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Flashcards in Introduction Deck (19):

What is the definition of Pathogenesis?

The mechanism of disease development e.g. the sequence of events occurring following exposure to the event.


What is the definition of morphological diagnosis?

based on the predominant lesions and refers to the structural changes that are seen in cells or tissues in association of the disease process e.g. bronchopneumonia


What is the definition of aetiological diagnosis?

Identifies the aetiology e.g. rhodococcus equi


How should tissues be fixed for histopathology?

In at least 10x their volume of buffered formalin.


What are the stains for fat, glycogen, fibrous tissue, haemosiderin, immunohistochemistry?

1) oil red o- bright red cells
2) Periodic acid Schiff- magenta cells
3) Masson's Trichrome- green cells
4) Perl's Prussian blue- blue
5) for specific diagnosis- Zhiel Neilson


What are the definitions of aplasia, agenesis, dysplasia?

1) defective development or congenital absence of a tissue
2)absence of primordial tissue- no development
3) altered size, shape and organisation of tissue.


How does cellular swelling occur?

hydropic degeneration will often result from hypoxia.
1) reduced ATP will cause a switch to anaerobic metabolism, depletion of glycogen and accumulation of lactate and inorganic phosphates. 2) inhibition of membrane sodium/potassium pumps and water moves into the cell.


What would a hydropic cell look like?

cells will have vacuolated cytoplasms, this can be rectified but if ballooning degeneration occurs then the cell will die. (the vacuoles get very large)


What are the 5 types of oncotic necrosis?

1)coagulative- cell outlines preserved due to delayed proteolysis (renal infarct), acute.
2)caseous- Friable 'cheese', chronic lesion, dystrophic cacification (TB)
3)liquefactive- cavities filled with liquid debris. Abscesses- pyogenic bacteria. CNS- little fibrous support.
4)gangrenous- follows on from coagulative: moist, dry, gas
5) fat- specific necrosis of fat (pancreatic fat necrosis)


What would you look for in a necrotic cell?

Pyknosis- shrinking of the nucleus
Karyorrhexis- splitting of the nucleus
Kayolysis- lysis of the nucleus
They cytoplasm will look more eosinophilic.


What are the histological features of apoptosis?

condensation of the chromatin, fragmentation of the cytoplasm and budding of the cytoplasm, the cells will appear shrunken.


What is lipodosis/fatty change?

accumulation of intrcytoplasmic lipid especially in the liver, muscle and kidney. This is due to the liver's essential role in fat metabolism.
Hepatic lipidosis can occur from- excessive FFAs entering the liver- starvation or toxic damage that affects the metabolism of the FAs and TGs.


What happens to glycogen in the liver?

It is abnormally accumulated associated with corticosteroid therapy, diabetes mellitus and glycogen storage disease. This will be seen as vacuolated cytoplasms (water, fat or glycogen).


What are the two types of calcification in pathology?

Dystrophic- serum levels are normal but Ca is deposited in dead or dying tissue because the cell couldn't regulate its Ca levels.
Metastatic- hypercalcaemia due to damage to intracellular organelles e.g. renal failure due to secondary hyperparathyroidism or vit D toxicity.


What are the 7 cell types that are associated with inflammation?

Neutrophils- lobed nucleus
Eosinophils- pink granules
Lymphocytes and plasma cells- highly stained, perinuclear halo due to high golgi activity as they produce Ig
Mast cells- basophillic, big round nucleus (toludene blue)
Macrophages- bigger than a lymphocyte
Fibroblasts- difficult to differentiate
Fibrosis- looks white


What is fatty infiltration?

When the hepatocyte is replaced by adipose cells in old age or obesity.


What are the four types of exudate?

Suppurative/purulent- many neutrophils, bacterial
Fibrinous- thin eosinophilic meshwork which coagulates
Serous- early in lesion development e.g. blister
Mucous/catarrhal- in resp or GIT where mucous secreting cells contribute. e.g. distemper


What is important about fibrinous exudate?

It is due to increased vascular permeability that allow fibrinogen to leak out and form fibrin, it is an acute phenomenon. Do not confuse with fibrosis which is a chronic event.


What are the definitions of an abscess and empyema?

1) localised area of liquefactive necrosis walled off by neutrophil accumulation- granulation/ fibrous tissue.
2)a hollow viscus filled with pus e.g. guttoral pouch empyema.