Eye

Question 1

What is the function of the orbit?

Answer 1

Protects eye and adexa, & serves as attachment site for extrinsic muscles

Question 2

Bones of the orbital margin:

Answer 2

frontal, maxillary, zygomatic, lacrimal, ethmoid

Question 3

The bony orbit is complete in the horse, ox, and goat. What does this mean?

Answer 3

the temporal process of the frontal bone joins the zygomatic arch to complete the orbit

Question 4

What completes the orbit in the dog?

Answer 4

orbital ligament- spans the region b/t the zygomatic process of the frontal bone and the frontal process of the zygomatic bone

Question 5

Structures contained within the orbit:

Answer 5

periorbita, eyeball, ocular adnexa, trochlea

Question 6

Periorbita

Answer 6

cone-shaped sheath of connective tissue that surrounds the caudal eyeball and ocular adnexa

Question 7

Ocular adnexa

Answer 7

accessory structures for protection (palpebrae, third eyelid, conjunctiva, retrobulbar fat), tear production (lacrimal gland/appartatus, gland of third eyelid), blood supply and innervation

Question 8

Trochlea

Answer 8

• a pulley-shaped cartilage that is attached to the dorsomedial wall of the orbit
• directs the course of the dorsal oblique muscle

Question 9

Three tunics of the eye:

Answer 9

Tunica externa (fibrous tunic)
Tunica media (vascular tunic, choroid)
Tunica interna (retina)

Question 10

Fibrous tunic:

Answer 10

• comprised of two regions: Cornea (transparent anterior 1/4) & Sclera (opaque posterior 3/4)
• continuous w/ dural layer of the CNS

Question 11

Vascular tunic

Answer 11

Composed of 3 regions:
-Choriod
-Ciliary body
-Iris
Continuous w/ pia-arachnoid layers of the CNS

Question 12

Choriod

Answer 12

• highly vascularized and pigmented; provides nourishment to globe
• black areas for light absorption
• tapetum lucidum is a brightly colored region, located superior to the optic disk, that reflects light

Question 13

Ciliary body

Answer 13

ciliary mm. and ciliary ligaments control the shape of the lens

Question 14

Iris

Answer 14

circular and radial mm. regulate the size of the pupil

Question 15

Iridic granulae

Answer 15

horse has “black bodies” (sunglasses) on pupillary margin

Question 16

Internal tunic

Answer 16

the retina, divided into two regions:

• Optical part (visual part covers the choroid)
• Blind part (non-visual part, covers ciliary body and iris) Cannot distinguish blind retina from ciliary body

Question 17

The optic retina has two layers:

Answer 17

• pigmented (outer) layer (stratum pigmentosum)
• nervous (inner) layer (pars nervosa retina) divided into nine layers
• divisions of retina can only be seen histologically

Question 18

The neuron processes of the ganglion cells of the retina converge to form the

Answer 18

optic nerve

Question 19

Ganglion cells

Answer 19

-bi-polar neurons whose cell bodies are located within the ganglion cell layer of the retina

Question 20

The optic nerve begins at the ______

Answer 20

optic disk, where these axonal processes exit the caudal aspect of the globe of the eye
“blind spot”
-retinal vessels also enter & leave here

Question 21

Anterior compartment

Answer 21

-located b/t the lens and cornea
-filled with aqueous humor
-divided by the iris into 2 chambers:
anterior chamber and posterior chamber

Question 22

Posterior compartmenT

Answer 22

• Located b/t the lens and fundus
• Contains the vitreous body
• helps maintain shape of eye
• maintains necessary intraocular pressure to prevent retinal detachment

Question 23

Vitreous body

Answer 23

• established during development and is maintained w/in the posterior compartment of the eye to maintain intraocular pressure
• degeneration (liquefaction) of the vitreous body may predispose to retinal detachment

Question 24

Aqueous humor

Answer 24

• continuously produced and reabsorbed
• secreted by ciliary body epithelium
• drained via the venous sinuses of the sclera at the iridocorneal angle
• increased fluid results in increased intraocular pressure (glaucoma)

Question 25

Intrinsic muscles of the eye

Answer 25

ciliary muscles and pupillary muscles

Question 26

Ciliary Muscles

Answer 26

- regulates shape of the lens - contraction relaxes tension of the suspensory ligaments and the lens fattens (accommodation) - regulated by the oculomotor nerve (PSNS)

Question 27

Pupillary muscles

Answer 27

- constrictor pupillae (circular) - regulated by the oculomotor by the oculomotor nerve (PSNS) - Dilator pupillae (linear, radial) - regulated by the SNS (neuron processes from cranial cervical ganglion)

Question 28

Adnexa of the eye

Answer 28

- Palpebrae: superior and inferior eyelids- palpebral fissure is the space b/t these - conjunctiva: palpebral and bulbar; continuous at the fornix - third eyelid: cartilage, superficial gland of the third eyelid - Lacrimal appartaus - Extrinsic muscles of the globe

Question 29

Both eyelids (palpebrae) are lined by haired skin externally and ____ internally

Answer 29

mucous membrane

Question 30

What anchors the commisures of the eyelids?

Answer 30

Medial and lateral palpebral ligaments | -medial ligament is more developed

Question 31

The ______ is a continuous mucous membrane that lines the inner palpebrae and part of the globe

Answer 31

conjunctiva

Question 32

Palpebral conjunctiva

Answer 32

- lines internal surface of palpebrae - continuous w/ outer skin of palpebrae and w/ bulbar conjunctiva at fornix - third eyelid is a fold of the inferior palpebral conjunctiva

Question 33

Bulbar conjunctiva

Answer 33

- reflects onto the surface of the globe at the fornix | - continuous w/ palpebral conjunctiva

Question 34

Concave fold of palpebral conjunctiva that protrudes from the medial angle of the eye

Answer 34

plica semilunaris (third eyelid)

Question 35

Plica semilunaris

Answer 35

- supported by a T-shaeped cartilage - superficial gland of the third eyelid - accessory lacrimal gland (mucous and serous secretions) - surrounds cartilage "stem" - deep gland also in cattle and swine

Question 36

Secretions of the _____ keep the surface of the eye moist and clean, and provide nourishment to the eye

Answer 36

lacrimal gland

Question 37

Process of lacrimal gland

Answer 37

- lacrimal gland secretes serous fluid into the superior conjunctival sac - secretion flows over cornea (blinking) - Passes through puncta and into lacrimal gland ducts - lacrimal lake - drains into nasolacrimal duct - dissipated via convection in nasal cavity

Question 38

Extrinsic muscles of the eye

Answer 38

- muscles of the globe: dorsal rectus, ventral rectus, lateral rectus, medial rectus, dorsal oblique, ventral oblique, retractor bulbi - muscles of the eyelids (palpebrae): levator palpebrae superioris, orbicularis oculi, retractor anguli oculi lateralis, levator anguli oculi medialis

Question 39

Function of the retractor bulbi m.

Answer 39

retract the eyeball deep into the orbit (protective mechanism, surrounds the optic nerve)