9. Ear Flashcards
1
Q
1. Describe the three general divisions of the ear.
A
- External ear into two parts;
- auricle (or pinna)
- external acoustic meatus – which ends at the tympanic membrane.
- Middle ear is located in temporal bone, and extends from the tympanic membrane to the lateral wall of the inner ear.
- Inner ear is located within the petrous part of the temporal bone. It lies between the middle ear and the internal acoustic meatus. Two main components:
- Bony labryinth
- membranous labyrinth
2
Q
Parts of the auricle of the external ear
A
- Helix/ Antihelix
- Tragus/antitragus
- lobule
- Concha
3
Q
- Describe the blood supply of the pinna.
A
External carotid A
- 1. Posterior auricular A.
- 2. Superficial temporal A.
4
Q
Innervation of the auricle (pinna) of the ear
A
- Great auricular N
- Auriculotemporal N of trigeminal N (V3)
- Auricular branch of vagus N (CN X)
- Facial N (CN7)
- Internal surface of the tympanic membrane is innervated by CN 9 (glosspharyngeal N)
5
Q
Internal surface of the tympanic membrane is innervated by ___________
A
CN 9 (glosspharyngeal N)
6
Q
Innervation of external surface of tympanic membrane
A
- Auriculotemporal N (CN V3) innervates 2/3
- Auricular branch of vagus (CN X)
7
Q
Auricular Hematomas
A
- Hit on side of ear -> blood accumulates in the perichondrium or cartilage of the ear, it can form a auricular hemotoma.
- This blood needs to be released. Otherwise: form abnormal cartilage -> cauliflower ear.
8
Q
External Acoustic Meatus
- Extends from _____ to _________
- What is it made out of?
A
- Extends from concha of auricle to tympanic membrane
- Lateral 1/3 is cartilage; medial 2/3 is bone.
9
Q
A child’s external auditory meatus is ______ than an adult’s.
A
shorter.
same size by 4. yo
10
Q
What is otitis externa?
A
Otitis externa (swimmer’s ear) is an infection to the external acoustic meatus. D/t
- 1. excessive moisture
- 2. trauma (cleaning/scratching)
- 3. things that block ear canal
- 4. Derm conditions
- 5. radiations
11
Q
What separates the external ear from middle ear?
A
TYMPANIC MEMBRANE (ear drum)
12
Q
The ____________ joins the middle ear to the nasopharynx.
A
The pharyngotympanic tube (eustachian tube) joins the middle ear to the nasopharynx.
13
Q
How is the typanic membrane divided?
A
- Anterior inferior
- Where cone of light is located.
- Anterior superior
- Posterior inferior
- Posterior superior
14
Q
On the inner surface of the tympanic membrane, the _______ attaches to the tympanic membrane, at a point called the_________
A
- On the inner surface of the membrane, the handle of malleus attaches to the tympanic membrane, at a point called the umbo of tympanic membrane.
15
Q
The handle of malleus continues superiorly, and at its highest point, a small projection called the____________.
A
lateral process of the malleus.
16
Q
What part of TM is more vascularized?
A
Superior part
17
Q
What is otitis media?
A
- Infection of the middle ear, causing inflammation and swelling of mucous membrane of tympanic cavity -> block pharyngotympanic tube (eustachian tube), which links nasopharynx to middle ear.
- Tympanic membrane will look red and bulge.
18
Q
Otitis media cause do what?
A
- block eustachian tube
- perforate tympanic membrane.
19
Q
How can we repair a ruptured ear drum?
A
- Conduct myringotomy- create an incision on the posterior inferior aspect of TM (because less vascular) to drain fluid and avoid injury to the chorda tympani nerve and auditory ossicles.
- Insert Tympanostomy or pressure-equalization (PE) tubes in the incision to allow drainage of effusion decrease pressure buildup.
20
Q
Fx of middle ear:
A
transmit vibrations from the tympanic membrane –> inner ear via the auditory ossicles.
