Pharyngeal arch

{{short description|Embryonic precursor structures in vertebrates}} {{Infobox embryology | Name = Pharyngeal arch | Latin = arcus pharyngei | Image = Pharyngeal arches.jpg | Width = 250 | Caption = Schematic of developing pharyngeal arches and [[pharyngeal pouch (embryology)|pouches]] in the [[human embryo]] at seried [[Carnegie stages]] (CS) | System = | CarnegieStage = 11–14 | Precursor = | GivesRiseTo = }} {{multiple image | align = right | direction = vertical | width = 257 | image1 = Gray979.png | alt1 = | caption1 = Floor of the pharynx of human embryo at about 26 days old | image2 = PharyngealArchHuman.jpg | alt2 = | caption2 = Scheme of the pharyngeal arches | image3 = Kiemenbogen.jpg | alt3 = | caption3 = Scheme of the pharyngeal arches{{unbulleted list |I–IV: pharyngeal arches |1–4: [[pharyngeal pouch (embryology)|pharyngeal pouches]] (inside) and/or [[pharyngeal grooves]] (outside) |a: [[Tuberculum laterale]] |b: [[Tuberculum impar]] |c: [[Foramen cecum (tongue)|Foramen cecum]] |d: [[Ductus thyreoglossus]] |e: [[Sinus cervicalis]]}} }} The '''pharyngeal arches''', also known as '''visceral arches''''','' are transient structures seen in the [[Animal embryonic development|embryonic development]] of [[human]]s and other [[vertebrate]]s, that are recognisable precursors for many structures.<ref name="Zbasnik">{{cite journal |last1=Zbasnik |first1=N |last2=Fish |first2=JL |title=Fgf8 regulates first pharyngeal arch segmentation through pouch-cleft interactions. |journal=Frontiers in Cell and Developmental Biology |date=2023 |volume=11 |article-number=1186526 |doi=10.3389/fcell.2023.1186526 |doi-access=free |pmid=37287454|pmc=10242020 }}</ref> In [[fish]], the arches support the [[Fish gill|gills]] and are known as the [[branchial arch]]es, or gill arches.

In the [[human embryo]], the arches are first seen during the fourth week of [[human embryonic development|development]]. They appear as a series of outpouchings of [[mesoderm]] on both sides of the developing [[pharynx]]. The [[vasculature]] of the pharyngeal arches are the [[aortic arches]] that arise from the [[aortic sac]].

==Structure== In [[human]]s and other [[vertebrates]], the pharyngeal arches are derived from all three [[germ layers]], (the primary layers of cells that form during [[embryonic development]]).<ref name=dev>{{cite journal |author=Graham A |title= Development of the pharyngeal arches |journal= Am J Med Genet A|volume= 119A|issue= 3|pages=251–256|year= 2003|pmid= 12784288 |doi=10.1002/ajmg.a.10980|s2cid= 28318053 }}</ref> [[Neural crest cells]] enter these arches where they contribute to features of the [[skull]] and [[facial skeleton]] such as bone and cartilage.<ref name = dev /> The existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development.<ref name= archevo>{{cite journal |vauthors=Graham A, Smith A |title= Patterning the pharyngeal arches|journal= BioEssays|volume=23|issue= 1|pages=54–61|year= 2001|pmid=11135309 |doi=10.1002/1521-1878(200101)23:1<54::AID-BIES1007>3.0.CO;2-5|s2cid= 10792335}}</ref>

The first, most anterior [[first pharyngeal arch|pharyngeal arch]] (in mammals) gives rise to the [[mandible]]. The second arch becomes the [[hyoid]] and jaw support.<ref name=dev />

In fish, the other posterior arches contribute to the branchial skeleton, which support the gills; in tetrapods the anterior arches develop into components of the ear, tonsils, and thymus.<ref name=vertebrates>{{cite journal |author= Kardong KV |title= Vertebrates: Comparative Anatomy, Function, Evolution|journal=Third Edition|volume=New York|issue= McGraw Hill|year= 2003}}</ref>

