Anterior surface facing down is a phrase used in medical terminology. This refers to the positioning and direction of the body. Anterior, or ventral, refers to the front part of the body. The anterior portion of the body is the chest, the face, the knees, everything that faces forward or those areas of the body one would see if they were looking directly into a mirror. The whole of the anterior is referred to as the anterior surface. Facing down indicates where the anterior portion is located. For example, if a person is lying flat on their stomach, they are lying anterior surface facing down.