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The orbicularis oculi muscle, situated just beneath the eyelid skin, is crucial in eyelid movement. While the orbicularis oculi muscle closes the eyelid, the levator palpebrae superioris muscle, also known as the Horner muscle, opens the eyelid. The levator palpebrae muscle is part of the elevator muscle group and is responsible for elevating and lowering the upper eyelid.
| Characteristics | Values |
|---|---|
| Muscle that opens the eyelid | Levator palpebrae superioris |
| Alternative name | Lavetor palpabrae superior muscles |
| Innervation | CN3 |
| Muscle that closes the eyelid | Orbicularis oculi |
| Alternative names | Orbicularis muscle, palpebral orbicularis |
| Innervation | CN7, cranial nerve VII (the facial nerve) |
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What You'll Learn
The levator palpebrae superioris muscle opens the eyelid
The eyelid consists of five main layers, with the skin and subcutaneous tissue forming the most superficial layer. The orbicularis oculi muscle is located just beneath the skin of the eyelid and is crucial in eyelid movement. This muscle extends from the medial to the lateral canthal region, enhancing the eyelid's structural integrity and functionality.
The orbicularis oculi muscle is a facial muscle that closes the eyelids. It is connected to the lacrimnal pump mechanism, which helps with tear drainage. The preseptal and pretarsal parts of the palpebral orbicularis oculi contract during blinking or eyelid closure. The muscle's action simultaneously pulls the lacrimal sac laterally and forward.
The levator palpebrae superioris muscle is responsible for opening the eyelid. It is part of the elevator muscle group. This muscle not only elevates and lowers the upper eyelid but also aids in the expression of fear. The palpebral apertures widen in the presence of fear or excitement when the eyes are widened. The widening of the apertures is a direct result of the increased sympathetic nervous system.
The levator palpebrae superioris muscle is the direct antagonist of the orbicularis oculi muscle. While the orbicularis oculi muscle closes the eyelids, the levator palpebrae superioris muscle raises the upper eyelid and exposes the front of the bulb of the eye. The orbital and palpebral portions of the orbicularis oculi muscle can work independently of each other. For example, the contraction of the orbital portion can reduce glare while the eyes are kept open by the relaxation of the palpebral portion.
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The orbicularis oculi muscle closes the eyelid
The orbicularis oculi muscle is a sphincter-like muscle in the face that closes the eyelids. It is situated just beneath the skin of the eyelid and extends from the medial to the lateral canthal region. This muscle enhances the eyelid's structural integrity and functionality. The main function of the muscle is to close the eyelids, but it also assists with tear drainage.
The orbicularis oculi has orbital and palpebral sections, each further subdivided to meet specific functional demands. The orbital portion of the orbicularis oculi primarily facilitates the forceful closure of the eyelids. Medially, this section attaches to the anterior limb of the medial canthal tendon and the surrounding periosteum. Laterally, it connects to the lateral palpebral raphe. The palpebral portion acts involuntarily, closing the lids gently, as in sleep or in blinking. The orbital portion is subject to conscious control.
The orbicularis oculi muscle interacts dynamically with the nasolacrimal duct system to facilitate tear drainage. The preseptal and pretarsal parts of the palpebral orbicularis oculi contract during blinking or eyelid closure. Consequently, the small channels draining tears from the eye's surface to the lacrimal sac, called canaliculi, are compressed. The muscle's action simultaneously pulls the lacrimal sac laterally and forward.
The lacrimial part of the orbicularis oculi draws the eyelids and the ends of the lacrimal canals medialward and compresses them against the surface of the globe of the eye. This part comprises two pieces: Horner's muscle and the muscle of Riolan. The latter helps hold the eyelids together to keep the lacrimal passage waterproof. The levator palpebrae superioris is the direct antagonist of the orbicularis oculi muscle, as it raises the upper eyelid and exposes the front of the bulb of the eye.
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The marginal portion of the palpebral orbicularis oculi muscle
The orbicularis oculi muscle 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 critical in eyelid movement and is involved in ocular protection and reflexes. It is situated just beneath the skin of the eyelids and extends from the medial to the lateral canthal region, enhancing the eyelid's structural integrity and functionality. The muscle is divided into orbital and palpebral sections, each further subdivided based on function.