The genetic and developmental basis of pharyngeal arch development is well characterized. It has been shown that [[Hox gene]]s and other developmental genes such as ''[[DLX gene family|DLX]]'' are important for patterning the anterior/posterior and dorsal/ventral axes of the [[branchial arch]]es.<ref name=jaw>{{cite journal |vauthors=Depew MJ, Lufkin T, Rubenstein JL |title=Specification of jaw subdivisions by Dlx genes|journal= Science |volume=298|issue=5592|pages=381–385|year= 2002|pmid= 12193642 |doi=10.1126/science.1075703|s2cid=10274300|doi-access=free}}</ref> Some fish species have a second set of jaws in their throat, known as [[pharyngeal jaw]]s, which develop using the same genetic pathways involved in oral jaw formation.<ref name=fish>{{cite journal |vauthors=Fraser GJ, Hulsey D, Bloomquist RF, Uyesugi K, Manley NR, Streelman T |title= An Ancient Gene Network Is Co-opted for Teeth on Old and New Jaws|journal= PLOS Biology |volume= 7|issue= 2|pages=0233–0247 |year= 2009|pmid= 19215146 |pmc=2637924 |doi= 10.1371/journal.pbio.1000031 |editor1-last=Jernvall |editor1-first=Jukka|doi-access= free}}</ref>

During [[embryonic development]], a series of pharyngeal arch pairs form. These project forward from the back of the embryo toward the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and arch 5 existing only transiently.<ref name = LARSEN1993 />

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.

Each pharyngeal arch has a [[cartilage|cartilaginous]] stick, a [[muscle]] component that differentiates from the cartilaginous tissue, an artery, and a [[cranial nerve]]. Each of these is surrounded by [[mesenchyme]]. Arches do not develop simultaneously but instead possess a "staggered" development.

[[Pharyngeal pouch (embryology)|Pharyngeal pouch]]es form on the [[germ layer#Endoderm|endodermal]] side between the arches, and [[pharyngeal groove]]s (or clefts) form from the lateral [[germ layer#Ectoderm|ectodermal]] surface of the [[neck]] region to separate the arches.<ref>{{cite web |last=McKenzie |first=James C.|url=http://www.med.howard.edu/anatomy/gas/wk7/Lecture%2024.htm |title=Lecture 24. Branchial Apparatus |publisher=Howard University |access-date=2007-09-09 |archive-url=https://archive.today/20030502115201/http://www.med.howard.edu/anatomy/gas/wk7/Lecture%2024.htm |archive-date=2003-05-02 }}</ref> In fish, the pouches line up with the clefts, and these thin segments become [[gill]]s. In mammals the [[endoderm]] and [[ectoderm]] not only remain intact but also continue to be separated by a [[mesoderm]] layer.

The development of the pharyngeal arches provides a useful landmark with which to establish the precise stage of embryonic development. Their formation and development corresponds to [[Carnegie stages]] 10 to 16 in [[mammals]], and [[Hamburger–Hamilton stages]] 14 to 28 in the [[model organism#Vertebrates|chicken]]. Although there are six pharyngeal arches, in humans the fifth arch exists only transiently during [[human embryogenesis|embryogenesis]].<ref name=development>{{cite web |url=http://isc.temple.edu/marino/embryology/parch98/parch_text.htm |title=Text for Pharyngeal Arch Development |last=Marino |first=Thomas A. |publisher=Temple University |access-date=2007-09-09 |archive-url=https://web.archive.org/web/20070909052409/http://isc.temple.edu/marino/embryology/parch98/parch_text.htm |archive-date=2007-09-09 }}</ref>

==First arch== The '''first pharyngeal arch''', also '''mandibular arch''' (corresponding to the first branchial arch of fish), is the first of six pharyngeal arches that develops during the fourth week of [[Human embryogenesis|development]].<ref name="William J. Larsen 2001">William J. Larsen (2001). Human embryology. Edinburgh: Churchill Livingstone. {{ISBN|0-443-06583-7}}</ref> It is located between the [[stomodeum]] and the [[first pharyngeal groove]].

