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| − | ==An Introduction to General Pathology==
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| − | * 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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| − |
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| − | ===Lesions===
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| − |
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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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| − |
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| − | ====Decription of Lesions====
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| − |
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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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| − |
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| − | *'''See [[General Pathology - Recognition and Description of Lesions|Recognition and Description of Lesions]]'''
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| − |
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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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| − |
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| − | ====Factors Involved in the Development of Disease====
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| − |
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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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| − |
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| − | ====Types of Agents Causing Disease====
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| − |
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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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| − |
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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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| − |
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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 [[General Pathology - Post-Mortem Change|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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| − | *#* [[General Pathology - Post-Mortem Change#Agonal Changes|Agonal]]
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| − | *# Those occuring '''after death'''
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| − | *#* Post-mortem
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| − |
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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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| − | ** Electronmicroscopy 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== | | ==General Pathology - Contents== |
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