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AnatomyEYE-SpecialSenses — Transcript

by Dr. Naveen Jalota, M.D. · 9,119 words · 1,327 segments · language en · Watch on YouTube

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0:00hello and welcome let's talk chapter 17
0:04chapter 17 takes us into our special
0:06senses so let's go through and let's
0:08discuss our special senses now when we
0:10discuss our special senses the first
0:13special sense that we want to go through
0:15and we want to discuss is going to be
0:16our sense of vision we will see the
0:21sense of vision and how it fully works
0:24in Physiology here in anatomy what we'll
0:27do is we'll lay down all of the
0:29anatomical components and then this way
0:32when you get to physiology you know
0:33exactly what you have there and you
0:35could just start putting all of these
0:36actors in the show to their roles and
0:40start seeing exactly how then the sense
0:42is going to work so let's start here
0:45with vision let me get this expanded all
0:49right come on all right all right so
1:00here we go so first here when we talk
1:03vision so we're gonna be talking about
1:05the eye is basically what we're going to
1:06be looking at now what we'll do first is
1:08we'll go through all of the accessory
1:11structures of the eye again if you're
1:12following along with my note-taker this
1:16makes life much easier for you as well
1:17so here we'll talk first the accessory
1:20structures of the eye now when we talk
1:22about the accessory structure of the eye
1:23the first accessory structure in
1:26relation to the eyes that we want to go
1:28through when we want to mention is going
1:29to be the eyebrows here we can
1:32appreciate the eyebrows the eyebrows you
1:34can see you're basically very short or
1:39most of the time short coarse hairs
1:43short coarse hairs and then they can get
1:47to longer longer and obviously providing
1:50us with more protection is what will
1:51interpret that as then okay so very
1:55short coarse hairs now where are they
1:58located so the location of the eye brows
2:02is going to be they are found overlying
2:05the supraorbital margin if you recall we
2:09were able to discuss supraorbital margin
2:11in the class
2:12before all of this happened and the
2:16supraorbital margin was one part we were
2:18talking about in relation to one of
2:21these bones here the frontal bone so
2:23here you can see that super orbital
2:25margin is going to be found we discussed
2:29it as being at the superior end of this
2:31orbital basically this orbital cavity so
2:35here now we have the eyelashes I'm sorry
2:38the eyebrows these eyebrows now are
2:40found overlying the supraorbital margins
2:43so the super orbital margin is what we
2:45have underneath here so when you were
2:48touching the eyebrows and underneath
2:52this region here you have all of that
2:54supraorbital margin so found overlying
2:57the super margin is going to be the
2:59eyebrows now when we go through we talk
3:01eyebrows their function first when we
3:03talk the function in relation to the
3:04eyebrows their number one function is
3:06that they're gonna help shade the eyes
3:08they will help shade the eyes they'll
3:11shade the eyes from sunlight that's
3:14number one number two I'd like you to
3:17know that they prevent perspiration they
3:20will prevent perspiration from trickling
3:24down the forehead they prevent
3:26perspiration from trickling down the
3:29forehead and reaching the eyes then you
3:33can see athletes athletes will do put
3:36basically even further protection where
3:38they're going to wear like headbands or
3:41for headbands I believe you call them
3:44and they're gonna provide even further
3:46protection from that perspiration and
3:48keep it from trickling down into the
3:50eyes next in let's talk eyelashes I'm
3:54sorry eyelids and then we'll get into
3:56the eyelashes so eyelids I'm just
3:58excited about eyelashes I guess um
4:00eyelids no we talk eyelids eyelids are
4:02also going to be known as your palpebrae
4:05so anatomically speaking your palpebrae
4:07now when we talk palpebrae they are
4:09mobile they are thin they are skin
4:14covered folds so they are mobile they're
4:17thin they're skin covered folds so again
4:21you can see right inside of here each of
4:25your
4:26eyelids your palpebrae now when we talk
4:30eyelid function where they found located
4:34they're found located anteriorly on the
4:36face or on the skull located anteriorly
4:39on the face of the skull just inferior
4:42to we can say right inferior to the
4:46eyebrows inferior to the eyebrows and
4:51what is their function when we look at
4:52their function their function is to
4:55protect the eyes their function is to
4:57protect the actual eye to protect the
5:00eye now some structures in relation to
5:06the eyelids and when we talk about some
5:08structures first structure we have here
5:10is the palpebral fissure the palpebral
5:13fissure now we talk puppy real fissured
5:17it's uh you can think of a scientific
5:20way of saying your eye lid slit your
5:24eyelid slit it's basically the space you
5:28have in between the superior and
5:30inferior eyelids so the palpebral
5:33fissure is your eyelid slit or the space
5:37you have in between the superior and
5:39inferior eyelids and this palpebral
5:42fissure is basically separating the
5:44eyelids separating the eyelids so here
5:48you can see what the eye open it's a
5:49more pronounced palpebral fissure versus
5:52the eyes closed
5:54all right that puppy-proof is your size
5:56is basically changing next we have the
6:00lateral and the medial comma Shores now
6:03when we talk about the latter on the
6:04video commoners they're basically the
6:06angles they are the angles of the eyes
6:12so lateral comma sure now here you've
6:14got the medial comma sure so angles of
6:19the eye medial and lateral next is a
6:25lack of occur uncle know we talked a
6:27lack or Morcar uncle the lacrimal
6:28Karanka
6:29is found at that medial comma sure so
6:31it's found at the medial commish or and
6:34the lacrimal car uncle is a bit of flesh
6:38it is a
6:40bit of flesh and it contains you'll see
6:44sebaceous and sweat glands
6:47it will contain sebaceous and sweat
6:50glands so the lacrimal car uncle
6:53and these sebaceous and sweat glands
6:57they are going to produce the whitish
7:01oily secretions they produce the whitish
7:05and oily secretions that are going to
7:07collect during sleep that will collect
7:11during sleep next we have the
7:17orbicularis oculi we have the
7:20orbicularis oculi and we talk about the
7:23orbicularis oculi navicular is oculi we
7:25talked I muscles and we went into that I
7:28muscle we've discussed that before so
7:31number one orbicularis oculi is gonna be
7:33found within the eyelid so we're
7:34discussing it here it's found within the
7:36eyelid and if you remember its action
7:40it's gonna help close the eye when the
7:42muscle contracts so that's in so it's
7:44encircling the eye in order to
7:46appreciate it what we could do is we can