21
Q
Parts of middle ear
A
- Tympanic cavity: medial to TM; contains ossicles (malleus, incus and stapes)
- Epitympanic recess – a space superior to the tympanic cavity, which lies next to mastoid cells and where malleus and incus extend to.
22
Q
What is the epitympanic recess?
A
- Part of the middle ear: A space superior to the tympanic cavity, which lies next to the mastoid air cells.
- Location of the head of malleus and incus, protecting them with bone.
23
Q
What are the borders of the middle ear (tympanic cavity)?
Roof, floor, lateral wall, medial wall, posterior wall, anterior wall.
A
- Roof (tegmental wall) is formed by tegmen tympani of temporal bone. It separates the middle ear from: middle cranial fossae.
- Floor (jugular wall) is a peice of bone that separates TC from: bulb on i_nternal jugular vein._
- Lateral (membranous) wall is the tympanic membrane and separates TC from: external ear
- Medial wall (labryinthe) is the lateral wall of the inner ear promontory (made by cochlea), oval window, round winow, promonince of canal for facial nerve- made by facial nerve) and separates TC from: Inner ear.
- Anterior (carotid wall) is made by opening for the pharyngotymapnic tube and canal for tensor tympani . and separates TC from: internal carotid A.
- Posterior wall (mastoid wall) is made by mastoid antrum and canal for facial nerve and separates TC from: mastoid air cells and facial canal.
24
Q
Contents of middle ear
A
- Ossicles (malleus, incus and stapes)
- Stapedius m and tensor tympani muscles
- Chorda tympani nerve
- Tympanic plexes
25
8. Describe the major landmarks and articulations of the three ossicles.
MALLEUS
**Malleus attaches to TM:**
* Head lies in the epitympanic recess and articulates with incus –
* Neck lies against flaccid part of tympanic membrane
* Chorda tympani crosses medial surface.
* Handle is embedded in tympanic membrane at the tip at the umbo.
*
26
8. Describe the major landmarks and articulations of the three ossicles.
## Footnote
**Incus**
* **_Head i_s located at the epitympanic recess and articulates with malleus**
* **Long limb attaches to stapes**
* **Short limb (just there)**
27
8. Describe the major landmarks and articulations of the three ossicles.
## Footnote
**Stapes**
Stapes
* **Head** articulates with incus –
* **Neck** is where stapedius m inserts –
* **Base** Inserts into oval window –
* has 2 limbs
28
9. Describe the location, insertion, innervation and function of the **tensor tympani** and **stapedius muscles.**
**Tensor tympani M**
* **Inserts**: handle of the malleus in the middle ear
* **Function**: pulls malleus medially -\> tensing the tympanic membrane-\> prevents damage from loud sounds.
* **I:** CN 5 (V3)
**Stapedius M**
* **Located**: inside pyramidal emince on the posterior wall
* **Inserts**: neck of stapes
* **Function**: Pull stages posterioly-\> tilt base in oval window -\> prevent damage fom loud sounds
* **I:** CN 7 (facial)
29
Action of **chorda tympani,** which runs through middle ear, medial surface of neck of malleus.
**Branch of facial nerve that carries parasympathetic fibers.**
**Responsible for taste to anterior 2/3 of tongue.**
30
What nerves come out of the **internal acoustic meatus?**
1. Vestibulocochlear N (CN 8)
2. Facial N (CN7)
Cochlea is located anteriorly.
31
**What is the path of facial N?**
**check earlier slides**
* 1. Originates at pontomedullary junction.
* 1. Enters the petrous temporal bone via internal acoustic meatus (w CN 8)
* 2. Upon exiting the internal auditory meatus -\> facial canal, which is divided into labyrinthine, tympanic, and mastoid segments.
* 3. Create geniculate ganglion, in the labyrinthe section, where it gives off greater petrousal N. -\> runs through the pterygoid canal and synapses at the pterygopalatine ganglion. Post synaptic fibers of the greater petrosal nerve innervate the lacrimal gland.
* 4. In the tympanic segment, the facial nerve runs through the tympanic cavity, medial to the incus.
* 5. The pyramidal eminence is the second bend in the facial nerve, where the nerve runs downward as the mastoid segment.
* 6. In the temporal part of the facial canal, just superior to stylomastoid foramen, the nerve gives rise to the stapedius and chorda tympani
* Crosses tympanic cavity medial to handle of malleus
* -\> petrotympanic fissue, between tympanic and petrous part of temporal bone
* -\> joints lingual N (CN V3) in the infratemporal fossa
* -\> The chorda tympani supplies taste fibers to the anterior two thirds of the tongue, and also synapses with the submandibular ganglion. Postsynaptic fibers from the submandibular ganglion supply the sublingual and submandibular glands.
* 7. When facial N comes out of the facial nerve gives rise to the posterior auricular branch. The facial nerve then passes through the parotid gland, which it does not innervate, to form the parotid plexus, which splits into five branches innervating the muscles of facial expression (temporal, zygomatic, buccal, marginal mandibular, cervical).
32
Tympanic N is a branch of what?
**Glossopharyngeal nerve. (CN9)**
33
Tympanic nerve gives rise to what?
**tympanic plexus**, which will give rise to **lesser petrosal nerve (parasympathetics)**
**_Hypoglossal N -\> typanic. N -\> tympanic plexis -\> lesser petrosal N_**
34
Path of tymapnic N.
1. Tympanic N. arises from CN IX (hypoglossal) at the petrous ganglion
2. Emerges with CN IX at jugular foramen.
3. TN enters middle ear vi_a tympanic canaliculus ni the petrous part of temporal bone_
4. Forms tympanic plexus on promontory of midder ear.
5. Lesser petrosal N branches off of tympanic plexus -\> goes through roof of tympanic cavity (aka tegmen tympanic) -\> middle cranial fossa
6. Leaves the foramen via foramen ovale
7. Parasympathetic fibers synpase at _otic ganglion_
8. Post synpatic fibers pass to _parotid gland via V3._
35
When is chorda tympani made?
IN THE FACIAL CANAL, before it leaves the **STYOLOMASTIOD FORAMEN**
36
The **inner ear** is located within the _petrous part of the temporal bone. I_t lies between the middle ear and the internal acoustic meatus, which lie laterally and medially respectively. The inner ear has two main components
**1. Bony labyrinth**
**2. Membranous labyrinth**
37
What is the **bony labyrinth**?
**Cavities filled with perilymph** in the petrous part of temporal bone:
1. cochlea,
2. vestibule and
3. three semi-circular canals.
38
What is the **membranous labyrinth?**
Series of communicating sacs and ducts inside the bony labyrinth filled with **endolymph**.
Made up of:
1. **Vestibular labyrinth** : Utricle and Saccule
1. Fx: gravity
2. **Semicircular ducts**
1. **Fx: acceleration**
3. **Cochlear labyrinth:** Cochlear duct
1. Fx: hearing
39
What. innervates inner ear?
**CN 8**
40
The presence of the duct creates what?
Two canals above and below it – the **scala vestibuli and scala tympani** respectively
41
Cochlear duct is seperated by the ?
**1. Vestibular membrane- separates it from the scala vestibuli**
**2. Basilar membrane - has the cochlear N.**
42
B.S of membranous labyrinth
**Internal auditory A. and V (labyrinthine artery)**
43
What is the Vestibule of the bony labyrinth?
**central part of the bony labyrinth.**
It is separated from the middle ear by the **oval window, where stapes is attached.**
Two parts of the membranous labyrinth; the saccule and utricle, are located within the vestibule.
44
Sound transmission:
sound waves move TM -\> move ossicles -\> stapedius moves oval window and creates sound waves -\> travel through perilymph of scala vestibuli -\> enter scala tympani -\> move basilar membrane of cochlear duct -\> stimulates cochlear n. -\> sound transmitted to brain
