Eye Anatomy Flashcards
1
Q
Orbit: Shape & Margins
A
Shape = like a 4-sided pyramid
Margins
- Superior
- formed by the frontal bone
- Lateral
- formed by the zygomatic process of the frontal bone
- Inferior
- formed by the zygomatic & maxillary bones
- Medial
- formed by the maxilla, lacrimal and frontal bones
2
Q
Orbit: Walls
A
- Roof
- Frontal and Sphenoid bones
- Posterior lateral wall
- Zygomatic & Sphenoid bones
- Floor
- Maxilla, Zygomatic and Palatine Bones
- Medial
- Ethmoid, Lacrimal, and Frontal Bones
3
Q
Optic Foramen (Canal)
A
-Apex of the orbit and lies within sphenoid bone
- Structures that enter the canal
- Optic Nerve
- Ophthalmic Artery
- Central Retinal Vein
4
Q
Superior Orbital Fissure
A
-Lies between the lesser and greater wings of the sphenoid bone
- Structures that pass thru
- superior and inferior divisions of the oculomotor nerve (III)
- Trochlear Nerve (IV)
- Lacrimal, Frontal, and Nasociliary branches of ophthalmic nerve
- Abducens Nerve (VI)
- Superior & Inferior divisions of ophthalmic vein
- Sympathetic fibers from cavernous plexus
5
Q
Nerves passing thru Superior Orbital Fissure
A
- Lacrimal Nerve
- Frontal Nerve
- Trochlear Nerve
- Superior division of Oculomotor Nerve
- Abducens Nerve
- Nasociliary Nerve
- Inferior division of Oculomotor Nerve
Live Frankly To See Absolutely No Insult
6
Q
Eyelids
A
Upper and lower eyelid are termed “palpebrae”
Fxn: protect and lubricate the eyes
Includes Tarsal Plate and Canthus
7
Q
Tarsal plate
A
- Fibrous layer
- gives the lids shape, strength and place for muscle attachment
8
Q
Canthus
A
- Where the upper and lower lids meet
- Lateral canthus & medial canthus
- Line thru lateral and medial canthus defines the angle of the palpebral fissure which is usually horizontal
- Down Syndrome: this line has an upward outward slant
- Epicanthic fold covers medial canthus and is characteristic of Asians and of certain chromosomal abnormalities
9
Q
Eyelids: Meibomian glands
A
- Lie underneath & within the tarsal plate
- Ducts open onto eyelids
- Secretions enable airtight closure of lids
- Glands can become infected (Chalazion)
creates the lipid (oil) layer of the tear film
a blockage can lead to evaporative dry eye
10
Q
Lipid (Oil) Layer
A
-Lubricates & Prevents evaporation
11
Q
Aqueous (water) layer
A
-Nourishes & Protects the cornea
12
Q
Mucin Layer
A
-Adheres tears to the eye
13
Q
Eyelid Movement
A
2 muscles
- Obicularis oculi
- closes the eyelids
- innervated by cranial nerve #7 (fish hook)
- Levator Palpebrae
- opens the eye
- innervated by cranial nerve #3 (pillar)
14
Q
Lacrima apparatus
A
Lacrimal Glands
- located within the eyelid & conjunctiva
- serous secretions = tears
Tears
- cleans & lubricates eye
- antibacterial enzyme lysozyme
Where do tears drain? Punctum
15
Q
Conjunctiva
A
- thin mucus membrane
- lines inner surface of both eyelids
- starts at the edge of the cornea (limbus) and flows back behind the eye, loops forward, and forms the inside surface of the eyelids
- extremely sensitive to irritation and inflammation
16
Q
Palpebral Conjunctiva
A
-lines the eyelids
17
Q
Ocular Conjunctiva
A
covers the eyeball
18
Q
3 Distinct Layers of eyeball
A
- Fibrous Tunic
- Vascular Tunic
- Internal or Neural Tunic
19
Q
Fibrous Tunic
A
-Sclera and Cornea
20
Q
Vascular Tunic
A
- Choroid
- Ciliary Body
- Iris
21
Q
Internal or Neural Tunic
A
- Retina
- Neural retinal layer
- Outer pigmented layer
22
Q
Sclera
A
- outer layer of eyeball
- tough
- opaque white fibrous layer (made of collagen)
- maintains shape of the globe
- is continous and connects to the transparent cornea anteriorly
- posteriorly continuous with the dura mater that surrounds the optic nerve
23
Q
Cornea
A
- convex clear front surface of the eye
- provides majority of the eye’s refractive power
- 5 layers
- Epithelium
- Bowman’s
- Stroma
- Desmemet’s membrane
- Endothelium
24
Q
Vascular layer (middle layer)
A
-composed of 3 regions
- Choroid
- Ciliary body
- Iris
25
Choroid
- one of the most vascular tissues in the entire body
| - melanocytes prevent the diffusion of light throughout the wall of the optic globe
26
Ciliary Body
- located immediately anteriorly to the choroid
- contains smooth ciliary muscles
- secretory function
- contributes to the production of aqueous humor
-controls shape of lens
27
Iris
-most anterior portion
- composed of 2 layers
- 2 layers of pigment forming cells
- 2 groups of smooth muscle fibers (control amount of light let in)
- sphincter pupillae muscle
- dilator pupillae muscle
