Unable to identify a muscle of the anterior thorax I was watching an YouTube Anatomy Video which goes over the major muscles of the anterior superficial thorax. There is a structure present throughout the video which goes unmentioned, and I can't seem to identify. ![enter image description here]( It is shown as a pair of structures, each running from the manubrium to the xiphisternal junction along the lateral margin of the anterior sternum, perhaps with a second head attaching to the costal cartilage. I'm probably missing something obvious, but for the life of me I can't think of what that could be.

This appears to be the sternalis muscle. The reason it is not mentioned may because it is not present in all individuals, and is therefore relatively poorly characterised.

The image is from `An Atlas of anatomy by regions` by John Charles Boileau Grant.

![enter image description here](

Another image of the muscle can be found in `Pocket Atlas of Human Anatomy` by Thieme:

![enter image description here]( ![enter image description here](