General pathology
Lec. 6&7
Dr. Ali Zeki
Macroscopical appearance of acute inflammation:
1-Catarrhal inflammation: it is that type of inflammation occur mainly in mucous
membrane and associated with mucosal congestion and edema.ex: the common
cold, and food poisoning.
2-Serous inflammation: inflammation that associated with abundant protein rich
fluid exudate with a relatively low cellular content. examples: inflammation of a
synovial joint, peritonitis.
3-Fibrinous inflammation: it is the inflammation associated with exudation of
large amount of (fibrinogen) plasma protein that lead to formation of fibrin coat
at site of inflammation ex: pericarditis .
4-Suppurative inflammation: It is the inflammation associated with extensive
neutrophils infiltration and pus formation, ex: appendicitis, and empyma of
gallbladder.
5-Membranous inflammation: it is the inflammation of the epithelial surface in
which it become coated by fibrin ,inflammatory cell and desquamated cells ,ex:
grey membrane seen in pharyngitis and laryngitis. in diphtheria.
6-Pseudmembranous inflammation: it is the inflammation that associated with
superficial mucousal ulceration seen pseudomembranous colitis due to
clostridium difficile.
Effects of acute inflammation:
1-Beneficial effects:
 Dilution of chemicals and toxin that produced by bacteria.
 Increase vascular permeability facilitate entry of antibodies to the
extravascular spaces, and that lead to lysis of micro-organisms.
 Transport drugs such as antibiotics to the site where bacteria are
multiplying.
 Fibrin formation from exudates fibrinogen act as a mechanical barrier
limit the bacterial movement and facilitate Phagocytosis.
 Deliver of oxygen and nutrient to the neutrophils that have high metabolic
activity.
 Stimulation of immune response by drainage the fluid that carry antigens
to the lymph nodes.
2- Harmful effect:
 Digestion of normal tissue: enzymes as collagenase and protease may
digest normal tissues resulting in tissue destruction.
 Swelling: in children the swelling of the epiglottis in acute epiglottitis due
to Haemophilus influenzae infection may obstruct the airway resulting in
death.
 Inflammatory swelling is especially serious when it occurs in enclosed
space such as the cranial cavity, thus acute meningitis or cerebral abscess
may raise intracranial pressure to the point where the blood flow into the
brain is impaired resulting in ischemic damage.
 Sever allergic reaction, like asthmatic attack at spring induced by pollen.
Systemic manifestation of acute inflammation:
 Pyrexia:
the neutrophils and macrophages produce compounds known as (endogenous
pyrogens), which act on the hypothalamus to set thermo regulatory mechanism at
a higher temperature.
 Leukocytosis:
neutrophilia occurs in pyogenic infection and tissue destruction, eosinophilia
occur in allergic reaction, and parasitic infections, and lymphocytosis seen in
viral infections, whooping cough and in chronic infections.
 Anemia :
Its either due to blood loss in inflammatory exudates like in ulcerative
colitis, or due to hemolytsis caused by bacterial toxins, and lastly due to bone
marrow suppression.
Out come of acute inflammation.
The out come of acute inflammation depend upon the followings:
1- Type of tissue involved.
2- Amount of tissue destruction.
3- Nature of injurious agents.
The possible outcomes of the acute inflammation are:
A -Resolution:
The term resolution means complete restoration of the tissue to normal after
episode of acute inflammation.
The conditions which favor resolution are:
1- Minimal tissue damage.
2- Occurrence in tissue with good regenerative capacity like (liver),
rather than in tissue can not regenerate like (central nervous system).
3- Rapid destruction of causative agents (phagocytosis of bacteria).
4- Rapid removal of fluid and debris by good local vascular drainage.
Best example for resolution is the lobar pneumonia.
B- Suppuration:
It’s the formation of pus (thick, creamy, yellowish fluid), which is a mixture
of living and dead neutrophils, bacteria, and cellular debris.
Its caused mainly by pyogenic bacteria like, (Staphylococcus aureus, and
Streptococcus pyrogens).
Once the pus begins to accumulate in a tissue, it become surrounded by a
"pyogenic membrane" that composed from new blood vessels and fibroblasts,
such a localized collection of pus called (abscess), for example the boil of the
skin, or the gluteal abscess at the site of I.M. injection.
If the pus accumulated in hollow viscus like (gall bladder), this resulting in
empyema. If the deep seated abscess drain it contain though a tract, this tract
called sinus or fissure.
C- Organization and fibrosis:
Fibrosis and scar formation may result from acute inflammation as followings:
1- If heavy deposit of fibrin are formed during the early stages of
inflammation, they may not be removed completely within a few days
by fibrinolytic enzymes, so fibrin not removed undergoes a process
called (organization), that is ingrowths of new capillary and
fibroblasts (granulation tissue formation). Its common process in
inflammation of synovial membrane of the joint, and the heart valves.
2- If the inflammation cause large mount of tissue damage and death.
3- If the acute inflammation progressed to chronic inflammation.
D- Progression to chronic inflammation:
If the agent causing acute inflammation is not removed, the acute inflammation
may progress to the chronic stage .
Chronic inflammation:
It is a slowly progressing inflammatory process that persists for weeks, months or
years after initial injury.
Differences from acute infection.
1- Chronic inflammation associated with more tissue destruction.
2- The main inflammatory cells are lymphocytes, plasma cells and macrophages.
3- It associated with granulation tissue formation and fibrosis rather than
exudates fluid formation.
Causes of chronic inflammation:
1- Progressive from acute inflammation, like chronic abscess due to inadequate
drainage of the pus, as in abscess of the bone, or associated with inflammation
induced by foreign material like surgical suture, implant, piece of wood, ...
2- Recurrent episodes of acute inflammation and best example for this is chronic
cholecystitis induced by repeated acute cholecystitis that associated with gall
stones, and also in case of osteomyelitis.
3- Primary chronic inflammation (ab initio):
This type of inflammation do not preceded by acute inflammation and this
inflammation seen in the follow conditions:
a- Exposure to potentially toxic, non-degradable substances like Silica, and
Asbestoses.
b- Exposure to certain infectious agents like (T.B., Leprosy, and fungal
infections).
c- In certain diseases that result from immune system abnormality, like
rheumatoid arthritis and Crohn's disease.
Macroscopical appearance of chronic inflammation:
A- Chronic ulcer like chronic peptic ulcer of the stomach.
B- Chronic abscess like in osteomyelitis.
C- Thickening of the wall of hallow viscus by fibrosis like in chronic
cholecystitis.
D- Granulomatous inflammation.
Granulomatous inflammation:
It is a distinctive pattern of inflammation characterized by
aggregation of activated and modified macrophages called epitheliod cells
exhibit vesicular nuclei, and eosinophillic cytoplasm that arranged in small
clusters or nodular collection cuffed by rim of lymphocytes, and some times
fibroblasts, this aggregate called granuloma. In T.B. granuloma there is caseous
necrosis formation characterized by soft, whitish, cheese-like material, the T.B.
granuloma also characterized by formation of Langhan's giant cell that arise by
fusion of many macrophages, in which their nuclei arranged at the periphery of
the giant cell giving characteristic horse shoe appearance.
Causes of granulomatous inflammation:
1- T.B., 2- Syphilis, 3- Leprosy, 4- fungal infection, 5- Sarcoidosis, and 6
reaction to foreign bodies like suture, or any indigestible substances .