Dominic Stone
The orbicularis oculi muscle, composed of orbital, palpebral, and deep palpebral parts, is responsible for closing the eyelids. This muscle is innervated by the facial nerve (CN VII) and its contraction can lead to partial or complete eyelid closure, protecting the eyes from bright light or blowing dust. The levator palpebrae superioris muscle, on the other hand, is responsible for opening the eyelid and is innervated by the oculomotor nerve (CN III). Together, these muscles play a crucial role in maintaining eye health and facilitating various facial expressions.
| Characteristics | Values |
|---|---|
| Muscle that closes the eyelid | Orbicularis oculi |
| Muscle that opens the eyelid | Levator palpabrae superior muscles |
| Innervation | Facial nerve (CN VII) |
| Orbital part pierced by | Supraorbital vein and zygomaticofacial nerve |
| Receives arterial blood from | Maxillary, superficial temporal and facial arteries |
| Function | Sphincter of the eyelids, involved in facial expression, ocular protection and reflexes |
| Structure | Flat, broad muscle that forms an ellipse around the circumference of the orbit |
| Parts | Orbital, palpebral and deep palpebral |
| Origin | Nasal part of frontal bone, frontal process of maxilla and medial palpebral ligament |
| Protective function | Partially or completely closes the eyelids, limiting exposure to potential damage from bright light or blowing dust |
| Isolated contraction of the palpebral part | Gently closes the eyelids, e.g. when blinking or sleeping |
| Contraction of the deep palpebral part | Pulls the eyelids and lacrimal papillae medially and dilates the lacrimal sac |
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What You'll Learn
- The orbicularis oculi muscle closes the eye
- The levator palpebrae superioris muscle opens the eye
- The oculomotor nerve (CN III) innervates the levator palpebrae superioris
- The orbicularis oculi is innervated by the zygomatic and temporal branches of the facial nerve (CN VII)
- The orbicularis oculi is composed of orbital, palpebral and deep palpebral parts
The orbicularis oculi muscle closes the eye
The orbicularis oculi muscle is responsible for closing the eye. This muscle is innervated by the zygomatic and temporal branches of the facial nerve (cranial nerve VII). The orbicularis oculi is considered the sphincter of the eyelids and is involved in facial expression, ocular protection, and reflexes.
The muscle consists of three parts: orbital, palpebral, and deep palpebral (or lacrimal). The orbital part of the muscle is pierced by two major neurovasculature structures: the supraorbital vein and the zygomaticofacial nerve. It attaches to various soft tissue structures of the periorbital region and has no bony insertions. The upper fibres of the orbital part merge with other muscles, finally inserting into the skin and subcutaneous tissue of the eyebrow.
The palpebral part of the orbicularis oculi originates from the superficial surface of the medial palpebral ligament. The muscle fibres compose the eyelids as they travel towards the lateral commissure of the eye, where the superior and inferior fibres unite and insert into the lateral palpebral ligament (raphe). Contraction of the palpebral part results in finer control of the eyelids, pulling the upper eyelids down and raising the lower ones. This action gently closes the eyelids during blinking or sleeping and can also occur involuntarily as a protective reflex.
The deep palpebral part of the muscle pulls the eyelids and lacrimal papillae medially and dilates the lacrimal sac, facilitating tear drainage across the cornea. The orbicularis oculi muscle runs beneath the skin of the eyelid and is involved in the blink reflex. When the innervating nerve is lesioned, as in Bell's palsy, the eyelid cannot be closed, leading to dryness of the conjunctiva and potential ulceration of the cornea.
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The levator palpebrae superioris muscle opens the eye
The levator palpebrae superioris muscle, also known as LPS, is the only muscle responsible for raising the upper eyelid. It is a skeletal muscle, not a smooth muscle, and it originates from the lesser wing of the sphenoid bone, attaching to the superior tarsal plate of the upper eyelid. The levator palpebrae superioris is innervated by the oculomotor nerve (CN III), which exits the brainstem between the superior and posterior cerebellar arteries.
The levator palpebrae superioris muscle plays a crucial role in eyelid function, working in tandem with other muscles and structures to maintain proper eyelid movement and eye health. One such structure is the Whitnall ligament, a transverse suspensory ligament that facilitates the transition of the horizontally oriented levator palpebrae superioris into the vertical levator aponeurosis. This ligament is part of the complex Koornneef orbital septae, providing support to the globe and other orbital components while serving as an auxiliary locomotor system.
The levator palpebrae superioris muscle receives its blood supply primarily from the ophthalmic and supraorbital arteries, which are branches of the internal carotid artery. These vessels connect to the superior peripheral arcade, providing circulation to the upper eyelid's superior aspect. Additionally, the levator palpebrae superioris muscle is associated with the superior tarsal muscle, also known as the Müller muscle. The superior tarsal muscle is a smooth muscle that attaches to the superior tarsal plate and lies posterior to the levator aponeurosis.
The levator palpebrae superioris muscle works in conjunction with other muscles to ensure proper eyelid function. For example, it is strongly associated with the superior rectus, superior tarsal, and orbicularis oculi muscles. The orbicularis oculi muscle, in particular, is responsible for closing the eye and is innervated by CN7. The levator palpebrae superioris muscle, on the other hand, is responsible for opening the eye and is innervated by CN3.
In summary, the levator palpebrae superioris muscle is a crucial component of eyelid function, specifically responsible for opening the eye by raising the upper eyelid. It has a rich blood supply and is innervated by the oculomotor nerve. This muscle works in coordination with other muscles and structures to ensure the smooth movement and protection of the eye.
