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| − | ==An Introduction to General Pathology==
| + | #REDIRECT[[:Category:General Pathology]] |
| − | | |
| − | * The term '''pathology''' is derived from:
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| − | ** '''Pathos''', or suffering
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| − | ** '''Logos''', or reasoning/logic.
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| − | * Pathology is defined as the study of disease including:
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| − | ** '''Aetiology''' - causal factor(s)
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| − | ** '''Pathogenesis''' - the development of the disease within the body.
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| − | ** '''Lesions''' - the observable structural changes in the tissues and fluids of the body.
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| − | ** '''Pathophysiology''' - the functional changes in diseased tissues.
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| − | ** '''Sequel''' - the consequences of the disease in the body.
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| − | ** '''Remote effects''' - the effect of disease in one tissue on other tissues in the body.
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| − | | |
| − | ===Lesions===
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| − | | |
| − | * Lesions are the abnormalities or changes seen in living tissues due to disease.
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| − | * Observed in
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| − | ** The live animal
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| − | ** Tissues surgically removed from the live animal
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| − | *** Biopsy/ excision
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| − | ** Animals soon after death
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| − | *** Necropsy, post-mortem examination.
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| − | | |
| − | ====Decription of Lesions====
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| − | | |
| − | * Descriptions of lesions is very important
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| − | * Whole organs, tissues or individual lesions are described under headings such as
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| − | *# Size
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| − | *# Shape
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| − | *# Colour
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| − | *# Weight
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| − | *#* Generally in relation to body weight
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| − | *# Texture and Consistency
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| − | *# Appearance of the cut surface
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| − | *# Contents of hollow organs
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| − | *# Position, relationships and effects on adjacent tissues
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| − | | |
| − | ===Disease===
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| − | | |
| − | ====Definition and Type====
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| − | | |
| − | * '''Disease''' is a definite morbid (illness producing) process, having a characteristic train of symptoms or signs.
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| − | ** May affect the whole body or any of its parts.
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| − | ** The disease's aetiology, pathology and prognosis may be known or unknown.
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| − | * There are two main categories of disease.
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| − | *# '''Acute'''
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| − | *#* Characterised by sudden onset and short duration.
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| − | *#* The outcome of acute disease may be:
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| − | *#** Death
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| − | *#** Resolution due to host defence response or clinical therapy
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| − | *#** Progression to chronic disease
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| − | *# '''Chronic'''
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| − | *#* Characterised by insidious onset and protracted course.
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| − | *#* The outcome of chronic disease may be:
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| − | *#** Progressive destruction of tissue
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| − | *#*** Compromises funtion and endangers life,
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| − | *#** The halting of the course of disease, with tissue repair by scarring.
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| − | | |
| − | ====Factors Involved in the Development of Disease====
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| − | | |
| − | * There are three factors which conspire with each other to produce disease.
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| − | *# '''The individual animal'''.
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| − | *#* In particular, the animal's nutritional and immune status
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| − | *#** This is modified by:
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| − | *#*** Recent or concurrent disease
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| − | *#*** Previous exposure to the agent(s) responsible
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| − | *# '''The disease-causing agent(s)'''.
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| − | *#* Most do not cause a uniform pattern of disease
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| − | *#** Host defences are important in determining the presentation of the disease.
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| − | *#* An agent's capacity to produce disease depends upon:
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| − | *#** The dose
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| − | *#** The virulence of the agent
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| − | *#* Several agents may be involved.
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| − | *#** Usually one agent debilitates, allowing others to exert a greater effect within the body
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| − | *#* The presence of an agent does not necessarily mean it is the cause of the disease!
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| − | *#* A pathogenic agent may be absent from the tissues, due to:
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| − | *#** Clinical therapy
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| − | *#** Host defence systems
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| − | *# '''Environment''', for example:
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| − | *#* Overcrowding of animals
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| − | *#* Mixing animals from differing origins
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| − | *#** Carriers are allowed to infect susceptible animals.
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| − | *#*** Carriers are animals which harbour the pathogenic agent but do not show signs of disease.
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| − | *#* Changes in management routine
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| − | | |
| − | ====Types of Agents Causing Disease====
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| − | | |
| − | # '''Infectious organisms'''
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| − | #* [[Viruses|Viruses]]
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| − | #* [[Bacteria|Bacteria]]
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| − | #* [[Fungi|Fungi]]
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| − | #* [[Parasites|Parasites]]
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| − | # '''Physical'''
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| − | #* Trauma
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| − | #* Pressure
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| − | #* Heat
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| − | #* Cold
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| − | #* Radiation
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| − | # '''Chemical'''
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| − | #* Toxic organic and inorganic substances
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| − | #* Toxins produced by infectious organisms
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| − | # '''Nutritional'''
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| − | #* Deficiencies of vitamins and trace elements
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| − | #* Excess vitamins and trace elements
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| − | # '''Genetic defects'''
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| − | #* There is a very wide range of potential defects.
