Pharyngeal arch

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Pharyngeal arch
Schematic of developing human fetus with first, second and third arches labelled
Details
Carnegie stage10
Identifiers
Latinarcus pharyngei
MeSHD001934
TEarch_by_E5.4.2.0.0.0.2 E5.4.2.0.0.0.2
Anatomical terminology
Sinus cervicalis

The pharyngeal arches, also known as visceral arches, are structures seen in the

branchial arches
, or gill arches.

In the

development. They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx. The vasculature of the pharyngeal arches is known as the aortic arches
.

In fish, the branchial arches support the gills.

Structure

In

hyoid and jaw support.[1] 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.[3] The genetic and developmental basis of pharyngeal arch development is well characterized. It has been shown that Hox genes and other developmental genes such as DLX are important for patterning the anterior/posterior and dorsal/ventral axes of the branchial arches.[4] Some fish species have a second set of jaws in their throat, known as pharyngeal jaws, which develop using the same genetic pathways involved in oral jaw formation.[5]

During human, and all vertebrate

development, a series of pharyngeal arch pairs form in the developing embryo. 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.[6]

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

cranial nerve. Each of these is surrounded by mesenchyme
. Arches do not develop simultaneously but instead possess a "staggered" development.

Pharyngeal 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.[7] In fish, the pouches line up with the clefts, and these thin segments become gills. 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

embryogenesis.[8]

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

first pharyngeal groove
.

Processes

This arch divides into a

muscles of mastication
.

Meckel's cartilage

mandible or lower jaw forms by perichondral ossification
using Meckel's cartilage as a 'template', but the maxillary 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

Muscles

Other

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 which is derived from the first arch.[11]

Blood supply

The artery of the first arch is the first aortic arch,[12] which partially persists as the maxillary artery.

Second arch

The second pharyngeal arch or hyoid arch is the second of fifth pharyngeal arches that develops in fetal life during the fourth week of development[9] 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.

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.[14] Dorsal ends of Reichert's cartilage 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 styloid process of the temporal bone. The cartilage between the hyoid bone and 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

Muscles

Nerve supply

Facial nerve (CN VII)

Blood supply

The artery of the second arch is the second

stapedial artery
in some mammals but atrophies in most humans.

Muscles derived from the pharyngeal arches

Pharyngeal muscles or branchial muscles are

somites
, pharyngeal muscles are developmentally formed from the pharyngeal arches.

Most of the skeletal musculature supplied by the cranial nerves (

general somatic efferent
innervation.

First arch

All of the

tensor veli palatini
.

Second arch

All of the pharyngeal muscles of the second pharyngeal arch are innervated by 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

stylopharyngeus which is innervated by the glossopharyngeal nerve
), and all the muscles of the larynx.

In humans

Amniotes have five arches, numbered 1 to 5.

trachea
.

The recurrent laryngeal nerves 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.[6]

Pharyngeal arch Muscular contributions[17] Skeletal contributions Nerve Artery
First (also called "
mandibular arch
")
tensor veli palatini
 Premaxilla,
mandible (only as a model for mandible not actual formation of mandible), zygomatic bone, part of the temporal bone,[18] the incus, and the malleus of the middle ear, also Meckel's cartilage and the sphenomandibular ligament
.		 Trigeminal nerve (part of V2[19] and V3)
Vidian artery
Second (also called the "
hyoid arch
")
auricular[15]
lesser horns and upper part of body), stylohyoid ligament,[15]
Reichert's cartilage		 Facial nerve (VII)
Stapedial artery
Third
Stylopharyngeus
greater horns and lower part of body), thymus
 Glossopharyngeal nerve (IX)
internal carotid
Fourth
tensor veli palatini
epiglottic cartilage[20]
 Vagus nerve (X), superior laryngeal nerve[21] Right 4th aortic arch: subclavian artery

Left fourth aortic arch: aortic arch

Fifth All intrinsic muscles of larynx except the cricothyroid muscle
corniculate cartilage, cuneiform cartilages[20]
Cranial root) (XI), recurrent laryngeal nerve[21]
 Right 5th aortic arch: pulmonary artery

Left fifth aortic arch: pulmonary artery and ductus arteriosus

See also

This article uses anatomical terminology.

References

  1. ^
    S2CID 28318053
    .
  2. S2CID 10792335
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  3. ^ Kardong KV (2003). "Vertebrates: Comparative Anatomy, Function, Evolution". Third Edition. New York (McGraw Hill).
  4. S2CID 10274300
    .
  5. PMID 19215146
    .
  6. ^
    ISBN 0-443-08724-5
    .
  7. ^ McKenzie, James C. "Lecture 24. Branchial Apparatus". Howard University. Archived from the original on 2003-05-02. Retrieved 2007-09-09.
  8. ^ Marino, Thomas A. "Text for Pharyngeal Arch Development". Temple University. Archived from the original on 2007-09-09. Retrieved 2007-09-09.
  9. ^
    ISBN 0-443-06583-7
  10. PMID 34716275
    .
  11. ^ Inderbir Sing, G.P Pal-Human Embryology
  12. ^ a b McMinn, R., 1994. Last's anatomy: Regional and applied (9th ed).
  13. ^ Sudhir, Sant, 2008.Embryology for Medical Students 2nd edition
  14. PMID 16441562
    .
  15. ^
    ISBN 978-0781790697
    .
  16. PMID 31402457
    .
  17. ^ "marshall.edu". Archived from the original on 2009-02-27. Retrieved 2007-09-09.
  18. ISBN 978-0781790697
    .
  19. S2CID 32707087
    .
  20. ^
    ISBN 0-914168-99-1
    .
  21. ^
    ISBN 0-7817-5309-0
    .

External links
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