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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 .
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.
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
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 branchial arch will normally develop around the 23rd to 26th day of gestation, also known as Carnegie stage 10. Usually, failure of this will result in isolated agnathia, but otocephaly may occur in exceptional circumstances. After agenesis of the first branchial arch, no cure is possible.
The six pharyngeal arches give rise to much of the skeletal and muscular tissue in the head and neck region. When the embryo is 42 days old, the mesenchymal arches can be recognized with its corresponding cranial nerve. [1] The first pharyngeal arch forms maxillary and mandibular processes.
The several components or degrees of development range from an ear tag, preauricular appendage, preauricular tag, or accessory tragus, to supernumerary ears or polyotia. [7] It is a relatively common congenital anomaly of the first branchial arch or second branchial arches.
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] The tooth bud (sometimes called the tooth germ) is an aggregation of cells that eventually forms a tooth and is organized into three parts: the enamel organ, the dental papilla and the dental follicle. [3]