- center of the iris is the pupil
- main function control amount of light hitting the retina
28
Inner Tunic: Retina
Function:
- Receive Visual Images
- Analyze them and transmit them to the brain
- Components
- optic disc: blind spot (no photoreceptors) where all the nerves go back into the brain
- Macula Lutea: lateral to optic disc
- Fovea centralis
- Neural Retina Layer
- Pigmented Layer
29
Inner Tunic: Retina: Neural Retina Layer
-Photoreceptors and associated neurons
- Function
- absorbing light rays and converting them into nerve signals transmitted to the brain
-contains rods and cones
30
Inner Tunic: Retina: Pigmented Layer
-immediately internal to choroid
- Function
- absorb light rays that pass through neural layer
-provides Vitamin A for photoreceptor cells
31
Photoreceptors
- Rods
- dark & light recognition
- Cones
- color recognition
32
Lens
-sits behind the iris
- 3 layers (like a peanut M&M)
- Capsule: thin saran wrap that hold lens in place
- Cortex: middle layer
- Nucleus: hard inner layer
-Zonules: holds capsule in place with suspensory ligaments that are connected to the ciliary body
33
Eyeball: 2 Cavities
Anterior Cavity
- Anterior Chamber
- Posterior Chamber
Posterior Cavity
-Vitreous Chamber
34
Eyeball: Divided into 3 Chambers
Anterior Chamber
- lies between the cornea & iris
- contains aqueous humor
- Posterior Chamber
- lies between the iris & lens
- contains aqueous humor
- Vitreous Chamber
- extends from the lens back to the retina
- contains vitreous humor
35
Anterior Cavity: Anterior & Posterior Chambers
- Anterior & Posterior Chambers
- contains aqueous humor
- filtrate of blood plasma produced by ciliary processes
- secreted into posterior chamber
- from posterior chamber flows through pupil into anterior chamber
- aqueous fluid is continually resorbed into vascular space called scleral venous sinus
- provides nutrients and oxygen to the lens and cornea
36
Posterior Cavity: Vitreous Chamber
- Vitreous Chamber
- Contains vitreous
- transparent gelatinous fluid
- produced by cells in the non-pigmented portion of the ciliary body
- fills the space from the lens to the posterior retina
- helps maintain the eye shape
- supports the retina
37
Muscles of the Eye: Superior Oblique
Superior Oblique
originates: sphenoid bone
inserts: sclera deep to the superior rectus muscle
innervated: trochlear nerve
function: abducts, depresses, laterally rotates the eyeball
38
Muscles of the Eye: Inferior Oblique
Inferior Oblique
originates: anterior part of orbital floor
inserts: sclera deep to the lateral rectus muscle
innervated: oculomotor nerve
function: abducts, elevates, & laterally rotates the eyeball
39
Muscles of the Eye: Superior Rectus
Superior Rectus
originates: common tendinous ring
inserts: sclera behind the corneoscleral junction
innervated: oculomotor nerve
function: elevates, adducts, & medially rotates the eyeball
40
Muscles of the Eye: Inferior Rectus
Inferior Rectus
originates: common tendinous ring
inserts: sclera behind the corneoscleral junction
innervated: oculomotor nerve
function: depresses, adducts, & laterally rotates the eyeball
41
Muscles of the Eye: Medial Rectus
Medial Rectus
originates: common tendinous ring
inserts: sclera behind the corneoscleral junction
innervated: oculomotor nerve
function: adducts the eyeball
42
Muscles of the Eye: Lateral Rectus
Lateral Rectus
originates: common tendinous ring
inserts: sclera behind the corneoscleral junction
innervated: abducent nerve
function: abducts the eyeball
43
Extrinsic Eye Muscles: Lateral Rectus
| Action & Controlling Cranial Nerve
Lateral Rectus
Action: Moves eye laterally
Controlling CN: VI (abducens)
44
Extrinsic Eye Muscles: Medial Rectus
| Action & Controlling Cranial Nerve
Medial Rectus
Action: Moves eye medially
Controlling CN: III (oculomotor)
45
Extrinsic Eye Muscles: Superior Rectus
| Action & Controlling Cranial Nerve
Superior Rectus
Action: elevates eye & turns it medially
Controlling CN: III (oculomotor)
46
Extrinsic Eye Muscles: Inferior Rectus
| Action & Controlling Cranial Nerve
Inferior Rectus
Action: depresses eye & turns it medially
Controlling CN: III (oculomotor)
47
Extrinsic Eye Muscles: Inferior Oblique
| Action & Controlling Cranial Nerve
Inferior Oblique
Action: elevates eye & turns it laterally
Controlling CN: III (oculomotor)
48
Extrinsic Eye Muscles: Superior Oblique
| Action & Controlling Cranial Nerve
Superior Oblique
Action: depresses eye & turns it laterally
Controlling CN: IV (trochlear)
