What is the term for a break in the skin surface or mucous membrane that exposes underlying tissues:

Open wound

Explanation:

A wound refers to an injured portion in the body which can be categorised into two types: the open and closed wound.

The open wound is the wound which is caused when an injury occurs in the skin and exposes the internal tissue and parts of the body while closed wound does not expose the internal parts of the body.

Thus, the open wound is the correct answer.