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| − | #** Some are incompatible with life
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| − | #** Others affect specific systems within the body
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| − | | |
| − | ====Aspects of Disease====
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| − | | |
| − | * There are many aspects of a disease that must be considered in order to understand it in full.
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| − | *# '''Incidence'''
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| − | *#* How much of the disease is present?
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| − | *#* Where is the disease found?
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| − | *#* In what species is the disease seen?
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| − | *# '''Aetiology'''
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| − | *#* Causal agent(s)
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| − | *#* Predisposing factors
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| − | *# '''Transmission'''
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| − | *#* How is the disease spread between individuals?
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| − | *#* Is the disease zoonotic?
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| − | *# '''Pathogenesis'''
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| − | *#* How the causal agent(s) exert their effect within the body.
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| − | *# '''Diagnosis'''
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| − | *#* History
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| − | *#* Clinical findings
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| − | *#** Clinical examination
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| − | *#** Clinical pathology
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| − | *#* Biopsy or post-mortem examination
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| − | *# '''Prognosis and Treatment'''
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| − | *# '''Control and Prevention'''
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| − | *#* The ideal situation
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| − | | |
| − | ====Post-Mortem Examination====
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| − | | |
| − | * Post-mortem examination (PME) investigates the observable structural changes in the animal.
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| − | * Information relating to the disease withing the body or specific tissue is gained from PME.
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| − | ** This includes information on the disease's
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| − | *** Aetiology (cause).
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| − | *** Pathogenesis (development).
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| − | * Several types of changes are encountered at post-mortem examination.
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| − | *# Those due to the '''disease'''
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| − | *#* Lesions
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| − | *# Those occuring '''immediately prior to death'''
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| − | *#* Agonal
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| − | *# Those occuring '''after death'''
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| − | *#* Post-mortem
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| − | | |
| − | ====Techniques Involved in Pathological Examination====
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| − | | |
| − | * '''Fluid examination'''
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| − | ** E.g. blood, urine, discharges from orifices and so on.
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| − | * '''Cytology'''
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| − | ** Examination of cells in smears, aspirates and fluids.
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| − | * '''Necropsy'''
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| − | ** Visual examination of the gross changes in the dead body.
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| − | * '''Histopathology'''
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| − | ** Microscopic examination of:
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| − | *** Tissues selected from the dead body after necropsy.
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| − | *** Biopsy/excision materials from lesions in the living animal.
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| − | * '''Histochemistry'''
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| − | ** Microscopic visualisation of enzymatic activity in tissues.
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| − | * '''Immunological methods'''
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| − | ** Specific antibody activity can be detected in tissues and fluids.
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| − | *** Examination of serum can show prior exposure to a particular infectious agent (i.e. specifice antibodies).
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| − | ** Specific antigens can be detected in tissues.
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| − | *** When linked to a marking agent (e.g. a fluorescent dye), an antibody can localise its antigen in the tissue.
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| − | * '''Electronmicroscopy'''
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| − | ** Electronmicrosopcy shows fine detail of the surfaces or internal structures of cells.
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| − | * '''Bacteriology/ Virology/ Parasitology'''
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| − | ** These techniques allow the isolation and identification of pathogenic bacteria, viruses and parasites.
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| − | * '''Toxicology'''
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| − | ** Analysis of tissues for particular poisons and toxins.
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| − | | |
| − | ==General Pathology - Contents==
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| − | | |
| − | ==Degenerations and Infiltrations==
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| − | | |
| − | * Degenerations and infiltrations are the morphological manifestation of an altered metabolism within the cell.
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| − | ** A particular kind of change within a cell or tissue may suggest that a specific type of alteration has occurred.
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| − | * Degenerations and infiltrations are types of structural changes.
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| − | ** These are best considered at a cellular level.
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| − | ** These structural changes are deviations from the cell's normal structure and function.
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| − | *** Parameters are outside the normal physiological range for the cell.
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| − | * '''Degeneration'''
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| − | ** The tissue cell shows some change in itself.
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| − | * '''Infiltration'''
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| − | ** Something accumulates in the cell or tissue.
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| − | | |
| − | ===Cellular Swelling===
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| − | | |
| − | this is the earliest detectable degenerative changes, and due to
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| − | impairment of the integrity of the cell membrane. - this is the mildest form of cellular
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| − | degeneration, and was first described about 100 years ago. It is the first stage in injury to a
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| − | cell and may be caused by a variety of insults.
