Review of Anatomy of the Eye

00:01 Welcome, we're going to go through a whole bunch of sessions together, looking at ophthalmology.

00:10 Basically, the way that the eye works and the pathology related to the eye.

00:14 And to really understand what's going on in the eye, we have to kind of understand the structure, we have to understand the anatomy.

00:21 So that's where we're going to start. I'm Rick Mitchell, you know that.

00:25 But I also want to acknowledge the hard work of Dr. José Mata, who has been instrumental in developing the slides that we're going to be seeing, and he shares as much as I do to the talks that you're going to hear.

00:40 Okay, with that, everyone has looked into someone else's eye, well, now, we're going to look at it a little bit more deeply and look at the individual structures.

00:51 So, on the left-hand side is the medial side, there would be a nose there.

00:56 On the lateral side, that's the lateral side, there'll be an ear on the right-hand side.

01:01 A couple of structures that we can identify immediately is that we have a medial canthus, and there will be a lateral canthus.

01:09 These are at opposite ends of the palpebral fissure.

01:13 So, the palpebral fissures, just the opening of the eye.

01:16 And we talked about the corners, as the canthi, or canthus, singular.

01:23 There is at the medial canthus, something called the lacrimal caruncle.

01:27 Basically, this is just a little bit of skin, overlying sweat and sebaceous glands.

01:31 It's also going to be the point that we will enter, the tears will enter into a tear duct and then drain out eventually through the nose.

01:39 So that's why we call it the lacrimal caruncle.

01:43 We have the upper and lower lids, the - so parts of the palpebral fissure are the lids, up and down.

01:51 We have a pupil, that's where the light gets in, that can hit the retina and that is basically a clear spot surrounded by the iris, which is the colored part of the eye.

02:03 That coloring is we'll talk about is what keeps the lights focused that it can only go in through the pupil.

02:09 The conjunctiva is a clear membranous vascularized structure that overlays the sclera, sclera is the whites of the eyes, and we'll talk about the sclera.

02:20 Sclera is going to be an important connective tissue kind of matrix that allows us to insert various muscles that will allow the eye to move.

02:28 The conjunctiva in most cases, is not very apparent, but it is highly densely vascularized.

02:34 And is going to be part of what maintains normal lubrication over the eye.

02:39 It can become inflamed. And we will talk about that.

02:44 So, we will talk about various pathologies that can occur on the eye, both on the outside of the eye, the inside of the eye, all the various structures of the eye.

02:53 And we'll identify those by this red box.

02:57 So, we will see red boxes in various places throughout all these various talks.

03:01 And so, for the outer part of the eye, for the external eye, the diseases that we're going to talk about are kind of the skin and some of the glands that are associated with the palpebral fissures, the upper and lower lids.

03:15 And this is blepharitis, chalazion, and hordeolums.

03:19 Hordeolums, much easier to say stye, and most people know what a stye is.

03:24 And the diseases that we'll talk about in the eye can be very focal, or they can be diffuse.

03:31 They can be infectious or non-infectious.

03:33 And we'll talk about all that various etiology.

03:36 So never fear, we're going to cover everything.

03:38 And prepare yourself, there'll be some images that will make you cringe, even as a pathologist, some of these make me cringe.

03:45 Okay. Another structure, we've already talked about, is the conjunctiva and when you have inflammation of that, that's conjunctivitis.

03:55 And basically, you are all aware as good medical students everywhere that any '-itis' is just inflammation of whatever's on the front of it.

04:03 So conjunctivitis is inflammation of the conjunctiva.

04:07 Blepharitis, is '-itis' inflammation of the blephs. That is the lids.

04:13 Okay, so, let's go forward.

04:16 We're going to peel back some of the skin now and look at some of the internal structures.

04:21 Again, same orientation of the eye, you can actually see the nasal cartilage over there on the left-hand side, nasal bone, and we are opening now to see the orbicularis oculi muscle, which is a circular muscle.

04:37 This is going to be important for closing the eyelids and assisting it's also - it's going to assist in the pumping of tears from the lacrimal gland which sits on the lateral side up above the eyelid, pump that lacrimal gland content into the eye and then, out through the nasal lacrimal duct.

04:57 That's why if you squeeze your eyes really tightly you we're actually causing the orbicularis oculi muscle to squeeze and you can actually induce some tears.

05:06 Okay, that's because you're squeezing the fluid out of the lacrimal gland. Cool, huh? Alright. There are diseases that will affect the orbicularis oculi muscle so it's innervated by a branch of the facial nerve, cranial nerve VII, and if that nerve is damaged, you will get something called Bell's palsy. And we'll return to that.