Acute inflammation Flashcards
What is inflammation?
This is fundamentally a protective response , designed to rid the organism of both the initial cause of cell injury (e.g., microbes, toxins) and the consequences of such
injury (e.g., necrotic cells and tissues).
Without inflammation infections would go unchecked,
wounds would never heal, and injured tissues might remain permanent festering sores.
In the
practice of medicine the importance of inflammation is that it can sometimes be inappropriately
triggered or poorly controlled, and is thus the cause of tissue injury in many disorders.
Inflammation is a complex reaction in tissues that consists mainly of responses of _____________
blood vessels
and leukocytes.
The body’s principal defenders against foreign invaders are ________________
plasma proteins and circulating leukocytes (white blood cells), as well as tissue phagocytes that are derived
from circulating cells.
The presence of proteins and leukocytes in the blood gives them the ability to home to any site where they may be needed.
Because invaders such as microbes and
necrotic cells are typically present in tissues, outside the circulation, it follows that the circulating cells and proteins have to be rapidly recruited to these extravascular sites.
The
inflammatory response coordinates the reactions of vessels, leukocytes, and plasma proteins to
achieve this goal
What triggers the vascular and cellular reactions of inflammation?
The vascular and cellular reactions of inflammation are triggered by soluble factors that are produced by various cells or derived from plasma proteins and are generated or activated in response to the inflammatory stimulus.
Microbes, necrotic cells (whatever the cause of cell
death) and even hypoxia can trigger the elaboration of inflammatory mediators, and thus elicit
inflammation.
Such mediators initiate and amplify the inflammatory response and determine its pattern, severity, and clinical and pathologic manifestations.
Inflammation may be acute or chronic , depending on the:
nature of the stimulus and the
effectiveness of the initial reaction in eliminating the stimulus or the damaged tissues.
Describe acute inflammation.
Acute
inflammation is rapid in onset (typically minu its main characteristics are the exudation of fluid and plasma proteins (edema) and
the emigration of leukocytes, predominantly neutrophils (also called polymorphonuclear
leukocytes). tes) and is of short duration, lasting for hours or a
few days;
When acute inflammation is successful in eliminating the offenders the reaction
subsides, but if the response fails to clear the invaders it can progress to a chronic phase.
What are the main characterisitcs of acute inflammation?
its main characteristics are the:
- exudation of fluid and plasma proteins (edema)
- and the emigration of leukocytes,
- predominantly neutrophils (also called polymorphonuclear leukocytes).
Describe chronic inflammation.
Chronic inflammation may follow acute inflammation or be insidious in onset.
It is of longer
durationandis associated with the presence of lymphocytes and macrophages, theproliferation of blood vessels, fibrosis, and tissue destruction.
When does inflammation terminated?
Inflammation is terminated when the offending agent is eliminated . The reaction resolves
rapidly, because the mediators are broken down and dissipated and the leukocytes have short
life spans in tissues.
In addition, anti-inflammatory mechanisms are activated that serve to
control the response and prevent it from causing excessive damage to the host.
The inflammatory response is closely intertwined with the process of repair .
T or F
True
When does repair begins?
At the same time
as inflammation destroys, dilutes, and walls off the injurious agent, it sets into motion a series of
events that try to heal the damaged tissue.
Repair begins during inflammation but reaches
completion usually after the injurious influence has been neutralized. In the process of repair
the injured tissue is replaced through regeneration of native parenchymal cells, by filling of the
defect with fibrous tissue (scarring) or, most commonly, by a combination of these two
processes
Inflammation may be harmful in some situations .
Mechanisms designed to destroy foreign
invaders and necrotic tissues have an intrinsic ability to injure normal tissues.
When inflammation is inappropriately directed against self tissues or is not adequately controlled, it becomes the cause of injury and disease.
In fact, in clinical medicine, great attention is given to
the damaging consequences of inflammation. Inflammatory reactions underlie common chronic
diseases, such as rheumatoid arthritis, atherosclerosis, and lung fibrosis, as well as lifethreatening
hypersensitivity reactions to insect bites, drugs, and toxins.
For this reason our
pharmacies abound with anti-inflammatory drugs, which ideally would control the harmful
sequelae of inflammation yet not interfere with its beneficial effects.
T or F
Inflammation may contribute to a variety of diseases that are not thought to be primarily due to
abnormal host responses.
