NEET MDS Lessons
General Pathology
CHRONIC INFLAMMATlON
When the inflammatory reaction instead of subsiding after the acute phase (or without entering an acute phase), persists as a smouldering lesion, it is called chronic inflammation. .
Characteristics
- Predominantly mononuclear response.
- Inflamation.and..repair going on simultaneously.
- Usually results in more prominent-scarring.
Causes:
Chronicity may be due to :
- Defective defence mechanisms.
- Persistence of injurious agent.
(a) Certain organisms resist phagocytosis and destruction e.g tubercle bacillus, fungi
(b) insoluble particulate matter e.g., crystals. fibres suture materials.
(c) Constants supply of causative agent as in autoimmune disease where body reacts against its own tissues.
- Defective healing.
Granulomatous inflammation
It is a type of chronic inflammation characterised by localised collections of histiocytes.
These cells are usually accompanied by lymphocytes, fibroblasts and giant cells also.
Granulomas are characteristically seen in diseases like tuberculosis. syphilis, leprosy, sarcoidosis, fungal infections etc. In some of these, the lesion is morphologically distinct enough to point to the type of underlying disease. These are sometimes called' specific' granulomas. Granulomas can also be elicited by particulate, insoluble foreign material e.g. granuloma, suture granuloma, cholesterol granuloma (organising haemorrhages).
HERPES SIMPLEX
An infection with herpes simplex virus characterized by one or many clusters of small vesicles filled with clear fluid on slightly raised inflammatory bases.
The two types of herpes simplex virus (HSV) are HSV-1 and HSV-2. HSV-1 commonly causes herpes labialis, herpetic stomatitis, and keratitis; HSV-2 usually causes genital herpes, is transmitted primarily by direct (usually sexual) contact with lesions, and results in skin lesions
Primary infection of HSV-1 typically causes a gingivostomatitis, which is most common in infants and young children. Symptoms include irritability, anorexia, fever, gingival inflammation, and painful ulcers of the mouth.
Primary infection of HSV-2 typically occurs on the vulva and vagina or penis in young adults
Herpetic whitlow, a swollen, painful, and erythematous lesion of the distal phalanx, results from inoculation of HSV through a cutaneous break or abrasion and is most common in health care workers.
Monocytosis:
Causes
-Infections causing lymphocytosis, especialy tuberculosis and typhoid.
-Monocytic leukaemia.
-Some auto immune diseases.
Urticaria (hives) refers to the presence of edema within the dermis and itchy elevations of the skin which may relate to either a Type I (MC) or Type III hypersensitivity reaction.
Type III hypersensitivity reaction.
- exaggerated venular permeability MC related to IgE mediated disease and release of histamine from mast cells.
Bacterial endocarditis
Endocarditis is an infection of the endocardium of the heart, most often affecting the heart valves.
A. Acute endocarditis
1. Most commonly caused by Staphylococcus aureus.
2. It occurs most frequently in intravenous drug users, where it usually affects the tricuspid valve.
B. Subacute endocarditis
1. Most commonly caused by less virulent organisms, such as intraoral Streptococcus viridans that can be introduced systemically via dental procedures.
2. Pathogenesis: occurs when a thrombus or vegetation forms on a previously damaged or congenitally abnormal valve. These vegetations contain bacteria and inflammatory cells. Complications can arise if the thrombus embolizes, causing septic infarcts.
Other complications include valvular dysfunction or abscess formation.
3. Symptoms can remain hidden for months.
4. Valves affected (listed most to least common):
a. Mitral valve (most frequent).
b. Aortic valve.
c. Tricuspid (except in IV drug users, where the tricuspid valve is most often affected).
Chemical Mediators In Inflammation
Can be classified as :
A. Neurogenic
Also called the Triple Response of Lewis. It involves neurogenic vasodilatation of arterioles due to antidromic axon reflex arc. The constituents of the response are:
1. arteriolar vasoconstriction followed by
2. arteriolar vasodilatation
3. swelling
B. Chemical
1. Amines: Histamine and 5 hydroxytryptamine. Released from platelets and mast cells.
Actions: Immediate and short lived.
Dilatation of arterioles.
Increased capillary premeability.
Kinins: Bradykinin and kallidin These are present in inactive from and are activated by kinin forming proteases
Actions:
Arteriolar dilatation.
Increased vascular permeability
Pain
Kinin forming proteases Plasmin and Kallikrein. Present as inactive precursors.
Cleavage products of complement C3a und C5a are called anaphylatoxins
Actions:
Histamine release from mast cells
Chemotaxis (also C567 )
Enhance phagocytosis.
Polymorph components
Cationic: proteins which cause
Increased permeability
Histamine release.
Chemotaxis of monocytes
Neutral proteases which:
Cleave C3 and C5 to active form
Convert Kininogen to Kinin
Increase permeability.
Acid proteases which liberate leucokinins
Slow reacting. substance of anaphylaxis: (SRS-A) is a lipid released from mast cell.
Action --Increases vascular permeability
Prostaglandins: E1 + E2 .
Platelets are rich source
Action:
Platelets are a rich source.
Vasodilatation.
Increased permeability.
Pain.
VIII. Miscellaneous: like
Tissue lactic acid.
Bacterial toxins.
Summary
Hepatitis A → ssRNA → Picornavirus → Oral–anal
Hepatitis B → dsDNA → Hepadnavirus → Sexual contact , Blood (needles), Perinatal
Hepatitis C → ssRNA → Flavivirus → Sexual contact , Blood (needles)
Hepatitis D → ssRNA → Deltavirus → Sexual contact, Blood (needles)
Hepatitis E → ssRNA → Calicivirus → Oral–anal