Eye conjuctiva and nicitating membrane

Question 1

What is the conjunctive?

Answer 1

highly vascular translucent mucous membrane

Question 2

What does the conjuctiva line?

where does it fuse?

Answer 2

lines the inside of the lids (the palpebral conjunctiva) from the junction with the skin and reflects back at the dorsal and ventral fornix to cover the nictitating membrane (the nictitating conjunctiva) and the rostral sclera (the bulbar conjunctiva). It fuses with the orbital fascia just behind the limbus.

Question 3

What do the various regions of the conjunctiva form?

Name the regions

Answer 3

Form Conjuctival sac

1. the palpebral conjunctiva
2. the nictitating conjunctiva
3. the bulbar conjunctiva

Question 4

What is the conjuctiva lines by and what cells does the epithelium contain?

Answer 4

lined by tear film. Conjunctival epithelium contains many goblet cells which produce the mucus portion of the tear film

The conjunctiva contains many mast cells, which means it is capable of dramatic inflammatory reactions when irritated

Question 5

Where is teh conjunctiva-associated lymphoid tissue

What else in it?

Answer 5

Underlying the stratified squamous layer is a connective tissue stroma containing conjunctiva-associated lymphoid tissue (CALT) superficially and nerves (from CN V) and blood vessels in the deep layer

Question 6

What is nicitating membrane?

Answer 6

third eyelid, is a reflection of conjunctiva containing a T-shaped (or near enough) cartilage support.

Question 7

Location of nicitating membrane

Answer 7

sits ventromedially in the conjunctival sac, and the free edge is snug against the eyeball. The free edge is usually pigmented, although some colour patterns leave it unpigmented.

Question 8

Is there a gland associated with the nicitating membrane?

Answer 8

gland which sits at its base and encircles the cartilage. This gland produces a considerable amount of the aqueous portion of the tear film, and hence its health must be preserved.

Question 9

Role of the third eyelid/ nicitating membrane

Answer 9

a protective role in addition to tear production, sweeping across the globe when the globe retracts during blinking. This is largely a passive action, but cats possess some striated muscle in their 3rd eyelid which enables them to actively protrude their lids. Sympathetic innervation to smooth muscle in the 3rd eyelid keeps it retracted between blinks.

Question 10

Where does tear film empty?

What are also on the membrane?

Answer 10

The tears empty into the conjunctival sac on the bulbar aspect of the 3rd eyelid. On this side of the membrane there are also numerous lymphoid follicles which give the inside of the 3rd eyelid a rough appearance.

Question 11

Muscles that affect movement of eyelid
name
CN
Action

Answer 11

o Orbicularis oculi muscle (CN VII – facial)
 Closure of lids
 Surrounds lacrimal canaliculi = helps squeeze tears thru drainage system

o Levator anguli oculi muscle (CN VII – facial)
 Acts to lift medial portion of upper lid

o Levator palpebrae superioris (CN III – ocular)
 Main elevator of upper lid