Inflammation, ischaemia, normal and abnormal development Flashcards
What is inflammation?
A reaction to injury or infection involving cells such as neutrophils and macrophages.
When is inflammation good?
Infection or injury.
When is inflammation bad?
Autoimmunity or when an over-reaction to a stimulus.
How is inflammation classified?
Acute and Chronic.
What happens in acute inflammation?
Sudden onset
Short duration
Usually resolves
What are the steps in acute inflammation?
Initial reaction of tissue to injury
Vascular component: dilatation of vessels
Exudative component: vascular leakage of protein-rich fluid
Neutrophil polymorph is the characteristic cell recruited to the tissue
Outcome may be resolution, suppuration (e.g. abscess), organisation, or progression to chronic inflammation
What are the causes of acute inflammation?
Microbial infections, e.g. pyogenic bacteria, viruses
Hypersensitivity reactions, e.g. parasites, tubercle bacilli
Physical agents, e.g. trauma, ionising radiation, heat, cold
Chemicals, e.g. corrosives, acids, alkalis, reducing agents,
Bacterial toxins
Tissue necrosis, e.g. ischaemic infarction
What are the essential characteristics of acute inflammation?
Rubor (red due to blood vessels)
Calor (heat due to blood vessels)
Tumor (swelling due to oedema)
Dolor (Pain due to sweeling and stretching, bradykinin, prostaglandin and serotonin also cause pain)
Loss of function is also characteristic.
What happens in chronic inflammation?
Slow onset or sequel to acute
Long duration
May never resolve
What cells are involved in inflammation?
Neutrophil polymorphs
Macrophages
Lymphocytes
Endothelial cells
Fibroblasts
Plasma cells
What are neutrophil polymorphs and what are their function?
Short lived cells
First on the scene of acute inflammation
Cytoplasmic granules full of enzymes that kill bacteria
Usually die at the scene of inflammation
Release chemicals that attract other inflammatory cells such as macrophages
What are macrophages and what are their fuction?
Long lived cells (weeks to months)
Phagocytic properties
Ingest bacteria and debris
May carry debris away
May present antigen to lymphocytes
What are lymphocytes and what are their function?
Long lived cells (years)
Produce chemicals which attract in other inflammatory cells
Immunological memory for past infections and antigens
What are endothelial cells and what happens to them in inflammation?
Line capillary blood vessels in areas of inflammation
Become sticky in areas of inflammation so inflammatory cells adhere to them
Become porous to allow inflammatory cells to pass into tissues
Grow into areas of damage to form new capillary vessels
What are fibroblasts?
Long lived cells
Form collagen in areas of chronic inflammation and repair
What is an example of acute inflammation?
Acute pancreatitis
Empyema of the gall bladder
Fibrinous pleuricy
What is involved with acute pancreatitis?
Unknown precipitating factor
Neutrophils appear
Blood vessels dilate
Inflammation of serosal surface occurs
Pain felt
Appendix either surgically removed or inflammation resolves or appendix bursts with generalised peritonitis and possible death
What is an example of chronic inflammation?
Tuberculosis
What is involved with tuberculosis?
No initial acute inflammation
Mycobacteria ingested by macrophages
Macrophages often fail to kill the mycobacteria
Lymphocytes appear Macrophages appear Fibrosis occurs
What is the difference between an exudate and a transudate?
Exudates have a high protein content due to increased vascular permeability whilst transudates have a low protein content due to a normal vascular permeability.
What is a granuloma?
An aggregate of epithelioiod histiocytes and a feature of some-specific chronic inflammatory disorders.
What is granulation tissue?
Granulation is an important component of healing and comprises small blood vessels in a connective matrix with myofibroblasts (A myofibroblast is a cell that is in between a fibroblast and a smooth muscle cell in phenotype)
What are histiocytes?
Specialised macrophages e.g. Kupffer cells
What is fibrin?
Deposited in blood vessels and tissues or on surfaces as a result of the action of thrombin or fibrinogen.
What does fibrous mean?
Describes the texture of non-mineralised tissue of which the principal component is collagen.
What happens in the early stage of acute inflammation?
