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==An Introduction to General Pathology==
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#REDIRECT[[:Category: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.
 
 
 
====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
 
*# '''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====
 
 
 
# '''Infectious organisms'''
 
#* [[Viruses|Viruses]]
 
#* [[Bacteria|Bacteria]]
 
#* [[Fungi|Fungi]]
 
#* [[Parasites|Parasites]]
 
# '''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
 
 
 
====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
 
 
 
====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).
 
* 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
 
 
 
====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. 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.
 
* '''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.
 
 
 
==General Pathology - Contents==
 
 
 
==Degenerations and Infiltrations==
 
 
 
*  Degenerations and infiltrations are the morphological manifestation of an altered metabolism within the cell.
 
** A particular kind of change within a cell or tissue may suggest that a specific type of alteration has occurred.
 
* Degenerations and infiltrations are types of structural changes.
 
** These are best considered at a cellular level.
 
** These structural changes are deviations from the cell's normal structure and function.
 
*** Parameters are outside the normal physiological range for the cell.
 
* '''Degeneration'''
 
** The tissue cell shows some change in itself.
 
* '''Infiltration'''
 
** Something accumulates in the cell or tissue.
 
 
 
===Cellular Swelling===
 
 
 
this is the earliest detectable degenerative changes, and due to
 
impairment of the integrity of the cell membrane. - this is the mildest form of cellular
 
degeneration, and was first described about 100 years ago. It is the first stage in injury to a
 
cell and may be caused by a variety of insults.
 
Lack of oxygen - anoxia - to a tissue and toxic influences are common causes of cellular
 
swelling. It is characterised by a moderate swelling of the individual cells, and is caused
 
by an influx of water into the cell.
 
The gross appearance of an organ diffusely affected with cloudy swelling is somewhat paler
 
than normal, perhaps partly due to the swollen cells also encroaching upon the tissue's own
 
blood vessels. Appreciable gross enlargement of the organ may be difficult to detect without
 
cutting into it. Because each individual cell is increased in size, the entire volume of the
 
organ is also increased, so that on cutting into the liver or kidney capsule, the cut ends may
 
retract somewhat due to the bulging outwards of the underlying swollen parenchyma. The
 
degree of swelling is not great and could be easily confused with early post-mortem changes
 
in the organ.
 
 
 
Histologically, the individual cells appear somewhat swollen. In H&E stained sections, the
 
cytoplasm appears redder in colour. A very important feature is that the nucleus is
 
normal. It is best appreciated in the liver and kidney in damage caused by circulating toxins
 
where the toxins are not powerful to actually kill the cells.
 
Cellular swelling is an important stage in degeneration, but not particularly commonly
 
observed on its own without more serious changes because it is also not easy to identify
 
unless the post- mortem examination is performed very soon after the animal's death, as early
 
post-mortem (autolytic) change in dead tissue looks rather similar.
 
It is also reversible, that is when the toxin is no longer exerting its effect, the tissue returns to
 
normal.
 
It may also be a transient stage in the more serious forms of degenerations which follow.
 
 
 
===Hydropic Degeneration===
 
===Cellular Fatty Change===
 
===Mucoid Degeneration===
 
===Hyaline Degeneration===
 
====Fibrinoid Degeneration====
 
====Amyloidosis====
 
===Glycogen Infiltration===
 
===Cellular Inclusions===
 
 
 
==Necrosis==
 
===Causes of Necrosis===
 
===Gross and Histological Features of Necrotic Lesions===
 
====Coagulation Necrosis====
 
====Liquefactive Necrosis====
 
====Caseation Necrosis====
 
===Sequel to Necrosis===
 
====Fat Necrosis====
 
====Gangrene====
 
 
 
==Post Mortem Change==
 
===Types of Post Mortem Change===
 
====Rigor Mortis====
 
 
 
====Post Mortem Clotting of Blood====
 
====Hypostatic Congestion====
 
====Post Mortem Imbibition of Blood====
 
====Inbibition of Bile Pigment====
 
====Gaseous Distenstion of the Alimentary Tract====
 
====Autolysis====
 
====Putrefaction====
 
 
 
==Pigmentation and Calcification==
 
 
 
