What term is used to describe paired structures on each side of the body?

The term used to describe paired structures on each side of the body is "bilateral." This term comes from the prefix "bi-" meaning two, and "lateral," which refers to the sides. In anatomy, bilateral structures are those that exist as mirrored pairs. For example, the kidneys, lungs, and eyes are all paired structures that are found on either side of the body. Understanding this term is fundamental when discussing anatomy, as it helps in describing the locations and relationships of various body parts in a clear and structured manner.

In contrast, unilateral refers to structures that are present on only one side of the body, which does not apply here. Infra is a prefix meaning "below" and doesn’t pertain to the concept of paired structures. Proximal refers to a position closer to the trunk of the body or point of attachment, which also does not relate to the idea of pairing on either side. Hence, bilateral is the appropriate term for describing paired anatomical structures.