TRUE
For instance, chronic inflammation may play a role in
atherosclerosis, type 2 diabetes, degenerative disorders like Alzheimer disease, and cancer. In
recognition of the wide-ranging harmful consequences of inflammation, the lay press has rather
melodramatically referred to it as “the silent killer.”
four cardinal signs of
inflammation:
- rubor (redness)
- , tumor (swelling)
- , calor (heat),
- and dolor (pain).
What is Rubor?
R for R
Redness
What is Tumor?
Obviously its SWELLING
What is calor ?
(heat)
C-heat
What is dolor?
pain
Dolores is PAIN. So never name someone DOLORes
The four cardinal signs
are typically more prominent in___________
acute inflammation than in chronic inflammation.
A fifth clinical
sign, _____________- was added by Rudolf Virchow in the 19th century.
loss of function (functio laesa),
inflammation is not a disease but a nonspecific response that has a salutary effect on its
host.
T or F
True
In 1793 the Scottish surgeon John Hunter noted what is now considered an obvious fact: that inflammation is not a disease but a nonspecific response that has a salutary effect on its
host.
Who discovered phagocytosis?
In the 1880s the Russian biologist Elie Metchnikoff discovered the process of phagocytosis by observing the ingestion of rose thorns by amebocytes of starfish larvae and of
bacteria by mammalian leukocytes.
[3] He concluded that the purpose of inflammation was to
bring phagocytic cells to the injured area to engulf invading bacteria.
This concept was
elegantly satirized by George Bernard Shaw in his play “The Doctor’s Dilemma,” in which one
physician’s cure-all is to “stimulate the phagocytes”! Sir Thomas Lewis, studying the
inflammatory response in skin, established the concept that chemical substances, such as
histamine (produced locally in response to injury), mediate the vascular changes of
inflammation. This fundamental concept underlies the important discoveries of chemical
mediators of inflammation and the use of anti-inflammatory drugs in clinical medicine.
Historical Highlights
97
Acute inflammation is a rapid host response that serves to deliver leukocytes and plasma proteins, such as antibodies, to sites of infection or tissue injury. Acute inflammation has three
major components:
- (1) alterations in vascular caliber that lead to an increase in blood flow ,
- (2) structural changes in the microvasculature that permit plasma proteins and leukocytes to leave the circulation,
- and (3) emigration of the leukocytes from the microcirculation, their accumulation in the focus of injury, and their activation to eliminate the offending agent
FIGURE 2-1 The major local manifestations of acute inflammation, compared to normal.
(1) Vascular dilation and increased blood flow (causing erythema and warmth);
(2) extravasation and extravascular deposition of plasma fluid and proteins (edema);
(3) leukocyte emigration and accumulation in the site of injury.
STIMULI FOR ACUTE INFLAMMATION
Acute inflammatory reactions may be triggered by a variety of stimuli:
- Infections (bacterial, viral, fungal, parasitic)
- Tissue necrosis
- Foreign bodies
- Immune reactions
How do infections cause inflammation?
Infections (bacterial, viral, fungal, parasitic) and microbial toxins are among the most common and medically important causes of inflammation.
Mammals possess many
mechanisms for sensing the presence of microbes.
What is a TLR?
Among the most important receptors
for microbial productsare the family of Toll-like receptors (TLRs), named after the Drosophila protein Toll, and several cytoplasmic receptors,which can detect bacteria,
viruses, and fungi ( Chapter 6 ).
Engagement of these receptors triggers signaling
pathways that stimulate the production of various mediators.
How does tissue necrosis promote inflammation?
Tissue necrosis from any cause, including ischemia (as in a myocardial infarct), trauma,
and physical and chemical injury (e.g., thermal injury, as in burns or frostbite;
irradiation; exposure to some environmental chemicals).
Several molecules released
from necrotic cellsareknown to elicit inflammation
What are the mediators released from necrosis that promote inflammation?
- these include uric acid,
- a purine metabolite;
- adenosine triphosphate,
- the normal energy store;
- a DNA-binding protein of unknown function called HMGB-1; and even DNA when it is released into the cytoplasm
- and not sequestered in nuclei, as it should be normally.
- [4] Hypoxia, which often underlies cell injury, is also itself an inducer of the inflammatory response. This response is mediated largely by a protein called HIF-1α (hypoxia-induced factor-1α), which is produced by cells deprived of oxygen and activates the transcription of many genes involved in inflammation, including vascular endothelial growth factor (VEGF), which increases vascular permeability
All inflammatory reactions share the same basic features, although different stimuli may induce
reactions with some distinctive characteristics. We first describe the typical sequence of events
in acute inflammation, and then the chemical mediators responsible for inflammation and the
morphologic appearance of these reactions.
