Pharyngeal arches

Embryology - 1 Dec 2023        Expand to Translate
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Introduction

Embryo Stage 14

The pharyngeal arches (branchial arch, Greek, branchial = gill) are a series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck. Each arch though initially formed from similar components will differentiate to form different head and neck structures. In humans, five arches form (1, 2, 3, 4 and 6) but only four are externally visible on the embryo.

Each arch has initially identical structures: an internal endodermal pouch, a mesenchymal (mesoderm and neural crest) core, a membrane (endoderm and ectoderm) and external cleft (ectoderm). Each arch mesenchymal core also contains similar components: blood vessel, nerve, muscular, cartilage.

Both the endocrine organs thymus and parathyroid have developmental origins from the pharyngeal pouches. Cranial nerves are also associated with specific cranial arches.

The arch arteries undergo extensive remodelling during development of the vascular system, in general the inferior arteries have major contributions and superior arteries have minor contributions. The endothelium of arch arteries 1 and 2 has been shown to have different embryonic origin from 3-6 (second heart field).

Note is a draft page and this topic is currently covered in more detail on the head Development page.

Links: pharyngeal arch | head | neural crest | endocrine

Some Recent Findings

Pharyngeal arch segmentation model Tbx1 and Foxi3

GATA3 is essential for separating patterning domains during facial morphogenesis "Neural crest cells (NCCs) within the mandibular and maxillary prominences of the first pharyngeal arch are initially competent to respond to signals from either region. However, mechanisms that are only partially understood establish developmental tissue boundaries to ensure spatially correct patterning. In the 'hinge and caps' model of facial development, signals from both ventral prominences (the caps) pattern the adjacent tissues whereas the intervening region, referred to as the maxillomandibular junction (the hinge), maintains separation of the mandibular and maxillary domains. One cap signal is GATA3, a member of the GATA family of zinc-finger transcription factors with a distinct expression pattern in the ventral-most part of the mandibular and maxillary portions of the first arch. Here, we show that disruption of Gata3 in mouse embryos leads to craniofacial microsomia and syngnathia (bony fusion of the upper and lower jaws) that results from changes in BMP4 and FGF8 gene regulatory networks within NCCs near the maxillomandibular junction. GATA3 is thus a crucial component in establishing the network of factors that functionally separate the upper and lower jaws during development." Pharyngeal pouches provide a niche microenvironment for arch artery progenitor specification "The paired pharyngeal arch arteries (PAAs) are transient blood vessels connecting the heart with the dorsal aorta during embryogenesis. Although PAA malformations often occur along with pharyngeal pouch defects, the functional interaction between these adjacent tissues remains largely unclear. Here, we report that pharyngeal pouches are essential for PAA progenitor specification in zebrafish embryos. We reveal that the segmentation of pharyngeal pouches coincides spatiotemporally with the emergence of PAA progenitor clusters. These pouches physically associate with pharyngeal mesoderm in discrete regions and provide a niche microenvironment for PAA progenitor commitment by expressing BMP proteins. Specifically, pouch-derived BMP2a and BMP5 are the primary niche cues responsible for activating the BMP/Smad pathway in pharyngeal mesoderm, thereby promoting progenitor specification. In addition, BMP2a and BMP5 play an inductive function in the expression of the cloche gene npas4l in PAA progenitors. cloche mutants exhibit a striking failure to specify PAA progenitors and display ectopic expression of head muscle markers in the pharyngeal mesoderm. Therefore, our results support a crucial role for pharyngeal pouches in establishing a progenitor niche for PAA morphogenesis via BMP2a/5 expression." Tbx1 and Foxi3 genetically interact in the pharyngeal pouch endoderm in a mouse model for 22q11.2 deletion syndrome "We investigated whether Tbx1, the gene for 22q11.2 deletion syndrome (22q11.2DS) and Foxi3, both required for segmentation of the pharyngeal apparatus (PA) to individual arches, genetically interact. We found that all Tbx1+/-;Foxi3+/- double heterozygous mouse embryos had thymus and parathyroid gland defects, similar to those in 22q11.2DS patients.... Several genes expressed in the PA epithelia were downregulated in both Tbx1 and Foxi3 null mutant embryos including Notch pathway genes Jag1, Hes1, and Hey1, suggesting that they may, along with other genes, act downstream to explain the observed genetic interaction. We found Alcam and Fibronectin extracellular matrix proteins were reduced in expression in Foxi3 null but not Tbx1 null embryos, suggesting that some, but not all of the downstream mechanisms are shared." OMIM - Tbx1 | OMIM - Foxi3 Hox genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs "The pharyngeal organs, namely the thyroid, thymus, parathyroids, and ultimobranchial bodies, derive from the pharyngeal endoderm during embryonic development. The pharyngeal region is a segmented structure comprised of a series of reiterated structures: the pharyngeal arches on the exterior surface, the pharyngeal pouches on the interior, and a mesenchymal core. It is well known that Hox genes control spatial identity along the anterior-posterior axis of the developing vertebrate embryo, and nowhere is this is more evident than in the pharyngeal region. Each of the distinct segmented regions has a unique pattern of Hox expression, which conveys crucial positional information to the cells and tissues within it. In the context of pharyngeal organ development, molecular data suggest that HOXA3 is responsible for specifying organ identity within the third pharyngeal pouch, and in its absence, thymus and parathyroid organogenesis fails to proceed normally" Foxi1 promotes late-stage pharyngeal pouch morphogenesis through ectodermal Wnt4a activation "The pharyngeal pouches are a series of epithelial outgrowths of the foregut endoderm. Pharyngeal pouches segment precursors of the vertebrate face into pharyngeal arches and pattern the facial skeleton. These pouches fail to develop normally in zebrafish foxi1 mutants, yet the role Foxi1 plays in pouch development remains to be determined. Here we show that ectodermal Foxi1 acts downstream of Fgf8a during the late stage of pouch development to promote rearrangement of pouch-forming cells into bilayers. During this phase, foxi1 and wnt4a are coexpressed in the facial ectoderm and their expression is expanded in fgf8a mutants. foxi1 expression is unaffected in wnt4a mutants; conversely, ectodermal wnt4a expression is abolished in foxi1 mutants. Consistent with this, foxi1 mutant pouch and facial skeletal defects resemble those of wnt4a mutants. These findings suggest that ectodermal Foxi1 mediates late-stage pouch morphogenesis through wnt4a expression. We therefore propose that Fox1 activation of Wnt4a in the ectoderm signals the epithelial stabilization of pouch-forming cells during late-stage of pouch morphogenesis."

