General Pathology

From WikiVet English
Jump to navigation Jump to search

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
    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 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.
    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 and /or
        • The virulence of the agent

c. several agents may be involved; usually one agent debilitates, allowing others to exert a greater effect within the body d. the presence of an agent does not necessarily mean it is the cause of the disease. e. the absence of a pathogenic (disease producing) agent from the tissues may be due to i. clinical therapy and/or ii. host defence systems 3. Environment - a. overcrowding of animals b. mixing animals from differing origins allows 'carriers' (animals which harbour the pathogenic agent but which do not show signs of disease) to infect susceptible animals c. changes in management routine

Types of Agents Causing Disease

Aspects of Disease

Post Mortem Examination

Techniques Involved in Pathological Examination

Degenerations and Infiltrations

Cellular Swelling

Hydropic Degeneration

Cellular Faty 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