A fistula uses a small tube to connect which two vessels?

A fistula is a medical connection between two vessels, specifically linking a vein and an artery. This type of connection is often used in the context of hemodialysis, where a vascular access point is created to facilitate the easy withdrawal and return of blood during treatment. By creating a fistula, the flow of blood from the artery into the vein increases the size and blood flow of the vein, making it suitable for repeated access in dialysis.

The other options do not accurately describe the function or purpose of a fistula, as they suggest connections between similar vessels or vessels and organs that do not fit the established use of a fistula in medical practice. The critical point here is understanding that a fistula specifically involves the joining of a vein to an artery to serve a medical need.