Branchial arch

Scanning electron micrograph of an 11.5 day old mouse foetus showing the limb buds, somites and branchial arches. The crown-rump length is approximately 9.5mm

The branchial arch is a fundamental structure in the embryological development of most vertebrates, including humans. It is also known as a pharyngeal arch or gill arch. The branchial arches are a series of bony "loops" present in the neck and head region of the embryo, which later give rise to various structures of the face, neck, and throat.

Development

The branchial arches begin to form during the fourth week of embryonic development. They are initially visible as a series of bulges on the lateral sides of the embryo. Each arch is separated from the next by a groove known as a branchial cleft or pharyngeal groove.

The arches are composed of a core of mesoderm, which is covered externally by ectoderm and internally by endoderm. The mesoderm within each arch gives rise to a cartilaginous bar, a muscle component, and an artery, known as the branchial arch artery.

Function

Each branchial arch gives rise to specific structures in the adult organism. For example, the first branchial arch forms the maxilla and mandible, two of the major bones of the face. The second arch forms structures such as the stapes, a small bone in the ear, and parts of the throat. The third and fourth arches contribute to the formation of the larynx and pharynx.

Clinical Significance

Abnormalities in the development of the branchial arches can lead to a variety of congenital disorders. These include Pierre Robin sequence, Treacher Collins syndrome, and DiGeorge syndrome, among others. These conditions can result in facial deformities, difficulties with breathing and swallowing, and other complications.

See Also

• Embryology
• Pharyngeal apparatus
• Pharyngeal pouch