Interestingly, this is one end of a passageway that houses our hearing and balance apparatus. On the cross-section, it is of oval shape. Internal acoustic meatus (meatus passage): Other than the foramen magnum, it is the most anterior of the holes in the posterior cranial fossa. The External Acoustic Meatus (meatus acusticus externus external auditory canal or meatus) extends from the bottom of the concha to the tympanic membrane : It is about 4 cm. It has a sigmoid form and runs from behind and above downward and forward. The canal is approximately 2.5 centimetres (1 in) long and 0.7 centimetres (0.28 in) in diameter. The external acoustic meatus conducts sound waves to the tympanic membrane. Size and shape of the canal vary among individuals. The external acoustic meatus (also external auditory canal, external auditory meatus or ear canal, Latin: meatus acusticus externus) is an air-filled tubular space that extends from the auricle of the external ear into the temporal bone to the tympanic membrane. The layer of epithelium encompassing the bony portion of the ear canal is much thinner and therefore, more sensitive in comparison to the cartilaginous portion. The bony part is much shorter in children and is only a ring ( annulus tympanicus) in the newborn.

The bony part forms the inner two thirds. Pronunciation of acoustic meatus with 1 audio pronunciations.

The cartilaginous portion of the ear canal contains small hairs and specialized sweat glands, called apocrine glands, which produce cerumen ( ear wax). Rate the pronunciation difficulty of acoustic meatus. The cartilage is the continuation of the cartilage framework of pinna. The elastic cartilage part forms the outer third of the canal its anterior and lower wall are cartilaginous, whereas its superior and back wall are fibrous. The human ear canal is divided into two parts.

The adult human ear canal extends from the pinna to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter. The annular cartilage encloses the horizontal part of the external ear canal. It is attached to the bony rim of the external acoustic meatus by fibrous tissue that permits some degree of movement of the external ear. In the posterior quadrants are the two vestibular nerves, while in the anterior quadrants are the other two - the mnemonic can be used to remember their position.The ear canal ( external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. A tubular cartilage piece, the annular cartilage surrounds the osseous external acoustic meatus (see Figure 1-7). In each quadrant, there is the passage of one nerve (see picture). Three components of the vestibulocochlear nerve (CN VIII)įour are the nerves and four are the quadrants of the IAC: anterosuperior, anteroinferior, posterosuperior, posteroinferior. In the portion beneath the crista falciformis are. Each portion is further subdivided by a vertical ridge into an anterior and a posterior part. A mnemonic to remember the relative position of nerves inside the internal auditory canal (IAC) is: The fundus of internal acoustic meatus is the lateral end of the internal aoustic canal.It is closed by a vertical plate, which is divided by a horizontal crest, the transverse crest (falcifom crest, crista falciformis), into two unequal portions.

Acoustic meatus