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Learning objectives

  • Identify the signs of inflammation and fever and explain why they occur
  • Explain the advantages and risks posed by inflammatory responses

The inflammatory response, or inflammation , is triggered by a cascade of chemical mediators and cellular responses that may occur when cells are damaged and stressed or when pathogens successfully breach the physical barriers of the innate immune system. Although inflammation is typically associated with negative consequences of injury or disease, it is a necessary process insofar as it allows for recruitment of the cellular defenses needed to eliminate pathogens, remove damaged and dead cells, and initiate repair mechanisms. Excessive inflammation, however, can result in local tissue damage and, in severe cases, may even become deadly.

Acute inflammation

An early, if not immediate, response to tissue injury is acute inflammation . Immediately following an injury, vasoconstriction of blood vessels will occur to minimize blood loss. The amount of vasoconstriction is related to the amount of vascular injury, but it is usually brief. Vasoconstriction is followed by vasodilation and increased vascular permeability, as a direct result of the release of histamine from resident mast cells. Increased blood flow and vascular permeability can dilute toxins and bacterial products at the site of injury or infection. They also contribute to the five observable signs associated with the inflammatory response: erythema (redness), edema (swelling), heat, pain, and altered function. Vasodilation and increased vascular permeability are also associated with an influx of phagocytes at the site of injury and/or infection. This can enhance the inflammatory response because phagocytes may release proinflammatory chemicals when they are activated by cellular distress signals released from damaged cells, by PAMPs , or by opsonins on the surface of pathogens. Activation of the complement system can further enhance the inflammatory response through the production of the anaphylatoxin C5a. [link] illustrates a typical case of acute inflammation at the site of a skin wound.

a) a diagram of a wound in the skin that has let pathogens enter. Mast cells release histamines which signal to cells in the blood stream. B) The cells have left the blood stream; these phagocytes are engulfing the pathogens.
(a) Mast cells detect injury to nearby cells and release histamine, initiating an inflammatory response. (b) Histamine increases blood flow to the wound site, and increased vascular permeability allows fluid, proteins, phagocytes, and other immune cells to enter infected tissue. These events result in the swelling and reddening of the injured site, and the increased blood flow to the injured site causes it to feel warm. Inflammation is also associated with pain due to these events stimulating nerve pain receptors in the tissue. The interaction of phagocyte PRRs with cellular distress signals and PAMPs and opsonins on the surface of pathogens leads to the release of more proinflammatory chemicals, enhancing the inflammatory response.

During the period of inflammation, the release of bradykinin causes capillaries to remain dilated, flooding tissues with fluids and leading to edema. Increasing numbers of neutrophils are recruited to the area to fight pathogens. As the fight rages on, pus forms from the accumulation of neutrophils, dead cells, tissue fluids, and lymph. Typically, after a few days, macrophages will help to clear out this pus. Eventually, tissue repair can begin in the wounded area.

Questions & Answers

what is cell
Avi Reply
is unit of life
Kamaluddeen
Ok
mohamed
who is an industrial microbiologist
Cynthia Reply
I want to know the biochemical composition of bacteria
Josh Reply
It contains peptidoglcon, DNA nd RNA
Asiya
bacteriophage disadvantage
Momina Reply
disease due to __________ abnormalities are termed primary immunodeficiencies
Tayee Reply
Some primary immunodeficiencies are due to a defect of a single cellular or humoral component of the immune system.
Prince
Examples of primary immunodeficiencies include: chronic granulomatous disease, X-linked agammaglobulinemia, selective IgA deficiency etc
Prince
thank you
Nana
explain microbial mutation
Emerald
what is mutation
Cynthia Reply
alteration in genetic makeup
UDEME
Hi, I'm new here. I'm Bello Abdul Hakeem from Nigeria.
BELLO Reply
welcome on board
Kamaluddeen
Thanks brother I'm an undergraduate. I hope to study for MBBS.
BELLO
pls guys help me out
Linda
what is limitation of plate
Linda
limitation of plate load test . there are some that should be considered while performing load test which are given below, this test is usually performed on relatively similar plate ,usually 1 or 2 square foot area the reason is that the plate of greater are the economically not feasible
yemi
iam new here my name shafiu umar from Nigeria
Shafiu
thanks shafiu
gambo
how to differentiate Gram positive from Gram negative bacteria?
Faheem
by the cell membrane
Tim
with gram staining which has 4 steps
Freedom
Mechanism of bacterial pathogenicity
rashida Reply
Toxicity
Ibrahim
write a short note on Algea
najaatu Reply
green minutes plants organisms that are produced in turf.
Prince
Algae is a kind of a photosynthetic organism, which is usually grown in the moist areas. These are usually the simple plants that grow near to the water bodies. It contains a kind of chlorophyll pigments that act as a primary coloring agent.
Avi
they are eukaryotic and most lived in fresh water. they are photosynthetic that's, they contain chlorophyll and store starch in discrete chloroplast.
Prince
are bacteria important to man
just Reply
yes, depending on the type of bacteria .eg the normal florals, the latic acid batteries etc are important to man
Lois
I mean latic acid bacterial
Lois
I don't understand this topic
Jane Reply
what topic is that
Rose
sahi kon hai bhosri ke
saurabh Reply
define metabolism of carbohydrates with example
Thavasi Reply
what is sterilization a
Sani
the process of keep equipment free from bacteria
shar
is it only bacteria?
Lois
no undesirable fungi and contamination also.
Khushbu
what is streak plate method
Offikwu
what is the biofilm
Dimingu
metabolism is the sum of all the biochemical reaction required for energy generation and use of that energy to synthesize cell materials from small molecules in environment.
Alex
boclenia
Pooja
what are granulocytes
Shawnitta Reply
e.coli
Sukhdeep
granulocytes are type of WBCs which contains granules in the cytoplasm
Owili
what is mutation
Cynthia
it is the interchange of genes from their normal sequence
Esther
is an heritable change of the base-pair sequence of genetic material
Elizabeth
suitable example for prokaryotes
Suvetha Reply
one of the possible early sources of energy was
Suvetha
uv radiation and lighting
Anisha
e coli is the example of prokaryotes
Sukhdeep
archaea too
Noel

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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