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| − | Lack of oxygen - anoxia - to a tissue and toxic influences are common causes of cellular
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| − | swelling. It is characterised by a moderate swelling of the individual cells, and is caused
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| − | by an influx of water into the cell.
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| − | The gross appearance of an organ diffusely affected with cloudy swelling is somewhat paler
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| − | than normal, perhaps partly due to the swollen cells also encroaching upon the tissue's own
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| − | blood vessels. Appreciable gross enlargement of the organ may be difficult to detect without
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| − | cutting into it. Because each individual cell is increased in size, the entire volume of the
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| − | organ is also increased, so that on cutting into the liver or kidney capsule, the cut ends may
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| − | retract somewhat due to the bulging outwards of the underlying swollen parenchyma. The
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| − | degree of swelling is not great and could be easily confused with early post-mortem changes
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| − | in the organ.
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| − | | |
| − | Histologically, the individual cells appear somewhat swollen. In H&E stained sections, the
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| − | cytoplasm appears redder in colour. A very important feature is that the nucleus is
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| − | normal. It is best appreciated in the liver and kidney in damage caused by circulating toxins
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| − | where the toxins are not powerful to actually kill the cells.
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| − | Cellular swelling is an important stage in degeneration, but not particularly commonly
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| − | observed on its own without more serious changes because it is also not easy to identify
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| − | unless the post- mortem examination is performed very soon after the animal's death, as early
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| − | post-mortem (autolytic) change in dead tissue looks rather similar.
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| − | It is also reversible, that is when the toxin is no longer exerting its effect, the tissue returns to
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| − | normal.
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| − | It may also be a transient stage in the more serious forms of degenerations which follow.
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| − | | |
| − | ===Hydropic Degeneration===
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| − | | |
| − | Hydropic degeneration - often indicates severe cellular damage due to viruses and is
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| − | a more severe or advanced form of cellular swelling in
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| − | which
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| − | a. the cells may swell up like a balloon prior to their destruction, or
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| − | b. there is a discrete bleb (vacuole) of fluid within the cytoplasm.
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| − | a. the former is sometimes called 'ballooning degeneration' and may occur in a variety of
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| − | conditions, but particularly viral conditions of epithelial tissue.
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| − | The best example is 'Foot and Mouth Disease' where
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| − | the virus attacks the stratum spinosum of the epithelium of
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| − | the tongue and feet. The affected cells are ballooned up
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| − | with water containing the replicating virus. The cells swell
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| − | until they burst and the fluid they contain forms
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| − | microvesicles (blisters) in this layer of the epithelium
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| − | which may later burst, shedding vast quantities of the
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| − | virus. When it bursts, the edges of the erosion look
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| − | ragged, but within weeks the germinal epithelium at the
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| − | base of the erosion regenerates the epithelium, leaving no
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| − | trace of a scar.
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| − | | |
| − | b. in vacuolar degeneration, the second type, the excess water is transferred to the
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| − | endoplasmic reticulum (ER) which swells and eventually fragments, leaving a fluid vacuole
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| − | in the cytoplasm. It commonly occurs in cells such as the hepatocyte, renal tubular
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| − | epithelium and pancreatic acinar cell which are very metabolically active and have welldeveloped
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| − | pumping mechanisms.
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| − | | |
| − | ===Cellular Fatty Change===
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| − | ===Mucoid Degeneration===
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| − | ===Hyaline Degeneration===
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| − | ====Fibrinoid Degeneration====
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| − | ====Amyloidosis====
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| − | ===Glycogen Infiltration===
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| − | ===Cellular Inclusions===
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| − | | |
| − | ==Necrosis==
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| − | ===Causes of Necrosis===
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| − | ===Gross and Histological Features of Necrotic Lesions===
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| − | ====Coagulation Necrosis====
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| − | ====Liquefactive Necrosis====
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| − | ====Caseation Necrosis====
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| − | ===Sequel to Necrosis===
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| − | ====Fat Necrosis====
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| − | ====Gangrene====
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| − | | |
| − | ==Post Mortem Change==
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| − | ===Types of Post Mortem Change===
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| − | ====Rigor Mortis====
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| − | | |
| − | ====Post Mortem Clotting of Blood====
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| − | ====Hypostatic Congestion====
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| − | ====Post Mortem Imbibition of Blood====
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| − | ====Inbibition of Bile Pigment====
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| − | ====Gaseous Distenstion of the Alimentary Tract====
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| − | ====Autolysis====
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| − | ====Putrefaction====
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| − | | |
| − | ==Pigmentation and Calcification==
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| − | | |
| − | ===Exogenous Pigmentation===
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| − | ====Carbon (Anthracosis)====
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| − | ====Pneumoconiosis====
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| − | ====Carotenoids====
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| − | | |
| − | ===Endogenous Pigmentation===
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| − | ====Melanin====
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| − | ====Blood Pigments====
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| − | =====Haemoglobin=====
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| − | =====Haemosiderin=====
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| − | =====Haematin=====
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| − | =====Jaundice=====