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Pharyngeal Arch | Pharyngeal Pouch | Pharyngeal Cleft | Pharyngeal Membrane | Pharyngeal Arch Artery | Pharyngeal Arch Cartilage

Older papers

These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table. See also the Discussion Page for other references listed by year and References on this current page. Endothelium in the pharyngeal arches 3, 4 and 6 is derived from the second heart field "Oxygenated blood from the heart is directed into the systemic circulation through the aortic arch arteries (AAAs). The AAAs arise by remodeling of three symmetrical pairs of pharyngeal arch arteries (PAAs), which connect the heart with the paired dorsal aortae at mid-gestation. Aberrant PAA formation results in defects frequently observed in patients with lethal congenital heart disease. How the PAAs form in mammals is not understood. The work presented in this manuscript shows that the second heart field (SHF) is the major source of progenitors giving rise to the endothelium of the pharyngeal arches 3 - 6, while the endothelium in the pharyngeal arches 1 and 2 is derived from a different source. During the formation of the PAAs 3 - 6, endothelial progenitors in the SHF extend cellular processes toward the pharyngeal endoderm, migrate from the SHF and assemble into a uniform vascular plexus. This plexus then undergoes remodeling, whereby plexus endothelial cells coalesce into a large PAA in each pharyngeal arch." heart

Pharyngeal Arch Development

• branchial arch (Gk. branchia= gill)
• arch consists of all 3 trilaminar embryo layers
• ectoderm - outside
• mesoderm - core of mesenchyme
• endoderm - inside

Pharyngeal Arch Components

This table gives an overview of what each arch will contribute to the embryo.