===Exogenous Pigmentation===
 
====Carbon (Anthracosis)====
 
====Pneumoconiosis====
 
====Carotenoids====
 
 
 
===Endogenous Pigmentation===
 
====Melanin====
 
====Blood Pigments====
 
=====Haemoglobin=====
 
=====Haemosiderin=====
 
=====Haematin=====
 
=====Jaundice=====
 
=====Haematoidin=====
 
=====Porphyria=====
 
====Lipofuscin====
 
 
 
 
 
===Mineralisation===
 
 
 
====Calcification====
 
=====Dystrophic=====
 
=====Metastatic (Hypercalcaemia)=====
 
 
 
==Circulatory Disorders==
 
 
 
===Introduction====
 
 
 
====Venous Congestion and Hyperaemia====
 
 
 
====Oedema====
 
 
 
 
 
====Dehydration====
 
 
 
====Shock====
 
 
 
====Haemorrhage====
 
=====Rhexis=====
 
=====Diapedesis=====
 
 
 
====Haemostasis====
 
 
 
====Thrombus====
 
=====Causes=====
 
=====Evolution=====
 
=====Embolism=====
 
=====Post Mortem Clots=====
 
 
 
====Disseminated Intravascular Coagulation====
 
 
 
==Inflammation==
 
 
 
===Cardinal Signs===
 
 
 
===Causes===
 
 
 
===Acute===
 
====Introduction====
 
====Sequence of Events====
 
====Fluids====
 
=====Serous=====
 
=====Catarrhal=====
 
=====Fibrinous=====
 
=====Diptheritic=====
 
=====Haemorrhagic=====
 
=====Purulent=====
 
=====Functions of Exudate=====
 
=====Sequel to Exudation=====
 
====Cells====
 
=====Neutrophils=====
 
=====Eosinophils=====
 
=====Mast Cells=====
 
=====Basophils=====
 
 
 
===Chronic===
 
====Introduction====
 
====Cells====
 
=====Macrophages=====
 
=====Lymphocytes=====
 
====Types====
 
=====Granulomatous Inflammation=====
 
=====Granulation Tissue=====
 
=====Lymphocytic Inflammation=====
 
 
 
===Changes in Inflammatory Cells Circulating in Blood===
 
====Neutrophilia====
 
====Neutopenia====
 
====Eosinophilia====
 
====Eosinopenia====
 
====Lymphocytosis====
 
====Lymphopenia====
 
====Plasma Cells====
 
====Monocytosis====
 
 
 
===Role of The Lymph Node in Inflammation===
 
 
 
===Healing and Repair===
 
====Introduction====
 
====Repair====
 
=====Regeneration=====
 
=====Replacement=====
 
====In Particular Tissues====
 
=====Skin=====
 
======First Intention======
 
======Second Intention======
 
=====Bones=====
 
=====Respiratory Tract=====
 
=====Alimentary Tract=====
 
=====Urinary Tract=====
 
=====Genital Tract=====
 
=====Central Nervous System=====
 
 
 
==Growth Disorders==
 
 
 
===Congenital===
 
====Causes====
 
====Malformations====
 
=====Cyclops=====
 
=====Bulldog Calf=====
 
=====Cleft Palate=====
 
=====Cystic Kidney=====
 
=====Spina Bifida=====
 
=====Hydrocephalus=====
 
=====Cerebellar Hypoplasia=====
 
=====Skeletal Malformations=====
 
=====Skin Defects=====
 
=====Muscular Defects=====
 
=====Cardiac Defects=====
 
=====Sexual Organ Malformation=====
 
=====Metabolic Diseases=====
 
 
 
===Growth Disorders During Life===
 
====Atrophy====
 
====Hypertrophy====
 
====Hypoplasia====
 
====Hyperplasia====
 
====Metaplasia====
 
====Dysplasia====
 
====Anaplasia====
 
====Neoplasia====
 
=====Benign Tumours=====
 
=====Malignant Tumours=====
 
=====Aetiology of Tumours=====
 
=====Phases of Tumour Growth=====
 
=====Tumour Classification and Nomenclature=====
 

Latest revision as of 12:42, 15 February 2011