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The eyelid is a thin fold of skin that covers and protects the eye. It is supplied by three cranial nerves and sympathetic nerve fibres. The eyelid contains several muscles, including the levator palpebrae superioris muscle, which elevates the upper eyelid, and the orbicularis oculi muscle, which is one of the superficial muscles of facial expression. The eyelids also contain the superior tarsal muscle, which is a smooth muscle that helps to raise the upper eyelid, and the lacrimal muscle, which compresses the lacrimal sac during blinking to facilitate tear drainage. The eyelids are essential for eye health and protection, and various surgical procedures can be performed on them for medical or cosmetic reasons.
| Characteristics | Values |
|---|---|
| Definition | A thin fold of skin that covers and protects the eye |
| Function | To retract and expose the cornea to the outside, giving vision; to keep the eyes moist by regularly spreading tears and other secretions on the eye surface; to protect the eye from foreign bodies |
| Muscles Involved | Orbicularis oculi; Levator palpebrae superioris; Superior tarsal muscle; Lacrimal |
| Nerve Supply | Cranial nerves (III, V, VII); Sympathetic nerve fibres; Oculomotor nerve; Facial nerve; Zygomaticofacial nerve; Trigeminal nerve |
| Medical Conditions | Blepharospasm (eyelid twitching); Ptosis (drooping eyelid); Entropion; Ablepharia (ablepharon); Chalazion; Trichiasis; Demodicosis |
| Surgery | Blepharoplasties; East Asian blepharoplasty; Epicanthoplasty |
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What You'll Learn
- The levator palpebrae superioris muscle retracts the eyelid
- The orbicularis oculi muscle is one of the superficial muscles of facial expression
- The palpebral portion is used for blinking and winking
- The lacrimal part compresses the lacrimal sac during blinking
- Blepharospasm is an involuntary spasm of the eyelid muscle
The levator palpebrae superioris muscle retracts the eyelid
The eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle is an extraocular muscle that retracts the eyelid, exposing the cornea to the outside, giving us vision. This can be done either voluntarily or involuntarily. The levator palpebrae superioris is also known as the elevating muscle of the upper eyelid.
The levator palpebrae superioris originates from the inferior surface of the lesser wing of the sphenoid bone, just above the optic foramen. It is a skeletal muscle that broadens and decreases in thickness, becoming the levator aponeurosis. This portion inserts on the skin of the upper eyelid, as well as the superior tarsal plate. The levator palpebrae superioris receives its blood supply from branches of the ophthalmic artery, specifically the muscular branches and the supraorbital artery. The blood is drained into the superior ophthalmic vein.
The levator palpebrae superioris is one of the six extraocular muscles in the orbit. It is a circumferential muscle of facial expression, innervated by the facial nerve. The main actions of the levator palpebrae muscle are the retraction and elevation of the superior eyelid and the widening of the palpebral fissure. These actions are limited by several anatomical features of the muscle, such as the lateral and medial attachments of the muscle's aponeurosis, which prevent further elevation of the eyelid once they are stretched maximally.
The levator palpebrae superioris muscle is essential for maintaining the normal position of the upper eyelid. It also aids in expressing feelings of fear, anger, and shock.
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The orbicularis oculi muscle is one of the superficial muscles of facial expression
The eyelids are thin folds of skin that cover and protect the eyes. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving us vision. This can be done either voluntarily or involuntarily. The eyelid also has a protective function, with the blink reflex protecting the eye from foreign bodies.
The orbicularis oculi can be categorized into three main parts: orbital, palpebral, and lacrimal (deep palpebral). The orbital portion extends in a wide, circular fashion around the orbit, interdigitating with other muscles of facial expression. It has a curved origin from the medial orbital margin, being attached to the superomedial orbital margin, maxillary process of the frontal bone, and medial palp. The orbital part of orbicularis oculi is pierced by two major neurovasculature structures: the supraorbital vein and zygomaticofacial nerve. Contraction of the orbital part pulls the skin of the forehead and cheek towards the nose and tightly closes the eyes, often for protective purposes.
The palpebral portion is used in blinking and voluntary winking, while the deep palpebral part pulls the eyelids and lacrimal papillae medially and dilates the lacrimal sac, facilitating tear drainage across the cornea. The palpebral part also exhibits a finer control of the eyelids by closing them gently during blinking or sleeping.
The lacrimal part originates from the posterior lacrimal crest of the lacrimal bone and from the medial palpebral ligament. Its fibres primarily insert into the lateral palpebral raphe, where they blend with adjacent muscle fibres and contribute to the overall structure of the eyelids. The lacrimal part compresses the lacrimal sac during blinking, which helps to facilitate tear drainage. This action creates a negative pressure within the sac, allowing tears to flow from the eye surface into the nasolacrimal duct. By drawing the eyelids medially, this portion aids in ensuring that tears are effectively distributed across the ocular surface, enhancing lubrication and protection against foreign particles. This muscle's interaction with the nasolacrimal duct system is vital for maintaining proper tear film stability and eye health.