===Processes=== This arch divides into a [[maxillary prominence|maxillary process]] and a [[mandibular process]], giving rise to structures including the [[bone]]s of the lower two-thirds of the face and the jaw. The maxillary process becomes the [[maxilla]] (or '''upper jaw''', although there are large differences among animals<ref>{{Cite journal | last1 = Higashiyama | first1 = Hiroki | last2 = Koyabu | first2 = Daisuke | last3 = Hirasawa | first3 = Tatsuya | last4 = Werneburg | first4 = Ingmar | last5 = Kuratani | first5 = Shigeru | last6 = Kurihara | first6 = Hiroki | title = Mammalian face as an evolutionary novelty | journal = PNAS | date = November 2, 2021 | volume = 118 | issue = 44 | article-number = e2111876118 | doi = 10.1073/pnas.2111876118 | pmc = 8673075| pmid=34716275 | bibcode = 2021PNAS..11811876H | doi-access = free }}</ref>), and [[palate]] while the mandibular process becomes the [[human mandible|mandible]] or '''lower jaw'''. This arch also gives rise to the [[Mastication#Muscles of mastication|muscles of mastication]].

===Meckel's cartilage=== [[Meckel's cartilage]] forms in the [[germ layer#Mesoderm|mesoderm]] of the mandibular process and eventually regresses to form the [[incus]] and [[malleus]] of the [[middle ear]], the anterior ligament of the malleus and the [[sphenomandibular ligament]]. The [[Human mandible|mandible]] or lower jaw forms by perichondral [[ossification]] using Meckel's cartilage as a 'template', but the mandible does ''not'' arise from direct ossification of Meckel's cartilage.

===Derivatives=== The skeletal elements and muscles are derived from mesoderm of the pharyngeal arches.

'''Skeletal''' *[[malleus]] and [[incus]] of the [[middle ear]] *[[maxilla]] and [[Human mandible|mandible]] *[[spine of sphenoid bone]] *[[sphenomandibular ligament]] *[[palatine bone]] *[[squamous part of temporal bone]] *[[anterior ligament of malleus]]

'''Muscles''' * [[muscles of mastication]] (chewing) **[[masseter]] ** [[medial pterygoid muscle|medial]] and [[lateral pterygoid muscle]]s **[[temporalis]] *[[mylohyoid muscle]] *[[digastric muscle]], anterior belly *[[tensor veli palatini muscle]] *[[tensor tympani muscle]]

'''Other'''

[[Mucous membrane]] and glands of the [[anterior two thirds of the tongue]] are derived from [[ectoderm]] and [[endoderm]] of the arch.

===Nerve supply=== The mandibular and maxillary branches of the [[trigeminal nerve]] ('''CN V''') innervate the structures derived from the corresponding processes of the first arch. In some lower animals, each arch is supplied by two cranial nerves. The nerve of the arch itself runs along the cranial side of the arch and is called post-trematic nerve of the arch. Each arch also receives a branch from the nerve of the succeeding arch called the pre-trematic nerve which runs along the caudal border of the arch. In human embryo, a double innervation is seen only in the first pharyngeal arch. The mandibular nerve is the post-trematic nerve of the first arch and [[chorda tympani]] (branch of facial nerve) is the pre-trematic nerve. This double innervation is reflected in the nerve supply of anterior two-thirds of [[Tongue#Innervation|tongue]] which is derived from the first arch.<ref>Inderbir Sing, G.P Pal-Human Embryology</ref>

===Blood supply=== The artery of the first arch is the first [[aortic arches|aortic arch]],<ref name="McMinn, R. 1994">McMinn, R., 1994. ''Last's anatomy: Regional and applied (9th ed).''</ref> which partially persists as the [[maxillary artery]].

