Branchial arch
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| Embryology: Branchial arch | ||
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| Schematic of developing fetus with first, second and third arches labeled. | ||
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| Floor of pharynx of human embryo about twenty-six days old. | ||
| Gray's | subject #13 65 | |
| Carnegie stage | 10 | |
| MeSH | A16.254.160 | |
| Dorlands/Elsevier | a_57/12149648 | |
In the development of vertebrate animals, the branchial arches (or pharyngeal arches) develop during the fourth and fifth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx.
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[edit] Development
These grow and join in the ventral midline. The first arch, as the first to form, separates the mouth pit or stomodeum from the pericardium. By differential growth the neck elongates and new arches form, so the pharynx has six arches ultimately.
[edit] Relations
Pharyngeal or branchial pouches form on the endodermal side between the arches, and pharyngeal grooves (or clefts) form from the lateral ectodermal surface of the neck region to separate the arches.
The pouches line up with the clefts, and these thin segments become gills in fish.
In mammals the endoderm and ectoderm not only remain intact, but continue to be separated by a mesoderm layer.
[edit] Specific arches
Each pharyngeal arch has a cartilaginous bar, a muscle component which differentiates from the cartilagenous tissue, an artery, and a cranial nerve.
There are six pharyngeal arches, but in humans the fifth arch only exists transiently during embryologic growth and development. Since no human structures result from the fifth arch, the arches in humans are I, II, III, IV, and VI.
More is known about the fate of the first arch than the remaining four. The first three contribute to structures above the larynx, while the last three contribute to the larynx and trachea.
[edit] First pharyngeal arch
| Pharyngeal arch | Muscular contributions | Skeletal contributions | Nerve |
| 1st (also called "mandibular arch") | muscles of mastication (temporalis, masseter, medial and lateral pterygoid) | maxilla, mandible, the incus and malleus of the middle ear | Trigeminal nerve (V2 and V3) |
| 2nd (also called the "hyoid arch") | Muscles of facial expression, buccinator, platysma, stapedius, stylohyoid, digastric posterior belly | Stapes, styloid process, hyoid (Lesser Horn and Part of Body) | Facial nerve (VII) |
| 3rd | Stylopharyngeus | Hyoid (Greater Horn and Part of Body) | Glossopharyngeal nerve (IX) |
| 4th and 6th | intrinsic muscles of larynx, pharynx; levator palati | thyroid cartilage, cricoid cartilage, epiglottic cartilage, arytenoid cartilages | Vagus nerve (X) |
[edit] See also
a Tuberculum laterale
b Tuberculum impar
c Foramen cecum
d Ductus thyreoglossus
e Sinus cervicalis
[edit] References
- 2006 - 2007 Dental Decks
- Harris, Edward F. (2002). Craniofacial Growth and Development.
- McMinn, R., 1994. Last's anatomy: Regional and applied (9th ed).
- Larsen Embryology.
