Physiology of Inflammation, Slides of Physiology

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PHYSIOLOGY OF

INFL AMMATION

P H Y S I O L O G Y

WHAT IS INFLAMMATION?

• The body’s response when damage of tissue occurs or when a pathogen damages body tissue
• When tissue damage occurs, mast cells (localised) and basophils (circulating) release a chemical called histamine
• Histamine causes local vasodilation and increases capillary permeability to recruit more leukocytes to the region
• Damaged cells also release chemotactic factors which attract leukocytes to the site of infection
• Inflammation is necessary to allow immune cells to access damaged tissue, ITS AN INDICATION OF DEFENCE MECHANISM.
• Increased blood flow causes redness and heat , while increased permeability releases fluids and causes swelling and tenderness
• Inflammation can be either short-term (ACUTE) or long-term (CHRONIC )

CAUSES OF INFLAMMATION

There are several factors which contribute to the cause of inflammation,

such as:

Physical: where heat, cold, radiation or mechanical trauma results in

inflammation.

Chemical: is the exposure to organic and inorganic poisons

Infectious agents: when invasive pathogens like bacteria , viruses

and other toxins such as fungi and parasites result in the cause of

inflammation

Immunological agents: is associated with cell-mediated and antigen-

antibody reactions which lead to inflammation response.

TYPES OF INFLAMMATION

There are two types of inflammation classifications , called acute and

chronic inflammation , which primary depends on the defence capacity of

host and the duration of response.

Acute inflammation: is short-term response to tissue damage , and it can

be caused in result of an infection, physical and chemical agents ,

necrosis and immune reactions. The stages of acute inflammation include ;

• Vasodilation
• Increased vascular permeability
• Movement of white blood cells

from blood vessels into the soft

tissue to site of inflammation

A TYPICAL CASE OF ACUTE INFLAMMATION

AT THE SITE OF A SKIN WOUND.

Image shows:

• Mast cells – detect injury
• Release histamine
• A inflammatory response is triggered
  • Histamine increases blood flow to wound site (dilute toxins and bacterial products at the site of injury)
  • Increased vascular permeability allows;
  • Fluid, Proteins, Phagocytes, & immune cells to enter infected tissue

CHRONIC INFLAMMATION

prolonged type of inflammation, consists of active inflammation & tissue destruction

and repair. Occurs simultaneously and is caused by recurrent episodes of acute inflammation.

Chronic inflammation is classified into two types called:

Chronic non-specific inflammation: is characterised by non-specific inflammatory cell

infiltration e.g. osteomyelitis. (bone infection)

Chronic granulomatous inflammation: is characterised by the formation of granulomas

such as tuberculosis (bacteria attacking lungs) or syphilis

Cells of chronic inflammation:

Macrophages and lymphocytes are activated to initiate the process of chronic inflammation.

• Activated macrophages - produce proteases , arachidonic acid metabolites and growth factors such as platelets and fibroblasts growth factors.
• Activated lymphocytes - produce fibroblast growth factor , which stimulates fibroblasts to produce collagen , this results in the formation of scaring. They also produce platelets and transforming growth factor-B.

HEALING OF TISSUE

There are two processes involved in tissue healing, where the body prepares to heal and restore damaged tissue to its normal structure.

1. Regeneration - healing occurs by proliferation of parenchymal cells & results in full restoration of original tissue.

2. Repair - healing occurs by proliferation of connective tissue elements which result in fibrosis and scaring.

In wound healing, the combination of healing and repair involves two ways;

Primary initiation healing: is characterised by uninfected, without large amount of tissue & cell loss.

Secondary initiation healing: is characterised by infected open wound with large amount of tissue and cell loss.

STAGES OF WOUND

HEALING

The stages of wound healing include 4

phases:

1 .Hemostasis: (prevent bleeding)

2 .Inflammation: (Defense mechanism)

3 .Proliferation: (Tissue regeneration)

4 .Maturation: (wound recovery)

STAGES OF WOUND HEALING

3. Proliferation: Wound is rebuilt with new tissue formed of collagen &

extracellular matrix.

• A new network of blood vessels is constructed for granulation tissue so it can receive

enough oxygen and nutrients.

• The myofibroblasts enable the wound to contact and grip wound edges to pull them

together.

4. Maturation: Remolding stage, involves collagen remolded from type 3 to type 1

• Initiates wound to fully close.
• Collagen fibers lie closer together and cross-link with another,
• this mechanism reduces scar thickness and makes the area of wounded skin more

firmer and stronger.

REFERENCES

• Junqueiras textbook
• https://teachmesurgery.com/skills/wounds/acute-inflammation/
• https://www.nursingtimes.net/clinical-archive/tissue-viability/wound-

management-1-phases-of-the-wound-healing-process-08-11-2015/

• https://www.karger.com/Article/Fulltext/
• https://www.sciencedirect.com/science/article/abs/pii/S

5X

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805548/
• https://www.britannica.com/science/inflammation