INFLAMMATION

Inflammation is defind as the local response of living tissue to injury due to any agent.

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).

Types of inflammation

Mainly two types: acute and chronic.

1- Acute inflammation:

Short duration [less than 8 hours].

Represent the early body reaction .

The outcome of acute inflammation is either elimination of the noxious stimulus followed by decline of the reaction and repair of the damaged tissue, or persistent injury resulting in chronic inflammation.

2- Chronic inflammation:

Longer duration .

Components of acute and chronic inflammatory responses

ACUTE INFLAMMATION

- Changes which take place usually within first few minutes to several hours afteran injury.

- Most commonly involves by PMNs.

The major local manifestations :

(1) Vascular dilation and increased blood flow (causing erythema and warmth)

(2) extravasation and deposition of plasma fluid and proteins (edema)

(3) leukocyte (mainly neutrophil) emigration and accumulation in the site ofinjury.

Acute Appendicitis Acute inflammation of the appendix not attributable to distinct inflammatory disorder.

Microscopic:

- Neutrophilic exudate may be found throughout the mucosa, submucosa, and muscularis propria.

- At a later stage, a prominent neutrophilic exudate generates a fibrinopurulentreaction over the serosa.

- Subserosal vessels are congested.

- Edema.

- Ulcerated mucosa.

- Debris in the lumen.

Gross:- appearance varies from normal to hemorrhagic and necrotic.- mucosa shows ulceration and hyperemia.- lumen may contain pus and blood or fecalith.- serosa often congested.

Allergic Nasal Polyp

- Due to recurrent attacks of rhinitis (allergic, inflammatory).

- Usually multiple and bi lateral and involve nasal cavity and paranasal sinuses.

Microscopic:

- Respiratory epithelium, often with squamous metaplasia.

- Edematous and loose stroma with hyperplastic mucous glands.

- Inflammatory infiltrate (lymphocytes, plasma cells, eosinophils, neutrophils, mast cells).

CHRONIC INFLAMMATION

- Chronic inflammation is inflammation of prolonged duration (weeks to months to years).

-Characterized by: coexisting inflammation, tissue injury, attempted repair by scarring, and immune response.

- The cellular infiltrate consists of mononuclear cells ( macrophages, lymphocytes, and plasma cells).

Chronic cholecystitis

Chronic inflammation of the gallbladder, typically secondary to gall stones.

Gross :

Variable mucosal appearance (granular, ulcerated, polypoid).

Normal to thickened gallbladder wall.

Microscopic:

- Chronic inflammation (lymphocytes ,plasma cells), with Rokitansky-Aschoff sinuses

- Smooth muscle hypertrophy

- Fibrosis

- Thick-walled blood vessels

GRANULOMATOUS INFLAMMATION

Granulomatous inflammation is a form of chronic inflammation characterized by collections of activated macrophages, often with T lymphocytes, and sometimes associated with central necrosis.

There are two types of granulomas, which differ in their pathogenesis.

- Immune granulomas: are caused by a variety of agents that are capable of inducing a persistent T cell-mediated immune response.

- Foreign body granulomas :are incited by foreign bodies, in the absence of T cell–mediated immune responses.

Tuberculosis(Necrotzinig granulomatous inflammation)

- Due to Mycobacteria tuberculosis.

- Special stain : Ziehl-neelsen.

Caseating granulomas:

Eosinophilic a cellular material (Caseous necrosis) surrounded by a layers of epitheloid macrophages or histiocytes and multinucleated giant cells , followed by lymphocytes, fibroblasts and varying degree of fibrosis .

Foreign Body Reaction

- Granulomatous inflammatory changes due to the presence of foreign /exogenous material.

- Non caseating granulomas consisting of histiocytes, usually epithelioid with central foreign body Multinucleated giant cells.

- Variable amounts of lymphocyte predominant chronic inflammation and reactive fibrosis.

A foreign-body giant cell is a collection of fused macrophages (giant cell) which are generated in response to the presence of a large foreign body. ... This is in contrast to a Langhans giant cell, where the nuclei are arranged on the border.

Tissue Repair

Repair, sometimes called healing, refers to the restoration of tissue architecture and function after an injury.

Repair of damaged tissue occures by two types of reactions:

- Regenerations by proliferation of residual (un-injured ) cells and maturation of tissue stem cells.

- deposition of connective tissue to form a scar.

Granulation tissue

Reddish connective tissue that forms on the surface of a wound when the wound is healing.

Microscopic:

vascular proliferation thin walled capillaries, loose

connective tissue matrix, edema, fibroblasts and

inflammatory cells (macrophages ,lymphocytes

and plasma cells).

Dr. Kinda Aswad