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Anatomy - Viscera - Test 2 > Lecture 30: Regions of the Head: The Orbit & Eye > Flashcards

Lecture 30: Regions of the Head: The Orbit & Eye Flashcards

1
Q

What is a blowout fracture of the orbit?

A

Common with blunt trauma to they eye, bones break to relieve pressure blood is putting on eye and fall into maxillary sinus

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2
Q

What bones form the supraorbital margin and what is significant about this margin?

A

Frontal Bone

Supraorbital notch - passage or vessels and nerves to the forehead

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3
Q

What bones form the infraorbital margin?

A

Zygomatic laterally and maxilla medially

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4
Q

What are the bones of the orbit (roof, floor, lateral, medial)?

A
  • Roof: frontal bone and lesser wing of sphenoid
  • Floor: maxilla (medial), zygomatic (lateral), palatine
  • Lateral: zygomatic, greater wing of sphenoid
  • Medial: maxilla, lacrimal bones, ethmoid, body of sphenoid (lacrimal and ethmoid very thin)
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5
Q

How does double vision happen?

A

Break orbital bones, fall into maxilla and extra ocular muscles get trapped and cannot move eye in normal way

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6
Q

If broken orbital bones are replaced with a titanium plate and trauma happens again what happens?

A

If trauma is repeated after replacement with titanium plate - no bones to break to reduce pressure on eye from blood (reduce damage) - irreversible damage

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7
Q

What are the weakest bones in the orbit?

A

Lacrimal and ethmoid

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8
Q

What is the superior orbital fissure?

A

Gap between lesser and greater wings of sphenoid where most vessels and nerves to the eyes move through

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9
Q

What are the 3 layers of the eye and their functions?

A

Outer coat: cornea and sclera, function for strength
Middle coat: uvea, formed by a number of different structure (carotid, ciliary body and iris), function is nutrition
Inner coat: retina, nerves for vision

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10
Q

What are the features of the sclera?

A
  • 5/6 of the eyeball
  • Maintains shape and offers resistance against forces
  • Provides attachment for extraocular muscles
  • Point of extreme strength and resistance
  • Made up of collagen laid down in a muddled way – series of whirls for greatest strength
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11
Q

What are the features of the cornea?

A
  • Anterior 1/6 of eyeball
  • Refracting component of eye
  • Avascular and transparent
  • 5 layers
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12
Q

What is special about the layers of the cornea?

A

Epithelium: constantly dividing cells
Stroma: fatty layer, transparent
Endothelium: finite number of cells, damage will require transplant, maintains water balance and thickness of cornea

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13
Q

Why is the cornea transparent?

A

Collagen fibrils are uniform in diameter, evenly spaced and run in parallel to each other (each lamellae)

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14
Q

How many lamellae in each stroma?

A

200-300

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15
Q

What happens when there is a scratch on different layers of the cornea?

A

Epithelium - repair in 7 days
Stroma - scarring due to disruption of collagen fibres
Endothelium - cornea cannot repair, transplant needed

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16
Q

What is the anterior chamber?

A

Area between iris and cornea

17
Q

Where does the aqueous humour drain?

A

Anterior chamber angle - trabecular meshwork - canal of schlemm - venous system

18
Q

What happens is anterior chamber angle is blocked?

A

Glaucoma

19
Q

What are the functions of the ciliary body in the uvea?

A
  • Forms aqueous humour
  • Tethers lens via ligaments and ciliary processes
  • Ciliary muscle for accommodaition
20
Q

What are the components of aqueous humour?

A

Watery - lots of ions, nutrients and minerals but little protein

21
Q

What is accommodation?

A

Under normal circumstances the ciliary muscle is relaxed with the lens sitting in the middle - ligaments pulling, lens is thin. When you contract ciliary muscle ligaments are not under tension and so lens gets fat when not under restriction - focus on something close up (accommodation)

22
Q

What are the features of the iris?

A
  • Colour part of eye
  • Changes pupil size via muscles
  • Sphincter pupillae – constricts pupil, PNS
  • Dilator pupillae – dilates pupil, SNS (muscular epithelium)
23
Q

What are the features of the choroid?

A
  • Middle layer of the 3 layers (sclera, choroid, retina)
  • 3 layers of blood vessels (big, medium, small) – most important is the choriocapillaris (sits just below the retina)
  • Small vessels sit just below the retina
  • Blood vessels are crucial for suppling nutrients to the outer retina – photoreceptors
24
Q

What of the optic nerve can you see in the eye?

A

Optic nerve head

25
Q

What is the macula?

A

Where no blood vessels are located, important for central vision, most important part is the fovea

26
Q

What is the posterior pole?

A

Region outside of the macula

27
Q

What is the ora serrata?

A

Edge of the retina, where the retina joins the other structures of the eyeball, looks like a serrated edge

28
Q

What are the features of the fovea?

A

High visual acuity, avascular, gets nutrients from choroid, high density of cones (important for daytime), no rods (remove anything that may impinge on the ability to see – only have photoreceptors present here)

29
Q

What forms the optic nerve?

A

Formed by the axons of ganglion cells as they exit the retina to pass visual info to higher cortical areas (3rd order neurons)

30
Q

How does the sclera move in relation to the optic nerve?

A

Optic nerve has to move through the layers of the eye – sclera and choroid. 2/3 of sclera fibres do a U-turn and run down the side of the optic nerve – other 1/3 travel across the optic nerve (lamina cribosa – siv)

31
Q

What is the lamina cribosa?

A

Meshwork of collagen fibres that go across the optic nerve to form a sieve, each hole contains the bundles of nerve fibres that project from the retina to the brain – this gives the retina structure.

32
Q

What happens if the lamina cribosa is bent?

A

Glaucoma

33
Q

Where does the blood supply for the eye originate and what are the branches?

A

Internal Carotid
Ophthalmic
-Central retinal
-Ciliary arteries

34
Q

What are the features of the central retinal artery?

A

Pierces optic nerve, passes down middle and fans over the surface of the retina, supplies inside retinal neurones (not photoreceptors) - 2nd and 3rd order

35
Q

What are the features of the short posterior ciliary arteries?

A

Supply optic nerve head and photoreceptors closest to the optic nerve

36
Q

What are the features of the long posterior ciliary arteries?

A

Pierce globe and move to front

37
Q

Where do posterior ciliary arteries travel?

A

Choroid

38
Q

What are the features of the anterior ciliary arteries?

A

Anterior ciliary artery doesn’t pierce the globe and travels outside the eyeball to the front and supplies anterior structures (conjunctiva, episclera, sclera and limbus), pass along extraocular muscles

39
Q

What leads to an episceral circle?

A

Inflammation in the eye - back flow into arteries that anastomose - poster ciliary and anterior ciliary arteries

Anatomy - Viscera - Test 2 (19 decks)

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