==Second arch== The '''second pharyngeal arch''' or '''hyoid arch''', is the second of five pharyngeal arches that develops in [[Prenatal development#Week 4 .2822-28 days from fertilization.29|fetal life]] during the fourth week of development<ref name="William J. Larsen 2001"/> and assists in forming the side and front of the [[neck]].

===Reichert's cartilage=== Cartilage in the second pharyngeal arch is referred to as Reichert's cartilage and contributes to many structures in the fully developed adult.<ref>Sudhir, Sant, 2008.''Embryology for Medical Students 2nd edition''</ref> 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]].<ref name=dev2>{{cite journal |author=Rodríguez-Vázquez JF |title= Morphogenesis of the second pharyngeal arch cartilage (Reichert's cartilage) in human embryos |journal= J. Anat.|volume= 208|issue= 2|pages=179–189|year= 2008|pmid= 16441562 |doi=10.1111/j.1469-7580.2006.00524.x |pmc=2100189}}</ref> Dorsal ends of Reichert's cartilage [[Ossification|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 [[temporal styloid process|styloid process]] of the [[temporal bone]]. The cartilage between the [[hyoid bone]] and [[temporal styloid process|styloid process]] will not remain as development continues, but its [[perichondrium]] will eventually form the [[stylohyoid ligament]].

===Derivatives===

'''Skeletal'''

From the cartilage of the second arch arises *[[Stapes]], *[[Temporal styloid process]], *[[Stylohyoid ligament]], and *[[Lesser cornu]] of the [[hyoid bone]].

'''Muscles''' *[[Facial muscles]] *[[Occipitofrontalis]] muscle *[[Platysma]] *[[Stylohyoid]] muscle *Posterior belly of [[digastric muscle]] *[[Stapedius]] muscle *Auricular muscles

===Nerve supply===

[[Facial nerve]] (CN VII)

===Blood supply=== The artery of the second arch is the second [[aortic arches|aortic arch]],<ref name="McMinn, R. 1994"/> which gives origin to the [[stapedial artery]] in some mammals but atrophies in most humans.

==Muscles derived from the pharyngeal arches== '''Pharyngeal muscles or Branchial muscles''' are [[striated muscle]]s of the head and neck. Unlike [[skeletal muscles]] that developmentally come from [[somites]], pharyngeal muscles are developmentally formed from the pharyngeal arches.

Most of the skeletal musculature supplied by the cranial nerves ([[special visceral efferent]]) is pharyngeal. Exceptions include, but are not limited to, the [[extraocular muscles]] and some of the muscles of the tongue. These exceptions receive [[general somatic efferent]] innervation.

===First arch=== All of the [[pharyngeal muscles]] that come from the first pharyngeal arch are innervated by the mandibular divisions of the [[trigeminal nerve]].<ref name=":0">{{Cite book|title = Langman's Medical Embryology|last = Sadler|first = Thomas W.|publisher = Lippincott Williams & Wilkins|date = February 2009|isbn = 978-0-7817-9069-7|pages = 366–369}}</ref> These muscles include all the [[muscles of mastication]], the anterior belly of the [[digastric]], the [[Mylohyoid muscle|mylohyoid]], [[tensor tympani]], and [[tensor veli palatini]].

===Second arch=== All of the pharyngeal muscles of the second pharyngeal arch are innervated by the [[facial nerve]]. These muscles include the [[facial muscles|muscles of facial expression]], the posterior belly of the [[digastric]], the [[stylohyoid]] muscle, the auricular muscle<ref name=":0" /> and the [[stapedius]] muscle of the middle ear.

===Third arch=== There is only one muscle of the third pharyngeal arch, the [[stylopharyngeus]]. The stylopharyngeus and other structures from the third pharyngeal arch are all innervated by the [[glossopharyngeal nerve]].

