Difference between revisions of "Introduction to General Pathology"

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==Introduction==
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{{review}}
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The term '''pathology''' is derived from '''Pathos''', or suffering and '''Logos''', or reasoning/logic. Pathology is defined as the study of disease including:
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{{toplink
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* '''Aetiology''' - causal factor(s)
+
|linkpage =General Pathology
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* '''Pathogenesis''' - the development of the disease within the body.
+
|linktext =General Pathology
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* '''Lesions''' - the observable structural changes in the tissues and fluids of the body.
+
|maplink = General Pathology (Content Map)
−
* '''Pathophysiology''' - the functional changes in diseased tissues.
+
|pagetype =Pathology
−
* '''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.
+
<br>
 +
==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==
−
Lesions are the abnormalities or changes seen in living tissues due to disease, and can be observed in:
 
−
* The live animal
 
−
* Tissues surgically removed from the live animal during biopsy or excision
 
−
* Necropsy or post-mortem examination.
 
  
−
===Description of Lesions===
+
* Lesions are the abnormalities or changes seen in living tissues due to disease.  
−
[[Recognition and Description of Lesions|Descriptions of lesions]] are very important. Whole organs, tissues or individual lesions are described under headings such as:
+
* Observed in
−
# Size
+
** The live animal
−
# Shape
+
** Tissues surgically removed from the live animal
−
# Colour
+
*** Biopsy/ excision
−
# Weight (generally in relation to body weight)
+
** Animals soon after death
−
# Texture and Consistency
+
*** Necropsy, post-mortem examination.
−
# Appearance of the cut surface
 
−
# Contents of hollow organs
 
−
# Position, relationships and effects on adjacent tissues
 
  
−
==Pathological changes to cells==
+
===[[General Pathology - Recognition and Description of Lesions|Description of Lesions]]===
−
Generally, disruptions at a cellular level usually involve changes or damage to the cells themselves, or they involve the presence of unexpected material within the cell, such as [[Pigmentation - Pathology|pigments]] or [[Mineralisation_-_Pathology#Calcification|calcified material]]. When cells begin to [[:Category:Degenerations and Infiltrations|degenerate]] or become [[:Category:Degenerations and Infiltrations|infiltrated]] by foreign material then cellular metabolism has been disrupted. The alteration in the structure of the cell can be suggestive of the metabolic abnormality that has occurred, and result in the cellular parameters extending beyond the normal physiological range for the cell.
 
  
−
There are several [[Cell Growth Disorders|changes in the size of cells]] and their respective organs that are commonly seen in pathological states:
+
* Descriptions of lesions is very important
−
*'''Atrophy''' is a decrease in the size of the cells and respective organ(s), occurring after the organ has reached it's normal size.
+
* Whole organs, tissues or individual lesions are described under headings such as
−
*'''Hypertrophy''' is an increase in the size of an organ due to an increase in size of the individual cells.
+
*# Size
−
*'''Hypoplasia''' is a reduction in the size of cells and tissues due to a failure to grow to the normal size which ranges from mild hypoplasia to almost complete absence. Almost complete absence is also called vestigial or rudimentary.
+
*# Shape
−
*'''Aplasia''' and '''agensis''' refer to complete absence of tissue.
+
*# Colour
−
*'''Hyperplasia''' is an increase in the size of an organ due to an increase in the numbers of cells present within it. Hypertrophy and hyperplasia may occur concurrently.
+
*# Weight
−
*'''Metaplasia''' is a transformation of one type of tissue into another and occurs solely in connective tissue and epithelium.
+
*#* Generally in relation to body weight
−
*'''Dysplasia''' is abnormal growth within a tissue
+
*# Texture and Consistency
−
*'''Anaplasia''' is a marked and irreversible loss of cellular differentiation with return to a more primitive state, which can be a feature of highly malignant tumours.
+
*# Appearance of the cut surface
−
*'''Neoplasia''' is a serious disturbance of growth of tissues
+
*# Contents of hollow organs
 +
*# Position, relationships and effects on adjacent tissues
  
−
The final pathological process that occurs at a cellular level is [[Necrosis - Pathology|necrosis]], which is the death of cells within the living body.
+
==Disease==
−
Two things happen when [[Necrosis - Pathology|necrosis]] occurs:
 
−
#Further changes can take place in the tissue itself.
 
−
#The surrounding unaffected living tissue can react to the necrotic tissue.
 
  
−
==Disease==
 
 
===Definition and Type===
 
===Definition and Type===
−
'''Disease''' is a morbid (illness producing) process, having a characteristic train of symptoms or signs. It may affect the whole body or any of its parts, and the disease's aetiology, pathology and prognosis may be known or unknown.
 
