eyelid

Eyelid
Upper and lower eyelids
Latin	palpebra inferior, palpebra superior
Gray's	subject #227 1025
Artery	lacrimal, superior palpebral, inferior palpebral
Nerve	upper: infratrochlear, supratrochlear, supraorbital, lacrimal lower: infratrochlear, branches of infraorbital
MeSH	Eyelids

An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration. "Palpebral" (and "blepharo") means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies.

Anatomy

Layers

The eyelid is made up of several layers; from superficial to deep, these are: skin, subcutaneous tissue, orbicularis oculi, orbital septum & tarsal plates, and palpebral conjunctiva. The meibomian glands lie within the eyelid and secrete the lipid part of the tearfilm.

Skin

The skin is similar to areas elsewhere, but has more pigment cells. In diseased persons these may wander and cause a discoloration of the lids. It contains sweat glands and hairs, the latter becoming eyelashes as the border of the eyelid is met.

Innervation

In humans, the sensory nerve supply to the upper eyelids is from the infratrochlear, supratrochlear, supraorbital and the lacrimal nerves from the ophthalmic branch (V1) of the trigeminal nerve (CN V). The skin of the lower eyelid is supplied by branches of the infratrochlear at the medial angle, the rest is supplied by branches of the infraorbital nerve of the maxillary branch (V2) of the trigeminal nerve.

Blood supply

In humans, the eyelids are supplied with blood by two arches on each upper and lower lid. The arches are formed by anastamoses of the lateral palpebral arteries and medial palpebral arteries, branching off from the lacrimal artery and ophthalmic artery, respectively.

Death

After death, it is common in many cultures to pull the eyelids of the deceased down to close the eyes. This is a typical part of the last offices.

See also

Disorders

Eyelid affected by Stye

• Blepharospasm
• Cellulitis
• Chalazion
• Dermatochalasis
• Ectropion
• Entropion
• Hay-Wells syndrome
• Ptosis
• Stye (Hordeolum)

Surgeries

• Asian blepharoplasty
• Blepharoplasty
• Epicanthoplasty

Additional images

Eye makeup	Bloodvessels of the eyelids, front view	Horizontal section through the eye of an eighteen days' embryo rabbit. X 30	Sagittal section of right orbital cavity
Sagittal section through the upper eyelid	The tarsi and their ligaments. Right eye; front view	The lacrimal apparatus. Right side

References

"eye, human."Encyclopædia Britannica from Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 2009.