INFLAMMATION By Dr : Gehan M ohamed Dr. Abdelaty Shawky. Intended Learning outcomes (ILOs):. Understanding the definition of Inflammation. Listing the classification of inflammation. Identifying the pathogenesis of Acute Inflammation.
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Dr: GehanMohamed Dr. AbdelatyShawky
* Definition: Local vascular, lymphatic and cellular reactions of living tissue against an irritant.
*Inflammation is a protective mechanism with the purpose of:
* Nomenclature of inflammation:
Inflammation is designated by adding the suffix “itis” to the English, Latin or Greek name of the organ affected :
* Causes of inflammation:(1) Living Irritants:Bacteria and their toxins, viruses, parasites and fungi. (2) Non Living Irritants: include: (a) Physical irritants: e.g. excess heat, excess cold and radiations. (b) Chemical irritants: e.g. concentrated acids, alkalis, organic and inorganic poisons. (c) Mechanical irritants: e.g. trauma, mechanical friction and foreign bodies. (d) Immunological: e.g. allergic inflammation.
(1) Acute Inflammation:
(2): chronic inflammation:
(3): subacute inflammation:
* Pathogenesis of acute Inflammation:
The acute inflammatory reaction consists of:
I. Local tissue damage. II. Local vascular reactions. III. Chemical mediators .
I. Local tissue damage:
- Occur in this sequence:
1.Transient vasoconstriction of the small arterioles:
2. Vasodilatation of the arterioles, venules and capillaries:
a. Direct action of histamine on the vascular wall. b. Local axon reflex.
3. Slowingof the Blood Stream (Stasis):
a. Increased viscosity of the blood due to formation inflammatory fluid exudates. This is the main cause of stasis.
b. Histamine causes swelling of the vascular endothelium which become sticky and offer mechanical resistance to the blood.
4. Formation of the Inflammatory Exudates:
The intravascular contents (plasma and cells) escape into the interstitial tissue spaces forming the inflammatory exudates which consists of a fluid component and a cellular component (leucocytes).
5. Dilatation of lymphatic vessels:
to accelerate the lymph flow and drains the fluid exudates.
Exudate : microscopy
Exudate rich in fibrin
Q. List the differences between exudate and transudate.
* Mechanism of formation:
1. Increased capillary permeability caused by histamine (the main cause).
2. Increased capillary hydrostatic pressure due to dilatation of the arterioles and increased blood flow.
3. Increased osmotic pressure of the interstitial tissue fluid as the large protein molecules split into smaller ones in the process of tissue necrosis. This acts as a suction force from the capillaries.
- High protein content, 4-8 gm% (the normal interstitial tissue fluid contains 1 gm% protein).
- High fibrinogen content (turbid & clots on standing).
- High specific gravity (above 1018).
- High cellular content (polymorphs & macrophages)
1. It dilutes toxins, chemicals and poisons, so minimizes their effects.
2. Brings antibodies from the blood to the site of inflammation.
3. Supplies nutrition for the cells and carries away waste products.
4. Fibrinogen forms a fibrin network, which acts as a mechanical barrier to the spread of infection and as a bridge for leucocytes to reach the irritant.