The palpebral portion of the orbicularis oculi muscle is thin and pale. It arises from the bifurcation of the medial palpebral ligament and is inserted into the lateral palpebral raphe at the outer corner of the eye. The palpebral portion contains the preseptal and pretarsal muscles, with the latter thought to be responsible for the spontaneous blink. The preseptal and pretarsal parts of the palpebral orbicularis oculi contract during blinking or eyelid closure, compressing the small channels that drain tears from the eye's surface to the lacrimal sac (canaliculi).
The palpebral orbicularis oculi muscle interacts with the nasolacrimal duct system to facilitate tear drainage. The muscle's action pulls the lacrimal sac laterally and forward, creating a negative pressure that draws tears down the nasolacrimal duct toward the nasal cavity. The lacrimal part of the orbicularis oculi draws the eyelids and the ends of the lacrimal canals medialward, compressing them against the surface of the globe of the eye to facilitate the tear pump into the lacrimal sac.
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The lacrimal part of the orbicularis oculi muscle
The orbicularis oculi muscle, located just beneath the skin around the eyes, is crucial for eyelid movement. It extends from the medial to the lateral canthal region, enhancing the structural integrity and functionality of the eyelids. The muscle has three distinct parts: palpebral, lacrimal, and orbital. The lacrimal part of the orbicularis oculi muscle, also known as the deep palpebral part, plays a significant role in tear drainage and eyelid function.
The contraction of the lacrimal part of the orbicularis oculi muscle pulls the eyelids and lacrimal papillae medially, dilating the lacrimal sac. This action creates a negative pressure within the sac, drawing tears and ensuring their passage down the nasolacrimal duct toward the nasal cavity. Additionally, the lacrimal part of the muscle compresses the lacrimal sac and gland, further improving tear flow and drainage.
The lacrimal portion of the orbicularis oculi muscle is also involved in the medial movement of the eyelids. When the eyelids close through the action of the orbicularis oculi muscle, the lacrimal part specifically draws the eyelids and the ends of the lacrimal canals medialward. This movement compresses the lacrimal canals against the surface of the globe of the eye, optimising the reception of tears.
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The orbital and palpebral portions of the orbicularis oculi muscle
The orbicularis oculi muscle is a sphincter-like muscle in the face that closes the eyelids. It is situated just beneath the skin of the eyelids and is responsible for eyelid movement. The muscle extends from the medial to the lateral canthal region, enhancing the eyelid's structural integrity and functionality. The muscle is divided into two sections: the orbital portion and the palpebral portion.
The orbital portion of the orbicularis oculi is the outer section of the muscle that surrounds the orbital rim. It originates from the nasal part of the frontal bone, the frontal process of the maxilla, and the medial canthal tendon. This portion is thicker and reddish in colour. It primarily facilitates the forceful closure of the eyelids. Medially, the orbital portion attaches to the anterior limb of the medial canthal tendon and the surrounding periosteum. Laterally, it connects to the lateral palpebral raphe. The orbital segment interdigitates with neighbouring muscles, such as the frontalis muscle.
The palpebral portion of the orbicularis oculi is the inner section of the muscle. It arises from the bifurcation of the medial palpebral ligament and forms a series of concentric curves. The palpebral portion is thin and pale in appearance. It is inserted into the lateral palpebral raphe at the outer corner of the eye. This portion contains the preseptal and pretarsal muscles, with the pretarsal orbicularis being responsible for the spontaneous blink. The palpebral part of the muscle is crucial for both voluntary and involuntary blinking.
The preseptal portion of the palpebral section covers the orbital septum and is under more voluntary control. It is less closely adherent to the skin, except at the medial and lateral canthi. The pretarsal portion, on the other hand, overlies the tarsal plates and contributes to involuntary blinking. It is closely adherent to the pretarsal skin, providing reflexive blink movement. Both the preseptal and pretarsal portions function together during blinking.
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Frequently asked questions
The levator palpebrae superioris muscle, also known as the levator palpabrae superior muscle, is responsible for opening the eyelid.
This muscle is innervated by CN3, also known as nerve 3 or the oculomotor nerve.
The eyelid muscles work together to open and close the eyelids, protecting the eyes and facilitating tear drainage.
The orbicularis oculi muscle, a sphincter-like muscle, is responsible for closing the eyelids and is innervated by CN7 or nerve 7 (the facial nerve).
Yes, conditions such as Bell's palsy and oculomotor palsy can impact the ability to open or close the eyelids due to nerve involvement.
