EAR (HEARING AND EQUILIBRIUM ORGAN)
Ear subdivides on auricle (outer ear), middle ear and internal ear. Auricle and external auditory meatus belong to outer ear. Middle ear contains a tympanic cavity and auditory tube (Eustachian). Internal ear composes an osseous labyrinth and membranous labyrinth.
AURICLE contains a cartilage covered by skin. In inferior part a cartilage is absent there is auricular lobule (earlobe). Also auricle has a helix, triangular fossa, antihelix, concha, tragus, antitragus.
External auditory meatus is open outside, in depth from cavity of middle ear it dissociates by tympanic membrane. External auditory meatus has cartilaginous part and inner osseous part. Cartilaginous part composes one-third length of auditory meatus. Osseous part occupies two thirds of auditory meatus. Auditory meatus is curved S-like and for its straightening attached to examination of tympanic membrane necessary to draw off auricle posterior, up and outside.
The external ear consists of the expanded portion named the auricula or pinna, and the external acoustic meatus. The former projects from the side of the head and serves to collect the vibrations of the air by which sound is produced; the latter leads inward from the bottom of the auricula and conducts the vibrations to the tympanic cavity.
The Auricula or Pinna is of an ovoid form, with its larger end directed upward. Its lateral surface is irregularly concave, directed slightly forward, and presents numerous eminences and depressions to which names have been assigned. The prominent rim of the auricula is called the helix; where the helix turns downward behind, a small tubercle, the auricular tubercle of Darwin, is frequently seen; this tubercle is very evident about the sixth month of fetal life when the whole auricula has a close resemblance to that of some of the adult monkeys. Another curved prominence, parallel with and in front of the helix, is called the antihelix; this divides above into two crura, between which is a triangular depression, the fossa triangularis. The narrow-curved depression between the helix and the antihelix is called the scapha; the antihelix describes a curve around a deep, capacious cavity, the concha, which is partially divided into two parts by the crus or commencement of the helix; the upper part is termed the cymba conchæ, the lower part the cavum conchæ. In front of the concha, and projecting backward over the meatus, is a small pointed eminence, the tragus, so called from its being generally covered on its under surface with a tuft of hair, resembling a goat’s beard.Поділитися цим: