ANA - W13 Flashcards
What does the external and middle ear consist of?
External: auricle and external acoustic meatus
Internal: tympanic cavity and auditory tube
what is the structur eof auricle and what does it connect?
elastic cartilage - connected to the temporal bone by the ligaments
- extrinsic auricular muscles - connect the auricle to the skull and scalp and
move the auricle as a whole - intrinsic auricular muscles connect the different parts of the auricle
- skin – firmly connected to the cartilage – more on the lateral side than on the
medial side, this skin contains sebaceous glands and hairs
How does the auricle collect the sound
its elevation and depressions collect the sound and act as a funncel, amplyfing the sound toward the EAM
Where does the EAM extend and pass?
it extends from the concha of the
auricle to the tympanic membrane
* it is S-shaped - in transverse
section
* it passes ventromedially and
upwards, then posteromedially and
again ventromedially with a slight
descent
Superior and inferior wall of EAM
superior wall
– runs almost horizontally
- shorter than inferior due
to the oblique position of the
tympanic membrane
- inferior wall – is convex and
longer than superior wall
Isthmus: narrowest part-in the body-cartilagineous junction
What two parts does EAM consist of?
cartilagineous part
– lateral part of EAM, cca 8mm
*
osseous part
– medial part of EAM, cca16 mm
- formed by temporal bone
– superior wall squamous part of the
temporal bone;
- inferior wall by the tympanic part
of the temporal bone
*
what is EAM lined by?
EAM is lined by the skin
containing tragi (hairs)
and ceruminous glands
– producing ear wax - cerumen
EAM relations
middle cranial fossa – above EAM
- mastoid process – behind EAM
- temporomandibular joint – in front of EAM
- middle ear – tympanic cavity – medial to EAM
What does the tympanic membrane form?
How does the centre of membrane look?
what does it have on external surface
- grey membrane
- oval in form, its circumference is thickened and forms fibrocartilaginous !!!ring which is fixed in tympanic sulcus of temporal bone
-Centre of membrane is drawn inwards by attachment of handle of malleus-convexity of inner ruface is named UMBO
- small fold on ext surface called ANT AND POST MALLEAR FOLDS-border trinagylar part of tympanic membrane-PARS FLACCIDA-is thin and lax part of membrane
- PARS TENSE-the rest major part-is tense-taught part
nerve supply of auricle/external ear
- sensory innervation is supplied by auriculotemporal nerve (mandibualr nerve V3) - IN FRONT OF EAR
- the cervial plexus (great auricular nerve-C2,C3, Lesser occipital nerve-C2) - REGION BEHIND AND BELOW (great is more below)
- facial nerve (VII) - for auricle itself
- Vagus (X) - for entrance to EAM
blood supply of externla ear
By external carotid artery and its branches:
- posterior auricular a->auricular and perforating a
- occipital a ?
- superficial temporal a–>anterior auricular branches
Examination of EAM
- pull sup, pst and a bit laterally—>straighten
- normal membrane: translucent, gray-redisht ting, handle of malleus is visible near the center, a cone of light is always demonstrated
- acute otitis media–>membrane is bright red and bulging with loss of the normal light reflection
perforation of tympanic membrane
- MYRINGOPLAST/TYMPANOPLASTY
- trauma and infection
- myringoplast: surgical, uses connective tissue scaffold or graft (temporal fascia) to support healing of perforation
what is the tympanic cavity and what levels do we have?
in temporal bone, biconcave lens
EPITYMPANUM-epitympanic recess-the part of tympanic cavity above the lvl of the roof of EAM
- suspension apparatus
- majority of ossicles
. through mastoid antrum-connect with mastoid cells
MESOTYMPANUM
- handle of malleus
-lenticular process of incus
-tendon of tensor tympanic
HYPOTYMPANUM
- leads into auidtory tube
Boundaries of tympanic cavity
lateral wall - membranous wall- by tympanic membrane
medial wall-labyrinthine wall - promontory, fenestra cochleae, fenestra vestibuli
floor- jugular wall
rood-tegmental wall-tegmen tympani
posterior wall - mastoid wall-the entrnce into mastoid antrum-cells
anterior wall - thin layer of bone that separates the tympanic cavity from the internal carotid a
relations of tympanic cavity
anterior: carotid canal
posterior: mastoid process
Superiro: middle cranial fossa
inferior: jugular fossa
mediall wall: labrrinth
lateral: tympanic membrane
the auditry ossicles
Auditory ossicles transmit
vibrations of the tympanic
membrane to the inner
ear
* malleus - hammer - is
attached to tympanic
membrane
- incus – anvil – is
interposed between
malleus and stapes - stapes - stirrup – is
ancored into the fenestra
vestibuli - ovale
tympanic cavity-muscles
tensor tympani muscle
F: its contraction pulls the handle of the
malleus medially, this way it tenses the
tympanic membrane,
- its contraction reduces the force of
vibrations in response to loud noises -
protection of the internal ear
I: trigeminal nerve -[V3]
- stapedius muscle
F: it pulls the stapes posteriorly and
prevents excessive oscillation, its
contraction is usually in response to
loud noises - protection of the internal
ear
I: facial nerve
blood and nerve supply of tympanic cavity
blood supply
branches of:
maxillary a.
posterior auricular a.
middle meningeal a.
ascending pharyngeal a.
- nerve supply:
tympanic plexus – composed of:
glossopharyngeal n. (sensory
and pararasympathetic),
caroticotympanic nerves
(sympathetic) - relations to the nerves:
facial nerve in facial canal –
related to the tympanic cavity
chorda tympani runs through
the tympanic cavity
mastoid antrum
- aditus to the mastoid
antrum (from tympanic
cavity) - the mastoid cells
THE AUDITORY TUBE –
THE PHARYNGOTYMPANIC
TUBE
parts
it connects the tympanic cavity with the
nasal part of the pharynx
* it equalizes pressure on both sides of thetympanic membrane
* it directs ventromedially and inferiorly
It consists of 2 parts:
* bony part (in temporal bone)
- the one-third nearest the middle ear
- begins in the anterior wall of the tympanic
cavity – in the tympanic opening of the
auditory tube
*cartilagineous part
- the remaining two-thirds
- formed by curved fibrocartilaginous plate
which ends on the lateral wall of the
nasopharynx - in pharyngeal opening of
auditory tube