Pharyngeal Arch	Nerve	Artery	Neural Crest (Skeletal Structures)	Muscles	Ligaments
1 (maxillary/mandibular)	trigeminal (CN V)	maxillary artery (terminal branches)	mandible, maxilla, malleus, incus	muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric	ant lig of malleus, sphenomandibular ligament
2 (hyoid)	facial (CN VII)	stapedial (embryonic) corticotympanic (adult)	stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone	muscles of facial expression, stapedius, stylohyoid, post. belly digastric	stylohyoid ligament
3	glossopharyngeal (CN IX)	common carotid, internal carotid arteries	greater cornu of hyoid, lower part of body of hyoid bone	stylopharyngeus
4	vagus (CN X) superior laryngeal branch	part of aortic arch (left), part right subclavian artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	crycothyroid, soft palate levator veli palatini (not tensor veli palatini)
6	vagus (CN X) recurrent laryngeal branch	part of left pulmonary artery (left), part of right pulmonary artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	larynx intrinsic muscles (not cricothyroid muscle)

Pharyngeal Arch Derivatives
Pharyngeal Arch	Nerve	Artery	Neural Crest (Skeletal Structures)	Muscles	Ligaments
1 (maxillary/mandibular)	trigeminal (V)	maxillary artery (terminal branches)	mandible, maxilla, malleus, incus	muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric	ant lig of malleus, sphenomandibular ligament
2 (hyoid)	facial (VII)	stapedial (embryonic) corticotympanic (adult)	stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone	muscles of facial expression, stapedius, stylohyoid, post. belly digastric	stylohyoid ligament
3	glossopharyngeal (IX)	common carotid, internal carotid arteries	greater cornu of hyoid, lower part of body of hyoid bone	stylopharyngeus
4	vagus (X) superior laryngeal branch	part of aortic arch (left), part right subclavian artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	crycothyroid, soft palate levator veli palatini (not tensor veli palatini)
6	vagus (X) recurrent laryngeal branch	part of left pulmonary artery (left), part of right pulmonary artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	larynx intrinsic muscles (not cricothyroid muscle)

Neural Crest

Cranial neural crest-derived mesenchymal cells (ectomesenchyme) migrate into pharyngeal arches from midbrain and hindbrain region forming:

• neurons
• Schwann cells
• smooth muscle cells
• osteoblasts
• chondrocytes
• odontoblasts

SHH secreted from pharyngeal arch 1 epithelium is necessary for early mandibular arch cell survival and later cartilage (Meckel's cartilage) condensation differentiation.

Links: cranial neural crest | neural crest

Arch Features

Each arch contains: artery, cartilage, nerve, muscular component

Arches and Phanynx Form the face, tongue, lips, jaws, palate, pharynx and neck cranial nerves, sense organ components, glands

• Humans have 5 arches - 1, 2, 3, 4, 6 (Arch 5 does not form or regresses rapidly)
• from in rostro-caudal sequence, Arch 1 to 6 from week 4 onwards
• arch 1 and 2 appear at time of closure of cranial neuropore

• Face - mainly arch 1 and 2
• Neck components - arch 3 and 4 (arch 4 and 6 fuse)

Arch Features

• • arch
  • groove
    • externally separates each arch
      • also called a cleft
    • only first pair persist as external auditory meatus
  • pouch
    • internally separates each arch
    • pockets from the pharynx
  • membrane
    • ectoderm and endoderm contact regions
    • only first pair persist as tympanic membrane
• Pharyngeal Arch 1 (Mandibular Arch) has 2 prominances
  • smaller upper- maxillary forms maxilla, zygomatic bone and squamous part of temporal
  • larger lower- mandibular, forms mandible
• Pharyngeal Arch 2 (Hyoid Arch)
  • forms most of hyoid bone
• Arch 3 and 4
  • neck structures

