Cell Injury: Reversible and Irreversible

Cell Injury: Introduction

• Cell injury is damage or defects within a body's cells.
• It is caused by changes or disturbances in the cell's internal or external environment.
• Cells are the basic units of tissues, organs, and systems.
• Cell injuries result from stress, which leads to changes in the internal and external environment.
• A cell's response to stress varies depending on several factors.
• Cell injury can be reversible or irreversible.

Flowchart Explanation

• Normal cells may adapt when exposed to moderate stress.
• High stress on a normal cell leads to cell injury.
• Cells can become injured after adapting to moderate stress if the originating stress continues to increase.
• Cell injury can be reversed if the stress is removed, allowing the cell to return to a normal state.
• Extreme stress leads to irreversible cell injury.
• Irreversible injury results in cell death.
• Necrosis and apoptosis are two types of irreversible cell injury.

Definitions

• Cellular adaptation is a process where cells survive adverse situations.
• Adaptation involves temporary or permanent changes in a cell’s shape, size, or type.
• Reversible cell injury occurs when mild to moderate stress is removed.
• Cells recover to their normal state after reversible cell injury.
• Irreversible cell injury happens when severe stress leads to cell death.
• Cells cannot recover from irreversible injuries.

Causes of Cell Injury

• Etiology is the study of the causes of cell injury.
• Cell injury is classified into two main categories: genetic and acquired.

Genetic Causes

• Cell injury due to defective genes or chromosomes is classified as genetic.
• Types of genetic defects include developmental defects, cytogenic abnormalities, single-gene disorders, and multifactorial inheritance.
• Developmental defects happen during fetal development.
• Cytogenic defects involve abnormalities in chromosome structure or number.
• Single-gene defects are also known as Mendelian disorders.
• Single-gene defects involve a specific gene defect
• Multifactorial inheritance disorders occur when multiple genes are defective.
• Disorders transfer through genes to offspring.

Acquired Causes

• Acquired causes are non-genetic factors leading to cell injury.
• These include physical, chemical, microbial, immunological, nutritional, and psychogenic agents.
• Hypoxia is a loss of oxygen supply.
• Ischemia is the loss of blood supply.
• Both hypoxia and ischemia are major causes of cell injury.

Physical Agents

• Physical trauma, such as accidents, can damage cells.
• Thermal trauma, such as burns or frostbite, affects cells.
• Exposure to electric current causes cell damage.
• UV rays or radiation in industrial settings can harm cells.
• Rapid changes in the atmosphere can damage cells.

Chemical Agents

• Chemical poisoning from substances like cyanide or arsenic causes injury.
• Strong acids and bases like Hydrochloric acid (HCl) and Sodium hydroxide (NaOH) cause cell damage.
• Environmental pollutants in the atmosphere can damage cells.
• Exposure to pesticides and insecticides can result in cell injury.
• Hypertonic salt solutions disrupt the cell.
• Alcohol, nicotine, and drugs are toxic substances that damage cells.

Microbial Agents

• Microbes such as bacteria, fungi, viruses, protozoa, and parasites disrupt cell functions.

Immunological Agents

• While the immune system protects, hypersensitivity or autoimmune disorders can cause cell injury.
• The body may reject a new organ because the immune system doesn't recognize it.
• Rejection by the immune system can lead to cell injury.

Nutritional Derangements

• Deficiencies or excesses of nutrients can lead to imbalances.
• These imbalances cause cell injury.
• Insufficiency can lead to anemia.
• Excessive intake of nutrients causes obesity.

Psychogenic Disorders

• Psychological factors such as anxiety, depression, and addictions can cause cell injury.