Ear Anatomy and physiology ENT 531 Shoog Alshammari, Shaikhah Almoudhi, Manar Alsubaiee, razan aljarbou, ghada almeshali

The ear divided into 3 main sections

External ( outer ) ear Shaikhah Almoudhi Manar Alsubaiee

External (Outer) Ear The external ear consists of: Auricle or pinna, External acoustic (auditory) canal, Cartilaginous part. Bony part. Tympanic membrane or the drumhead, Pars tensa. Pars flaccida (SHRAPNELL’S membrane)

Auricle or Pinna cont. Reconstruction of the middle ear Made up with elastic cartilage. “incisura terminalis” area between the tragus and crus of helix. Source of several graft materials for the surgeon such as : Reconstruction of the middle ear Correct the depressed nasal bridge by conchal cartilage. Repair of defects of nasal ala .

External Acoustic Canal Extends from the bottom of the concha to the tympanic membrane. It is not a straight tube (S shape). Measures about 24mm along its posterior wall.

Ex. Acoustic Canal cont. The canal is divided into two parts: Cartilaginous: outer one-third (8 mm), contains ceruminous and pilosebaceous glands which secrete wax. Bony: inner two-thirds (16 mm). Clinically, to visualize the tympanic membrane, the pinna has to be pulled upwards, backwards and laterally so as to bring the two parts in alignment.

Tympanic Membrane It forms the partition between the external acoustic canal and the middle ear. It is obliquely set, concave, oval shape.

Pars tensa: thick (more fibrous tissue). Tympanic membrane can be divided into two parts: Pars tensa: thick (more fibrous tissue). Forms most of the TM . Its periphery form the annulus tympanicus. The central part is called Umbo. Cone of light in the Anteroinferior quadrant Pars flaccida (SHRAPNELL’S membrane): thin (less fibrous tissue). Annulus Tympanicus

Layers of tympanic membrane: 1- outer epithelial layer: Which is continuation with the skin lining the meatus. 2- inner mucosal layer: Which is continuation with the mucosa of the middle ear. 3- middle fibrous layer: which encloses the handle of malleus.

Relations of external acoustic meatus: 1- Superior: middle cranial fossa 3- Posterior: Mastoid air cells, facial nerve 2- Anterior : Temporomandibular joint 4- Inferior: parotid gland

Middle Ear Razan aljarbou

Middle Ear It is an air-containing cavity in the petrous part of the temporal bone It contains: 3 Ossicles. Mastoid. Aditus and antrum Eustachian tube.

Boundaries of middle ear Anterior Wall  thin bony plate with two openings; for the auditory tube and the tensor tympani muscle. It separates the middle ear from the internal carotid artery. Posterior Wall (mastoid wall) it consists of a bony partition between the tympanic cavity and the mastoid air cells. Superiorly, there is a hole in this partition, allowing the two areas to communication. This hole is known as the aditus to the mastoid antrum.

Middle Ear Mastoid : Aditus : Large, air-containing cavity in the upper part of mastoid. It has three types: Well-Pneumatized or cellular: Mastoid cells are well-developed and intervening septa are thin. Diploetic: Mastoid consists of marrow spaces and a few air cells. Sclerotic or acellular: There are no cells or marrow spaces. Aditus : Aditus is an opening through which the attic communicates with the antrum.

Middle Ear 3.Ossicles are: Malleus : long handle attached to the eardrum. incus : the bridge. Stapes: the footplate, the smallest bone in the body and It joins the incus to the oval window of the inner ear. Their function is to amplify sound vibrations.

The middle ear together with the Eustachian tube, Aditus, Antrum and mastoid air cells is called middle ear cleft

Muscles of middle ear Tensor Tympani: attaches to handle of malleus limits movements of malleus & stiffens eardrum to prevent its damage. Innervated by tympani nerve, a branch of the mandibular division of the trigeminal nerve. Stapedius (Smallest skeletal muscles ): attaches to stapes Its action is to dampen down vibrations of stapes innervated by the nerve to stapedius, a branch of the facial nerve.

Inner Ear Shoog Alshammari

• Consists of: 1. Labyrinth: A. Bony Labyrinth, its parts: Bony Cochlea Vestibule Bony semicircular canals

B. Membranous Labyrinth, its parts: Cochlear duct Saccule and utricle Membranous semicircular ducts

2. Internal Auditory Canal, Contains: Vestibulocochlear nerve Facial nerve

Venous drainage Three veins; internal auditory veins Vien of cochlear aqueduct Vien of vestibular aqueduct

Functions of the inner ear: important organ for hearing and balance of body

Development of ear cochlea Vestibular labyrinth Middle ear meatus pinna Development 3rd 8th 6th Begins 20th 30th 28th Completes

Blood and Nerve Supply Ghada AlMeshaali

External Ear Supply Superficial temporal artery. Blood supply: Superficial temporal artery. Anterior Auricular branches of superficial temporal artery. Posterior Auricular artery. Nerve supply: Greater auricular nerve. Auriculotemporal nerve. Auricular branch of vagus.

Middle Ear Supply Blood Supply: Anterior tympanic branch of maxillary artery Stylomastoid branch of posterior auricular artery. Nerve Supply: Tympanic plexus. Formed by: Tympanic branch of glossopharyngeal. Sympathetic fibers from the plexus around the internal carotid artery. 2. Chorda tympani branch of the facial nerve.

Inner Ear Supply Blood Supply: Labyrinthine Artery. Nerve Supply: Vestibulocochlear nerve (VIII).

? Questions

References Dhingra, P. (2010). Diseases of ear, nose and throat. New Delhi: Elsevier. TeachMeAnatomy. (2017). The Middle Ear. [online] Available at: http://teachmeanatomy.info/head/organs/ear/middle-ear/ [Accessed 6 Mar. 2017]. Drake, R., Vogl, W., Mitchell, A., Tibbitts, R., Richardson, P. and Horn, A. (2018). Gray's basic anatomy. Philadelphia, PA: Elsevier.

Thank you Shoog Alshammari 121220205 Shaikhah Almoudhi 121220206 Manar Alsubaiee 121220242 razan aljarbou 121220153 ghada almeshali 121220243