Ear

•  The walls of the external acoustic meatus 1/3 are formed by cartilage, whereas the inner 2/3 are formed by the 


  temporal bone.
• The tympanic membrane is connected to the surrounding temporal bone by a

  fibrocartilaginous ring.
• On the inner surface of the membrane, the handle of malleus attaches to the tympanic membrane, at a point called the _____ of tympanic membrane. The handle of malleus continues superiorly, and at its highest point, a small projection called the ____ of the malleus can be

  
  

  1. umbo

  2. lateral process

  
• complications of tympanic membrane? what is otitis media?

  An infection of the middle ear (otitis media) causes pus and fluid to build up behind the tympanic membrane. This causes an increase in pressure within the middle ear, and eventually the eardrum can rupture.

  
• Auricle anatomy? which part is not cartilganeous?

  lobule being the only part not supported by cartilage

  A) concha

  B) tragus

  C) antitragus

  D) lobule

  E) antihelix

  F) helix

  
• vasculature of external ear?

  The external ear is supplied by branches of the external carotid artery:

  • Posterior auricular artery
  • Superficial temporal artery
  • Occipital artery
  • Maxillary artery (deep auricular branch) – supplies the deep aspect of the external acoustic meatus and tympanic membrane only.

  A) maxillary

  B) Posterior Auricle

  C) occipital

  D) Superficial temporal

  
• innervation of external ear?

  • Greater auricular nerve (branch of the cervical plexus) – innervates the skin of the auricle
  • Lesser occipital nerve (branch of the cervical plexus) – innervates the skin of the auricle
  • Auriculotemporal nerve (branch of the mandibular nerve) – innervates the skin of the auricle and external auditory meatus.
  • Branches of the facial and vagus nerves – innervates the deeper aspect of the auricle and external auditory meatus

  
• which nerves is responsible for involuntary cough?

  Some individuals can complain of an involuntary cough when cleaning their ears – this is due to stimulation of the auricular branch of the vagus nerve (the vagus nerve is also responsible for the cough reflex).
• Which part of the auricle is LEAST likely to be affected by an auricular haematoma?

  The lobule is a non-cartilaginous structure, and therefore is unlikely to be affected by an auricular haematoma

  
• The middle ear lies within the 

  temporal bone
• Middle ear

  • Rectangular box shape
  • Has a roof and floor
  • Has medial and lateral walls
  • Has anterior and posterior walls

  
• Posterior wall (mastoid wall)


  • Superiorly, there is a hole in this partition, allowing the two areas to communicate. This hole is known as the

  aditus to the mastoid antrum. It consists of a bony partition between the tympanic cavity and the mastoid air cells.

  
• Anterior wallof middle ear

  A 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.

  
• medial and lateral wall of middle ear?

  Medial wall

  Formed by the lateral wall of the internal ear, contains a prominent bulge produced by the facial nerve

  Lateral wall

  Made up of the tympanic membrane and the lateral wall of the epitympanic recess.

  
• floor and roof of middle ear

  Floor

  Known as the jugular wall, it consists of a thin layer of bone, which separates the middle ear from the internal jugular vein

  Roof

  Formed by a thin bone from the petrous part of the temporal bone. It separates the middle ear from the middle cranial fossa.

  
• bones of middle ear?

  The bones of the middle ear are the auditory ossicles – the malleus, incus and stapes. They are connected in a chain-like manner, linking the tympanic membrane to the oval window of the internal ear.

  
• parts of middle ear?

  The middle ear can be divided into two parts:

  Tympanic cavity – located medially to the tympanic membrane. It contains three small bones known as the auditory ossicles: the malleus, incus and stapes. They transmit sound vibrations through the middle ear.

  Epitympanic recess – a space superior to the tympanic cavity, which lies next to the mastoid air cells. The malleus and incus partially extend upwards into the epitympanic recess.

  
• what are mastoid ear cells?

  present in middle ear.

  The mastoid air cells are located posterior to epitympanic recess. They are a collection of air-filled spaces in the mastoid process of the temporal bone. The air cells are contained within a cavity called the mastoid antrum. The mastoid antrum communicates with the middle ear via the aditus to mastoid antrum.

  The mastoid air cells act as a ‘buffer system‘ of air –  releasing air into the tympanic cavity when the pressure is too low.

  
• what is acoustic reflex? innervation of the muscles involved?

  in the middle ear, the tensor tympani and stapedius contract in response to loud noise, inhibiting the vibrations of the malleus, incus and stapes, and reducing the transmission of sound to the inner ear. This action is known as the acoustic reflex.

  tensor tympani

  tensor tympani nerve, a branch of the mandibular nerve.

  stapedius

   facial nerve.

  
• what is auditory tube? why middle ear infections are more common in children?

  The auditory tube (eustachian tube) is a cartilaginous (first 2/3) and bony tube (1/3) that connects the middle ear to the nasopharynx. It acts to equalise the pressure of the middle ear to that of the external auditory meatus.