7:48move over and we can move over to this
7:50slide right inside of here and you can
7:54appreciate that orbicularis oculi right
7:57outside of there and you should have
7:59that idea from the previous exam that we
8:01just took exam 3 where we discussed the
8:03orbicularis oculi and how you found it
8:05encircling the eye and then when it
8:07contracted its action was to protect the
8:09eye close the eye next that we have the
8:14levator palpebrae superioris muscle now
8:16levator palpebrae superioris you can
8:18appreciate if you listen to the name
8:21it's giving you all the information
8:23you're gonna need to know right inside
8:25of there levator action palpebrae and
8:30superior is so action and location
8:32you've got all inside of there next and
8:35we have our tarsal plate the tarsal
8:39plate is basically connective tissue
8:43sheets so you can see that in the
8:45superior eyelid and you've got the same
8:47thing in the inferior eyelid as well
8:48their connective tissue
8:51they're gonna support the eyelids that
8:53will support the eyelids and also what
8:56they do is they help anchor the two
8:58muscles that we've just mentioned there
9:00you could see providing support and
9:04anchoring the orbicularis oculi and then
9:07also here you see on the inferior and in
9:11the superior you can see the levator
9:13palpebrae superioris coming in there as
9:15well next thing you have your tarsal
9:19glands when we talk about the glands of
9:21tarsal glands they're going to be
9:23embedded in the tarsal plates they're
9:26embedded in the tarsal plates and
9:28they're ducks and they're ducks do you
9:33see TS they're ducks are going to open
9:42at the eyelid edge there ducks will open
9:48at the eyelid edge just posterior to the
9:54eyelashes posterior to the eyelashes so
10:01you can see those openings are right
10:03along this edge here and the same thing
10:06right along this edge right inside of
10:08here so that's the glands in the side we
10:15described and in there ducts opening
10:17right at that surface now they're gonna
10:20produce an oily secretion these glands
10:22produce an oily secretion and the slowly
10:26secretion is gonna help to lubricate the
10:29eyelids it helps to lubricate the
10:32eyelids and keeps those eyes those
10:35eyelids from sticking together and it
10:39will keep those eyelids from sticking
10:42together next and we have our eye lashes
10:50our eyelashes the much-anticipated
10:53structure here eyelashes they're going
10:56to project from the free margin of each
10:58eyelid you can see that they're
11:01projecting from the free margin of each
11:03eyelid and these eyelashes are richly
11:07innervated they're richly innervated by
11:10nerve endings
11:11they are richly innervated by nerve
11:14endings so anything that touches them
11:17anything that touches those eyelashes it
11:19triggers the blinking reflex it will
11:22trigger the blinking reflex next here on
11:30this image we can appreciate the
11:32conjunctiva know we discussed
11:33conjunctive or the conjunctiva is going
11:35to be a transparent mucous membrane it
11:39is a transparent mucous membrane the
11:45conjunctiva is going to be found located
11:47surrounding the cornea it is found
11:51surrounding the cornea and you can say
11:55covering or lining the eyelids so
11:59surrounding the cornea and covering or
12:02lining the eyelids the function we
12:11talked about the function of the
12:12conjunctive or the function of the
12:13conjunctiva is to produce a lubricating
12:15mucus its function is to produce a
12:17lubricating mucus that's going to
12:20prevent that will keep the eyes from
12:23drying out that will prevent the eyes
12:26from drying out there are some
12:33structures here in relation to the
12:35conjunctive itself as well so a few
12:37divisions we can say of the conjunctiva
12:40now first we have what we call the
12:42palpebral conjunctiva again if you
12:44listen to words just those words alone
12:47are telling you exactly where you need
12:48to go
12:48so palpebrae we already discussed and
12:51now conjunctive in relation to the puppy
12:52right here you can see the superior and
12:55here you've got inferior and
13:00here we can appreciate the bulbar
13:01conjunctiva the bulbar conjunctiva is a
13:04segment surrounding the cornea segments
13:08surrounding the cornea not between the
13:12two between the two
13:14you've got the conjunctival sac the
13:17conjunctival sac this conjunctival sac
13:21now is a slit like space it is a slit
13:25like space and it's going to be found
13:27between the two conjunctiva and this is
13:32the space where your contact lenses will
13:34be found lying right because the contact
13:36lenses will be overlying the cornea and
13:38they're usually a little bit bigger than
13:40the cornea and they'll go around
13:43overlying that bulb are conjunctiva
13:49sometimes slightly and then basically
13:52resting in the space in between the two
13:53and sometimes they get lost in this
13:57conjunctival sac as well then you gotta
14:00go in there pull them out the pain of
14:03contact lenses next in here we've got
14:07soaked injectable sac there as well
14:09let's talk then the lacrimal apparatus
14:12the lacrimal a fraud I'm sorry before we
14:14jump back conjunctivitis you should
14:18probably have heard of her be familiar
14:20with now conjunctivitis is inflammation
14:22again if you listen to the words itis
14:24we've talked about being inflammation
14:26now of conjunctiva so conjunctivitis
14:29then we talk conjunctivitis inflammation
14:31of the conjunctiva inflammation of the
14:32conjunctival leaves that conjunctiva
14:34usually being red irritated and
14:36producing secretions and not just the
14:39conjunctiva but then also you'll see you
14:41have secretions being produced by the
14:42other components there as well trying to
14:44kind of wash out whatever it is there
14:46and trying to get rid of whatever it is
14:47there and most of the time
14:50conjunctivitis is diagnosed as being
14:52viral and in cause really nothing that
14:56you could do there avoid social
14:58distancing and kind of like what we're
15:00doing now and you know basically keep it
15:03clean and don't irritate it even further
15:06bacterials where you can bring in some
15:07antibiotics you know and so forth but so
15:11conjunctivitis inflammation of the
15:13conjunctive
15:13what I'd like you to know and then when
15:15you get to varmint you get to other
15:16classes microwave and they might discuss
15:19these causative agents and the
15:22treatments they're for the conditions as
15:24well so conjunctivitis next in here
15:28let's move down let's talk about the
15:31lacrimal apparatus tent so let's move
15:32images let's go to this even from this
15:35image this image here let's talk
15:38lacrimal apparatus and we talk lacrimal
15:39apparatus the lacrimal apparatus it's
15:42going to consist of a few parts so we'll
15:43go through all the different parts and
15:45then we'll see what it's going to do as
