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The branchial system is typically used for respiration and/or feeding. Many fish have modified posterior gill arches into pharyngeal jaws, often equipped with specialized pharyngeal teeth for handling particular prey items (long, sharp teeth in carnivorous moray eels compared to broad, crushing teeth in durophagous black carp).
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 development. [10] It is located between the stomodeum and the first pharyngeal groove .
Pattern of the branchial arches. I-IV branchial arches, 1–4 pharyngeal pouches (inside) and/or pharyngeal grooves (outside) a Tuberculum laterale b Tuberculum impar c Foramen cecum d Ductus thyreoglossus e Sinus cervicalis
Originally it was the lower of two cartilages which supported the first branchial arch in early fish. Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw. [1] In early fish and in chondrichthyans (cartilaginous fish such as sharks), Meckel's cartilage continued to be the main component of the lower jaw.
The first three arches include a single basibranchial surrounded by two hypobranchials, ceratobranchials, epibranchials and pharyngobranchials. The median basibranchial is covered by a toothplate. The fourth arch is composed of pairs of ceratobranchials and epibranchials, and sometimes additionally, some pharyngobranchials and a basibranchial.
Cyclostomi, often referred to as Cyclostomata / s ɪ k l oʊ ˈ s t ɒ m ə t ə /, is a group of vertebrates that comprises the living jawless fishes: the lampreys and hagfishes.Both groups have jawless mouths with horny epidermal structures that function as teeth called ceratodontes, and branchial arches that are internally positioned instead of external as in the related jawed fishes. [1]
The first, most anterior pharyngeal arch gives rise to the oral jaw. The second arch becomes the hyoid and jaw support. [5] In fish, the other posterior arches contribute to the brachial skeleton, which support the gills; in tetrapods the anterior arches develop into components of the ear, tonsils, and thymus. [7]
If teeth do not start to develop at or near these times, they will not develop at all. A significant amount of research has focused on determining the processes that initiate tooth development. It is widely accepted that there is a factor within the tissues of the first branchial arch that is necessary for the development of teeth. [2]