Orbit and adnexa

Question 1

Recognize the variations in structure and functional implications of those differences between carnivores and herbivores

Answer 1

carnivores- incomplete orbital bone, orbital ligament holds globe in place; allows for more movement of the globe within the orbit; allows jaw to open further
herbivores- orbital rim is complete, less jaw movement; better protection of the globe within the socket

Question 2

Identify the different tissue types that make up the eyelids and their functions

Answer 2

Tissue types:
Skin- protect from trauma
Orbicularis oculi m.- open/close eyelids
Tarsal plate with glandular tissue- oil portion of tear film that keeps aqueous portion from evaporating
Palpebral conjunctiva- thin, transparent tissue that covers the outer surface of the eye; secretes oils and mucous that moisten and lubricate the eye
May or may not have cilia (eyelashes)

Question 3

Recognize the function of the tear film and its constituents, where it is produced and how it drains from the ocular surface

Answer 3

tear film: Cleanse and lubricate the ocular surface; Provides nutrition and O2; Antimicrobial defense; Maintains optically uniform surface;
Aqueous component– lacrimal glands
Lipid component – meibomian glands
Mucin component – conjunctival goblet cells
Secretory: Orbital lacrimal gland, gland of TE; Meibomian glands, conjunctival goblet cells;
Drainage: Puncta at medial canthus; Lacrimal sac duct; Nasal puncta

Question 4

Know the function and structural anatomy of the third eyelid

Answer 4

Function: lubricate eye, protect globe, tear production, tear distribution
Structure: conjunctiva on both sides of gland; located in ventral nasal corner of eye except birds/owls where it is the dorsal nasal corner

Question 5

orbit

Answer 5

bony protection for globe; bones that make up the orbit can vary between species; can be open (carnivores) or closed (herbivores)

Question 6

third eyelid

Answer 6

a.k.a nictitans, nictitating membrane
Function: lubricate eye, protect globe, tear production, tear distribution
Structure: conjunctiva on both sides of gland; located in ventral nasal corner of eye except birds/owls where it is the dorsal nasal corner

Question 7

closed bony orbit

Answer 7

herbivores, bone is complete circle

Question 8

open bony orbit

Answer 8

carnivores, bone not complete, orbital ligament covers open portion

Question 9

spectacle

Answer 9

fused, transparent eyelids, shed concurrent with skin; no blinking mechanism; retained spectacle causes clouding vision

Question 10

orbital ligament

Answer 10

present in open bony orbit; helps hold globe in orbit

Question 11

keratoconjunctivitis sicca

Answer 11

dry eye; dysfunction, typically of the aqueous portion of tear film

Question 12

distichiasis

Answer 12

problems with cilia (eyelashes); eyelash goes through glandular openings and contact eye

Question 13

cilia

Answer 13

a.k.a. eyelashes; help protect globe from foreign debri

Question 14

eyelid musculature

Answer 14

responsible for opening and closing eyelids

Question 15

adnexa

Answer 15

periorbital structures

Question 16

lacrimal glands

Answer 16

act to lubricate the eye; consist of mucous, aqueous and oily portion

Question 17

foramina

Answer 17

opening that allows for nerves, arteries and veins

Question 18

extraocular muscles

Answer 18

insert on posterior aspect of globe; move eyes in different directions; lateral/dorsal/ventral muscles pull the eye; oblique muscles rotate the globe; retractor bulbi can suck the eye back into orbit

Question 19

meibomian glands

Answer 19

AKA Tarsal glands; Contribute a portion of the tear fluid; Line the eyelid margin