Difference between revisions of "Pharyngeal arches"

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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.  
 
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.  
  
Several endocrine organs {{thymus}}, {{parathyroid}} develop from  
+
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).{{#pmid:27955943|PMID27955943}}
 
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).{{#pmid:27955943|PMID27955943}}
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* '''{{Hox}} genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs'''{{#pmid:30604847|PMID30604847}} "The pharyngeal organs, namely the {{thyroid}}, {{thymus}}, {{parathyroid}}s, 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"
 
* '''{{Hox}} genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs'''{{#pmid:30604847|PMID30604847}} "The pharyngeal organs, namely the {{thyroid}}, {{thymus}}, {{parathyroid}}s, 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'''{{#pmid:29932895|PMID29932895}} "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."
+
* '''Foxi1 promotes late-stage pharyngeal pouch morphogenesis through ectodermal Wnt4a activation'''{{#pmid:29932895|PMID29932895}} "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."
 +
 
 
* '''Branchial anomalies in children: A report of 105 surgical cases'''{{#pmid:29287855|PMID29287855}} "Branchial anomalies (BAs) account for 20% of all congenital masses in children. We sought to review the incidence of involvement of individual anomalies, diagnostic methods, surgical treatment, and complications of BAs in children. ...A total of 33 (31.4%) cases presented with first BAs, 13 (12.4%) presented with second BAs, and 59 (56.2%) presented with third and fourth BAs, including 6 cases of congenital lower neck cutaneous fistula."
 
* '''Branchial anomalies in children: A report of 105 surgical cases'''{{#pmid:29287855|PMID29287855}} "Branchial anomalies (BAs) account for 20% of all congenital masses in children. We sought to review the incidence of involvement of individual anomalies, diagnostic methods, surgical treatment, and complications of BAs in children. ...A total of 33 (31.4%) cases presented with first BAs, 13 (12.4%) presented with second BAs, and 59 (56.2%) presented with third and fourth BAs, including 6 cases of congenital lower neck cutaneous fistula."
 
|}
 
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Latest revision as of 02:21, 25 July 2019

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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).[1]


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
Historic Head Embryology  
1909 Head Malformations | 1922 Aortic-Arch System | 1925 Pharyngeal Diverticula | 1926 Precervical Sinus

Some Recent Findings

  • Hox genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs[2] "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[3] "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."
  • Branchial anomalies in children: A report of 105 surgical cases[4] "Branchial anomalies (BAs) account for 20% of all congenital masses in children. We sought to review the incidence of involvement of individual anomalies, diagnostic methods, surgical treatment, and complications of BAs in children. ...A total of 33 (31.4%) cases presented with first BAs, 13 (12.4%) presented with second BAs, and 59 (56.2%) presented with third and fourth BAs, including 6 cases of congenital lower neck cutaneous fistula."
More recent papers  
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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

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[1] "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

Head arches cartoon.jpg Pharyngeal arch structure cartoon.gifStage13 pharyngeal arch excerpts.gif

  • 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:


SHH secreted from pharyngeal arch 1 epithelium is necessary for early mandibular arch cell survival and later cartilage (Meckel's cartilage) condensation differentiation.[5]

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[1]

"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)[6]

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).[7]


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)

References

  1. 1.0 1.1 1.2 Wang X, Chen D, Chen K, Jubran A, Ramirez A & Astrof S. (2017). Endothelium in the pharyngeal arches 3, 4 and 6 is derived from the second heart field. Dev. Biol. , 421, 108-117. PMID: 27955943 DOI.
  2. Gordon J. (2018). Hox genes in the pharyngeal region: how Hoxa3 controls early embryonic development of the pharyngeal organs. Int. J. Dev. Biol. , 62, 775-783. PMID: 30604847 DOI.
  3. Jin S, O J, Stellabotte F & Choe CP. (2018). Foxi1 promotes late-stage pharyngeal pouch morphogenesis through ectodermal Wnt4a activation. Dev. Biol. , 441, 12-18. PMID: 29932895 DOI.
  4. Li W, Xu H, Zhao L & Li X. (2018). Branchial anomalies in children: A report of 105 surgical cases. Int. J. Pediatr. Otorhinolaryngol. , 104, 14-18. PMID: 29287855 DOI.
  5. Billmyre KK & Klingensmith J. (2015). Sonic hedgehog from pharyngeal arch 1 epithelium is necessary for early mandibular arch cell survival and later cartilage condensation differentiation. Dev. Dyn. , 244, 564-76. PMID: 25626636 DOI.
  6. Richany SF. Bast TH. and Anson BJ. The development of the first branchial arch in man and the fate of Meckel's cartilage. (1956) Q Bull Northwest Univ Med Sch. 30(4):331-55. PMID: 13408429.
  7. {{Ref-AnsonBastRichany1956}

Additional Images

Historic Images

Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic Textbook" and "Historic Embryology" 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 and interpretations 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

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

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

Terms

Head Terms (expand to view) 
  • branchial arch - see pharyngeal arch.
  • 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.
  • 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.
  • 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.
  • 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.
  • turricephaly - see oxycephaly.
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Cite this page: Hill, M.A. (2019, September 16) Embryology Pharyngeal arches. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Pharyngeal_arches

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