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The oculomotor nerve (CN III) innervates the levator palpebrae superioris
The oculomotor nerve, also known as cranial nerve III or CN III, is responsible for several important functions related to the eyes and vision. One of its key roles is to provide motor innervation to various extraocular muscles, including the levator palpebrae superioris.
The levator palpebrae superioris muscle is essential for maintaining the normal position of the upper eyelid. It works in conjunction with other muscles, such as Müller's muscle and the frontalis muscle, to ensure the eyelid opens and closes properly. The oculomotor nerve innervates the levator palpebrae superioris, enabling it to function correctly.
The oculomotor nerve originates in the midbrain, specifically from the oculomotor nucleus located within the midbrain's ventral aspect. As it exits the brainstem, it passes near the caudal end of the mammillary bodies. The nerve then traverses the cavernous sinus and continues through the supraorbital fissure before reaching the orbit of the eye.
Within the orbit, the oculomotor nerve divides into superior and inferior branches. The superior branch provides motor innervation to the levator palpebrae superioris, allowing it to elevate the upper eyelid. This action is crucial for maintaining proper eyelid function and protecting the eye.
Additionally, the oculomotor nerve has parasympathetic functions related to the eye. It supplies the sphincter pupillae, causing pupil constriction and regulating the amount of light entering the eye. It also innervates the ciliary muscles, which play a role in adjusting the shape of the lens for different visual ranges.
Dysfunction of the oculomotor nerve can lead to clinical issues such as ptosis, where the upper eyelid droops due to paralysis of the levator palpebrae superioris. This condition can be corrected through surgical procedures, such as attaching weights to the upper eyelid to counter the muscle's action.
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The orbicularis oculi is innervated by the zygomatic and temporal branches of the facial nerve (CN VII)
The orbicularis oculi muscle is responsible for closing the eyelids. It is innervated by the zygomatic and temporal branches of the facial nerve (CN VII). The facial nerve is the seventh cranial nerve, arising from the brain stem and extending posteriorly to the abducens nerve and anteriorly to the vestibulocochlear nerve. It plays a crucial role in facial expressions and ocular protection.
The zygomatic branch of the facial nerve is responsible for innervating the middle part of the face, while the temporal branch innervates the upper portion of the face, including the frontalis and corrugator supercilii muscles. These branches work together to enable the orbicularis oculi muscle to perform its functions.
The orbicularis oculi muscle is a flat, broad muscle that forms an ellipse around the orbit of the eye. It consists of three parts: the orbital, palpebral, and deep palpebral segments. Each part has its own specific attachments and functions. The orbital part, for example, overlays the orbital rim and originates from the frontal bone, maxilla, and medial palpebral ligament.
The proper functioning of the orbicularis oculi muscle is essential for maintaining eye health. It is involved in blinking and eyeball hydration, and its paralysis can lead to dry eye syndrome (keratoconjunctivitis sicca). This condition is characterised by redness, inflammation, irritation, discharge, and eye fatigue.
Furthermore, the orbicularis oculi muscle is involved in reflexive eye protection. For instance, when exposed to bright light or blowing dust, the muscle contracts, partially or completely closing the eyelids to shield the eyes from potential damage. This protective function is vital for safeguarding the delicate structures of the eye.
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The orbicularis oculi is composed of orbital, palpebral and deep palpebral parts
The orbicularis oculi muscle is responsible for closing the eyelids. It is a facial muscle that surrounds the orbit and extends into nearby regions of the head, including the eyelids, eyebrows, temporal and infraorbital regions. The muscle is innervated by the facial nerve (cranial nerve VII). It receives arterial blood from three branches of the external carotid artery: the maxillary, superficial temporal, and facial arteries.
The orbicularis oculi is composed of three main parts: the orbital, palpebral, and deep palpebral (or lacrimal) parts. Each part has its own specific attachments and functions. The orbital part overlays the orbital rim and originates from the nasal part of the frontal bone, the frontal process of the maxilla, and the medial palpebral ligament. It is thicker and reddish in colour, and its fibres form a complete ellipse around the circumference of the orbit. The orbital part also blends with other muscles of facial expression, such as the frontalis and corrugator supercilii muscles.
The palpebral part originates from the medial palpebral ligament. Its muscle fibres compose the eyelids as they travel towards the lateral commissure of the eye. The superior and inferior fibres unite and insert into the lateral palpebral ligament (raphe). The palpebral part is further divided into the marginal, pretarsal, and preseptal parts. The pretarsal orbicularis is believed to be responsible for the spontaneous blink.
The deep palpebral or lacrimal part originates from the lateral surface and lacrimal crest (superior part) of the lacrimal bone. Its fibres course laterally, passing posterior to the lacrimal sac. Some fibres insert into the superior and inferior tarsi of the eyelids, while others continue past the tarsi to insert into the lateral palpebral ligament. The lacrimal part of the orbicularis oculi facilitates the tear pump into the lacrimal sac, helping to hydrate and protect the eyes.
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Frequently asked questions
The orbicularis oculi muscle, also known as the orbital muscle, closes the eye.
The orbicularis oculi muscle is involved in facial expressions, ocular protection, and reflexes. It is innervated by the zygomatic and temporal branches of the facial nerve (CN VII).
The palpebral part of the orbicularis oculi muscle controls the eyelids, allowing for blinking and sleeping. It also has a protective function, keeping the eye moist and free of irritating particles.
The orbital part of the orbicularis oculi muscle extends in a circular fashion around the orbit, interdigitating with other muscles of facial expression. It has no bony insertions but attaches to various soft tissue structures of the periorbital region.
When the nerve that controls the orbicularis oculi muscle is damaged, it can lead to Bell's palsy, a condition where a person cannot blink or completely close their eyelid, resulting in dryness and potential ulceration of the cornea.