===Fourth and sixth arches=== All the pharyngeal muscles of the fourth and sixth arches are innervated by the superior laryngeal and the recurrent laryngeal branches of the [[vagus nerve]].<ref name=":0" /> These muscles include all the muscles of the palate (exception of the [[tensor veli palatini]] which is innervated by the [[trigeminal nerve]]), all the muscles of the pharynx (except [[stylopharyngeus]] which is innervated by the [[glossopharyngeal nerve]]), and all the muscles of the larynx.

==In humans== It has been proposed that the five arches in amniotes numbered 1–4 and 6, be re-named as simply 1–5.<ref name="Graham">{{cite journal |last1=Graham |first1=Anthony |last2=Poopalasundaram |first2=Subathra |date=11 Aug 2019 |title=A reappraisal and revision of the numbering of the pharyngeal arches |journal=J. Anat. |volume=235 |issue=6 |pages=1019–1023 |doi=10.1111/joa.13067 |pmid=31402457 |pmc=6875933 }}</ref> The fifth arch is seen to be a transient structure and becomes the sixth arch, (the fifth being absent). More is known about the fate of the first arch than the remaining four. The first three contribute to structures above the larynx, whereas the last two contribute to the [[larynx]] and [[Vertebrate trachea|trachea]].

The [[recurrent laryngeal nerve]]s are produced from the nerve of arch 5, and the laryngeal cartilages from arches 4 and 5. The superior laryngeal branch of the vagus nerve arises from arch 4. Its arteries, which project between the nerves of the fourth and fifth arches, become the left-side arch of the aorta and the right [[subclavian artery]]. 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.<ref name=LARSEN1993>{{cite book|last1=Larsen|first1=William J.|title=Human embryology|date=1993|publisher=Churchill Livingstone|location=New York|isbn=0-443-08724-5|pages=318–323}}</ref>

{| class="wikitable" ! Pharyngeal arch !! Muscular contributions<ref>{{cite web |url=http://musom.marshall.edu/anatomy/grosshom/z_devbranc.html |title=marshall.edu |access-date=2007-09-09 |archive-url=https://web.archive.org/web/20090227080017/http://musom.marshall.edu/anatomy/grosshom/z_devbranc.html |archive-date=2009-02-27 }}</ref> !! Skeletal contributions !! Nerve !! [[Aortic arches|Artery]] |- | 1st (also called "[[mandibular arch]]") || [[Muscles of mastication]], anterior belly of the [[digastric]], [[Mylohyoid muscle|mylohyoid]], [[tensor tympani]], [[tensor veli palatini]] || Premaxilla, [[maxilla]], [[Human mandible|mandible]] (only as a model for mandible not actual formation of mandible), [[zygomatic bone]], part of the [[temporal bone]],<ref name=":1">{{Cite book|title = Langman's Medical Embryology|last = Sadler|first = Thomas W.|publisher = Lippincott Williams & Wilkins|date = February 2009|isbn = 978-0-7817-9069-7|pages = 366–372}}</ref> the [[incus]], and the [[malleus]] of the middle ear, also [[Meckel's cartilage]] and the [[sphenomandibular ligament]]. || [[Trigeminal nerve]] (part of V2<ref name=V2>{{cite journal |vauthors=Higashiyama H, Kuratani S |title= On the maxillary nerve|journal= Journal of Morphology |volume= 275 |issue= 1|pages=17–38 |year= 2014|pmid= 24151219 |doi= 10.1002/jmor.20193 |s2cid= 32707087}}</ref> and V3) || [[External carotid artery]], [[Inferior alveolar artery]] (especially the [[mylohyoid]] branch), [[Maxillary artery]], [[Vidian artery]] |- | 2nd (also called the "[[hyoid arch]]") || [[Muscles of facial expression]], [[buccinator]], [[platysma]], [[stapedius]], [[stylohyoid]], [[Digastric#Posterior belly|posterior belly of the digastric]], [[Auricular muscles|auricular]]<ref name=":0" /> || [[Stapes]], [[temporal styloid process]], [[hyoid bone]] ([[hyoid#Horns|lesser horns]] and upper part of body), [[stylohyoid ligament]],<ref name=":0" /> Reichert's cartilage || [[Facial nerve]] (VII) || [[Superior thyroid artery]], [[Ascending pharyngeal artery]], [[Inferior tympanic artery]], [[Caroticotympanic arteries|primitive hyoid artery]], [[Stapedial artery]] |- | 3rd || [[Stylopharyngeus]] || [[Hyoid bone]] ([[hyoid#Horns|greater horns]] and lower part of body), [[thymus]]|| [[Glossopharyngeal nerve]] (IX) || [[Common carotid artery|common carotid]], [[internal carotid]] |- | 4th || [[Cricothyroid muscle]], all intrinsic muscles of [[soft palate]] (including [[levator veli palatini]]) ''except'' [[tensor veli palatini]] || [[Thyroid cartilage]], [[epiglottic cartilage]]<ref name="isbn0-914168-99-1">{{cite book |author1=Netter, Frank H. |author2=Cochard, Larry R. |title=Netter's Atlas of human embryology |publisher=Icon Learning Systems |location=Teterboro, N.J |year=2002 |isbn=0-914168-99-1 |page=227}}</ref>|| [[Vagus nerve]] (X), [[superior laryngeal nerve]]<ref name="BRS">{{cite book |author=Kyung Won Chung |title=Gross Anatomy (Board Review) |publisher=Lippincott Williams & Wilkins |location=Hagerstown, Maryland |year=2005 |isbn=0-7817-5309-0 }}</ref> || Right 4th aortic arch: [[subclavian artery]] Left 4th aortic arch: [[aortic arch]] |- | 6th (5th is obliterated) || All intrinsic muscles of [[larynx]] except the [[cricothyroid muscle]] || [[Cricoid cartilage]], [[arytenoid cartilage]]s, [[corniculate cartilage]], [[cuneiform cartilages]]<ref name="isbn0-914168-99-1" /> || [[Accessory nerve]] ([[Cranial root of accessory nerve|Cranial root]]) (XI), [[recurrent laryngeal nerve]]<ref name="BRS" /> || Right 6th aortic arch: [[pulmonary artery]]<br /> Left 5th aortic arch: [[pulmonary artery]] and [[ductus arteriosus]] |}

