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Introduction_to_Pathology.ppt

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					Introduction to Pathology

   PATH 303   General Pathology      4(3-2)




                            Zubair Latif
 Pathology
• Pathos (suffering or disease) logos (science)
• Pathology is the study of structural and
  functional changes of body in disease,
  including changes in cell, tissues, organs and
  body fluids.
• Pathology forms a bridge between basic
  studies of Anatomy, Physiology, biochemistry
  and clinical subjects of Medicine and Surgery
Disease

• French word “Des” (away) “aise” (ease)

• it is a condition in which the individual
  suffers from discomfort i.e. not at
  harmony with its environment.
 Lesion
It is the abnormal structural or functional
  change in the body as a result of disease
  and may be detected by gross (necropsy),
  microscopic (histopathology) or
  biochemical methods (clinical pathology).
Pathognomonic lesion
An alternation that indicates without doubt
 the cause of a particular disease e.g.
 finding of Negri bodies in rabies etc
Pathogenesis
• It is a progressive development of a
 disease process from its initiation to
 conclusion in recovery or death.

• Disease is a dynamic process which
 progresses from molecular or bio-chemical
 alternations to structural (ultrastructural,
 microscopic and gross lesions) and to
 functional changes which are seen as
 signs and symptoms of disease.
                                        Functio
                                        nal
                          Structural
Pathological
  changes      Moderate




                                 Time
Diagnosis
 • It is the identification of disease through
   the clinical examination and application of
   various laboratory tests.
 • A pathological diagnoses should include
   lesions, etiology (cause) pathogenesis and
   clinical consequences.
Prognosis
• It is the estimation of the clinician or
  pathologist regarding the expected outcome
  of disease like favorable, guarded or grave
  ete
 Etiology
• It is a study of the causes of disease.
• An etiologic agent induces cell and tissue
  injury leading to clinical manifestations of
  disease
• There are numerous causes of disease
  which are divided into
     1. Exogenous (Environmental or extrinsic factors)
     2. Intrinsic Internal defects
Biological agents (infectious agents,
pathogens, microorganisms)
• These are diverse group of biological
 agents, ranging from a few nm to a few
 meters in size. The disease producing
 biological agents mostly have a parasitic
 mode of life and include prions, viruses,
 chlamydia, rickettsia, mycoplasma,
 bacteria, fungi, protozoa and metazoa.
Characteristics of microbiological
agents
• Biological associations and relationships.
• Commensals: coexistence without injury or
  benefit
• Symbiotic: Mutually beneficial coexistence.
Example: microflora and fauna in the rumen and
  colon of herbivores and E.coli in the gut of
  humans producing vit.K.
• Parasitic/Predators: causing morbidity and
  mortality in the host (man and animals)
Portal of entry in the body:

• Lungs and mucociliary mechanisms
• Mouth and GIT. Gastric acidity
• Intact membranes
• Size of inoculum-MID 50 and MLD 50
Host defense mechanisms.

• Humoral- innate natural immunity,
  acquired immunity, antibody formation.
• Cellular defense- Phagocytosis by
  neutrophils and monocytes.
Survival of microorganisms in the
body:
• Spreading factor- Hyaluronidase
• Evasion of phagocytosis- capsule
  formation
• Sequestration-coagulase,collagenase,
  organotropism
Intracellular localization

• Facultative- Mycobacterium, Brucella,
  Histoplasma, Nocardia, Toxoplasma,
  Theileria
• Obligate- Rickettsia, Viruses, Plasmodium.
How microorganisms cause disease



• Host factors- age, nutrition, immune
 status, intercurrent disease, opportunistic
 infection, predisposing factors
General mechanism of disease
production:
• Dysfunction and death of host cells
• Release of endotoxins and exotoxins
• Induction of immune and inflammatory
 responses causing injury and disease.
Mechanisms of viral injury:

• Host cell receptors
• Type- specific transcription factors
• Crossing physical barriers
• Immune cell-mediated killing
• Alteration of apoptosis pathway
Mechanisms of viral injury:
                       cont…..
• Induction of cell proliferation and
  transformation
• Inhibition of host cell DNA,RNA or protein
  synthesis
• Damage to plasma membrane
• Damage to cells involved in antimicrobial
  defense
Mechanisms of bacterial injury:
  Depends upon their ability to
(a)Adhere to host cells
(b)Invade the cells and tissues
(c)To deliver toxins that damage the cells
  and toxins
• Bacterial adherence to host cells
Mechanisms- Adhesins, fibrils and fimbrae
Virulence of intracellular bacteria:

• Facultative intracellular bacteria
• Subversion of host immune response
• Inhibition of synthesis of host cell proteins
Elaboration of bacterial endotoxins:

• Septic shock
• Disseminated intravascular coagulation
• cytokines
Bacterial endotoxins

• Bacterial enzymes
• Inhibition of protein synthesis
• Cellular necrosis
• Neurotoxins- Cl.Botulinum and Cl.Tatani,
 paralysis, respiratory failure

				
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