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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".
In all jawed fish (gnathostomes), the first arch pair (mandibular arches) develops into the jaw, the second gill arches (the hyoid arches) develop into the hyomandibular complex (which supports the back of the jaw and the front of the gill series), and the remaining posterior arches (simply called branchial arches) support the gills.
The molars are broad, flat, multi cuspid teeth and are the main grinding surface. Jaw action is not a simple crushing one but rather a definite sideways grinding. Panda jaws have a large zygomatico-mandibularis muscle, which is responsible for the sideways movement of the jaw. The glenoid is very deep, preventing back and forth movement of the jaw.
Jawless fish and sharks only possess a cartilaginous endocranium, with the upper and lower jaws of cartilaginous fish being separate elements not attached to the skull. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines a chin.
Pharyngeal muscles or Branchial muscles are striated muscles of the head and neck. Unlike skeletal muscles that developmentally come from somites, pharyngeal muscles are developmentally formed from the pharyngeal arches. Most of the skeletal musculature supplied by the cranial nerves (special visceral efferent) is pharyngeal.
In early fish and in chondrichthyans (cartilaginous fish such as sharks), Meckel's cartilage continued to be the main component of the lower jaw. But in the adult forms of osteichthyans (bony fish) and their descendants (amphibians, reptiles, birds, and mammals), the cartilage is covered in bone – although in their embryos the jaw initially ...
Their jaw muscles are tuned to power through big trees and carry them back to their dam. [9] Ants use their powerful jaws to lift material back to the colony. They can carry several thousand times their weight due to their bite and are adapted to use this to forage for their colonies. [ 10 ]
The upper jaw, or pertaining thereto. maxillae, maxillaries The hindmost bones of the upper jaw; preceded by the premaxillaries. median, medially Pertaining to the middle. median fins Fins located on the median line of the fish; the dorsal, anal and caudal fins. mediolateral Between the middle and the sides. melanophore