Pharyngeal arch

Called the gill arch, also Branchialbogen ( Arcus branchiales ), pharyngeal arch, pharyngeal arch or visceral arch ( Southern German is used as the plural mostly ' arcs '), are developments of the foregut in vertebrates. The process of formation is referred to as Branchiomerie. In the mammalian embryo to form six such sheets, the fifth and sixth is usually applied only rudimentary.

Typical of the gill arches are their metameric structure, ie, each gill arch is structurally constituted the same. Thus, each gill arch a core of mesoderm, later a cartilage and muscle conditioning resulting from the a Kiemenbogennerv from the neural crest and branchial arch artery. However, seriale or metameric sequence of the branchial arch nerves has nothing in common with the segmental arrangement of the spinal nerves. Head and trunk region are organized differently, in other words, the Branchiomerie the gill arch and the metamerism of the body wall are to be considered independently.

In fishes, the membranes between furrow and tear a bag and there are the definitive gills. The existence of such branchial arches and clefts and in embryos of higher vertebrates was first described by Martin Rathke.

Branchial arch

Each gill arch has a branchial arch artery and vein, a Kiemenbogennerv as well as a muscle and a cartilage model. From the branchial arches many organs, which are therefore referred to as branchial organs develop in higher vertebrates.

First gill arch

From the first branchial arch ( mandibular arch ) results in large parts of the face such as the upper jaw (maxilla ), lower jaw ( mandible ) and palate as well as the malleus and incus (but not the stirrup). The cartilage model is known as Meckel 's cartilage.

From the muscular system the muscles of mastication occurs. The artery of the first gill arch regresses largely, but is involved to a small extent in the formation of the external carotid artery and maxillary artery. The first branchial arch nerve is the fifth cranial nerve, the trigeminal nerve.

Second branchial arch

The second branchial arch is also known as the hyoid arch (or hyoid arch ). For him, the upper part of the hyoid bone is formed ( Cornu minus; smaller part of the corpus ), the styloid process of the temporal bone and cartilage from the upper part and the ossicles stapes.

From the muscular system causes the muscles of facial expression, and the stapedius, the stylohyoid muscle and the posterior portion of the digastric muscle. The second branchial arch nerve is the seventh cranial nerve, the facial nerve. The corresponding artery develops first for A. stapedial. But this in turn recedes completely, so that only one remains avascular foramen in the stapes left.

Third branchial arch

The third branchial arch cartilage develops into the lower part of the hyoid bone ( greater horn; greater part of the corpus ), muscle conditioning to muscle stylopharyngeus, which is innervated accordingly in adults from the third branchial arch nerve, the ninth cranial nerve, glossopharyngeal nerve.

The artery of the third gill arch develops together with the dorsal aorta to the internal carotid artery.

Fourth branchial arch

The fourth branchial arch and its cartilage form around the upper part of the larynx. From the muscular system, the outer muscles of the larynx and part of the throat muscles arises. The fourth branchial arch nerve is the superior laryngeal nerve, branch of the vagus nerve ( tenth cranial nerve) which innervates a portion of the laryngeal muscles.

The arteries of the fourth branchial arch develop on both sides in different ways: from the left aortic arch artery arises from the right subclavian artery artery.

Fifth gill arch

The fifth gill arch formed only rudimentary or no effect. There are no definitive structures.

Sixth branchial arch

The sixth branchial arch and its cartilage forms around the lower part of the larynx. The muscular system evolves accordingly to the inner muscles of the larynx. The 6th Kiemenbogennerv is the recurrent laryngeal nerve, a branch of the vagus nerve ( tenth cranial nerve) which innervates a portion of the laryngeal muscles.

The arteries of the sixth branchial arch develop on both sides different: Links incurred by the pulmonary trunk and the ductus arteriosus, the right pulmonary artery.

Pharyngeal pouches

Between the six branchial arches are produced inside the five pharyngeal pouches or gill slits ( pharyngeal Sacci ), from the endoderm also develop definitive structures.

• From the first pharyngeal pouch of the recess tubotympanicus from which form the tympanic cavity and the Eustachian tube ( auditory tube ) is produced. Through a connection to the first pharyngeal cleft formed the outer ear canal.

• The second pharyngeal pouch forms the plant for the palatine tonsil.

• From the wall material of the third pharyngeal pouch, the lower parathyroid glands ( parathyroid gland inferior) and the thymus develop.

• Except in mammals - - the Ultimobranchialkörper from the fourth pharyngeal pouch, the upper parathyroid glands ( parathyroid gland superior) as well as form.

• From the material of the fifth pharyngeal pouch, the C - cells, which migrate into the thyroid gland in mammals develop.

Pharyngeal clefts

Externally created four pharyngeal or branchial grooves ( sulci branchiales or ductus branchiales ). It is only from the first pharyngeal cleft produces a definite structure: it forms by communicating with the first pharyngeal pouch the external auditory canal and the eardrum.

With the growth of the second branchial arch, the second, third and fourth furrow are generally closed. If this closure is incomplete, to cervical fistulae and cysts can form.