acute and chronic inflammation Flashcards
Acute Inflammation(AI)
Initial, rapid response: infections/tissue damage
• Within minutes/hours
• Short duration: several hours/ few days
• Exudation of fluid & plasma proteins (oedema)
• Emigration of leukocytes (neutrophils)
• When it fails to clear the stimulus: progress to a protracted phase
of chronic inflammation (CI).
Chronic Inflammation
It is of longer duration
• Associated with more tissue destruction
• Presence of lymphocytes and macrophages
• Proliferation of blood vessels
• Deposition of connective tissue
Cardinal Signs of Inflammation
Rubor (Redness) • Tumor ( Swelling) • Calor (Heat) • Dolor ( Pain) • Functio laesa(Loss of function
Components of Acute & Chronic Inflammation
Blood vessels dilate: slow down blood flow & increase their
permeability
• Characteristics of the endothelium lining change: leukocytes migrate
into the tissues.
• Leukocytes are activated: Ingest & destroy microbes and dead cells
Sequence Of Events of inflammation
Recognition of offending agent by host cells in extravascular tissue • Recruitment of leukocytes and plasma proteins into the tissues • Removal of the stimulus for inflammation • Regulation of the response • Repair of damaged tissue
The acute inflammatory response involves
Vascular changes
b) Cellular events (leukocytes)
Vasodilation
Induced by the action of several mediators:
histamine on vascular smooth muscle
• Earliest manifestations of AI
• First involves the arterioles and then leads to
opening of new capillary beds in the area.
• Increased blood flow: heat & redness
(erythema)
Stasis
Slower blood flow, concentration of red cells in small vessels,
and increased viscosity of the blood.
• Engorgement of small vessels
• Vascular congestion & localized redness
• Neutrophils, accumulate along the vascular endothelium
• Endothelial cells are activated by mediators: express increased
levels of adhesion molecules
exudate
an extravascular fluid that has a high protein
concentration & contains cellular debris
transudate
fluid with low protein content, little or no
cellular material, and low specific gravity
Oedema
an excess of fluid in the interstitial tissue or
serous cavities & can be an exudate or a transudate
Pus
purulent exudate: leukocytes, dead cells & microbes
Recruitment of Leukocytes to sites of infection and injury
In the lumen: margination, rolling, & adhesion to
endothelium.
2. Transmigration across the endothelium (diapedesis)
3. Migration in interstitial tissues toward a chemotactic
stimulus
Diapedesis
Leukocytes insert pseudopods into the interendothelial junctions & squeeze through to assume a position between the endothelial cell & the basement membrane • Traverse the basement membrane & escape into the extravascular space
Serous Inflammation
Exudation of cell poor fluid into spaces created by cell injury or into body cavities lined • Increased vascular permeability) or from the secretions of mesothelial cells • Transudate e.g. Skin blister from a burn
Fibrinous Inflammation
Vascular leaks are large/there is a local pro-coagulant stimulus (e.g. cancer cells) • Fibrinogen leaks & Fibrin is formed • Characteristic of inflammation lining body cavities e.g. pericardium • Lead to scarring - organisation
Purulent (Suppurative) Inflammation
An exudate - neutrophils, liquefied debris of
necrotic cells, and edema fluid(pus).
• Bacterial infection (pyogenic)-staphylococci
• Produced by seeding of pyogenic bacteria
• Acute appendicitis
Ulcers
A local defect of the surface of an organ • Produced by the shedding of inflamed necrotic tissue. • Peptic ulcer • Chronic = Fibroblasts, scarring and inflammatory cells
Outcomes of Acute Inflammation
Complete resolution - little tissue destruction & removal of
microbes
• Healing by scarring, or fibrosis in tissue incapable of
regeneration
• Chronic inflammation- persistence of agent or disturbance
in healing
Substances that initiate & regulate inflammatory reactions
vasoactive amines, lipid products (prostaglandins
and leukotrienes), cytokines (including chemokines), and complement
activation.
Causes of Chronic Inflammation
Persistent infections e.g. Mycobacteria
• Hypersensitivity diseases - excessive activation of immune system/
unregulated immune responses against microbes or common
environmental substances
• Prolonged exposure to potentially toxic agents e.g. silicosis
• Sometimes takes specific pattern - granulomatous reaction
• Fibrosis may dominate the late stages
Granulomatous Inflammation
Collections of activated macrophages(epithelioid cells) • Epithelioid cells & multinucleated giant cells • Foreign body granulomas (talc) • Immune granulomas (cytokines e.g. IL2
Differential of Granulomatous Inflammation
Limited number of conditions that cause it (some life-threatening)
• TB granuloma, referred to as a tubercle
• Leprosy
• Syphilis
• Disease of Unknown aetiology - Sarcoidosis
• Crohn disease
pyrogens
Substances that induce fever