15:46well no it's going to consist of you can
15:48see a gland and the gland is gonna
15:51secrete into some ducks and the Ducks
15:53will take these secretions into the eye
15:55you can see and then from the eye
15:56they're gonna make their way into other
15:59basically openings and eventually into a
16:02drainage system that helps to take
16:05ventilator secretions though tears into
16:08you can see the nasal cavity into the
16:12nasal cavity so now you should people to
16:16understand why when you cry you also
16:19have already knows there as well these
16:21secretions are being hyper secreted and
16:23then you've got this increased drainage
16:26occurring there as well so the location
16:29let's talk location of the slack room
16:30apparatus right the lack of apparatus
16:33you can see is gonna be found
16:35surrounding the eye it is found
16:38surrounding the eye and in the nasal
16:42cavity surrounding the eye and in the
16:46nasal cavity function function is to
16:51secrete secretions that's what the gland
16:53is there for and then the rest of the
16:55components are going to help to drain
16:57tears so secrete secretions and then
17:01drain tears so let's talk about some
17:05structures first some structures we have
17:06first structures the lacrimal gland the
17:09lacrimal gland you can appreciate here
17:11on the lateral aspect the lacrimal gland
17:13is located above the orbit located above
17:17the orbit at the lateral end above the
17:21orbit as we described at the lateral end
17:23and this lacrimal gland is going to
17:25release
17:26dilute its gonna release a dilute saline
17:30solution it releases a dilute saline
17:33solution what we refer to as tears now
17:38we've got the expiratory ducts of the
17:40lacrimal glands you can see the
17:42excretory ducts of the lacrimal glands
17:44are gonna help to drain those secretions
17:46and remember we're talking ducts so here
17:48you should be able to understand what
17:50type of glands we're talking about right
17:53very good
17:54I know you got that answer we're talking
17:57excretory ducts so ducts exocrine glands
18:04right endocrine glands are ductless
18:06we've docked so here then you can
18:09appreciate the lacrimal putas so the x
18:12squared ducts are going to drain those
18:13secretions from the gland and into the
18:15eye now here we can appreciate the
18:18lacrimal pool or ocular puncta are going
18:21to be these two tiny openings they look
18:23like little red dots there are two tiny
18:26openings they look like little red dots
18:28and they're visible they are visible on
18:32the medial margin of each eyelid they
18:35are visible on the medial margin of each
18:37eyelid you can appreciate the inferior
18:39lacrimal pota right inside of here and
18:41here right on top we've got the superior
18:44lacrimal putas right on top these punta
18:51saw a pair they're going to lead us to
18:54the lacrimal canaliculi lacrimal
18:57canaliculi lacrimal canaliculi also is a
18:59pair superior and inferior and the
19:02lacrimal canaliculi will drain those
19:04tears from the poop dust of the punto
19:06will take these secretions from the eye
19:08and introduce them then to the next
19:10component which is the lacrimal
19:12canaliculi now the lacrimal canaliculi
19:14will take these secretions and it all
19:16guide these secretions to the lacrimal
19:19sac to the lacrimal sac so here you can
19:23appreciate it now the lacrimal sac the
19:25lacrimal sac then we'll drain these
19:28tears in two you can see the nasal
19:31lacrimal duct into the nasolacrimal duct
19:36so the lacrimal sac carries tears from
19:38the canaliculi
19:40to the duct and the light nasolacrimal
19:42duct will then carry these tears from
19:45the lacrimal sac into the nasal cavity
19:50now we talk nasal cavity you can see
19:52more specifically speaking where the
19:53nasal cavity we're at inferior nasal
19:59Concha and in here we had the me ADIS
20:02and you can see that opening of that
20:05nasal aqueduct right at that dorsal
20:09aspect of that inferior nasal Concha or
20:15into the inferior nasal me8 as you can
20:19say let's discuss then your extrinsic
20:26eye muscles we've talked about them
20:28before let's look at them then in
20:30greater detail so this is one view here
20:33another view here right lateral view
20:37superior view and then you can see all
20:39three views together and then here you
20:41got that two lateral view there by
20:43itself as well let's go here so here
20:45when we talk extrinsic eye muscles first
20:47structure you can appreciate here is
20:49going to be the annular ring the annular
20:52ring the annular ring is also known as a
20:53common tenderness ring it's found at the
20:56back of the orbit you can see it right
20:58inside of there back in the orbit right
21:01behind here this common tenderness ring
21:04it is going to be important because
21:06we'll see it's found at the back of the
21:08orbit and it's the origin sight it's the
21:10origin side of the four rectus muscles
21:12it is the origin sight of the four
21:15rectus muscles these muscles these
21:20muscles are the most precisely and
21:22rapidly controlled skeletal muscles in
21:25the entire body
21:26these muscles are going to be the most
21:28rapidly controlled and precisely
21:35controlled skeletal muscles in the body
21:40right during the exam days mine are
21:43working up to par they're perfect there
21:47I joke with you guys and tell you my
21:50eyes are faster than a convenience store
21:53surveillance
21:54you know just to make sure everybody has
21:56got the same exact opportunity that
21:59nobody needs any extra opportunity to be
22:03able to cheat or anything there so here
22:07we can see again they're going to be the
22:09most precisely and rapidly controlled
22:12skeletal muscles in the body so let's
22:14talk them the four rectus muscles first
22:16of them we'll get into the obliques so
22:18first we've got the superior rectus
22:19muscle the superior rectus muscle you
22:21can appreciate here from this frontal
22:23view very nicely right inside of here
22:25from this superior view you can see here
22:27very nicely and then from this lateral
22:29view you can appreciate right here on
22:31top and we talk superior rectus muscles
22:33superior rectus muscle it elevates the
22:36eye when you talk about its action now
22:37you thought you were done with maoi well
22:39here it goes again
22:40yeah it's going to be responsible for
22:42elevating the eyes and turning it
22:45medially so it elevates the eye and
22:48turns the eye medially next and we have
22:54the inferior rectus inferior rectus you
22:56can appreciate from the front of you
22:57right inside of here lateral view right
23:01inside of here superior view it's tough
23:06to see underneath there because of the
23:08superior blocking it we talk inferior
23:12rectus inferior rectus depresses the eye
23:14and turns it medially it depresses the
23:18eye and turns it medially leave your
23:23rectus medial rectus is going to move
23:27the eye medially medially here we can