==Terminology== It has been proposed that the arches be re-named simply as 1–5. The argument is the existence of the fifth arch (and pouch), held to be a transient structure in the embryo.<ref name="Graham"/><ref name="Graham2023">{{cite journal |last1=Graham |first1=Anthony |last2=Hikspoors |first2=Jill P. J. M. |last3=Anderson |first3=Robert H. |last4=Lamers |first4=Wouter H. |last5=Bamforth |first5=Simon D. |title=A revised terminology for the pharyngeal arches and the arch arteries |journal=Journal of Anatomy |date=October 2023 |volume=243 |issue=4 |pages=564–569 |doi=10.1111/joa.13890|pmid=37248750 |pmc=10485586 }}</ref>

==Additional images== <gallery> File:Gray41.png| Schematic of developing [[human embryo]] with first (mandibular), second (hyoid), pharyngeal arches and third arches labelled </gallery>

==See also== {{Anatomy-terms}} * [[Branchial cleft cyst]] * [[Congenital cartilaginous rest of the neck]] * [[First arch syndrome]] * [[Splanchnocranium]]

==References== {{Reflist}}

==External links== * {{cite journal |vauthors=Graham A, Okabe M, Quinlan R |title=The role of the endoderm in the development and evolution of the pharyngeal arches |journal=J. Anat. |volume=207 |issue=5 |pages=479–87 |year=2005 |pmid=16313389 |doi=10.1111/j.1469-7580.2005.00472.x |pmc=1571564 }}

{{Embryology of head and neck}} {{Authority control}}

[[Category:Vertebrate anatomy]] [[Category:Pharyngeal arches]] [[Category:Animal developmental biology]] [[Category:Otorhinolaryngology]] [[Category:Embryology]]