Final answer:
The structures located laterally along the anterior border of the SCM muscle that are remnants of the clefts are the branchial arches. They play a crucial role in the formation of the head and neck during embryonic development.
Step-by-step explanation:
The structures located laterally along the anterior border of the SCM (sternocleidomastoid) muscle that are remnants of the clefts are the branchial arches. The branchial arches are a series of embryonic structures that develop in the neck region and give rise to various anatomical features, including the muscles, bones, and nerves of the face and neck.
During development, the branchial arches fuse and form the structures we see in the adult human anatomy. They play a crucial role in the formation of the head and neck during embryonic development.
For example, the first branchial arch contributes to the formation of the lower jaw (mandible) and certain muscles in that region. Similarly, the second branchial arch gives rise to the hyoid bone and muscles associated with swallowing.