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| − | =====Haematoidin=====
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| − | =====Porphyria=====
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| − | ====Lipofuscin====
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| − | | |
| − | | |
| − | ===Mineralisation===
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| − | | |
| − | ====Calcification====
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| − | =====Dystrophic=====
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| − | =====Metastatic (Hypercalcaemia)=====
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| − | | |
| − | ==Circulatory Disorders==
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| − | | |
| − | ===Introduction====
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| − | | |
| − | ====Venous Congestion and Hyperaemia====
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| − | | |
| − | ====Oedema====
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| − | | |
| − | | |
| − | ====Dehydration====
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| − | | |
| − | ====Shock====
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| − | | |
| − | ====Haemorrhage====
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| − | =====Rhexis=====
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| − | =====Diapedesis=====
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| − | | |
| − | ====Haemostasis====
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| − | | |
| − | ====Thrombus====
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| − | =====Causes=====
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| − | =====Evolution=====
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| − | =====Embolism=====
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| − | =====Post Mortem Clots=====
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| − | | |
| − | ====Disseminated Intravascular Coagulation====
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| − | | |
| − | ==Inflammation==
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| − | | |
| − | ===Cardinal Signs===
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| − | | |
| − | ===Causes===
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| − | | |
| − | ===Acute===
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| − | ====Introduction====
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| − | ====Sequence of Events====
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| − | ====Fluids====
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| − | =====Serous=====
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| − | =====Catarrhal=====
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| − | =====Fibrinous=====
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| − | =====Diptheritic=====
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| − | =====Haemorrhagic=====
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| − | =====Purulent=====
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| − | =====Functions of Exudate=====
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| − | =====Sequel to Exudation=====
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| − | ====Cells====
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| − | =====Neutrophils=====
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| − | =====Eosinophils=====
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| − | =====Mast Cells=====
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| − | =====Basophils=====
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| − | | |
| − | ===Chronic===
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| − | ====Introduction====
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| − | ====Cells====
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| − | =====Macrophages=====
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| − | =====Lymphocytes=====
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| − | ====Types====
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| − | =====Granulomatous Inflammation=====
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| − | =====Granulation Tissue=====
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| − | =====Lymphocytic Inflammation=====
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| − | | |
| − | ===Changes in Inflammatory Cells Circulating in Blood===
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| − | ====Neutrophilia====
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| − | ====Neutopenia====
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| − | ====Eosinophilia====
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| − | ====Eosinopenia====
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| − | ====Lymphocytosis====
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| − | ====Lymphopenia====
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| − | ====Plasma Cells====
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| − | ====Monocytosis====
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| − | | |
| − | ===Role of The Lymph Node in Inflammation===
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| − | | |
| − | ===Healing and Repair===
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| − | ====Introduction====
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| − | ====Repair====
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| − | =====Regeneration=====
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| − | =====Replacement=====
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| − | ====In Particular Tissues====
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| − | =====Skin=====
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| − | ======First Intention======
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| − | ======Second Intention======
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| − | =====Bones=====
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| − | =====Respiratory Tract=====
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| − | =====Alimentary Tract=====
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| − | =====Urinary Tract=====
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| − | =====Genital Tract=====
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| − | =====Central Nervous System=====
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| − | | |
| − | ==Growth Disorders==
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| − | | |
| − | ===Congenital===
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| − | ====Causes====
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| − | ====Malformations====
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| − | =====Cyclops=====
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| − | =====Bulldog Calf=====
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| − | =====Cleft Palate=====
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| − | =====Cystic Kidney=====
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| − | =====Spina Bifida=====
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| − | =====Hydrocephalus=====
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| − | =====Cerebellar Hypoplasia=====
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| − | =====Skeletal Malformations=====
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| − | =====Skin Defects=====
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| − | =====Muscular Defects=====
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| − | =====Cardiac Defects=====
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| − | =====Sexual Organ Malformation=====
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| − | =====Metabolic Diseases=====
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| − | | |
| − | ===Growth Disorders During Life===
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| − | ====Atrophy====
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| − | ====Hypertrophy====
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| − | ====Hypoplasia====
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| − | ====Hyperplasia====
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| − | ====Metaplasia====
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| − | ====Dysplasia====
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| − | ====Anaplasia====
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| − | ====Neoplasia====
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| − | =====Benign Tumours=====
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| − | =====Malignant Tumours=====
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| − | =====Aetiology of Tumours=====
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| − | =====Phases of Tumour Growth=====
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| − | =====Tumour Classification and Nomenclature=====
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