Difference between revisions of "General Pathology"
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===[[General Pathology - Post-Mortem Change|Post-Mortem Change]]=== | ===[[General Pathology - Post-Mortem Change|Post-Mortem Change]]=== | ||
− | + | ===[[General Pathology - Pigmentation and Calcification|Pigmentation and Calcification]]=== | |
==Pigmentation and Calcification== | ==Pigmentation and Calcification== |
Revision as of 12:04, 21 August 2007
An Introduction to General Pathology
- The term pathology is derived from:
- Pathos, or suffering
- Logos, or reasoning/logic.
- Pathology is defined as the study of disease including:
- Aetiology - causal factor(s)
- Pathogenesis - the development of the disease within the body.
- Lesions - the observable structural changes in the tissues and fluids of the body.
- Pathophysiology - the functional changes in diseased tissues.
- Sequel - the consequences of the disease in the body.
- Remote effects - the effect of disease in one tissue on other tissues in the body.
Lesions
- Lesions are the abnormalities or changes seen in living tissues due to disease.
- Observed in
- The live animal
- Tissues surgically removed from the live animal
- Biopsy/ excision
- Animals soon after death
- Necropsy, post-mortem examination.
Decription of Lesions
- Descriptions of lesions is very important
- Whole organs, tissues or individual lesions are described under headings such as
- Size
- Shape
- Colour
- Weight
- Generally in relation to body weight
- Texture and Consistency
- Appearance of the cut surface
- Contents of hollow organs
- Position, relationships and effects on adjacent tissues
Disease
Definition and Type
- Disease is a definite morbid (illness producing) process, having a characteristic train of symptoms or signs.
- May affect the whole body or any of its parts.
- The disease's aetiology, pathology and prognosis may be known or unknown.
- There are two main categories of disease.
- Acute
- Characterised by sudden onset and short duration.
- The outcome of acute disease may be:
- Death
- Resolution due to host defence response or clinical therapy
- Progression to chronic disease
- Chronic
- Characterised by insidious onset and protracted course.
- The outcome of chronic disease may be:
- Progressive destruction of tissue
- Compromises funtion and endangers life,
- The halting of the course of disease, with tissue repair by scarring.
- Progressive destruction of tissue
- Acute
Factors Involved in the Development of Disease
- There are three factors which conspire with each other to produce disease.
- The individual animal.
- In particular, the animal's nutritional and immune status
- This is modified by:
- Recent or concurrent disease
- Previous exposure to the agent(s) responsible
- This is modified by:
- In particular, the animal's nutritional and immune status
- The disease-causing agent(s).
- Most do not cause a uniform pattern of disease
- Host defences are important in determining the presentation of the disease.
- An agent's capacity to produce disease depends upon:
- The dose
- The virulence of the agent
- Several agents may be involved.
- Usually one agent debilitates, allowing others to exert a greater effect within the body
- The presence of an agent does not necessarily mean it is the cause of the disease!
- A pathogenic agent may be absent from the tissues, due to:
- Clinical therapy
- Host defence systems
- Most do not cause a uniform pattern of disease
- Environment, for example:
- Overcrowding of animals
- Mixing animals from differing origins
- Carriers are allowed to infect susceptible animals.
- Carriers are animals which harbour the pathogenic agent but do not show signs of disease.
- Carriers are allowed to infect susceptible animals.
- Changes in management routine
- The individual animal.
Types of Agents Causing Disease
- Infectious organisms
- Physical
- Trauma
- Pressure
- Heat
- Cold
- Radiation
- Chemical
- Toxic organic and inorganic substances
- Toxins produced by infectious organisms
- Nutritional
- Deficiencies of vitamins and trace elements
- Excess vitamins and trace elements
- Genetic defects
- There is a very wide range of potential defects.
- Some are incompatible with life
- Others affect specific systems within the body
- There is a very wide range of potential defects.
Aspects of Disease
- There are many aspects of a disease that must be considered in order to understand it in full.
- Incidence
- How much of the disease is present?
- Where is the disease found?
- In what species is the disease seen?
- Aetiology
- Causal agent(s)
- Predisposing factors
- Transmission
- How is the disease spread between individuals?
- Is the disease zoonotic?
- Pathogenesis
- How the causal agent(s) exert their effect within the body.
- Diagnosis
- History
- Clinical findings
- Clinical examination
- Clinical pathology
- Biopsy or post-mortem examination
- Prognosis and Treatment
- Control and Prevention
- The ideal situation
- Incidence
Post-Mortem Examination
- Post-mortem examination (PME) investigates the observable structural changes in the animal.
- Information relating to the disease withing the body or specific tissue is gained from PME.
- This includes information on the disease's
- Aetiology (cause).
- Pathogenesis (development).
- This includes information on the disease's
- Several types of changes are encountered at post-mortem examination.
- Those due to the disease
- Lesions
- Those occuring immediately prior to death
- Agonal
- Those occuring after death
- Post-mortem
- Those due to the disease
Techniques Involved in Pathological Examination
- Fluid examination
- E.g. blood, urine, discharges from orifices and so on.
- Cytology
- Examination of cells in smears, aspirates and fluids.
- Necropsy
- Visual examination of the gross changes in the dead body.
- Histopathology
- Microscopic examination of:
- Tissues selected from the dead body after necropsy.
- Biopsy/excision materials from lesions in the living animal.
- Microscopic examination of:
- Histochemistry
- Microscopic visualisation of enzymatic activity in tissues.
- Immunological methods
- Specific antibody activity can be detected in tissues and fluids.
- Examination of serum can show prior exposure to a particular infectious agent (i.e. specifice antibodies).
- Specific antigens can be detected in tissues.
- When linked to a marking agent (e.g. a fluorescent dye), an antibody can localise its antigen in the tissue.
- Specific antibody activity can be detected in tissues and fluids.
- Electronmicroscopy
- Electronmicrosopcy shows fine detail of the surfaces or internal structures of cells.
- Bacteriology/ Virology/ Parasitology
- These techniques allow the isolation and identification of pathogenic bacteria, viruses and parasites.
- Toxicology
- Analysis of tissues for particular poisons and toxins.