23:31appreciate the medial rectus back here
23:34and then right on this side here medial
23:39rectus so moves the I medially lateral
23:43rectus moves the eye
23:44laterally lateral rectus you can
23:48appreciate here on the lateral aspect
23:50it's been cut here and here you can
23:54appreciate on the opposite side of the
23:56medial and then the last two are going
24:01to be the obliques and we talk obliques
24:02we've got first superior oblique muscle
24:05the superior oblique you
24:07see here coming in at an oblique fashion
24:11like the name says superior oblique now
24:15superior oblique it depresses the eye
24:17it's action is to depress the eye and
24:23turns it laterally so it depresses the
24:26eye and it turns it laterally in
24:32relation to superior oblique muscle you
24:34can also appreciate this trope glia
24:36right inside this little corner the
24:38trochlea right up in there trochlea
24:41right up in here trow clea trochlea is a
24:44fibrocartilaginous loop
24:46it's a fibrocartilaginous loop that's
24:49responsible for providing support to the
24:53superior oblique muscle so it's a pulley
24:58you can kind of think of or a
25:00fibrocartilaginous loop and it's
25:05suspended from the frontal bone
25:07suspended from the frontal bone provide
25:10support to the superior oblique muscle
25:13as we've described next time we have our
25:18inferior oblique the inferior oblique
25:20you can appreciate from this lateral
25:22view and then also from this anterior
25:25view the frontal view this inferior
25:28oblique now is going to be responsible
25:31for elevating the eye and turning it
25:33laterally it elevates the eye and turns
25:37it laterally elevates the eye and turns
25:42it laterally next thing you can see is
25:45your cranial nerves you need to go
25:47through and you've got to know every
25:48single one of those cranial nerves we've
25:49gone through them we've already talked
25:50about them we've discussed them in the
25:52last class as well here you have a
25:55little mnemonic a little mnemonic a good
25:58way to remember that you can think of
25:59here this chemical formula we're big
26:03fans of chemistry right so one way to
26:06remember is will apply chemistry here
26:09lr6
26:11will write our chemical formula for
26:13everything involved here all right it's
26:15a this is a like chemistry so we like
26:19everything balanced we want to make sure
26:20we know what
26:21is happening where and how many of what
26:23we have so here we can see it's quickly
26:35easy way to remember them lateral rectus
26:38six nerve superior oblique cranial nerve
26:44number four correct and then the rest of
26:51them all create a number between
26:54all creative three lateral rectus appear
26:56oblique and the rest of them it saves
27:04you study time if you use it to your
27:06advantage
27:09let's move next then let's talk more
27:12about the eye let's talk about the eye
27:15and we talk about the eye so you've
27:16taken care of all of that let's go
27:18through here is a nice image depicting
27:19the eye I like this image here a little
27:21bit better it's a bit more descriptive
27:24sugar when we look at the eye the eye is
27:26shaped as a sphere it's got about two
27:31two and a half centimeter diameter or
27:34one inch diameter you can think of no
27:37you look at the eye you can see only the
27:41anterior one sixth only the anterior
27:44one-sixth of the eyes surface is visible
27:47the rest is enclosed and protected the
27:51rest is enclosed and protected now the
27:55protection the protection you've seen
27:57comes from first you had bone right that
28:02bone all the different bones help to
28:05form that orbital cavity right so you
28:08got to be responsible for knowing all
28:09those different bones in there we've
28:10discussed before and then you've got
28:12inside of there adipose fat let's
28:15actually move back to this picture right
28:17inside of here you can actually
28:19appreciate the hollow chamber that
28:20cavity and then you can see how it's
28:23going to be occupied by adipose so we
28:26talk fat fat occupies all of the orbit
28:29that's not occupied by the eye when I've
28:34dissected the
28:35it's not something that just comes out
28:37easy it's it's real tough and when we do
28:39our dissection in the class you would
28:41actually be doing a sheep dissection
28:43sheep eye dissection what happens is we
28:45do our cut right up in here so the eye
28:47is closed and we'll make a cut right
28:49above the eyelid and make our way in
28:51right here on top trying to keep the
28:53whole eye preserve and then basically
28:55duct fingers you guys stick our fingers
28:57in there and without causing damage to
29:00the eye we've got to get that eye out of
29:01there and basically be cutting all this
29:04connective tissue and separating that
29:06eye from all the connective tissue so
29:08the orbit you've got fat you've got
29:12there as well now here you can see the
29:16eyes so it looks shape of a sphere okay
29:18same thing here as you see here so here
29:24you can see we've got two poles here
29:26South Pole north pole right Santa Claus
29:29is living at one no here we've got an
29:32anterior Pole we've got a posterior Pole
29:34right just like our biosphere we've got
29:36a South Pole and a North Pole those are
29:38going to be the most southern in the
29:39most northern points of the sphere well
29:41here we have the most anterior most
29:42posterior points now let's go through
29:46let's discuss the layers of the eye and
29:48we talked about the layers the eyes
29:49gonna get divided up into three major
29:50layers into three major layers that
29:52we're gonna go through we're going to
29:53check out so the first layer we can see
29:55here is going to be the fibrous layer
29:58now the fibrous layer we can appreciate
30:00right outside of here the fibrous layer
30:03is the outermost layer it is the outer
30:07most layer this fibrous layer is dense a
30:13vascular connective tissue and it gets
30:18divided up into two regions it gets
30:20divided up into two regions you can see
30:23here you have first what we call the
30:26sclera here what we have first the
30:29sclera making its way all the way around
30:34second we have we're going to see the
30:38cornea let's talk first sclera so again
30:43I told you this first layer the fibrous
30:46layer has two regions to it
30:48the sclera we'll discuss first the
30:51sclera you can see it forms the
30:53posterior portion it forms the posterior
30:57portion and the bulk okay where you can
31:00see the majority you can see that here
31:02it forms the posterior portion or the
31:05bulk or the majority we said of this
31:10fibrous layer it is tough its tendon
31:17like and it protects and shapes the
31:24eyeball protects and shapes the eyeball
31:29and also it's gonna provide a sturdy
31:33anchoring site it provides a sturdy
31:38anchoring site for those extrinsic eye
31:41muscles we've just gone through and
31:42discussed now we talked about the sclera
