THE EYELIDS

Question 1

Accessory Visual Structures

The orbits and orbital region anterior to the eyeballs contain and protect the
eyeballs and accessory visual structures which include:

Answer 1

• Eyelids - bound the orbits anteriorly, controlling exposure of the anterior eyeball
• Extraocular muscles – position the eyeballs and raise the superior eyelids
• Nerves & Vessels – in transit to the eyeballs and muscles

• Mucous membrane (conjunctiva) – lining the eyelids and anterior aspect of the eyeballs and
most of the lacrimal apparatus, which lubricates it

• Orbital fat – forms a matrix in which the structures of the orbit are embedded

orbital fascia

Question 2

eyelids

Answer 2

The eyelids are moveable folds that cover the eyeball anteriorly when closed, thereby protecting it from injury
and excessive light.

• They also keep the cornea moist by spreading the lacrimal fluid

Question 3

conjunctiva

Answer 3

The eyelids are covered externally by a thin skin and internally by transparent mucous membrane, the palpebral
conjunctiva

This part of the conjunctiva is reflected onto the eyeball, where it is continuous with the bulbar conjunctiva.

• This part of the conjunctiva is thin and transparent and attaches loosely to the anterior surface of the eyeball.

• The bulbar conjunctiva, loose and wrinkled over the sclera (where it contains small, visible blood vessels), is
adherent to the periphery of the cornea).

• The lines of reflection of the palpebral conjunctiva onto the eyeball form deep recesses, the superior and
inferior conjunctival fornices

• The conjunctival sac is the space-bound by the palpebral and bulbar conjunctivae; it is a closed space when
the eyelids are closed, but opens via an anterior aperture, the palpebral fissure (the gap between the eyelids),
when the eye is open The conjunctival sac is a specialized form of mucosal “bursa” that enables the eyelids to
move freely over the surface of the eyeball as they open and close.

Question 4

The palpebral part of the conjunctiva is reflected onto the eyeball, where it is continuous with the

Answer 4

bulbar conjunctiva

Question 5

tarsus

Answer 5

• The superior (upper) and inferior (lower) eyelids are strengthened by dense bands of connective tissue, the
superior and inferior tarsi (singular = tarsus), which form the “skeleton” of the eyelids

• Fibres of the palpebral portion of the orbicularis oculi (the sphincter of the palpebral fissure) are in the
connective tissue superficial to the tarsi and deep to the skin of the eyelids

• Embedded in the tarsi are tarsal glands that produce a lipid secretion that lubricates the edges of the eyelids
and prevents them from sticking together when they close.

o The lipid secretion also forms a barrier that lacrimal fluid does not cross when produced in normal
amounts. When production is excessive, it spills over the barrier onto the cheeks as tears.

Question 6

eyelashes

Answer 6

The eyelashes (cilia) are in the margins of the eyelids

Question 7

the large sebaceous gland associated with the eyelashes is

Answer 7

ciliary glands

Question 8

ligaments

Answer 8

Between the nose and the medial angle of the eye is the medial palpebral ligament, which connects the
tarsi to the medial margin of the orbit

• The orbicularis oculi originates and inserts onto this ligament.

• A similar lateral palpebral ligament attaches the tarsi to the lateral margin of the orbit, but it does not
provide for direct muscle attachment

Question 9

orbital septum

Answer 9

1. is a fibrous membrane that spans from the tarsi to the surface of the orbit where it becomes continuous with the periosteum
2. keeps the orbital fat contained and limits spread of infection from the orbit
3. the septum contributes to the posterior fascia of the orbicularis oculi