Aband of tough connective tissue in the midline of the anterior abdominal wall called the serves as a muscle attachment.

Linea Alba is the tough connective tissue in midline of anterior abdominal wall which acts as muscle attachment.

Explanation:

A white line which is in a fibrous structure is Linea Alba. This runs down in the abdomen's middle in case of human beings and other vertebrates. In human beings it runs from xiphoid process to the pubic syphysis. This linea Alba is white in nature and this is consists of collagen connective tissues.  

There is no blood vessels or nerves present in linea alba. This mainly consists of some connective tissues. Tissues in connective nature and that is present in the anterior abdominal wall middle and acts as muscle attachment is Linear Alba.