  The tube is shorter and straighter in children, therefore middle ear infections tend to be more common in children than adults.

  
• what is mastoiditis?

  Middle ear infections (otitis media) can spread to the mastoid air cells. Due to their porous nature, they are a suitable site for pathogenic replication.

  The mastoid process itself can get infected, and this can spread to the middle cranial fossa, and into the brain, causing meningitis.

  If mastoiditis is suspected, the pus must be drained from the air cells. When doing so, care must be taken not to damage the nearby facial nerve.

  
• why tympanic membrane is light?

  because if discoloured , --- complications/infections
• functions of inner ear?

  inner ear has 2 following functions:

  The inner ear is the innermost part of the ear, and houses the vestibulocochlear organs. It has two main functions:

  • To convert mechanical signals from the middle ear into electrical signals, which can transfer information to the auditory pathway in the brain.
  • To maintain balance by detecting position and motion.
• parts of inner ear? the labyrinths?

  the inner ear has two main components – the bony labyrinth and membranous labyrinth.

  • Bony labyrinth – consists of a series of bony cavities within the petrous part of the temporal bone. It is composed of the cochlea, vestibule and three semi-circular canals. All these structures are lined internally with periosteum and contain a fluid called perilymph.
  • Membranous labyrinth – lies within the bony labyrinth. It consists of the cochlear duct, semi-circular ducts, utricle and the saccule. The membranous labyrinth is filled with fluid called endolymph.

  
• what are the openings of inner ear?

  The inner ear has two openings into the middle ear, both covered by membranes.

  The oval window

  lies between the middle ear and the vestibule,

  round window

  separates the middle ear from the scala tympani (part of the cochlear duct).

  
• Bony labyrinth of the inner ear contains? What membranous labyrinth structures are present in these?

  Cochlea, vestibule, semicircular canals

  Vestibule

  The vestibule is the central part of the bony labyrinth. It is separated from the middle ear by the oval window,

  Two parts of the membranous labyrinth; the saccule and utricle, are located within the vestibule.

  Cochlea

  cochlea duct of the membranous labyrinth

  Semi-circular Canals

  They contain the semi-circular ducts, which are responsible for balance

  They have a swelling at one end, known as the ampulla.

  
• the cochlear duct divides the cochlea into which parts?and is held in place by?

  the cochlear duct creates two perilymph-filled chambers above and below:

  • Scala vestibuli: Located superiorly to the cochlear duct. As its name suggests, it is continuous with the vestibule.
  • Scala tympani: Located inferiorly to the cochlear duct. It terminates at the round window.

  
  

  
  

  2. held in place by spiral lamina

  
• describe the course of CNIII?

  The inner ear is innervated by the vestibulocochlear nerve (CN VIII). It enters the inner ear via the internal acoustic meatus, where it divides into the vestibular nerve (responsible for balance) and the cochlear nerve (responsible for hearing):

  • Vestibular nerve – enlarges to form the vestibular ganglion, which then splits into superior and inferior parts to supply the utricle, saccule and three semi-circular ducts.
  • Cochlear nerve – enters at the base of the modiolus and its branches pass through the lamina to supply the receptors of the Organ of Corti.

  
• what is membranous labryinth and what is endolymph?

  the membranous labyrinth is a continuous system of ducts filled with endolymph. It lies within the bony labyrinth, surrounded by perilymph. It is composed of the cochlear duct, three semi-circular ducts, saccule and the utricle.

  The cochlear duct is situated within the cochlea and is the organ of hearing. The semi-circular ducts, saccule and utricle are the organs of balance (also known as the vestibular apparatus).

  
• anatomy of choclear duct?

  creates two canals above and below it – the scala vestibuli and scala tympani respectively.

  The cochlear duct can be described as having a triangular shape:

  • Lateral wall – Formed by thickened periosteum, known as the spiral ligament.
  • Roof – Formed by a membrane which separates the cochlear duct from the scala vestibuli, known as the Reissner’s membrane.
  • Floor – Formed by a membrane which separates the cochlear duct from the scala tympani, known as the basilar membrane.

  The basilar membrane houses the epithelial cells of hearing – the Organ of Corti.

  
• how endolymph drains?

  the Endolymph drains from the saccule and utricle into the endolymphatic duct. The duct travels through the vestibular aqueduct to the posterior aspect of the petrous part of the temporal bone. Here, the duct expands to a sac where endolymph can be secreted and absorbed.

  
• venous drainage of inner ear?

  the Venous drainage of the inner ear is through the labyrinthine vein, which empties into the sigmoid sinus or inferior petrosal sinus.

  
• what is meneire's disease?

  the Meniere’s disease is a disorder of the inner ear, characterised by episodes of vertigo (dizziness due to inner ear disturbance), low-pitched tinnitus (tinnitus) , and hearing loss.

  The symptoms are thought to be caused by an excess accumulation of endolymph within the membranous labyrinth, causing progressive distension of the ducts. The resulting pressure fluctuations damage the thin membranes of the ear that detect balance and sound.