Acute Inflammation

Question 1

What are the causes of acute inflammation?

Answer 1

Foreign bodies
Immune reactions
Infections and microbial toxins
Tissue necrosis
Trauma
Physical and chemical agents (thermal injury, irradiation, environmental chemicals)

Question 2

What are the clinical signs of acute inflammation?

Answer 2

Rubour (redness)
Color (heat)
Tumour (swelling)
Dolor (pain)
Loss of function (enforces rest and reduces chance of further damage)

Question 3

What is acute inflammation?

Answer 3

A rapid response to an injurious agent that aims to deliver mediators of host defence (leukocytes and plasma proteins) to the site of injury without interrupting blood flow to other tissues.

Question 4

What is the first thing that happens during acute inflammation?

Answer 4

Vasodilatation of arterioles.
Brought about by vasoactive mediators e.g. histamine. When arterioles dilate, this increases the flow in capillaries, causing capillary pressure to rise, changing the delivery of fluid and leukocytes to the site of injury.

Question 5

What occurs after vasodilatation?

Answer 5

The walls of the venules of the microcirculation (which have thin walls) become leaky, allowing plasma to escape through tiny gaps between endothelial cells.
This results in an increased haematocrit and increased resistance to blood flow within the venules. The lumens of upstream vessels dilate and blood flow slows down. The increased pressure results in greater exudation of fluid into the tissue spaces, delivering plasma proteins to the site of injury.

Question 6

What is histamine?

Answer 6

Histamine is a key mediator in early inflammation. It is a vasoactive amine (along with serotonin), which are usually the first mediators to appear during inflammation. In acute inflammation, histamine produces pain, arteriolar dilatation and increased permeability of venules.
Fluid leakage occurs as histamine causes endothelial cells to contract and pull apart, creating gaps for plasma proteins to leak out.

Question 7

Why are histamine and serotonin so quickly available in acute inflammation?

Answer 7

Histamine and serotonin are available immediately from preformed supplied, and are already present in cells within the tissue and platelets.
Histamine is stored in the granules of mast cells, basophils and platelets and is released in response to many stimuli, e.g. physical damage, immune reactions and complement components.
Serotonin is stored in the granules of platelets.