Eyelids

 

👁️ Eyelids (Palpebrae) Anatomy

The eyelids consist of multiple layers, each playing a specific role in protection, secretion, and movement.

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📚 Layers of the Eyelid (Superficial → Deep):

1. Skin

   • Thin, delicate, with no subcutaneous fat

   • Contains sweat and sebaceous glands

2. Subcutaneous tissue

   • Loose connective tissue

   • Allows mobility over the underlying muscle

3. Orbicularis oculi muscle

   • Skeletal muscle responsible for closing the eyelids

   • Has two parts:

     • Palpebral part (gentle closure)

     • Orbital part (forceful closure)

   • Innervated by CN VII (Facial nerve)

4. Submuscular areolar tissue

   • Loose connective tissue layer beneath the muscle

   • Contains blood vessels and nerves

5. Tarsal plates (tarsus)

   • Dense fibrous connective tissue

   • Provides structure and rigidity to the eyelids

   • Contains Meibomian glands (sebaceous glands that secrete the oily layer of tear film)

6. Palpebral conjunctiva

   • Mucous membrane lining the inner surface of the eyelid

   • Continues as bulbar conjunctiva over the sclera

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🔍 Key Glands in the Eyelid:

Gland	Secretion Type	Function
Meibomian glands	Sebaceous	Prevent tear evaporation (lipid layer)
Glands of Zeis	Sebaceous	Lubricate eyelashes
Glands of Moll	Apocrine sweat	Contribute to tear film and immunity
Accessory lacrimal glands (Krause & Wolfring)	Serous	Support tear production

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📌 Muscles Involved in Eyelid Movement:

Muscle	Function	Innervation
Orbicularis oculi	Closes eyelid	CN VII (Facial nerve)
Levator palpebrae superioris	Elevates upper lid	CN III (Oculomotor)
Müller's muscle (superior tarsal)	Assists lid elevation	Sympathetic fibers

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🌟 Functions of the Eyelids:

• Protect the globe from foreign bodies and trauma

• Spread and maintain the tear film

• Assist in drainage of tears (via lacrimal pump)

• Provide structural support for the ocular surface

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🧾 Clinical Relevance:

• Ptosis: Drooping of the upper eyelid (CN III or sympathetic lesion)

• Blepharitis: Inflammation of the eyelid margins

• Chalazion: Blockage of Meibomian gland

• Hordeolum (stye): Infection of Zeis or Moll gland

• Entropion / Ectropion: Inward/outward turning of the lid margin