CAUSESE or ETIOLOGY OF CELL INJURY

1. CAUSES/ETIOLOGY OF CELL INJURY
By- Dipesh Gamare

3. Developmental defects
are group of abnormalities during fetal life due to errors in morphogenesis.
• Certain chemicals, drugs, physical and biological are known to induce suc birt defects
are known as teratogens. The study of teratogen is called as teratology. The result of
teratogen is formation of defective organ called as mal-formation. It results in following:
intrauterine death, intrauterine growth retardation, functional defects, and
malformation.
• The effect of teratogens in inducing developmental defects are depend upon following
factors,
Variable susceptible to teratogens
• Intrauterine stage
• Dose of teratogen
• Specifically of developmental defect for specific teratogen.
• Some clinical important examples are as
Thalidomide malformation, fetal hydantoin syndrome, fetal alcohol syndrome, torch
effect

4.  CYTOGENIC DEFECTS (KERYOTYPIC):
• Human germ cells contain 23 chromosomes (haploid or n) while all the nucleated
somatic cells contain 23 pairs of chromosomes (diploid or 2n).
• They are 44 autosomes and 2 sex chromosomes which are xx or xy.
• Mainly the abnormalities of chromosomes are divided in to two: numerical and
structural.
Numerical: the abnormalities occur due to increase or decrease number of total
chromosomes.
• 1. Polyploidy: it is the term used for number of chromosomes which is the
multiple of haploid number.
• 2. Aneuploidy: it is not exact multiple number of chromosomes but hypodiploid
(2N-1 or monosomy) and hyperdiploid (2N+1 or trisomy)
• E.g. of cytogenetic defects
• Down syndrome
• Klinefelter syndrome
• Turner syndrome

5.  Single gene defects: (mendelian syndrome)
• The classic laws of inheritance of characteristics were outlined by austrian
scientist monk gregor mendel in 1866 based on his observation of cross-breeding
of red & white garden peas.
• Single gene defect follows classic mendelian patterns of inheritance and are
called as mendelian syndrome or disorder.
• It is results of mutation of a single gene.
• (Mutation is the term applied to permanent changes in DNA of cell. If person
have mutated germ cell will be subjected to inheritance of discharacter to the
offspring)
• Ex, sickle cell anemia, beta-thalassamia.

6. DISORDERS WITH MULTIFACTORIAL INHERITANCE
• This disorder results from both genetic as well as environmental factor.
• Ex, colors of hair, eyes, skin, height, intelligence etc.
• These disorders of multifactorial inheritance include cleft lips, diabetes mellitus,
hypertension, ccf etc.

7. STORAGE DISEASES (INBORN ERRORS OF METABOLISM)
• These errors are introduced during or before birth. In such cases, the new born is
containing deficiency or lack of enzymes.
• Ex, glucose-6-dehydrogenase deficiency may cause hemolytic diseases.
• Storage of carbohydrate, proteins and lipids take place abnormally.

8. Acquired causes of cell injury
 HYPOXIA AND ISCHEMIA:
• Cells of different tissues essentially require oxygen to generate energy and
perform metabolic function.
• Deficiency of oxygen results in hypoxia or anoxia means failure to carry out above
activities.
• The most common causes for hypoxia are: ischemia, anaemia, co-poisoning,
cardiorespiratory insufficiency and increase demand of tissues.

9.  PHYSICALAGENTS:
• Physical agents for cell injury are:
• Mechanical trauma (Road accident)
• Thermal trauma ( Heat and cold)
• Electricity
• Radiation ( U.V. Radiation)
• Rapid changes in atmosphere pressure.
•

10.  CHEMICALS AND DRUGS:
• Increase level of chemicals and drugs cause the cell injury:
• Chemical poisons
• Strong acids and alkali
• Environmental pollutants
• Insecticides and pesticides
• Oxygen at high concentration
• Hypertonic glucose and salts
• Alcohol and narcotic drugs
• Therapeutic administration of drug

11.  MICROBIAL AGENTS:
• Injuries by microbes include infection caused by bacteria, rickettsiae, viruses, fungi,
protozoa, metazoa and other parasites.
 IMMUNOLOGICAL AGENTS:
• Immunity is double edge sword. It means, it protects against various injuries agents but
itself may cause cell injury.
• Example, hypersensitivity reactions, anaphylactic reactions, autoimmune diseases.
 NUTRITIONAL DERANGEMENT:
• A deficiency or an excess of nutrients may results in nutritional imbalances.
• Nutritional deficiency diseases may be due to overall deficiency of nutrients
(starvation), protein calorie (marasmus, kwashiorkor), minerals (anaemia) or of trace
elements.
• Nutritional excess is a problem of societies results from obesity, in atherosclerosis,
heart diseases and hypertension.

12. PSYCHOLOGICAL FACTORS:
• There are number of specific biochemical or morphological changes in common
acquired mental diseases due to mental stress, strain, anxiety, overwork and
frustration.
• Problems of drug addiction, alcoholism and smoking results in various diseases
such as liver damage, chronic bronchitis, lung cancer, peptic ulcer, hypertension,
ischemic heart diseases etc.
THANK YOU