In the early stages, oedema fluid, fibrin and neutrophil polymorphs accumulate in the extracellular spaces of the damaged tissue.
The presence of the cellular component, the neutrophil polymorph, is essential for a histological diagnosis of acute inflammation.
What are the three processes of acute inflammation? (In relation to vessels and formation of product)
Changes in vessel calibre and, consequently, flow
Increased vascular permeability and formation of the fluid exudate
Formation of the cellular exudate – emigration of the neutrophil polymorphs into the extravascular space.
How is the cellular exudate formed?
The accumulation of neutrophil polymorphs within the extracellular space is the diagnostic histological feature of acute inflammation.
The stages whereby leucocytes reach the tissues are shown in the next figure.
What do the endogenous chemical mediators cause?
Vasodilatation
Emigration of neutrophils
Chemotaxis
Increased vascular permeability
Itching and pain.
What are the plasma factors?
The plasma contains four enzymatic cascade systems:
Complement
The kinins,
The coagulation factors and the
Fibrinolytic system
which are interrelated and produce various inflammatory mediators.
What are the endogenous chemical mediators of the acute inflammatory response?
What causes vascular dilation?
Histamine
Prostaglandins
PGE2/I2
VIP
Nitric oxide
PAF
What causes increased vascular permeability?
Transient phase – histamine
Prolonged phase – mediators such as bradykinin, nitric oxide, C5a, leucotriene B4 and PAF, potentiated by prostaglandins
What causes adhesion of leukocytes?
Interleukins.
What does the outcome of acute inflammation depend on?
The type of tissue present and the amount of tissue destruction which in turn depend on the nature of the injurious agent.
What are the outcomes of inflammation?
Resolution
Suppuration (Suppuration is the process of pus forming)
Organisation
Progression to chronic inflammation
What does suppuration involve?
Excessive exudate.
What is pyrexia?
Raised body temperature.
What are some systemic effects of inflammation?
Pyrexia
Constitutional symptoms
Weight loss
Reactive hyperplasia of the reticuloendothelial system
Haematological changes
Amyloidosis
How can chronic inflammation take place?
Primary chronic inflammation
Transplant rejection
Progression from acute inflammation
Recurrent episodes of acute inflammation
What are the macroscopic appearances of chronic inflammation?
Chronic ulcer
Chronic abscess cavity
Thickening of the wall of a hollow viscus
Granulomatous inflammation
Fibrosis
What are the microscopic appearances of chronic inflammation?
Lymphocytes plasma cells and macrophages.
A few eosinophil polymorphs may be present, but neutrophil polymorphs are scarce.
Some of the macrophages may form multinucleate giant cells.
Exudation of fluid is not a prominent feature, but there may be production of new fibrous tissue from granulation tissue.
There may be evidence of continuing destruction of tissue at the same time as tissue regeneration and repair.
Tissue necrosis may be a prominent feature, especially in granulomatous conditions such as tuberculosis.
What is involved with connective tissue proliferation? How are these processes regulated?
The predominant features in repair are angiogenesis followed by fibroblast proliferation and collagen synthesis resulting in granulation tissue.
These processes are regulated by low molecular weight proteins called growth factors which bind to specific receptors on cell membranes and trigger a series of events culminating in cell proliferation.
What are some examples of chronic inflammation?
Chronic peptic ulcer of the stomach
Gall bladder chronic cholecystitis
What are the characteristics of Langhans’ giant cells and where are they seen?
Horseshoe arrangement of peripheral nuclei at one pole of the cell. Tuberculosis.
What are the characteristics of foreign body giant cells and where are they seen?
Large cells with nuclei randomly scattered throughout their cytoplasm.
They are characteristically seen in relation to particulate foreign body material.
What are the characteristics of Touton giant cells and where are they seen?
Central ring of nuclei, peripheral to which there is lipid material.
They are seen when macrophages attempt to ingest lipids, and in xanthomas / dermatofibromasof the skin.
What is repercussion injury?
Body produces reactive oxygen species after you give the tissue blood back too fast.
What is in a plaque?
Fibrous tissue.
Lipids - cholesterol.
(crystals).
Lymphocytes.
