What occurs to tissue in cases of gangrene?

In cases of gangrene, the primary process involved is the permanent damage or death of cells within the affected tissue. Gangrene occurs due to a loss of blood supply, which can result from various factors such as infection, injury, or vascular diseases. When blood flow is restricted or cut off, oxygen and essential nutrients are no longer delivered to the tissue, leading to cellular death. This can also lead to the breakdown of tissue, which may become necrotic and result in significant complications.

The other options describe processes that do not accurately represent what happens in gangrene. For instance, tissue swelling and fluid retention may occur in different conditions but not specifically as a characteristic of gangrene. Similarly, increased blood flow and healing would be contradictory to the state of tissue in gangrene, where blood supply is compromised. Cells surviving and regenerating is also not applicable, as the hallmark of gangrene is the irreversible damage to the cells due to necrosis. Thus, the correct understanding of gangrene emphasizes the loss and death of cells within the affected tissue.