31:48the sclera you'll see it is continuous
31:51with dura mater and it is pierced by you
31:59can see here the optic nerve it's
32:01pierced posteriorly by the optic nerve
32:05the optic nerve penetrates through and
32:08makes its way through it next then we
32:13have the cornea now we talk cornea
32:16cornea is a vascular as we described the
32:19end it forms the anterior sixth of the
32:23fibrous layer so it's very small it
32:24forms the anterior sixth of the fibrous
32:27layer
32:39two birds are fighting a crow Raven and
32:42smaller bird pretty interesting so next
32:48in here we've got it forming again the
32:52anterior one sixth okay that's all it
32:54forms you can see the rest of it is all
32:55sclera so here we can see now when we
32:59talk about the cornea the cornea it
33:02bulges us it's transparent okay it's
33:04transparent and you can see from its
33:07junction with the sclera it bulges
33:11anteriorly so from that junction with
33:14the sclera you see it bulges anteriorly
33:20it's transparent as they describe so the
33:23crystal clear cornea I want you to know
33:27forms a window the crystal clear cornea
33:31forms a window that will let light enter
33:35the eye next and we have the second
33:44layer the second layer is called the
33:46vascular layer now when we talk about
33:49the vascular layer the vascular layer it
33:51forms the middle coat of the eyeball so
33:55it forms so it's a second layer we're
33:57gonna discuss it's here in red it forms
34:00the middle coat of the eyeball you see
34:03why I say that this vascular layer is
34:06also called the lluvia also known as the
34:09UVA and it's going to be divided up into
34:11three regions lluvia
34:25first region choroid the choroid we can
34:31appreciate right back inside of here the
34:35choroid I'd like you to know is blood
34:39vessel rich the choroid so hence the
34:43name vascular layer right now choroid is
34:45blood vessel rich it's got a dark brown
34:49membrane you can see - its structure
34:51it's got a dark brown membrane - its
34:54structure and the choroid forms it forms
34:58the posterior 5/6 you can think of of
35:03the vascular layer you can say forms the
35:05majority of the vascular layer even the
35:10second division here i want you to know
35:13about the second region we can say here
35:15is going to be now the ciliary body the
35:19ciliary body is the choroid anteriorly
35:22so again here we've got the choroid
35:25making its way all around here what they
35:27did is they cut it just so you could
35:28appreciate what it looks like underneath
35:30there as well so here it makes its way
35:32around and you can see that there's
35:34three different layers so makes its way
35:35out around underneath here coming around
35:38and you can see that it becomes the
35:40ciliary body and we talked about the
35:42ciliary body the ciliary body is the
35:45choroid anteriorly as i've described
35:47it's a thickened ring of tissue it is a
35:51thickened ring of tissue that encircles
35:56the lens it's a thickened ring of tissue
35:59that encircles the lens now the ciliary
36:03body the ciliary body is made up of a
36:06couple of different parts the first part
36:08here I'd like you to know about is the
36:09ciliary processes here we have ciliary
36:12processes and these processes are
36:14basically interlacing smooth muscle
36:18bundles they are interlacing smooth
36:21muscle bundles the ciliary muscles
36:24they're also known as and the ciliary
36:28processes are going to be important in
36:31controlling the shape of the lens
36:36they're important in controlling the
36:38shape of the lens of the shape of the
36:39lens is going to be controlled when we
36:41talk about physiology vision processing
36:44you'll see the eye is going to have to
36:47make adaptations when we want to look at
36:50something close and one of those is
36:55going to be the shape of the lens
36:59changing and then when we versus when we
37:02look at something far away it'll be a
37:04different shape compared to what it was
37:06we're looking at objects that are close
37:09so the shape change is gonna be
37:14important next and here we have our
37:18ciliary Zhaan Ewell's now the ciliary
37:20zhonya's are also known as the
37:22suspensory ligaments and they're gonna
37:25be found extending from the ciliary
37:27processes to the lens they extend from
37:30the ciliary processes to the lens then
37:34circle you can see and help hold the
37:39lens in its upright position in the eye
37:42so the ciliary zhan Ewell's so you're
37:47suspensory ligaments we describe them as
37:49as well they are going to be extending
37:53from the ciliary processes to the lens
37:57they will extend to the lens from those
38:00processes these annuals encircle and
38:06help hold the lens in its upright
38:10position in the eye so you can see those
38:14on eul's they're very nicely your
38:18suspensory ligaments and they're gonna
38:20be involved with changing the shape next
38:27when we have the iris the iris now the
38:31iris is going to be the anterior
38:34keynesian continuation of that ciliary
38:36body you can see so right inside of here
38:38now we've got the iris there's a one
38:40view of the iris we can see the iris
38:44from here as well right inside of here
38:48it's a visible colored part of
38:50I underneath the cornea the cornea is a
38:53transparent part we said underneath
38:55there now is what you're seeing so
38:56coming back to this picture you can see
38:58the corneas right out there and
39:00underneath there
39:01is the iris so when we talk about the
39:04iris iris is the visible colored part of
39:06the eye
39:07it's the visible colored part of the eye
39:09this is what you look at and you
39:12determine somebody's eye color you say
39:14Oh your eyes are green your eyes are
39:15blue or your eyes are brown because
39:17you're looking at that iris so the iris
39:20is the visible colored part of the eye
39:22it's the most anterior portion where
39:25it's at the most anterior position of
39:28the vascular layer you can think of it's
39:30found at the most anterior position of
39:32the vascular layer it lies between the
39:36cornea and the lens so you can see there
39:39it's found lying between the cornea and
39:40the lens here you've got the cornea
39:42anterior to it and the lens then dorsal
39:44to it it's continuous with the ciliary
39:47body as we can see there it's continuous
39:51with the ciliary body and it itself has
39:58two pupil a it itself has two pupil
40:03lengths to be able to appreciate those
40:05pupil a we'll move over to this picture
40:07right in here to appreciate them but
40:09before we do that let's come back here
40:11let's talk about the pupil now we talked
40:14about the people the pupil is around
40:15central opening it's around central
40:18opening of the iris it's a round central
40:23opening of the iris now this pupil it
40:25regulates the passage of light into the
40:29eye it will regulate the passage of
40:32light into the eye it regulates the
40:36passage by constricting or dilating that
