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The upper jaw, or maxilla [12] [13] is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible (lower jaw), which is also a fusion of two halves at the mandibular symphysis. In bony fish, the maxilla is called the "upper maxilla," with the mandible being the "lower maxilla".
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).
Fish jaw: The primary oral jaws open and close the mouth, and a second set of pharyngeal jaws are positioned at the back of the throat. Ichthyology terms; Hallucigenia;
The second arch becomes the hyoid and jaw support. [2] 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. [4] The genetic and developmental basis of pharyngeal arch development is well characterized.
There is the presence of calcified strengthened cartilaginous jaws, calcified struts within the jaws and a lever 'nutcracker' system that amplifies the force of the jaw adductor muscles. The fusion of the palatoquadrate and mandibular symphysis, a restricted gape and asynchronous activation of the jaw adductors are key elements in the ...
Incisive bone is a term used for mammals, and it has been generally thought to be homologous to premaxilla in non-mammalian animals. However, there are counterarguments. According to them, the incisive bone is a novel character first acquired in therian mammals as a composition of premaxilla derived from medial nasal prominence and septomaxilla derived from maxillary promine
The primitive jawless fish have only a single testis located in the midline of the body, although even this forms from the fusion of paired structures in the embryo. [ 41 ] Under a tough membranous shell, the tunica albuginea , the testis of some teleost fish, contains very fine coiled tubes called seminiferous tubules .
In vertebrates, the maxilla (pl.: maxillae / m æ k ˈ s ɪ l iː /) [2] is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. [3] [4] The two maxillary bones are fused at the intermaxillary suture, forming the ...