External Ear

00:01 Welcome to this presentation on the anatomy of the ear.

00:05 The first thing that we want to take a look at is the ear is divided into three regions.

00:14 The first region is going to be that of the external ear, and we see the external ear shaded in green, that would include this outer funnel shaped structure called the auricle.

00:27 We then have the external acoustic meatus.

00:32 And then the most medial aspect of the external ear will be the tympanic membrane that we see right in through here.

00:41 Moving medially, we have this more centralized area of the ear.

00:46 This is referred to as the middle ear.

00:48 The middle ear is air-filled, and it's called also the tympanic cavity.

00:57 And then the most medial aspect of the ear is going to be the internal ear, which we see right in through here.

01:05 The internal ear contains the vestibulocochlear apparatus.

01:10 And this apparatus is concerned with the reception of sound, as well as the maintenance of balance.

01:18 And we'll take a look at each of these three regions in greater detail.

01:24 First, we'll start with the external ear.

01:28 And we're looking at the auricle.

01:31 The auricle has various structural features that are associated with it.

01:35 The outer rim of the auricle that we see in through here is referred to as the helix.

01:41 And then just the inferior to that the upper part of the auricle we have two ridges that are curved.

01:48 This one's more prominent in through here.

01:51 And these two prominent curvatures referred to as the antihelix.

01:58 And then as we come a little bit below, inferior to the antihelix is this depressed area called the cymba, and then just below that leading into the external acoustic meatus is an area of the auricle called the cavum.

02:13 Collectively, the cymba and the cavum form at the concha.

02:18 And these structural areas are collecting the sound waves and funneling them into the external acoustic meatus.

02:28 Inferior to the cavum, we have this flap of the auricle and this flap of tissue is referred to as the tragus.

02:38 Now, let's take a look at the blood supply of the auricle.

02:42 The blood supply to the auricle is from anterior auricular arteries as well as from posterior auricular artery.

02:51 So this is fairly easy to keep in mind.

02:53 Here are the anterior auricular arterial branches supplying the auricle here more anteriorly.

03:00 The anterior auricular arteries or branches of the superficial temporal artery, and this is your superficial temporal artery which is a branch of the external carotid artery.

03:10 The posterior auricular artery is going to be a branch of the external carotid artery.

03:18 And you'll see the posterior auricular artery right in through here.

03:24 And then here it is branching from the external carotid artery.

03:29 Innervation of the auricle is depicted here.

03:32 The main nerve supply to the auricle is going to be from the greater auricular nerve.

03:38 These are from spinal cord segments C2 and C3.

03:42 And then the other main nerve supply is going to be the auriculotemporal branch of the mandibular nerve (V sub 3) Mandibular nerve is a branch of the trigeminal nerve.

03:53 We also have some contributions from the vagus nerve and the facial nerve.

03:59 And you see the red triangles in here representing contributions from the vagus nerve.

04:06 And then the round blue objects here represent some contributions from the facial nerve.

04:14 Here we're looking at the external acoustic meatus.

04:19 The lateral 1/3 of the external acoustic meatus is going to be bounded by cartilage.

04:26 And then the medial 2/3 is going to be surrounded by bone specifically the petrous portion, of the temporal bone.

04:36 The lateral portion, the external acoustic meatus is cartilaginous.

04:41 The medial portion that we see in through here is osseous.

04:45 If we look above or superior we see the middle cranial fossa, and if we go back to the osseous portion the external acoustic meatus and go posterior, we will find ourselves amongst the mastoid air cells, and it's a thin layer of bone that separates those mastoid air cells from the external acoustic meatus.

05:12 The deepest part of the external acoustic meatus is situated below the epitympanic recess, which is the most superior part of the tympanic cavity.

05:25 And this deep part of the external acoustic meatus slice anteroinferior to the mastoid antrum.

05:33 The lamina bone that separates it from the antrum is only one to two millimeters thick, and provides the transmeatal approach of oral surgery.

05:45 So, by going posterior here, you can bypass the tympanic membrane and then perform microsurgical techniques within the middle ear cavity.

05:56 The outer part of the skin that's associated with the external acoustic meatus is going to be a thicker skin.

06:05 And this outer 1/3 of the thicker skin will contain your serinus glands as well as sebaceous glands.

06:14 When you get into the inner 2/3 and you're associated with the bony tissue, the skin is going to become much thinner.

06:26 And then the most medial structure here, that would be the very limiting part of the external ear is your tympanic membrane.

06:35 Here we're looking at the tympanic membrane.

06:39 This is the lateral portion of the tympanic membrane.

06:43 We see various components of the tympanic membrane, The first component that we see in through here is the posterior malleplar fold.

06:53 At this point, we see an area of the tympanic membrane that's referred to as the pars flaccida.

07:02 In through here, we see another molecular fold.

07:05 This one is located anteriorly.

07:07 So this is the anterior malleolar fold.

07:11 This structure here represents the lateral process of the malleus.

07:17 This area represents the handle of the malleus.

07:22 And kind of centrally and in thoroughly located we have this eminence the umbo.

07:29 And then right below that we have an area that tympanic membrane that demonstrates the cone of light.

07:36 The tympanic membrane is vascularized by branches that come from the maxillary artery.

07:44 Innervation of the tympanic membrane.

07:47 First is the external innervation of the tympanic membrane.

07:53 Part of the tympanic membrane that faces into the external acoustic meatus.

07:57 Trigeminal nerve is the main sensory nerve to this area tympanic membrane with contributions not only from the facial nerve, but also the vagus.

08:09 On the inner side of the tympanic membrane, that surface which faces the middle ear.

08:16 The glossopharyngeal is the innervation.