[2] Neural crest cells enter these arches where they contribute to features of the skull and facial skeleton such as bone and cartilage.

Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue.

In mammals the endoderm and ectoderm not only remain intact but also continue to be separated by a mesoderm layer.

Skeletal Muscles Other Mucous membrane and glands of the anterior two thirds of the tongue are derived from ectoderm and endoderm of the arch.

The mandibular and maxillary branches of the trigeminal nerve (CN V) innervate the structures derived from the corresponding processes of the first arch.

This double innervation is reflected in the nerve supply of anterior two-thirds of tongue which is derived from the first arch.

[14] In contrast to the Meckel's cartilage of the first pharyngeal arch it does not constitute a continuous element, and instead is composed of two distinct cartilaginous segments joined by a faint layer of mesenchyme.

[15] Dorsal ends of Reichert's cartilage ossify during development to form the stapes of the middle ear before being incorporated into the middle ear cavity, while the ventral portion ossifies to form the lesser cornu and upper part of the body of the hyoid bone.

Caudal to what will eventually become the stapes, Reichert's cartilage also forms the styloid process of the temporal bone.

The cartilage between the hyoid bone and styloid process will not remain as development continues, but its perichondrium will eventually form the stylohyoid ligament.

Most of the skeletal musculature supplied by the cranial nerves (special visceral efferent) is pharyngeal.

The stylopharyngeus and other structures from the third pharyngeal arch are all innervated by the glossopharyngeal nerve.

On the right side, the artery of arch 5 is obliterated while, on the left side, the artery persists as the ductus arteriosus; circulatory changes immediately following birth cause the vessel to close down, leaving a remnant, the ligamentum arteriosum.

During growth, these arteries descend into their ultimate positions in the chest, creating the elongated recurrent paths.

The argument is the existence of the fifth arch (and pouch), held to be a transient structure in the embryo.