Topic 12: Ocular Appendages

Question 1

What are ocular appendages

Answer 1

Structres attached to the eyeball. Aka ocular adnexa

Question 2

Describe conjunctiva and its location

Answer 2

A thin, almost transparent mucous membrane that lines the inside of the eyelids and anterior surface of the eyeball

Question 3

Describe the regions of conjunctiva

Answer 3

(1) palpebral/tarsal conjunctiva: lines upper and lower lids
(2) forniceal/fornix: junction between (upper and lower) palpebral/tarsal and bulbar
(3) bulbar conjunctiva: lines the exposed part of the sclera

Question 4

Explain layers of the conjunctiva

Answer 4

(1) epithelium: non-keratinised, made up of goblet cells (provide mucin that make up mucus layer of tear film)
(2) stroma: BVs and fibres, contains Accessory Glands Of Krause And Wolfring (lacrimal glands that produce aqueous layer of tear film)

Question 5

State blood and nerve supply of conjunctiva

Answer 5

Anterior ciliary artery (limbal BVs) & Lacrimal artery

CN5 (trigeminal nerve - ophthalmic & maxillary division)

Question 6

Describe eyelashes

Answer 6

• aka celia. Short and curved hairs located in both eyelid margins, grow upward & outward
• longer and more numerous on upper lid
• defense mechanism: initiate reflex blink on the slightest contact with foreign particles (each follicle surrounded by nerves with low threshold of excitation)

Question 7

State the layers of the eyelid

Answer 7

(Anterior-most) skin, subcutaneous tissue, muscles, submascular areolar tissue, fibrous layer/tarsal plate (posterior-most)

Question 8

Explain skin layer of eyelid

Answer 8

• outermost. Soft, elastic, fine
• contains cilia: reflex blink
• contains sweat glands (modified= glands of moll)
• contains gland of Zeis (sebaceous gland) that contributes to the lipid layer of TF

Question 9

Explain subcutaneous & submuscular layer of eyelid

Answer 9

Connective tissue below skin. Has no fat so that skin can roll easily

Connective tissue below muscle

Question 10

Explain muscle layer of eyelid

Answer 10

(1) LPS (levator palpebrae superioris) muscle aids in elevation of upper lid. Voluntary action
(2) muller/tarsal muscle sustains LPS action/keeps upper eyelid open. Involuntary action ie. keeping lids open when awake
(3) OO (Orbicularis oculi) muscle helps with eyelid closure
(4) Riolan’s muscle ensures good closure of lid (upper & lower lids in close contact)

Question 11

Explain fibrous layer/tarsals plate of eyelid

Answer 11

• Innermost, in contact with palpebar conjunctiva
• made up of dense fibrous tissues: makes eyelid have shape and firmness
• contains meibomian/tarsal glands which contribute to the lipid layer of the tear film

Question 12

Summarise functions of the eyelid

Answer 12

To protect the cornea

(1) defense mechanism: reflex blink by eyelashes
(2) lid movements
(3) blinking aids in spreading of tears and keeps ocular surface moist

Question 13

State blood & nerve supply of eyelids

Answer 13

Facial artery & lacrimal artery

CN5 (trigeminal) - upper & lower lids

CN7 (facial nerve) - lower lids, OO, riolans muscle (lid closure)

CN3 (oculomotor) - LPS, tarsal muscle (lid open)

Question 14

Explain function, nerve & blood supply of eyebrows

Answer 14

F: prevent sweat from dripping into eyelids, facial expression

NS: CN7 (facial) - orbicularis oculi (depresses eyebrow) & frontalis muscle (elevate eyebrow)

BS: supraorbital artery, supratrochlear artery

Question 15

Explain bells phenomenon

Answer 15

Normal eye phenomenon. Eyes rotate upward under closed lid

Question 16

Explain bells palsy

Answer 16

An ocular pathology

• weakness/paralysis of CN7/facial nerve
• loss of forehead & brow movements (due to frontalis muscle weakness)
• inability to fully close eye of affected side (due to orbicularis oculi muscle & riolans muscle weakness)
• drooping of lower eyelid, excessive tearing on affected side (droopy lower lid and defective tear drainage)
• droopy appearance of affected side, droopy lower lip (due to facial muscle weakness)

Question 17

State lacrimal apparatus structures according to their function

Answer 17

Secretion: lacrimal gland, accesory gkands of krause and wolfring

Drainage: puncta, canaliculi, lacrimal sac, naso-lacrimal duct

Question 18

Describe the layers of tear film

Answer 18

(1) mucus layer - in contact with corneal epithelium, hydrophillic, contributed by goblet cells
(2) aqueous layer - middle layer, hydrophillic, contributed by lacrimal gland & accessory lacrimal gland of krause & wolfrings
(3) lipid layer - in contact with atmosphere, hydrophobic, contributed by meibomian gland & gland of zeis

Question 19

Explain function of mucin TF

Answer 19

(1) decrease surface tension of tear film (hydrophillic coating over the hydrophillic corneal epithelium) to enhance SPREAD & STABILITY of TF
(2) lubricate ocular surface & reduces lid-globe friction during blinking
(3) hydrates underlying corneal epithelium
(4) provides foundation for a smooth optical surface by covering irregular corneal spaces

Question 20

Explain function of aqueous of TF

Answer 20

(1) enables gaseous exchange
(2) hydrating medium for epithelial cells & carries metabolites to them
(3) flush away noxious substances
(4) provide delivery route for WBC and immunoglobulins to epithelium for immune response
(5) lubricate lid-globe interface to reduce blink friction
(6) contains lysozyme for antibacterial activity

Question 21

Explain function of lipid TF

Answer 21

(1) forms hydrophobic layer
(2) reduces evaporation of aqueous TF
(3) forms tears meniscus along lid margins to prevent outflow of tears there
(4) prevents lid margins from sticking tgt

Question 22

Explain blinking for tear circulation & drainage

Answer 22

Pre-blink: tears enter puncta by capillary action

During blinking: OO contracts and pulls on the lateral wall of lacrimal sac, pushing the tears into sac

Post-blink: OO relaxes, sac collapses, and tears are drained into the nasolacrimal duct

Question 23

State blood and nerve supply to lacrimal apparatus

Answer 23

Lacrimal artery & medial palpebral artery

CN5/trigeminal for tear secretion

CN7/facial for tear drainage

Question 24

explain spontaneous blink and its functions

Answer 24

involuntary, occurs at periodic intervals when awake and NOT DEPENDENT ON RETINAL STIMULATION

(1) maintains moisture of the exposed globe surface by preventing evaporation of TF
(2) spreads & distributes a uniform layer of tears
(3) assists in drainage of tears