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The palpebral portion is used for blinking and winking
The eyelid is a thin fold of skin that covers and protects the eye. The palpebral portion of the orbicularis oculi muscle is used for blinking and winking. The orbicularis oculi muscle can be categorized into three main parts: orbital, palpebral, and lacrimal (deep palpebral). The palpebral portion is further divided into preseptal and pretarsal components. The preseptal orbicularis and pretarsal orbicularis are responsible for gentle blinking. The pretarsal orbicularis is thought to be responsible for the spontaneous blink.
The palpebral portion acts involuntarily, closing the lids gently, as in sleep or in blinking. The orbital portion, on the other hand, is subject to conscious control. The two portions can work independently of each other. For example, the orbital portion can contract to furrow the brows and reduce glare, while the palpebral portion simultaneously relaxes to keep the eyes open.
Blinking is an essential function of the eye that helps spread tears across and remove irritants from the surface of the cornea and conjunctiva. It also plays a role in tear film maintenance by distributing the tear film over the cornea during blinking. The palpebral portion of the orbicularis oculi muscle is the main muscle that controls the closing of the eye during blinking. The levator palpebrae superioris muscle, which elevates the upper eyelid, is responsible for opening the eye.
In addition to its role in blinking, the palpebral portion is also used for voluntary winking. The lacrimal part of the palpebral portion, which includes the lacrimal orbicularis, also plays a crucial role in tear drainage. During blinking, the lacrimal orbicularis compresses the lacrimal sac, creating a negative pressure that allows tears to flow from the eye surface into the nasolacrimal duct. This action helps maintain proper tear film stability and eye health.
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The lacrimal part compresses the lacrimal sac during blinking
The eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, enabling vision. The orbicularis oculi muscle is one of the superficial muscles of facial expression and can be categorized into three main parts: orbital, palpebral, and lacrimal (deep palpebral).
The lacrimal part of the orbicularis oculi muscle is responsible for compressing the lacrimal sac during blinking. This process facilitates tear drainage by creating negative pressure within the sac, allowing tears to flow from the eye surface into the nasolacrimal duct. The nasolacrimal duct system is vital for maintaining proper tear film stability and eye health.
The lacrimal gland, or tear gland, is an almond-shaped exocrine gland located above the eyeball, in the anterior part of the upper outer aspect of each orbit. It is responsible for secreting lacrimal fluid, or tear fluid, onto the surface of the eyeball. This fluid forms the aqueous portion of the multilayered tear film, which lubricates, protects, and provides nutrients to the conjunctiva and cornea.
The lacrimal gland consists of two connecting parts: the larger orbital part and the smaller palpebral part. The orbital part sits on the lateral margin of the levator palpabrae superioris muscle, while the palpebral part is located along the inner surface of the eyelid. The lacrimal gland plays a crucial role in maintaining eye health and protecting the ocular surface.
During blinking, the lacrimal part of the orbicularis oculi muscle contracts and compresses the lacrimal sac. This compression facilitates tear drainage by creating negative pressure within the sac. The tears, or lacrimal fluid, produced by the lacrimal gland, drain into the lacrimal sac through a series of canals. From the lacrimal sac, the tears then flow into the nasolacrimal duct and eventually into the nasal cavity.
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Blepharospasm is an involuntary spasm of the eyelid muscle
The eyelid is a thin fold of skin that covers and protects the eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be done either voluntarily or involuntarily. The palpebral portion of the orbicularis oculi muscle is used in blinking and voluntary winking, while the orbital portion is used in forced closure. The lacrimal part compresses the lacrimal sac during blinking, facilitating tear drainage.
The most common factors that cause the eyelid to twitch are fatigue, stress, and caffeine. Blepharospasm is not considered harmful and therefore there is no treatment available. However, patients are advised to get more sleep and reduce their caffeine intake. The condition is fairly rare, with approximately 2,000 new cases diagnosed each year in the United States. It tends to occur in middle-aged people and is more frequent in women than in men.
The most common treatments for blepharospasm are medication and periodic injections of botulinum toxin into the eyelid muscles. Patients who do not respond well to these treatments are candidates for surgery. The most effective surgical treatment is protractor myectomy, the removal of muscles responsible for eyelid closure.
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Frequently asked questions
An eyelid is a thin fold of skin that covers and protects the eye.
The levator palpebrae superioris muscle, also known as the elevating muscle of the upper eyelid, retracts the eyelid.
The levator palpebrae superioris muscle elevates the upper eyelid, exposing the cornea and enabling vision.
Blepharospasm, or eyelid twitching, is an involuntary spasm of the eyelid muscle. It is not considered harmful and therefore has no treatment. However, patients are advised to get more sleep and reduce their caffeine intake.
Ptosis is when the upper eyelid droops or sags due to weakness, paralysis, or damage to the nerves controlling the levator palpebrae superioris muscle or the superior tarsal muscle.
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