40:39basically that pupil that iris so how
40:43does that happen that happens thanks to
40:44the two sets of muscles you have here
40:46the sphincter pupil in the dilator pupil
40:48a and here you can see when each of them
40:51get activated this also happens to mimic
40:53either sympathetic or parasympathetic
40:54response that we've already gone through
40:56have discussed so here we can see first
40:59we've got our sphincter pupil a now when
41:01we discuss our sphincter pupil a iris
41:03pink
41:04pupil a or the circular muscles are also
41:06known as are going to be pupil a that
41:11are going to function in close vision
41:13and bright light so in close vision when
41:17you're looking at something really close
41:19or in bright light the sphincter pupil a
41:25will contract and when the sphincter
41:28pupil a contract
41:30this causes the pupils to constrict
41:35decreasing the quantity of light being
41:38allowed into the eye so again in close
41:40vision and also in bright light for
41:44example when you wake up in the morning
41:47so here you can appreciate those finger
41:50pupil a activating and when they
41:53activate again they're going to cause
41:55constriction muscle contraction is gonna
42:00cause a constriction of that pupil size
42:03its width is also set of parasympathetic
42:06responses we described before the
42:10opposite we can see with the other set
42:13of muscles that dilator pupil they are
42:15the radial muscles now in distant vision
42:20in distant vision and dim light so
42:24distant vision and dim light is going to
42:27get the dilator pupil a to contract so
42:32in distant vision and dim light the
42:36dilator pupil in contract and the pupil
42:40dilates and the pupil dilates and when
42:45the people dilates what is this going to
42:46do it's gonna allow more light to make
42:49its way into the eye so that's why
42:51distant vision you're trying to look at
42:54something far away we want to be able to
42:56see so a distant vision the dilated
43:01pupil it will cause the pupil to dilate
43:04allowing more light to enter into the
43:07eye allowing us to see what we're trying
43:10to see that
43:14then we move to the third layer the
43:16third layer now we can appreciate here
43:17is going to be the inner layer or the
43:20innermost layer of the eyeball and this
43:23inner layer is a very delicate - layered
43:27retina it's a very delicate - layered
43:31retina when we talk about this retina
43:35first we have what we call the pigmented
43:38layer the pigmented layer the pigmented
43:42layer is the outer layer of the - it's
43:48the outer layer of the - it's basically
43:55a single thick lining a single-cell
44:01thick lining a single-cell thick lining
44:06so it's just a single cell thick that's
44:08it and this pigmented layer it a but the
44:13choroid it's found lying right next to
44:15the choroid so from here we can't
44:17appreciate the two layers so what we'll
44:18do is we'll zoom in on this red now we
44:22zoom in on the retina here now you can
44:24appreciate those two layers now so here
44:29let me orient you you've got that
44:32pigmented layer right inside here I told
44:33you it's a budding at Porat which you
44:34see right inside of there
44:35here's the rest of them the retina let's
44:39zoom in on this even further
44:42here is your pigmented layer I said it's
44:45a single-cell thick lining single self
44:48Nick that's it and here's the rest of it
44:51the rest of the retina so this is the
44:54pigmented layer of the red and the rest
44:58of you is gonna be called a neural layer
45:00of the retina the neural layer of the
45:03retina whiny role I mean just look at
45:05the picture tells you everything
45:08photoreceptors you can see bipolar cells
45:11and we've got ganglion cells now when we
45:16talk about the pigmented layer so it's
45:17the outer single self declining at
45:20eighty buds the choroid and it's going
45:22to extend anteriorly to cover the
45:24ciliary body
45:27and the posterior face of the iris it
45:30extends anteriorly to cover the ciliary
45:33body and the posterior face of the iris
45:36it's got a few jobs number one it's to
45:39contain vitamin A it contains vitamin A
45:42and vitamin A is going to be required
45:44you'll see by the photo pigment which is
45:47within the photoreceptor which is
45:50embedded within the pigmented layer all
45:53right so when parents told you eat your
45:55carrots they weren't lying
45:56they knew that vitamin A inside those
45:58carrots is going to get absorbed and
46:01placed inside of that pigmented layer
46:05second job is that they're gonna absorb
46:07light the pigmented cells are going to
46:11absorb light and prevent it from
46:13scattering choroid does that as well and
46:16they'll do the same thing they're gonna
46:17prevent this light from scattering and
46:20help to process that image we're trying
46:22to see next then you have the neural
46:26layer so let's go back into here you can
46:28see the neural layer now we talk neural
46:31layer the neural layer is the
46:33transparent inner layer it's the
46:36transparent inner layer and it extends
46:40anteriorly it extends anteriorly to
46:45cover so it extends anteriorly to the
46:52posterior margin of the ciliary body it
46:55extends anteriorly to cover the
46:58posterior margin of the ciliary body
47:03also appreciated here is the aura
47:06Sarada when we talk about the aura
47:09Sarada the aura Sarada is going to be a
47:13salt toothed margin it is a saw tooth
47:18margin and this is where the neural
47:25layer blends into the ciliary body this
47:29is where the narrow layer blends into
47:31the ciliary body so
47:39we back then we can appreciate the
47:42photoreceptors again if you have this
47:45note-taker my students you know for my
47:48class at least you guys get the note
47:50takers you guys know how to use the
47:51website it's not that uncommon I know
47:54people from other classes that tell me
47:55they use it as well a so here
47:59photoreceptors so you see we went from
48:01the aura Sarada again this is all in
48:03relation to that neural layer so now the
48:05photoreceptors so we talk photoreceptors
48:08now photoreceptors are found a budding
48:11the pigmented layer so they a but the
48:13pigmented layer and they're going to
48:16help spread signals in response to light
48:19they will help spread signals in
48:23response to light so again we are on the
48:34retina you can appreciate now that
48:36retina in its entirety you see why we
48:41mentioned the aura sirata there and that
48:45we were deep into excuse me the
48:48photoreceptors so get on the note-taker
48:53it follows all in sequence now these
48:57photoreceptors photoreceptors they're
49:01gonna help spread signals in response to
49:02light you have two types you have rods
49:05and you have cones which are rods you
49:08can see you just right off the bat rods
49:10are going to be more numerous in
49:12quantity they're found to be more
49:14numerous in quantity the rods are dim
49:17light and peripheral vision receptors
