Question

1. Define basic terminology used in the study of human diseases

2. Discuss the pathogenesis of disease

3. Describe the standard precaution guidelines for disease prevention

4. Identify the predisposing factors to human diseases

5. Explain the difference between diagnosis and prognosis of a disease

6. Describe some common tests used to diagnose disease states

Answer 1

1. The word 'Pathology' is derived form two Greek words- 'Pathos' meaning suffering and 'logos' meaning study. Pathology is the scientific study of structure and function of the body in disease or in other words , pathology consists of abnormalities that occur in normal anatomy (including histology) and physiology owing to disease

2.Pathophysiology/pathogenesis includes study of disodered function or breakdown of homeostasis in diseases

Pathogenesis of cell injury

Injury to the normal cell by one or more above listed etiologic agents may result in a state of reversible or irrversible cell injury

1. Type, duration and severity of injurious agents

The extent of cell injury depends upon type, duration and severity of the stimulus. for eg: small dose of chemical toxin or short duration of ischemia cause reversible cell injury while large dose of the same chemical agent or persistent ischemia cause cell death

2.Type, status and adaptability of target cells

Cells's nutritional and metabolic status and its adaptability to hostile environment determine the extend of cell injury. for eg: skeletal muscle can withstand hypoxic injury for long time whereas cardiac muscle suffers irreversible injury within20-30 minutes of hypoxia

3.Underlying intracellular phenomenon

certain essential biochemical phenomenon underlie all forms of cell injury

• Mitochondrial damage causing ATP depletion
• cell-membrane damae during the metabolic and transmemebrane exchange
• Release of toxic free radicals

4. morphologic consequences

The ultrastructural changes become apparent earlier than light microscopic changes. The morphologic changes in reversible cell injury ( such as hydropic swelling) are more evident and occur earlier than morphologic changes in cell death (eg: in myocardial infarction)

Answer to question 3

Disease prevention is described in health activites on primary, secondary and tertiary levels

Primary prevention

It is true prevention:it preceeds disease or dysfunction,and is applied to patients considered physically and emotionally healthy. primary prevention aimed at health promotion includes ; health educaton programs, immunizations, physical and nutritional fitness activites. The main aim is to maintain or improve general health of individuals, family and community

Secondary prevention

focuses on individuals who are experiencing health problems or illness at risk of developing complications or worsening conditions. Activities are directed at diagnosis and prompt intervention therby reducing severity and enabling the patient to return a normal level of health as early as possible. It includes screeniing techniques and treating early stages of diseases to limit disability by averting or delaying the consequences of advanced disease

Tertiary prevention

This level of prevention occurs when a defect or disease is permanent or irreversible. It involves minimizing the effects of long-term disease or disability by interventions directed at preventing complications and deterioration. Activites are directed at rehabilitation rather than diagnosis and treatment. Care at this level helps patients acheive a high level of functioning as possible, despite the limitations caused by illness or impairement. This level of care is called preventive care because it involves preventing futher disability or reduced functioning

Answer to question 4

To understand the pathology of diseases one must understand the etiology of cell injury

The cells may be broadly injured in two major ways:

1.Acquired

2.Genetic

Acquired causes of cell injury

• Hypoxia and ischemia
• physical agents
• chemical agents and drugs
• microbial agents
• Immunologic agents
• nutritional derangements
• Aging
• Psychogeneic diseases
• Iatrogenic factors
• Idiopathic diseases

Hypoxia and ischemia

Deficiency in oxygen or hypoxia result in failure to carry out energy production by cells. the most common mechanism of hypoxia is disruption of blood supply to the cells (ischemia). It can also results from anaemia, heart diseases, lung diseases and increased demand of tissue

Physical Agents

• physical agents in the causation of diseases are described below:
• Mechanical trauma (eg: road accidents)
• Thermal trauma (by heat and cold)
• Electricity
• Radiation
• Rapid changes in atmospheric pressure

Chemicals and drugs

• Chemical poisons such as cyanide, arsenic, mercury
• Strong acids and alkalies
• Environmental Pollutants
• Insecticides and pesticides
• Oxygen at high concentration
• Hypertonic glucose and salt
• Social agents such as alcohol and narcotic drugs
• Therapeutic administration of drugs

Microbial agents

Injuries by microbes include infections caused by bacteria,rickettsaie, virus, fungi,protozoa,metazoa and other parasites

Immunologic agents

• Hypersensitivity reactions
• Anaphylatic reactions
• Autoimmune disease

Nutritional derangements

A deficiency or excess may result in nutritional imbalance. Protien energy malnutrition(nutrition deficiency)

Due to excess nutrition- diseases like artherosclerosis, CAD etc

Aging

Cellular aging or senescence leads to impaired ability of the cells to undergo replication and repair and ultimately lead to cell death culminating in the death of the individual

Psychogenic diseases

Excessive anxiety, depression, stress, schizophrenia may lead to substance abuse disorders. These problems of drug addiction, smoking and alcoholsm causes organic diseases like cirrohosis, lung cancer, bronchial asthma, peptic ulcer diseases etc

Iatrogenic causes

There are some diseases as well as death attributed to iatrogenic causes(physician induced). Eg: occurrence of disease or death due to error in judgement by the physician

Idiopathic cause

Exact cause is not known. for eg: idiopathic hypertension

Genetic causes

• Developmental defects: anencephaly-spina bifida , fetal alcohol syndrome, congenital syphilis
• Cytogenetic or karyotypic defects: down'ssyndrome, klinfilter's syndrome
• Single gene defects:siikle cell disease, beta-thalassemia
• Multifactorial inheritence disorders: cleft lip and cleft palate
• Other pediatric diseases