768
UNIT 4
Maintenance of the Body
21
sensitizing effects of released prostaglandins and kinins. Aspirin
and some other anti-inflammatory drugs produce their analgesic
(pain-reducing) effects by inhibiting prostaglandin synthesis.
Although edema may seem detrimental, it isn’t. Te surge of
protein-rich fluids into the tissue spaces sweeps foreign material
into lymphatic vessels for processing in the lymph nodes. It also
Inflammatory chemicals also increase the permeability of local
capillaries. Consequently,
exudate
—fluid containing clotting fac-
tors and antibodies—seeps from the blood into the tissue spaces.
Tis exudate causes the local
swelling
, also called edema, that
presses on adjacent nerve endings, contributing to a sensation of
pain
. Pain also results from the release of bacterial toxins, and the
Tissue injury
Release of inflammatory chemicals
(histamine, complement,
kinins, prostaglandins, etc.)
Arterioles
dilate
Increased capillary
permeability
Local hyperemia
(increased blood
flow to area)
Locally increased
temperature increases
metabolic rate of cells
Leaked protein-rich
fluid in tissue spaces
Possible temporary
impairment of
function
Leaked clotting
proteins form interstitial
clots that wall off area
to prevent injury to
surrounding tissue
Temporary fibrin
patch forms
scaffolding for repair
Healing
Capillaries
leak fluid
(exudate formation)
Attract neutrophils,
monocytes, and
lymphocytes to
area (chemotaxis)
Release of leukocytosis-
inducing factor
Leukocytosis
(increased numbers of white
blood cells in bloodstream)
Leukocytes migrate to
injured area
Margination
(leukocytes cling to
capillary walls)
Diapedesis
(leukocytes pass through
capillary walls)
Phagocytosis of pathogens
and dead tissue cells
(by neutrophils, short-term;
by macrophages, long-term)
Area cleared of debris
Pus may form
Heat
Redness
Pain
Swelling
Signs of inflammation
Initial stimulus
Physiological response
Result
Innate defenses
Internal defenses
Figure 21.3
Inflammation: flowchart of events.
The four cardinal signs of acute
inflammation are shown in red boxes, as is impaired function, which in some cases constitutes
a fifth cardinal sign.
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