3 ORBIT AND EYE

Question 1

A

Answer 1

Ciliary body

Question 2

B

Answer 2

Iris

Question 3

C

Answer 3

Lens

Question 4

D

Answer 4

Aqueous humour

Question 5

E

Answer 5

Cornea

Question 6

F

Answer 6

Canal of Schlemm

Question 7

G

Answer 7

Conjunctiva

Question 8

H

Answer 8

Fovea

Question 9

I

Answer 9

Optic disk

Question 10

J

Answer 10

Sclera

Question 11

K

Answer 11

Choroid

Question 12

L

Answer 12

Retina

Question 13

M

Answer 13

Macula

Question 14

N

Answer 14

Vitreous humor

Question 15

What are the lacrimal glands?

Answer 15

• Paired exocrine glands that secrete the aqueous layer of the tear film

Question 16

What is the nasolacrimal duct?

Answer 16

• Also known as the tear duct
• Carries tears from the lacrimal sac of the eye into the nasal cavity
• Duct begins in the eye socket (between the maxillary and lacrimal bones), from where it passes posteriorly and inferiorly
• This duct allows the draining of tears into the nasal cavity, where they will then be removed or ingested and components broken down in the stomach
  
  • [This means that if there is a blockage in the duct, the eyes are not drained, causing them to become watery and at higher risk of infection]

Question 17

What is the action of the Levator palpebrae superioris?

Answer 17

Elevates superior eyelid

Question 18

What is the action of the superior rectus?

Answer 18

Elevates (adducts and rotates eyeball medially)

Question 19

What is the action of the medial rectus?

Answer 19

Adducts eyeball

Question 20

What is the action of the inferior rectus?

Answer 20

Depresses, adducts and
rotates eyeball laterally

Question 21

What is the action of the lateral rectus?

Answer 21

Abducts eyeball

Question 22

What is the action of the superior oblique?

Answer 22

Abducts, depresses and
medially rotates eyeball

Question 23

What is the action of the inferior oblique?

Answer 23

Abducts, elevates and
laterally rotates eyeball

Question 24

What are the intrinsic muscles of the eye? What type of muscle are they?

Answer 24

Ciliary muscle, pupillary sphincter muscle, and pupillary dilator muscle. They are all smooth muscle.

Question 25

What is this?

Answer 25

Ciliary muscles

Question 26

What is the innervation of the ciliary muscle?

Answer 26

* The muscles are dually innervated by the autonomic nervous system * Parasympathetic innervation activates the muscle for contraction * Sympathetic innervation has an inhibitory effect on the level of parasympathetic activity

Question 27

What is the function of the ciliary muscles?

Answer 27

* Contraction and relaxation of the ciliary muscles changes the thickness and curvature of the lens, therefore controlling the focussing power of the eye * Contraction of the muscle allows for the lens to bunch up, increasing its focussing power (the suspensory ligaments are allowed to become slack) * Relaxation of the ciliary muscles causes the lens to become thinner and flat, decreasing the focussing power (the suspensory ligaments become stretched/tight)

Question 28

What is the innervation of the dilator pupillae?

Answer 28

* It receives sympathetic innervation (long ciliary nerves, non-myelinated sympathetic fibres) * Its parasympathetic innervation appears less significant

Question 29

What is the function of the dilator pupillae?

Answer 29

* This is the radial muscle of the iris that is able to dilate the pupil

Question 30

What is the innervation of the sphincter pupillae?

Answer 30

* The muscle is innervated by parasympathetic fibres (short ciliary nerves)

Question 31

What is the function of the sphincter pupillae?

Answer 31

*decreases diameter, constricting pupil

Question 32

What are the boundries of the Orbit?

Answer 32

The walls of the orbit are contributed above by the frontal bone, medially by the ethmoid and lacrimal bone, laterally by the zygomatic bone and floor by zygomatic and maxillary bone.

Question 33

What are the different holes in the orbital cavity? What do they contain?

Answer 33

The orbital cavity has superior and inferior orbital fissure to transmits cranial nerves (III, IV, V and VI) and the optic canal for the optic nerve and the ophthalmic artery. The common tendinous ring, around the fissure and the optic canal provides origin to the extraocular muscles.

Question 34

Answer 34

Question 35

Answer 35

Question 36

What is the Conjunctiva?

Answer 36

The sclera is covered by a transparent layer of stratified squamous epithelium called the conjunctiva.

Question 37

What is the function of the conjunctiva?

Answer 37

Helps lubricate eyes (produces mucus and tears - less than lacrimal glands) as well as immune surveillance.

Question 38

What is the function of the eyelid?

Answer 38

* protect eyes from mechanical injury + excessive light * Maintain + distribute eye's tear film during blinking * Helps keep surface of eyes lubricated.