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The orbicularis oculi muscle, situated just beneath the eyelid skin, is responsible for closing the eyes. It is a sphincter-like muscle that 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, with the orbital portion facilitating the forceful closure of the eyelids. The palpebral portion, on the other hand, acts involuntarily, gently closing the eyelids during sleep or blinking.
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What You'll Learn
- The orbicularis oculi muscle closes the eyes
- The levator palpebrae superioris opens the eyes
- The palpebral portion of the orbicularis oculi acts involuntarily, closing the eyes during sleep
- The orbicularis oculi is innervated by CN7
- Paralysis of the orbicularis oculi can result in an inability to close the eye
The orbicularis oculi muscle closes the eyes
The orbicularis oculi muscle is responsible for closing the eyes. It is a sphincter-like muscle in the face that closes the eyelids. This muscle arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament. The muscle fibres pull the upper eyelids down and raise the lower ones, thereby closing the eyes.
The orbicularis oculi muscle consists of an orbital, palpebral, and deep palpebral part. The orbital part overlays the orbita and draws the skin of the forehead and cheek towards the nose when contracted. This protective function can partially or completely close the eyelids, reducing exposure to potential damage from bright light or blowing dust. The palpebral part is thin and pale and arises from the bifurcation of the medial palpebral ligament. It forms a series of concentric curves and is inserted into the lateral palpebral raphe at the outer corner of the eye. The palpebral part is responsible for the spontaneous blink and can involuntarily close the eyelids as a reflex mechanism. This protective action wipes tears across the surface of the eyeball, keeping it moist and free of irritating particles.
The lacrimal part of the orbicularis oculi is a small, thin muscle situated behind the medial palpebral ligament and lacrimal sac. It arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone and divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia. The lacrimal orbicularis facilitates the tear pump into the lacrimal sac and draws the eyelids and ends of the lacrimal canals medialward, compressing them against the surface of the globe of the eye. This action places the eye in a favourable position for receiving tears and also compresses the lacrimal sac. The lacrimal part comprises two muscles: Horner's muscle and the muscle of Riolan, with the latter helping to hold the eyelids together to keep the lacrimal passage waterproof.
The orbicularis oculi muscle is involved in blinking and eyeball hydration, and its paralysis can result in an inability to close the eye and failure to blink. This causes inefficient lubrication and a condition known as dry eye syndrome, which can manifest with redness, inflammation, irritation, discharge, and eye fatigue. Injury to the orbicularis oculi from overuse may also result in headaches, eyestrain, or sinus headaches, especially if poor eyesight is not corrected with proper eyewear.
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The levator palpebrae superioris opens the eyes
The levator palpebrae superioris is the muscle that opens the eye. It is innervated by nerve 3, also known as the oculomotor nerve. This muscle is responsible for raising the upper eyelid and exposing the front of the bulb of the eye.
The levator palpebrae superioris is part of a group of muscles called the circumorbital and palpebral muscles, which surround the eye. These muscles work together to control the movement of the eyelids and protect the eyes. The levator palpebrae superioris is the direct antagonist of the orbicularis oculi muscle, which closes the eye.
The orbicularis oculi muscle is a sphincter-like muscle in the face that surrounds the eye and controls the closure of the eyelids. It arises from several structures in the face, including the frontal bone, the maxilla, and the medial palpebral ligament. The muscle fibres extend laterally, forming a thin layer that surrounds the eyelids and spreads over the temple and cheek.
The orbicularis oculi muscle has several parts, including the orbital, palpebral, and deep palpebral portions. The palpebral portion is responsible for the spontaneous blink and can also close the eyelids involuntarily as a reflex mechanism. This protective action helps to keep the eye moist and free of irritating particles. The orbital portion, on the other hand, is subject to conscious control and can be used to convey non-verbal messages or expressions.
The levator palpebrae superioris and orbicularis oculi muscles work in tandem to control the opening and closing of the eyes. Together, they ensure that the eyes are properly protected and lubricated, while also facilitating non-verbal communication through winks or blinking.
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The palpebral portion of the orbicularis oculi acts involuntarily, closing the eyes during sleep
The orbicularis oculi muscle is responsible for closing the eyes. It is a sphincter-like muscle in the face that arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament. It is the only muscle capable of closing the eye, and its primary function is eyelid closure. The muscle is innervated by CN7.
