Acute InflammationAcute Inflammation

Faculty of Medicine & Health Sciences

ObjectivesObjectives Describe the range of situations in which an acute

inflammatory reaction can occur List the main steps in the acute inflammatory response Describe the composition of an acute inflammatory

exudate and some of its clinical effects Describe the functions of the components of the acute

inflammatory exudate Describe most likely consequences of acute inflammatory

reaction & its role as starting point for recovery & repair

DefinitionDefinition

What is the acute inflammatory response?

Answer: It is the most common response of the body tissues to an area of nearby damage

What sort of things stimulate What sort of things stimulate the acute inflammatory the acute inflammatory

response?response?

microorganisms (esp bacterial) trauma (eg surgical incision) ischaemic necrosis (“infarction”) radiation damage (eg sunburn) chemical damage (eg acids, alkalis)

What is the purpose of the What is the purpose of the acute inflammatory reaction ?acute inflammatory reaction ?

to destroy or neutralise the damaging agent

to liquefy and remove dead tissue to prepare the damaged area for

healing

How does it do this?How does it do this? by the production of an acute inflammatory

exudate derived from blood components from capillaries adjacent to the damaged areas

the acute inflammatory exudate comprises: fluid fibrin neutrophils, but also a few macrophages and

lymphocytes

How does the exudate work?How does the exudate work?

fluid dilutes any toxins fluid carries nutrients, mediators,

antibodies fibrin - function is speculative NEUTROPHILS - actively phagocytic

of living tissue (eg bacteria), but also necrotic debris

What are the stages in What are the stages in exudate formation ?exudate formation ?

STEP 1 Blood vessels near to damaged tissue

become dilated Blood flow initially increases, then slows

down Axial flow pattern of blood is lost

WHY DOES THIS HAPPEN ?

Vessels dilateVessels dilate

substances released by dead tissue act on blood vessels

Endothelial cells swell & Endothelial cells swell & retract; vessels leak.retract; vessels leak.

water, salts and protein leak out into damaged area an important protein is fibrinogen

Neutrophils marginate & Neutrophils marginate & emigrateemigrate

neutrophils stick to endothelial cells neutrophils migrate through capillary into damaged area.

NEUTROPHIL MARGINATION NEUTROPHIL MARGINATION

HISTOLOGY of margination of neutrophils in a capillary

EXUDATION EXUDATION ….….

HISTOLOGY- fluid, proteins and neutrophils move into area of damage

CLINICAL TYPES OF CLINICAL TYPES OF EXUDATEEXUDATE

SEROUS PURULENT FIBRINOUS FIBRINO-PURULENT

A SEROUS EXUDATEA SEROUS EXUDATE

there is excess fluid accumulation,; here it is in pericardial sac

A PURULENT EXUDATEA PURULENT EXUDATE

a purulent exudate in the meninges

HISTOLOGY OF PURULENT HISTOLOGY OF PURULENT EXUDATEEXUDATE

note the live and dead neutrophils

A FIBRINOUS EXUDATEA FIBRINOUS EXUDATE

note the shaggy exudate on the surface of the pericardium

HISTOLOGY OF FIBRINOUS HISTOLOGY OF FIBRINOUS EXUDATEEXUDATE

note the masses of pink-staining fibrin

Mediators of inflammationMediators of inflammation

Vascular changes Cellular Changes Mediated by a series of mediators of acute

inflammation MUST be studied from a textbook. This knowledge is the basis of understanding the

treatment of inflammatory conditions WILL be examined

•Cell-derived factors•Plasma derived factors•PRIVATE STUDY

WHO WAS CELSUS, AND WHO WAS CELSUS, AND WHO CARES ?WHO CARES ?

his cardinal signs calor dolor rubor tumor

Acute inflammation:clinicalAcute inflammation:clinical Malaise, fever, pain, rapid pulse Neutrophil leukocytosis Elevated ESR Increased acute phase proteins

IL-1 induced e.g. CRP

Acute inflammation:summaryAcute inflammation:summary the most common early tissue response to

tissue damage exudate is derived from local vessels vascular flow and permeability altered neutrophils are the main effector cells activation of endothelium is a key process chemical mediators attract neutrophils into

tissues

Acute inflammation:summaryAcute inflammation:summary Neutrophils kill microorganisms and break

down damaged tissue Neutrophils are short-lived cells Macrophages play a small role The exudate can vary in composition

Purulent, fibrinous, serous

Private StudyPrivate Study

Endothelial activation factors mediating vessel changes neutrophil margination & emigration Phagocytosis mediators of acute inflammation in general