inflammation II lect 6

General pathology

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, and that lead to iron deficiency anemia, or due to hemolytsis caused by bacterial toxins and lead to hemolytic anemia, and lastly due to bone marrow suppression that caused ablastic anemia..

Out come of acute inflammation:
The outcome 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 .