Which of the following best describes ischemia?

Ischemia is best described as insufficient blood supply to a particular tissue or organ. This condition can result from various factors, including blockages in blood vessels due to atherosclerosis, blood clots, or compression of blood vessels. When blood supply is reduced, the affected tissues do not receive adequate oxygen and nutrients, which are crucial for their function and survival. Thus, ischemia can lead to damage or dysfunction of the tissues, and if prolonged, it may result in tissue death or necrosis.

In contrast, other options involve processes that do not accurately define ischemia. An excess blood flow indicates a different condition, characterized by hyperemia, while normal oxygen supply means that tissues are receiving adequate blood flow and oxygen. Fluid accumulation refers to edema or other conditions not related to the direct supply of blood and oxygen, further differentiating it from ischemia.