Arch Arteries

Endothelium in the pharyngeal arches 3, 4 and 6 is derived from the second heart field

"Oxygenated blood from the heart is directed into the systemic circulation through the aortic arch arteries (AAAs). The AAAs arise by remodeling of three symmetrical pairs of pharyngeal arch arteries (PAAs), which connect the heart with the paired dorsal aortae at mid-gestation. Aberrant PAA formation results in defects frequently observed in patients with lethal congenital heart disease. How the PAAs form in mammals is not understood. The work presented in this manuscript shows that the second heart field (SHF) is the major source of progenitors giving rise to the endothelium of the pharyngeal arches 3 - 6, while the endothelium in the pharyngeal arches 1 and 2 is derived from a different source. During the formation of the PAAs 3 - 6, endothelial progenitors in the SHF extend cellular processes toward the pharyngeal endoderm, migrate from the SHF and assemble into a uniform vascular plexus. This plexus then undergoes remodeling, whereby plexus endothelial cells coalesce into a large PAA in each pharyngeal arch."

Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Pharyngeal Arch 1

cranial nerve CN V trigeminal

See Meckel's cartilage, facial canal and associated structures by Richany (1956)

Historic: 1956 first branchial arch

Pharyngeal Arch 2

cranial nerve CN VII facial

See Reichert's cartilage, facial canal and associated structures by Anson (1956).

Historic: 1956 second branchial arch

Pharyngeal Arch 3

cranial nerve CN IX glossopharyngeal

Pouch 3

Pharyngeal pouch III is the embryonic origin of endodermal component of the thymus (that also has a neural crest contribution).

Pharyngeal Arch 4

cranial nerve CN X vagus - superior laryngeal branch

Pharyngeal Arch 6

cranial nerve CN X vagus - recurrent laryngeal branch

part of right pulmonary artery (right)

Additional Images

Historic Images

Historic Disclaimer - information about historic embryology pages

Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Frazer JE. The second visceral arch and groove in the tubo-tympanic region. (1914) J Anat Physiol. 48(4): 391-408. PMID 17233005

• Second Pharyngeal Arch
• 

  12 mm embryo

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  16 mm embryo

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  27mm embryo

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  35mm embryo

Frazer JE. Development of the larynx. (1910) J Anat. 44: 156-191. PMID 17232839

• Embryonic Larynx Development
• 

  embryo 5 mm

• 

  embryo 6 mm

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  embryo 7.5 mm

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  embryo 8.5 mm

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  embryo 12 mm

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  embryo 6.6 mm

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  embryo 22 mm

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  embryo 35 mm

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  embryo 9.5 mm

Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia.

• Pharynx
• 

  Fig 314 Pharynx embryo Klb (Kromer-Pfannenstiel

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  Fig 315 Pharynx embryo Rob. Meyer No. 335

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  Fig 316 Pharynx embryo Hah

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  Fig 317 Pharynx embryo Rob. Meyer No. 300

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  Fig 318 model shown in Fig. 317

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  Fig 319 Pharyngeal pouches embryo Hah

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  Fig 320 Pharyngeal region embryo BR

• 

  Fig 321 Branchial derivatives embryo 11.7 mm

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  Fig 322 Pharynx embryo 21 mm

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  Fig 323 Pharynx embryo 24.4 mm

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  Fig 324 Branchiogenic derivatives in man

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  Fig 325 Section through embryo BR

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  Fig 326 Section through embryo BR

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  Fig 327 Section through embryo BR

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  Fig 328 Section through embryo BR

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  Fig 329 branchiogenic organs embryo 26 mm

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  Fig 330 Laryngeal region embryo Nat2