  
−
There are two main categories of disease:
+
* '''Disease''' is  a definite morbid (illness producing) process, having a characteristic train of symptoms or signs.
−
# '''Acute''' - characterised by sudden onset and short duration.
+
** May affect the whole body or any of its parts.
−
#* The outcome of acute disease may be:
+
** The disease's aetiology, pathology and prognosis may be known or unknown.
−
#** Death
+
* There are two main categories of disease.
−
#** Resolution due to [[:Category:Immunology|host defence response]] or clinical therapy
+
*# '''Acute'''
−
#** Progression to chronic disease
+
*#* Characterised by sudden onset and short duration.
−
# '''Chronic''' - characterised by insidious onset and protracted course.
+
*#* The outcome of acute disease may be:
−
#* The outcome of chronic disease may be:
+
*#** Death
−
#** Progressive destruction of tissue, which compromises function and  endangers life,
+
*#** Resolution due to host defence response or clinical therapy
−
#** The halting of the course of disease, with tissue repair by scarring.
+
*#** Progression to chronic disease
 +
*# '''Chronic'''
 +
*#* Characterised by insidious onset and protracted course.
 +
*#* The outcome of chronic disease may be:
 +
*#** Progressive destruction of tissue
 +
*#*** Compromises function and  endangers life,
 +
*#** The halting of the course of disease, with tissue repair by scarring.
  
 
===Factors Involved in the Development of Disease===
 
===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, which may be modified by recent or concurrent disease, and/or previous exposure to the agent(s) responsible.
+
* There are three factors which conspire with each other to produce disease.
−
#'''The disease-causing agent(s)'''. Most do not cause a uniform pattern of disease. The host defences are important in determining the presentation of the disease. An agent's capacity to produce disease depends upon the dose and the virulence of the agent. Bear in mind that several agents may be involved - often one agent debilitates, allowing others to exert a greater effect that normal within the body. The presence of an agent does not necessarily mean it is the cause of the disease! On occasions, a pathogenic agent may be absent from the tissues, due to either clinical therapy or the action of the host defence systems
+
*# '''The individual animal'''.
−
#'''Environment''', for example: in the overcrowding of animals, mixing animals from differing origins and interaction with carriers are allowed to infect susceptible animals. Carriers are animals which harbour the pathogenic agent but do not show signs of disease. Changes in management routine may also affect susceptibility to disease.
+
*#* In particular, the animal's nutritional and immune status
 +
*#** This is modified by:
 +
*#*** Recent or concurrent disease
 +
*#*** Previous exposure to the agent(s) responsible
 +
*# '''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
 +
*# '''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.  
 +
*#* Changes in management routine
  
 
===Types of Agents Causing Disease===
 
===Types of Agents Causing Disease===
 +
 
# '''Infectious organisms'''
 
# '''Infectious organisms'''
 
#* [[Viruses|Viruses]]
 
#* [[Viruses|Viruses]]
Line 84: Line 112:
 
#* Excess vitamins and trace elements
 
#* Excess vitamins and trace elements
 
# '''[[Congenital and Neonatal Disease - Pathology|Genetic defects]]'''
 
# '''[[Congenital and Neonatal Disease - Pathology|Genetic defects]]'''
−
#* There is a very wide range of potential defects; some are incompatible with life whilst others affect specific systems within the body
+
#* There is a very wide range of potential defects.
 +
#** Some are incompatible with life
 +
#** Others affect specific systems within the body
  
 
===Aspects of Disease===
 
===Aspects of Disease===
−
There are many aspects of a disease that must be considered in order to understand it in full.
+
 
−
# '''Incidence''' refers to how much of the disease is present, where the disease is found and in what species is the disease seen?
+
* There are many aspects of a disease that must be considered in order to understand it in full.
−
# '''Aetiology''' refers to the causal agent(s) and includes predisposing factors
+
*# '''Incidence'''
−
# '''Transmission''' describes how a disease is spread between individuals, and includes the important question 'is the disease zoonotic'?
+
*#* How much of the disease is present?
−
# '''Pathogenesis''' describes how the causal agent(s) exert their effect within the body.
+
*#* Where is the disease found?
−
# '''Diagnosis''' - this is reached on considering the clinical history and findings with reference to the clinical examination and the presence of any pathology. Confirmation is reached by monitoring the response to treatment or by biopsy or post-mortem examination
+
*#* In what species is the disease seen?
−
# '''Prognosis and Treatment'''
+
*# '''Aetiology'''
−
# '''Control and Prevention'''
+
*#* 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
  
 
==Post-Mortem Examination==
 
==Post-Mortem Examination==
−
Post-mortem examination (PME) investigates the observable structural changes in the animal. Information relating to the disease within the body or specific tissue is gained from PME, including information on the disease's aetiology and pathogenesis.
 
  
−
Several types of changes are encountered at post-mortem examination.
+
* Post-mortem examination (PME) investigates the observable structural changes in the animal.
−
* Those due to the '''disease''', including [[Recognition and Description of Lesions|visible lesions]]
+
* Information relating to the disease within the body or specific tissue is gained from PME.
−
*Those occurring '''immediately prior to death''', known as [[Post-Mortem Change - Pathology#Agonal Changes|agonal changes]]
+
** This includes information on the disease's
−
* Those occurring '''after death''', or [[Post-Mortem Change - Pathology|post-mortem]]
+
*** Aetiology (cause).
 +
*** Pathogenesis (development).
 +
* Several types of [[General Pathology - Post-Mortem Change|changes]] are encountered at post-mortem examination.
 +
*# Those due to the '''disease'''
 +
*#* Lesions
 +
*# Those occuring '''immediately prior to death'''
 +
*#* [[General Pathology - Post-Mortem Change#Agonal Changes|Agonal]]
 +
*# Those occuring '''after death'''
 +
*#* Post-mortem
  
