immediately after the bone is fractured and lasts for several days.

Bone production: Begins when the clotted blood formed by inflammation is replaced with fibrous tissue and cartilage (known as soft callus).

Bone remodeling: The final phase of bone healing, which goes on for several months.

Systemic factors

• Advancing age and general immobility
• Obesity
• Smoking
• Malnutrition
• Deficiency of vitamins and trace elements
• Systemic malignancy and terminal illness
• Shock of any cause
• Chemotherapy and radiotherapy
• Immunosuppressant drugs, corticosteroids, anticoagulants
• Inherited neutrophil disorders, such as leucocyte adhesion deficiency

Impaired macrophage activity