Splanchnocranium
The splanchnocranium (or visceral skeleton) is the portion of the cranium that is derived from pharyngeal arches. Splanchno indicates to the gut because the face forms around the mouth, which is an end of the gut.[1] The splanchnocranium consists of cartilage and endochondral bone. In mammals, the splanchnocranium comprises the three ear ossicles (i.e., incus, malleus, and stapes), as well as the alisphenoid, the styloid process, the hyoid apparatus, and the thyroid cartilage.[2]
In other tetrapods, such as amphibians and reptiles, homologous bones to those of mammals, such as the quadrate, articular, columella, and entoglossus are part of the splanchnocranium.[2]
Evolution
[edit]Gill slits are thought to have been present in the most recent common ancestor of living deuterostomes; they are present in modern hemichordates and lancelets.[3] In lancelets, numerou gill slits are present; they are used for filter feeding as well as respiration. Haikouichthys, among the earliest known vertebrates, is thought to have been similar. However, Haikouichthys is believed to have had nine cartilaginous pharyngeal arches. The visceral skeleton evolved from structures like these.[3]
Among early gnathostomes, the first or first two[4] pharyngeal arches came to make up the jaws and the second (and to a lesser degree, the third) came to make up the hyoid apparatus. Among fishes, the remaining arches remained as the gills, while among tetrapods they were lost or highly reduced.[4]
Divisions
[edit]Mandibular arch
[edit]The mandibular arch comprises the ancestral portions of the upper and lower jaws. Ancestrally, these elements are the palatoquadrate and Meckel's cartilage, which are only rarely fully ossified among vertebrates.[4] Developmental evidence suggests that the palatoquadrate and Meckel's cartilage represent serial homologues of the epibranchial and the ceratobranchial, respectively.[5] The joint between the two cartilages ancestrally represents the jaw joint; in mammals, it has been modified and serves as a portion of the middle ear.[4]
Hyoid arch
[edit]Ancestrally, the hyoid arch helps to support the floor of the mouth. It has undergone significant modification in different clades. In teleosts, the arch allows for cranial kinesis; in basal tetrapods, the arch helped to support the tongue (as part of the hyoid apparatus) as well as bracing the skull, later forming part of the middle ear.[4] In mammals, the hyoid arch contains Reichert's cartilage.[7]
Branchial arch I-V
[edit]In chondrichthyans and teleosts, elements of these arches form distinct elements, divided into the pharyngobranchials, epibranchials, ceratobranchials, hypobranchials, and basibranchials.
In tetrapods, elements of the first and second branchial arch form part of the hyoid apparatus. Elements of the second and third branchial arches may make up the laryngeal and thyroid cartilages; the fourth and fifth arches are absent in tetrapods.[4]
See also
[edit]References
[edit]- ↑ Wilkins, Adam S. (2017). "How the Face Develops". Making Faces. Harvard University Press. p. 56. ISBN 9780674725522.
- 1 2 Kent, George C.; Carr, Robert K. (2001). Comparative Anatomy of the Vertebrates (9th ed.). New York, NY: McGraw-Hill. ISBN 0-07-303869-5.
- 1 2 3 4 DeLaurier, April (2019-03). "Evolution and development of the fish jaw skeleton". WIREs Developmental Biology. 8 (2). doi:10.1002/wdev.337. ISSN 1759-7684. PMC 8299565. PMID 30378758.
{{cite journal}}: Check date values in:|date=(help) - 1 2 3 4 5 6 Kardong, Kenneth (2015). Vertebrates: Comparative Anatomy, Function (7th ed.). McGraw-Hill.
- ↑ Gillis, J. Andrew; Modrell, Melinda S.; Baker, Clare V. H. (2013-02-05). "Developmental evidence for serial homology of the vertebrate jaw and gill arch skeleton". Nature Communications. 4 (1): 1436. doi:10.1038/ncomms2429. ISSN 2041-1723. PMC 3600657. PMID 23385581.
- ↑ Block, A. J.; Mabee, P. M. (2012-07). "Development of the mandibular, hyoid arch and gill arch skeleton in the Chinese barb Puntius semifasciolatus : comparisons of ossification sequences among Cypriniformes". Journal of Fish Biology. 81 (1): 54–80. doi:10.1111/j.1095-8649.2012.03307.x. ISSN 0022-1112.
{{cite journal}}: Check date values in:|date=(help) - ↑ Kitazawa, Taro; Fujisawa, Kou; Narboux-Nême, Nicolas; Arima, Yuichiro; Kawamura, Yumiko; Inoue, Tsuyoshi; Wada, Youichiro; Kohro, Takahide; Aburatani, Hiroyuki; Kodama, Tatsuhiko; Kim, Ki-Sung; Sato, Takahiro; Uchijima, Yasunobu; Maeda, Kazuhiro; Miyagawa-Tomita, Sachiko (2015-06-15). "Distinct effects of Hoxa2 overexpression in cranial neural crest populations reveal that the mammalian hyomandibular-ceratohyal boundary maps within the styloid process". Developmental Biology. 402 (2): 162–174. doi:10.1016/j.ydbio.2015.04.007. ISSN 0012-1606.
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