Vascular smooth muscle comes from mesodermal tissue, specifically the mesenchyme surrounding developing vessels in the lateral plate mesoderm. As the primitive blood vessels form, these mesodermal cells differentiate into smooth muscle cells that encase the endothelial tube, giving the muscular layer of arteries and veins. The heart muscle arises from cardiac mesoderm, neural crest cells contribute to smooth muscle in some cranial vessels, and endoderm forms gut lining and related organs, not vascular smooth muscle. Therefore, the smooth muscle of vessel walls is derived from the somatic part of the lateral plate mesoderm.

Torticollis presents as an abnormal head position caused by unilateral shortening or spasm of the sternocleidomastoid muscle, leading to a tilt of the head toward the affected side with the chin rotated to the opposite side. While congenital torticollis is common, there are also acquired forms that develop later due to muscle spasm, trauma, infections, inflammatory conditions, ocular misalignment, or cervical dystonia. Because both congenital and acquired forms exist, the statement that there is only a congenital form is false. The other points fit the typical picture: involvement of the sternocleidomastoid, a head tilt with some rotation, and the alternate name Wryneck.

Occipital somites are the embryologic source of tongue musculature. The myotomal cells from these somites migrate into the developing tongue and differentiate into all its muscles—both intrinsic and the extrinsic muscles—forming the tongue’s motor apparatus, which is why the tongue muscles are said to originate from the occipital region. They are innervated by the hypoglossal nerve. By contrast, other muscle groups arise from different embryologic sources: extrinsic eye muscles come from preotic mesoderm, muscles of mastication from the first pharyngeal arch, and muscles of facial expression from the second pharyngeal arch.

The muscles of the back are organized by depth from the surface: superficial, intermediate, and deep intrinsic layers. The superficial intrinsic back muscles sit closest to the skin and fascia; splenius capitis is in this superficial layer, lying on top of deeper muscles and helping to extend and rotate the head. The other options belong to the deeper transversospinalis group, which includes muscles that span multiple vertebrae to stabilize and fine-tune movements. Semispinalis capitis, rotatores, and multifidus are all deeper back muscles involved in more nuanced stabilization and control of the spine. Because splenius capitis sits in the superficial layer, it is the superficial intrinsic back muscle among these options.