耳部結構與功能

ANAT0MY OF THE EAR

I. Temporal bone

1. Divided to four parts: Squama, mastoid, petrous , tympanic
2. sutures and fissures
1) petrosquamous fissure(Korner's septum)
2) Tympanomastoid suture (posterior to the notch of Rivinus)
3) Tympanosquamous suture ( anterior to the notch of rivinus)
4) petrotympanic fssure or Glaser's fissure (Chorda tympani).

 

 

Anatomy of the Ear and Physiology of Hearing (basics)

II.External ear

1.Auricle

1) Auricle is maae of elastic cartilage, the cartilaginous canal of fiorocartilage
2) Skin:

(1) thinner than most of the skin elsewhere in the body.
(2) Without a protective layer of fat and witn essentially only one layer of blood vessels.

3) The muscles attched tne auricle to the temporal bone: anterior, posterior and superior m.
4) Lymphatic drain to anteriorly, inferiorly and posterioly
5) Sensory nerves:
Cervical. plexus (C2, C3) → Qreater auricu.Lar N. (→ Lesser occipital N.)
Arnold's N. (Vagus N.) → Auricular br.
Mandibular N. → Auriculotemporal N.

 

 

 

2.External auditory canal.

1) The length of the canal in adult is 25 to 30 mm (anterior-inferior length is longer ——30 mm).
2) The cartilaginous canal constitutes 1/3 of tne ext. auditory canal (whereas the eustachian tube
is 2/3 cartilaginous), the remaining 2/3 is osseus.
3) Skin

(1) cartilaginous portion: sebaceous glands,ceruminous glands and hair follicles
(2) Bony portion: Is tight and has no Subcutaneous tissue except periosteum.

4) Boudaries of external auditory canal

(1) Anteriorly: Mandibular fossa (parotid)
(2) Posteriorly; Mastoid
(3) Superiorly: (Medially) Epitympanic recess (Laterally) Cranial cavity
(4) Inferiorly: Parotid

5)Sensory nerves:
auriculotemporal auricular br. of X
br. of VII(smal1 postero-superior area of eardrum and ext auditory canal)

 

III.Middle ear:

Tympanic membrane.
2.Tympanic cavity: epitympani, mesotympani, hypotympani.
3.Mastoid antrum.
4.Pneumatic system of the temporal bone
5.Eustachian tube.

 

physiology of hearing

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Auditory Transduction

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IV. Inner ear:

1.Osseous labyrinth

a.Vestibule
b.Semicircular canala
c.Cochlea

 

2.Membranous labyrinth

A.Cochear duct ( scala media )
b.Saccule
c.Utricle
d.Semicircular canals
e.Endolymphatic duct and sac

3.Acoustic nerve

a.Cochlear segment.
b.Vestibular segment.

 

4.Vessels:

a.Anterior inferior cerebella A.(80%)
b.Accessory ant. cerebella A. (17%)
c.Posterior inferior cerebella A.(3%)