49:22they are dim light and peripheral vision
49:27receptors nor rods they allow us to see
49:34tones of gray they allow us to perceive
49:37tones of gray gray colors next we have
49:43our cones cones they operate in bright
49:47light so there are our bright light
49:50receptors and they
49:53- with high acuity color vision they
49:57provide us with high acuity color vision
50:02they will allow us to see colors such as
50:06blue green red plus a hue of these
50:12colors when they're mixed
50:21so our color receptors versus our grey
50:26color receptors great tone receptors you
50:29can say now color receptors we have I
50:31told you blue green and red so when you
50:33talk colorblindness which affects males
50:37right because of the genetic pattern of
50:40inheritance so here these individuals
50:45now will be lacking one of those
50:48pigments okay they'll be lacking either
50:52blue pigment or green pigment and red
50:55pigment this will then allow them to see
50:56those various colors next in the pathway
51:01are your bipolar cells we've discussed
51:03these types of neurons we said that
51:04they're found very rare in the body and
51:06this is one of the other places you're
51:09gonna find them
51:09these bipolar cells now what they do is
51:12they receive signals from those
51:13photoreceptors and they will then pass
51:18along these signals to the ganglion
51:20cells so they're kind of like the middle
51:21cells you can think of so they receive
51:25signals they're stimulated from the
51:27photoreceptor and then they in turn
51:29stimulate or send these signals to the
51:31ganglion cells ganglion cells are the
51:37cells where the actual action potential
51:40is going to be generated right because
51:44we've talked about where the action
51:45potential is gonna be generated in the
51:47dendrite I'm sorry it's going to be in
51:49the axon so here you can see the
51:52dendrites for each of these neurons here
51:56you've got their cell bodies and in here
51:59you can see their axons there's no
52:02action potential generated in these
52:04receptor cells nor in these cells here
52:09so action potentials will be generated
52:12in the axons of your ganglion cells
52:16these cells they come together they're
52:18found lying close together you can see
52:20their axons make these right angle turns
52:23or 90-degree turns and those axons all
52:27come together to form the optic nerve as
52:31we've described before a nerve is
52:33collection of
52:35excellent here moving back you can
52:41appreciate that optic nerve here as well
52:43here's all those ganglion cells from the
52:44top row look at these cells are also
52:46their axons making these 90-degree or
52:48right angle turns helping to make this
52:51optic nerve part up here and then this
52:53optic nerve part down here you've got
52:54the whole nerve in its entirety
53:00next in here we can appreciate the
53:03horizontal cells and the amacrine cells
53:06here we've got horizontal cells and
53:08we've got some amacrine cells these
53:10horizontal cells and amacrine cells are
53:12other types of neurons and what they're
53:15going to do is they're going to play a
53:16role in visual processing they will play
53:19a role in visual processing the other
53:21three we mentioned they're top three
53:24you've got to know them or four because
53:27rods and cones optic nerve so you should
53:33be able to tell me that what cells make
53:34it up or even more specifically what
53:36part of the cell now in relation to that
53:39optic nerve we've got the optic disk so
53:41going back to this picture you can see
53:43the optic disk this is one way we will
53:46see it the optic disk is the blind spot
53:49it's the blind spot because it lacks
53:53because it lacks photoreceptors this is
53:57where the optic nerve exits the eye this
54:01is where the optic nerve exits the eye
54:03and this is found as a weak spot this is
54:10found as a weak spot in the fundus
54:14basically in the posterior wall you can
54:20see of the eye so here if we were to
54:23look at the eye now width and a fallow
54:26scope right making your way into your
54:29partner's pupil and looking right in you
54:32would see this image so here you can
54:35actually appreciate the optic disk this
54:38is the blind spot again why is it the
54:40blind spot very good no photoreceptors
54:45exist here very good
54:50next then looking lateral to the optic
54:53disc you can appreciate the macula lutea
54:55the macula lutea it's an oval region
54:59lateral to the blind spot of each eye an
55:02oval region lateral to an oval region
55:12lateral to the optic disk of each eye
55:28next and we have our fovea centralis the
55:35fovea centralis is a minut pit it's a
55:39minut pit in the center of the macula
55:42lutea it's a minut pit in the center of
55:46the macula lutea the fovea centralis is
55:50going to contain a high concentration of
55:53cones it contains a high concentration
55:55of cones and this high concentration of
55:59cones is going to provide us with high
56:02acuity color vision it will provide us
56:06with high acuity color vision next in
56:13here we can appreciate the central
56:14artery in the central vein the central
56:17artery in the central vein are going to
56:19service so they serve the inner
56:23two-thirds of the neural retina they
56:26service the inner two-thirds of the
56:30neural retina and they're found entering
56:32and exiting that eye right through the
56:36optic nerve and you can see them there
56:43as well
56:49so here there's another view of an
56:55ophthalmoscope being used to look at the
57:03inside of the eye
57:09next you can appreciate here how the
57:11lens in the Salieri's annual are going
57:15to be responsible for dividing the eye I
57:17want you to know the lens and the Sealy
57:20Ares annuals are gonna help divide the
57:23eye they're gonna help divide the eye
57:24into two segments it will help divide
57:28the eye into two segments now here when
57:30we go through we look at them dividing
57:31the eyes into two segments here you've
57:34got first the posterior segment the
57:36posterior segment is going to be found
57:38posterior to the lens and those ciliary
57:41zhan Ewell's now the posterior segment
57:45is going to be filled with a clear gel
57:48going to be filled with the clear gel
57:50and this clear gel is a it's a clear gel
57:56it's a vitreous humour is its name
57:59vitreous humour let's discuss more of
58:02this vitreous humour this vitreous humor
58:03I would like you to know is going to be
58:05formed it will be formed in the embryo
58:11so it gets formed in the embryo and it
58:14lasts for a lifetime and it will last
58:17for a lifetime
58:19this vitreous humor has a few functions
58:23you can see it here they've cut it a
58:26little bit here and then you can see the
58:28bottom part of it right inside of here
58:29this vitreous humor number one it's
58:32going to be responsible for transmitting
58:34light it transmits light number two it
58:39supports the lens supports the lens and