 
==Techniques Involved in Pathological Examination==
 
==Techniques Involved in Pathological Examination==
  
−
* '''Fluid examination''' e.g. blood, urine, discharges.
+
* '''Fluid examination'''
−
* '''Cytology''' - collect and examine cells in smears, aspirates and fluids.
+
** E.g. blood, urine, discharges from orifices and so on.
−
* '''Necropsy''', which is a visual examination of the gross changes in the dead body.
+
* '''Cytology'''
−
* '''Histopathology'''; microscopic examination of:
+
** Examination of cells in smears, aspirates and fluids.
−
** Tissues selected from the dead body after necropsy.
+
* '''Necropsy'''
−
** Biopsy/excision materials from lesions in the living animal.
+
** Visual examination of the gross changes in the dead body.
−
* '''Histochemistry'''; microscopic visualisation of enzymatic activity in tissues.
+
* '''Histopathology'''
−
* '''Immunological methods''' such as testing for specific antibody activity in tissues and fluids.
+
** Microscopic examination of:
−
** Examination of serum can show prior exposure to a particular infectious agent (i.e. specific antibodies).
+
*** Tissues selected from the dead body after necropsy.
 +
*** Biopsy/excision materials from lesions in the living animal.
 +
* '''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. specific antibodies).
 
** Specific antigens can be detected in tissues.
 
** 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.
+
*** When linked to a marking agent (e.g. a fluorescent dye), an antibody can localise its antigen in the tissue.
−
* '''Electronmicroscopy''' which reveals the fine detail of the surfaces or internal structures of cells.
+
* '''Electronmicroscopy'''
−
* '''Bacteriology/ Virology/ Parasitology'''; these techniques allow the isolation and identification of pathogenic bacteria, viruses and parasites.
+
** Electronmicroscopy shows fine detail of the surfaces or internal structures of cells.
−
* '''Toxicology'''; analysis of tissues for particular poisons and toxins.
+
* '''Bacteriology/ Virology/ Parasitology'''
−
 
+
** These techniques allow the isolation and identification of pathogenic bacteria, viruses and parasites.
−
 
+
* '''Toxicology'''
−
[[Category:General Pathology|A]]
+
** Analysis of tissues for particular poisons and toxins.

Revision as of 20:47, 13 August 2009

 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.


WikiPathWikiPath Banner.png
()Map GENERAL PATHOLOGY (Map)



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.

Description of Lesions

  • Descriptions of lesions is very important
  • Whole organs, tissues or individual lesions are described under headings such as
    1. Size
    2. Shape
    3. Colour
    4. Weight
      • Generally in relation to body weight
    5. Texture and Consistency
    6. Appearance of the cut surface
    7. Contents of hollow organs
    8. 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.
    1. 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
    2. Chronic
      • Characterised by insidious onset and protracted course.
      • The outcome of chronic disease may be:
        • Progressive destruction of tissue
          • Compromises function and endangers life,
        • The halting of the course of disease, with tissue repair by scarring.

Factors Involved in the Development of Disease

  • There are three factors which conspire with each other to produce disease.
    1. 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
    2. 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
    3. 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.
      • Changes in management routine

Types of Agents Causing Disease

  1. Infectious organisms
  2. Physical
    • Trauma
    • Pressure
    • Heat
    • Cold
    • Radiation
  3. Chemical
    • Toxic organic and inorganic substances
    • Toxins produced by infectious organisms
  4. Nutritional
    • Deficiencies of vitamins and trace elements
    • Excess vitamins and trace elements
  5. Genetic defects
    • There is a very wide range of potential defects.
      • Some are incompatible with life
      • Others affect specific systems within the body

Aspects of Disease

  • There are many aspects of a disease that must be considered in order to understand it in full.
    1. Incidence
      • How much of the disease is present?
      • Where is the disease found?
      • In what species is the disease seen?
    2. Aetiology
      • Causal agent(s)
      • Predisposing factors
    3. Transmission
      • How is the disease spread between individuals?
      • Is the disease zoonotic?
    4. Pathogenesis
      • How the causal agent(s) exert their effect within the body.
    5. Diagnosis
      • History
      • Clinical findings
        • Clinical examination
        • Clinical pathology
      • Biopsy or post-mortem examination
    6. Prognosis and Treatment
    7. Control and Prevention
      • The ideal situation

Post-Mortem Examination

  • Post-mortem examination (PME) investigates the observable structural changes in the animal.
  • Information relating to the disease within the body or specific tissue is gained from PME.
    • This includes information on the disease's
      • Aetiology (cause).
      • Pathogenesis (development).
  • Several types of changes are encountered at post-mortem examination.
    1. Those due to the disease
      • Lesions
    2. Those occuring immediately prior to death
    3. Those occuring after death
      • Post-mortem

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.
  • 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. specific 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.
  • Electronmicroscopy
    • Electronmicroscopy 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.
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