Chapter 5 - Section 5.6 - Study Guide - Assess Your Learning Outcomes - Page 173: 8

Necrosis is a type of cell death that occurs due to factors like injury, disease, or lack of blood supply. There are several varieties of necrosis, each with distinct characteristics and underlying causes. Here are three common varieties of necrosis: 1. **Infarction Necrosis:** - **Definition:** Infarction necrosis occurs when there is a blockage or obstruction in the blood vessels, leading to inadequate blood supply (ischemia) and subsequent cell death in a specific tissue or organ. - **Causes:** It is commonly caused by the blockage of an artery, often due to a blood clot (thrombus) or an embolus (a clot or debris that travels through the bloodstream and lodges in a smaller vessel). - **Examples:** Myocardial infarction (heart attack) occurs when a coronary artery becomes blocked, leading to the death of heart muscle cells. Cerebral infarction (stroke) can occur when a blood vessel in the brain is blocked. 2. **Dry Gangrene (Coagulative Necrosis):** - **Definition:** Dry gangrene is characterized by the gradual death of tissue, often in extremities like fingers and toes, due to a lack of blood supply. It typically appears dry, shrunken, and dark in color. - **Causes:** It is commonly associated with chronic conditions such as diabetes and atherosclerosis, which can lead to narrowed blood vessels and reduced blood flow to the affected areas. - **Appearance:** Dry gangrene often appears as a hard, cold, and mummified tissue. It is relatively slow to progress and is less prone to infection than other forms of gangrene. 3. **Gas Gangrene (Clostridial Myonecrosis):** - **Definition:** Gas gangrene is a severe and rapidly progressing form of necrosis caused by bacterial infection, typically involving Clostridium species (e.g., Clostridium perfringens). These bacteria produce toxins that destroy tissue and release gas into the affected area. - **Causes:** It usually occurs as a result of deep tissue injuries, such as puncture wounds, surgery, or compound fractures, which provide an anaerobic (low-oxygen) environment ideal for the growth of these bacteria. - **Appearance:** Gas gangrene is characterized by the presence of gas bubbles within the affected tissue, which gives it a crepitus (crackling) sensation when touched. The tissue may also appear swollen, discolored, and emit a foul odor. It's essential to note that while these are some common varieties of necrosis, there are other forms, including liquefactive necrosis, caseous necrosis (typically seen in tuberculosis), and fibrinoid necrosis (associated with immune reactions and blood vessel damage). The type of necrosis observed depends on factors such as the underlying cause, tissue involved, and the body's response to injury or infection. Prompt medical attention and treatment are crucial when necrosis occurs to prevent further complications.

Necrosis is a type of cell death that occurs due to factors like injury, disease, or lack of blood supply. There are several varieties of necrosis, each with distinct characteristics and underlying causes. Here are three common varieties of necrosis: 1. **Infarction Necrosis:** - **Definition:** Infarction necrosis occurs when there is a blockage or obstruction in the blood vessels, leading to inadequate blood supply (ischemia) and subsequent cell death in a specific tissue or organ. - **Causes:** It is commonly caused by the blockage of an artery, often due to a blood clot (thrombus) or an embolus (a clot or debris that travels through the bloodstream and lodges in a smaller vessel). - **Examples:** Myocardial infarction (heart attack) occurs when a coronary artery becomes blocked, leading to the death of heart muscle cells. Cerebral infarction (stroke) can occur when a blood vessel in the brain is blocked. 2. **Dry Gangrene (Coagulative Necrosis):** - **Definition:** Dry gangrene is characterized by the gradual death of tissue, often in extremities like fingers and toes, due to a lack of blood supply. It typically appears dry, shrunken, and dark in color. - **Causes:** It is commonly associated with chronic conditions such as diabetes and atherosclerosis, which can lead to narrowed blood vessels and reduced blood flow to the affected areas. - **Appearance:** Dry gangrene often appears as a hard, cold, and mummified tissue. It is relatively slow to progress and is less prone to infection than other forms of gangrene. 3. **Gas Gangrene (Clostridial Myonecrosis):** - **Definition:** Gas gangrene is a severe and rapidly progressing form of necrosis caused by bacterial infection, typically involving Clostridium species (e.g., Clostridium perfringens). These bacteria produce toxins that destroy tissue and release gas into the affected area. - **Causes:** It usually occurs as a result of deep tissue injuries, such as puncture wounds, surgery, or compound fractures, which provide an anaerobic (low-oxygen) environment ideal for the growth of these bacteria. - **Appearance:** Gas gangrene is characterized by the presence of gas bubbles within the affected tissue, which gives it a crepitus (crackling) sensation when touched. The tissue may also appear swollen, discolored, and emit a foul odor. It's essential to note that while these are some common varieties of necrosis, there are other forms, including liquefactive necrosis, caseous necrosis (typically seen in tuberculosis), and fibrinoid necrosis (associated with immune reactions and blood vessel damage). The type of necrosis observed depends on factors such as the underlying cause, tissue involved, and the body's response to injury or infection. Prompt medical attention and treatment are crucial when necrosis occurs to prevent further complications.