<P> The hyoid bone is important to a number of physiological functions, including breathing, swallowing and speech . It is also thought to play a key role in keeping the upper airway open during sleep, and as such, the development and treatment of obstructive sleep apnea (OSA; characterized by repetitive collapse of the upper airway during sleep). A mechanistic involvement of the hyoid bone in OSA is supported by numerous studies demonstrating that a more inferiorly positioned hyoid bone is strongly associated with the presence and severity of the disorder . Movement of the hyoid bone is also thought to be important in modifying upper airway properties, which was recently demonstrated in computer model simulations . A surgical procedure that aims to potentially increase and improve the airway is called hyoid suspension . </P> <P> Due to its position, the hyoid bone is not easily susceptible to fracture . In a suspected case of murder or physical abuse, a fractured hyoid strongly indicates throttling or strangulation in an adult . However, this is not necessarily the case in children and adolescents, where the hyoid bone is still flexible as ossification is yet to be completed . </P> <P> The hyoid bone is derived from the lower half of the second gill arch in fish, which separates the first gill slit from the spiracle, and is often called the hyoid arch . In many animals, it also incorporates elements of other gill arches, and has a correspondingly greater number of cornua . Amphibians and reptiles may have many cornua, while mammals (including humans) have two pairs, and birds only one . In birds, and some reptiles, the body of the hyoid is greatly extended forward, creating a solid bony support for the tongue . The howler monkey Alouatta has a pneumatized hyoid bone, one of the few cases of postcranial pneumatization of bones outside Saurischia . </P> <Table> <Tr> <Td> <Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> The hyoid bone of a gecko with attached tracheal rings </Td> </Tr> </Table> <Table> <Tr> <Td> </Td> </Tr> <Tr> <Td> Hyoid bones of various birds . </Td> </Tr> </Table> </Td> </Tr> </Table>

This structure protrudes in the front of the neck an is also called the adams apple