Why do blood vessels undergo series of changes during inflammation?
In inflammation, blood vessels undergo a series of changes that are designed to maximize the
movement of plasma proteins and circulating cells out of the circulation and into the site of
infection or injury.
what is an exudation?
The escape of fluid, proteins, and blood cells from the vascular system into
the interstitial tissue or body cavities is known as exudation.
What is a transudate?
In contrast, a transudate is a fluid
with low protein content (most of which is albumin), little or no cellular material, and low specific
gravity.
It is essentially an ultrafiltrate of blood plasma that results from osmotic or hydrostatic
imbalance across the vessel wall without an increase in vascular permeability ( Chapter 4 ).
What is an edema?
Edema denotes an excess of fluid in the interstitial tissue or serous cavities; it can be either an
exudate or a transudate.
What is a purulent exudate?
Pus, a purulent exudate, is an inflammatory exudate rich in leukocytes
(mostly neutrophils), the debris of dead cells and, in many cases, microbes
How is a transudate formed?
Formation of transudates and exudates.
B, A transudate is formed when fluid leaks out because of increased hydrostatic pressure or decreased osmotic pressure.
C, An exudate is formed in
inflammation, because vascular permeability increases as a result of increased
interendothelial spaces
What is the normal hydrostatic pressure at arterial end?
A, Normal hydrostatic pressure (blue
arrows) is about 32 mm Hg at the arterial end of a capillary bed
What is the normal hydrostatic pressure at the venous end?
12 mm Hg at the venous
end;
What is the mean colloid osmotic pressure of tissues?
the mean colloid osmotic pressure of tissues is approximately 25 mm Hg (green arrows),
which is equal to the mean capillary pressure.
Therefore, the net flow of fluid across the
vascular bed is almost nil.
The vascular reactions of acute inflammation consist of ________________
changes in the flow of blood and the
permeability of vessels.
Proliferation of blood vessels (angiogenesis) is prominent during repair
and in chronic inflammation; this process is discussed in Chapter 3 .
Changes in Vascular Flow and Caliber
Changes in vascular flow and caliber begin early after injury and consist of the following.
- Vasodilation
- increased permeability of the microvasculature
- vascular congestion
-
stasis develops, blood leukocytes, principally neutrophils, accumulate along the
vascular endothelium.
What is the earliest manifestations of acute inflammation?
Vasodilation is one of the earliest manifestations of acute inflammation.
Is it true that in inflammtion after vasodilation sometimes it
follows a transient constriction of arterioles, lasting a few seconds.
T or F
T
Vasodilation first
involves the : __________
arterioles and then leads to opening of new capillary beds in the area.
Vasodilation results in:
The
result is increased blood flow.
which is the cause of heat and redness (erythema) at the
site of inflammation.
Vasodilation
Vasodilation is induced by the action of several mediators, notably
________ on vascular smooth muscle
histamine and nitric oxide (NO),
What quickly follows vasodilation?
Vasodilation is quickly followed by increased permeability of the microvasculature , with
the outpouring of protein-rich fluid into the extravascular tissues; this process is
described in detail below.
What quickly foillows after vasodilatation?
Vasodilation is quickly followed by increased permeability of the microvasculature , with
the outpouring of protein-rich fluid into the extravascular tissues; this process is
described in detail below.
The loss of fluid and increased vessel diameter lead to :
The loss of fluid and increased vessel diameter lead to slower blood flow, concentration
of red cells in small vessels, and increased viscosity of the blood.
These changes result
in dilation of small vessels that are packed with slowly moving red cells, a condition
termed stasis, which is seen as vascular congestion (producing localized redness) upon
examination of the involved tissue
What is stasis ?
These changes result
in dilation of small vessels that are packed with slowly moving red cells, a condition
termed stasis, which is seen as vascular congestion (producing localized redness) upon
examination of the involved tissue
What happens after stasis develops?
As stasis develops, blood leukocytes, principally neutrophils, accumulate along the
vascular endothelium.
At the same time endothelial cells are activated by mediators produced at sites of infection and tissue damage, and express increased levels of
adhesion molecules.
Leukocytes then adhere to the endothelium, and soon afterward they migrate through the vascular wall into the interstitial tissue, in a sequence that is
described later
A hallmark of acute inflammation is ________________
increased vascular permeability leading to the escape of a protein-rich exudate into the extravascular tissue, causing edema
Several mechanisms are
responsible for the increased vascular permeability
- Contraction of endothelial cells
- Endothelial injury
- Increased transport of fluids and proteins