Terms

Head Terms (expand to view)

acephaly - term meaning absence of head, see skull and head abnormalities. branchial arch - see pharyngeal arch. brachycephaly - term meaning premature fusion of coronal suture, see skull and head abnormalities. clefting - the way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures, see palate and head abnormalities. coronal suture - skull term for the fibrous connective tissue joint that connects the frontal bone with the parietal bones. cranial fossae - skull term for the base bones of the cranial vault that form a container and support for the brain. cranial vault - skull term for the space formed by bones of the skull that enclose the brain. cysts - refers to a cervical sinus abnormality, remants of the cervical sinus remains as a fluid-filled cyst lined by an epithelium, see pharyngeal arch and head abnormalities. dolichocephaly - see scaphocephaly. exencephaly - term meaning brain outside skull, see skull and head abnormalities. fistula - refers to a pharyngeal membrane abnormality, a tract extends from pharynx (tonsillar fossa) beween the carotid arteries (internal and external) to open on side of neck, see pharyngeal arch and head abnormalities. lambdoid suture (lambdoidal suture) skull term for the fibrous connective tissue joint that connects the parietal bones with the occipital bone, and is continuous with the occipitomastoid suture. macrocephaly - term meaning large head, see hydrocephalus, skull and head abnormalities. Meckel's cartilage - (pharyngeal arch 1 cartilage) The mandible forms by intramembranous ossification beside this transient cartilage. The middle ear malleus and incus are thought to form from the ends of this cartilage. metopic suture - skull term for the fibrous connective tissue joint that connects the two fontal bones. In the adult skull this suture is not always present. micrencephaly - term meaning small brain, see neural, skull and head abnormalities. otocephaly - term meaning absence of lower jaw, see skull and head abnormalities. oxycephaly - (turricephaly) term meaning premature fusion of coronal suture + others, see skull and head abnormalities. pharyngeal arch - (branchial arch) a structure that forms in the cranial region of the embryo having contributions from all germ layers. In humans, the arches appear in week 4 (GA week 6) in a rostra-caudal sequence and are numbered (1, 2, 3, 4, and 6). Each arch contributes a different part of the head and neck and the associated components. pharyngeal cleft - (groove) surface ectoderm that externally separates each pharyngeal arch. In humans, only first pair persist as the outer ear external auditory meatus. pharyngeal groove - see pharyngeal cleft. pharyngeal membrane - surface ectoderm and pharynx endoderm contact region lying between each pharyngeal arch. In humans, only the first membrane pair persist as the tympanic membrane. pharyngeal pouch - pharynx endoderm internal out-pocketing that separates each pharyngeal arch. plagiocephaly - term meaning premature unilateral fusion of coronal or lambdoid sutures, see skull and head abnormalities. Reichardt's cartilage - (pharyngeal arch 2 cartilage) The superior portion of the hyoid forms the ventral portion of this cartilage and the middle ear stapes is thought to form from the ends of this cartilage. sagittal suture - skull term for the fibrous connective tissue joint that connects the two parietal bones in the midline. scaphocephaly - (dolichocephaly) term meaning premature fusion of sagittal suture, see skull and head abnormalities. sinuses - refers to a pharyngeal groove (cleft) abnormality, when a portion of the pharyngeal groove persists and opens to the skin surface, located laterally on the neck, see pharyngeal arch and head abnormalities. squamosal suture - skull term for the fibrous connective tissue joint that connects the squamous portion of the temporal bone with the parietal bones. suture - skull term for a fibrous connective tissue joint. In humans, the main sutures are coronal, sagittal, lambdoid and squamosal sutures, with the metopic suture (frontal suture) occurring as an anatomical variant in the adult skull. trigonocephaly - term meaning premature fusion of metopic suture, see skull and head abnormalities. turricephaly - see oxycephaly. vestiges - refers to a cartilaginous or bony developmental remnants that lie under the skin on side of neck, see pharyngeal arch and head abnormalities.

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Cite this page: Hill, M.A. (2023, December 1) Embryology Pharyngeal arches. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Pharyngeal_arches

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© Dr Mark Hill 2023, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G