58:45it helps hold the neural retina against
58:49a pigmented layer so it supports the
58:51lens and supports the retina by keeping
58:56the neural layer against the pigmented
58:58layer and it's going to contribute to
59:06intraocular pressure and it contributes
59:09to intraocular pressure it helps to
59:14counteract the pulling force of the
59:17extrinsic eye muscles it's helping to
59:19counteract
59:23the pulling force of the extrinsic eye
59:26muscles next then anterior to the lens
59:34and the ciliary zhonya's we've got the
59:36anterior segment now we talk anterior
59:39segment the anterior segment is
59:41subdivided by the iris now it gets
59:45subdivided by the iris
59:48it'll get subdivided by the iris into a
59:52posterior chamber and an anterior
59:56chamber so when we talk posterior
59:59chamber posterior chamber is found
1:00:01between the iris and the lens found
1:00:05between the iris and the lens and then
1:00:10we've got the anterior chamber the
1:00:12anterior chamber is found between the
1:00:15cornea and the iris found between the
1:00:18cornea and the iris next and we have our
1:00:24aqueous humor when we talk a quiesce
1:00:27humor aqueous humor is going to fill the
1:00:29entire anterior segment it will fill the
1:00:34entire anterior segment now when we talk
1:00:46a quiesce humor aqueous humor so it
1:00:48fills the entire anterior segment the
1:00:51aqueous humor is a clear fluid it is a
1:00:55clear fluid it is similar in composition
1:00:58to blood plasma it's a clear fluid
1:01:04similar in composition to blood plasma
1:01:10let's zoom in on the sentir chamber and
1:01:16the anterior segment and posterior
1:01:19segment here now and posterior chamber
1:01:24in greater detail we can see so
1:01:25posterior segment anterior segment enter
1:01:31segment gets further subdivided into a
1:01:33anterior chamber and posterior chamber
1:01:37here you can appreciate now also the
1:01:39scleral venous sinus the scleral venous
1:01:43sinus number one it's found you can see
1:01:47at the junction of you can see the
1:01:49coolest sclera and the cornea it's also
1:01:52known as the canal of schlemm also known
1:01:56as the canal of schlemm it's an unusual
1:02:03venous channel
1:02:05it's an unusual venous channel that
1:02:08encircles the eye it encircles the eye
1:02:18and when it encircles the eye you can
1:02:24see its job now is to drain its job is
1:02:30to drain secretions it's job is to drain
1:02:36these secretions that are going to be
1:02:38produced now by the ciliary body now if
1:02:46this canal gets blocked
1:02:49if this canal gets blocked what happens
1:02:53now the pressure inside the eye can
1:02:56increase the pressure in the eye can
1:03:00increase causing glaucoma in the patient
1:03:07causing glaucoma and the patient
1:03:10increasing the pressure so the canal of
1:03:15schlemm are the sclera venous sinus an
1:03:18important structure there next and we
1:03:20have our lens we have our lens now when
1:03:25we talk lens we talk lens lenses a by
1:03:30convex structure it is a by convex
1:03:34structure so we say it's by convex both
1:03:37sides are convex it's transparent it is
1:03:42flexible and like I've mentioned to you
1:03:46before it will change shape it changes
1:03:49shape
1:03:50to allow precise focusing of light on
1:03:54the retina it will change shape to allow
1:03:57precise focusing of light on the retina
1:04:04this lens is gonna be enclosed it's
1:04:07gonna be enclosed in a thin elastic
1:04:10capsule it is enclosed in a thin elastic
1:04:15capsule and the lens is held in place
1:04:18just posterior to the iris we said it's
1:04:23going to be held in place just posterior
1:04:26to the iris by the ciliary zhan Ewell's
1:04:30by the suspensory ligaments the lens is
1:04:37a vascular the lens has two regions to
1:04:43it it's got basically one part that's
1:04:46the lens epithelium the lens epithelium
1:04:50is going to be confined to the end to
1:04:53the anterior lens surface it's confined
1:04:57to the anterior lens surface and then
1:05:05the bulk of the lens you'll see is made
1:05:07up of lens fibers lens fibers now these
1:05:17fibers they contain no nuclei and very
1:05:21few organelles
1:05:29so here we're going to see the fibers
1:05:32are gonna contain transparent precisely
1:05:34folded proteins also found here are
1:05:38going to be precisely folded proteins
1:05:40called crystal lens called crystal ins
1:05:54and here now we can appreciate the
1:05:58visual projection pathway that basically
1:06:01light is going to take to make its way
1:06:04to the cortex to stimulate that
1:06:06occipital cortex or our occipital lobe
1:06:11which contains the visual cortex here
1:06:17now you can see we've got the optic
1:06:20nerve from the right eye and we've got
1:06:22the optic nerve from the left eye and
1:06:24here we can see we've got these fibers
1:06:30from this eye making their way over and
1:06:33continuing on the same side while some
1:06:38of those fibers cross over to the
1:06:40opposite side and you see that exact
1:06:43same thing happening with the left eye
1:06:44fibers as well so when they cross over
1:06:47that creates that optic chiasma as we've
1:06:49discussed before the optic chiasm is the
1:06:51crossover point of the optic nerve and
1:06:53you see now how that crossover point is
1:06:55formed so those fibers that continue on
1:06:58this side you can see they continue back
1:06:59up this way and they're going to make
1:07:02their way up to the lateral geniculate
1:07:03nucleus of the thalamus same thing is
1:07:07happening on the right side now these
1:07:10fibers coming from opposite sides here
1:07:13you can see these fibers from the left
1:07:14eye coming and now they're making their
1:07:16way in - you can see the protecta
1:07:20nucleus and the superior colliculi same
1:07:24thing happening on this side from there
1:07:26then this information is gonna make its
1:07:28way all the way back to that visual
1:07:30cortex and that's why then in physio you
1:07:35guys going to do a test where you're
1:07:36going to be able to shine light into one
1:07:39eye and you're gonna see the same
1:07:40response and the other eye as well
1:07:47so here you can see vision problems so
1:07:51normal any tropic eye what happens in a
1:07:53normal Emmy tropic eye light is gonna
1:07:55focus right on to the retina and there's
1:07:57no problems but now here when we talk
1:08:00hyperopic ir a myopic eye where you have
1:08:05hyperopia myopia those focal points
1:08:08aren't on the actual retina you can see
1:08:12here in hyperopia it's behind that
1:08:17retina so we have to get convex lenses
1:08:20for the patients to help restore the
1:08:23focal plane back on to the retina so
1:08:28here in a myopic eye nearsightedness
1:08:31the focal plane is in front of the rim
1:08:32and we have to provide a concave lens
1:08:36which will then provide that focal plane
1:08:39to be restored
1:08:50so this will conclude the first part of
1:08:53this chapter

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