Science & Technology in Action

12th Edition

Inflammatory Diseases

MSD

The innate immune system is always ready to fight infection while the adaptive (or ‘specific’) immune system is activated when the innate system fails to stop infection. Inflammatory disease can be caused by an autoimmune response in which the body’s immune system attacks normal healthy tissue mistaking it for a pathogen.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Introduction
Inflammation
is a word we are all familiar with, but do we know exactly what it is? It is localized physical condition in which part of the body becomes reddened, swollen, hot, and frequently painful, especially as a reaction to injury or infection. Inflammation is part of innate immunity, i.e. you are born with it ― it is not a ‘learned’ reaction. It is the second line of defence to a ‘threat’, after barriers such as the skin and mucus. All living things have innate immunity but mammals and other vertebrates have developed a greatly advanced system that can attack specific threats and this is called the specific immune system.

One of the major signs that the immune system is active is infl ammation and this occurs as two types: acute and chronic.

Acute inflammation starts rapidly, often within a few minutes of contact, and may occasionally quickly become severe if it is linked to an allergy. For example, a few people are allergic to bee stings which can result in rapid swelling. This swelling can lead to airways being closed especially if the sting is around the face area and can lead to death if not treated immediately.

The signs and symptoms of acute inflammation are only present for a few days or, at most, up to a few weeks. Typical examples we will all have experienced are scratches, nettle stings, aches and pains caused by overly vigorous exercise, or the effects of being hit by a hard object such as a stone or hockey ball.

There are five main signs of acute infl ammation. These occur mainly on the surface ― inflammation of inner organs is hidden from view.

  • Redness - Blood vessels (arterioles) in the affected area dilate (become wider) to increase blood flow. The increased blood flow causes the area to become red due to extra red blood cells in the vicinity.
  • Swelling is caused by an accumulation of tissue fluid. The capillaries become swollen and more permeable, so fluid and blood proteins move into the spaces between cells. This swelling is called oedema
  • Pain: The inflamed area is likely to be painful, due to the release of chemicals that stimulate nerve endings. The swelling pushes against the sensitive nerve endings, which send pain signals to the brain. However, the brain learns to ignore most of them, unless pressure against the nerve endings increases, e.g. when the area is touched or moves. Some inner organs may not produce pain as they have no pain receptors.
  • Heat: the presence of more blood in the affected area makes it feel hot to the touch when compare to unaffected areas.
  • Immobility is caused by oedema and increased sensitivity and can lead to some loss of normal movement and function.

Quiz questions

  1. Only mammals and vertebrates have an innate immune system. false
  2. Inflammation is always associated with pain. false
  3. A high plant diet can reduce the risk of developing cancer. true
  4. NSAIDs relieve pain but also reduce inflammation. true
  5. Ice packs should be left in place for at least 20 minutes after an injury. false
  6. Excess weight has no effect on inflammation of the joints. false
  7. Allergic reactions are less common now due to chemical additives in food. false
  8. Oedema is a swelling caused by excess blood fluid leaking from capillaries. true
  9. A pathogen is any disease causing organism. true
  10. Many autoimmune diseases are triggered by infections. true
  11. Chronic inflammation is short term. false
  12. Mast cells are intermediaries in the inflammatory response. true

Glossary of terms

inflammation
A local reaction when tissue becomes swollen, or infected; usually accompanied by redness
pathogen
a microorganism that is capable of causing disease in a specific host
histamine
a substance produced by the body; it role is complex and seems to facilitate the local response of blood cells to a threa
vertebrate
an animal with a backbone composed of vertebrae
allergy
an excessive biochemical response to something that is not inherently dangerous
autoimmune
autoimmune diseases are those in which the body's defence system attacks the body's own cells
tissue fluid
Liquid that has escaped from blood capillaries and surrounds the cells.
acute inflammation
inflammation that starts suddenly (e.g. due to injury)
chronic inflammation
inflammation that doesn't stop or heal
corticosteroids
naturally occurring hormones that reduce inflammation
dilate
become larger
ImSAID
Immune Selective Anti-inflammatory Derivatives; peptides that have anti-inflammatory properties
innate immunity
immunity that is 'built-in' rather than acquired
irritation
reaction to some unpleasant substance
lactose intolerance
an inability (or decreased ability) to digest lactose (milk sugar)
mammal
vertebrates that feed their young on milk
mast cells
a type of white blood cell that is involved in the immune response
NSAID
Nonsteroidal anti-inflammatory drugs
oedema
swelling due to build up of fluid in tissues
phagocytic white blood cells
white blood cells that ingest bacteria etc.
specific immunity
acquired immunity
topical formulation
a medication that is applied to a particular part of the body