The orbicularis oculi can be divided into three types: orbital, preseptal, and pretarsal. The orbital portion is thicker and of a reddish colour. Its fibres form a complete ellipse without interruption at the lateral palpebral commissure. The preseptal portion is thin and pale, and is formed by two half-ellipses of muscle fibres bifurcated by the medial and lateral canthal tendons. The lacrimal part is a small, thin muscle, about 6 mm in breadth and 12 mm in length, situated behind the medial palpebral ligament and lacrimal sac.
The palpebral portion of the orbicularis oculi is responsible for the involuntary closure of the eyes during sleep. It also closes the eyes when blinking. This protective action helps to keep the eyes moist and free of potentially irritating particles by wiping the tears produced by the lacrimal gland across the surface of the eyeball. The palpebral portion acts gently, closing the eyelids without any conscious effort.
The orbicularis oculi is a complex muscle with a complicated spatial arrangement of myofibers. It is involved in eyeball hydration and has important clinical consequences in day-to-day life. Paralysis of the facial nerve (Bell's palsy, stroke, trauma, or infection) can result in an inability to close the eyes and a failure to blink, leading to dry eye syndrome.
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The orbicularis oculi is innervated by CN7
The orbicularis oculi muscle is a flat, broad muscle that forms an ellipse around the circumference of the orbit. It is composed of three parts: the orbital, palpebral, and deep palpebral parts, each with its own specific attachments. The orbital part overlays the orbital rim and originates from the frontal bone, maxilla, and lacrimal bone, extending into the soft tissues of the periorbital region. The palpebral part is involved in blinking and eyeball hydration, while the deep palpebral part facilitates tear drainage across the cornea by pulling the eyelids and lacrimal papillae medially and dilating the lacrimal sac.
The orbicularis oculi muscle is innervated by the cranial nerve VII (CN7), also known as the facial nerve. It receives its blood supply from three branches of the external carotid artery: the maxillary, superficial temporal, and facial arteries. Additionally, the ophthalmic artery, a branch of the internal carotid artery, supplies this muscle.
The function of the orbicularis oculi muscle is to close the eyes. It is considered the sphincter of the eyelids and plays a role in facial expression, ocular protection, and reflexes. Contraction of the orbital part of the muscle draws the skin of the forehead and cheeks towards the nose, partially or completely closing the eyelids to protect against bright light or blowing dust. However, repeated contractions can lead to the formation of "crow's feet" wrinkles at the lateral angle of the eyelids.
The orbicularis oculi muscle is also involved in the blink reflex, and lesions to the innervating facial nerve (CN VII) can result in Bell's palsy, characterized by an inability to blink or completely close the eyelid, leading to dryness of the conjunctiva and potential ulceration of the cornea.
The muscle that opens the eye, on the other hand, is the levator palpebrae superioris, which is innervated by the oculomotor nerve (CN III). Contraction of this muscle lifts the superior eyelid, and its paralysis leads to a condition called ptosis, where the upper eyelid cannot be elevated.
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Paralysis of the orbicularis oculi can result in an inability to close the eye
The orbicularis oculi is a muscle in the face that closes the eyelids. It is considered the sphincter of the eyelids and is involved in blinking, eyeball hydration, facial expression, ocular protection, and reflexes. The muscle extends between three bones of the viscerocranium (frontal bone, maxilla, and lacrimal bone) and the soft tissue structures of the periorbital region. It surrounds the orbit and extends into nearby regions of the head, including the eyelids, eyebrows, temporal, and infraorbital regions.
Paralysis of the orbicularis oculi muscle can result in an inability to close the eye, leading to exposure of the cornea and significant corneal irritation. This condition, known as exposure keratopathy, is characterized by redness, irritation, and a feeling of a foreign body in the eye. If left untreated, exposure keratopathy can progress to ulcerations, scarring, and even blindness. The inability to close the eye due to orbicularis oculi paralysis can also cause dry eye syndrome (keratoconjunctivitis sicca), which is characterized by redness, inflammation, irritation, discharge, and fatigue of the eyes.
The orbicularis oculi muscle consists of three main parts: the orbital, palpebral, and deep palpebral (or lacrimal) parts. The orbital part is under conscious control and draws the skin of the forehead, temple, and cheek towards the nose, providing protection from bright light or blowing dust. The palpebral part acts involuntarily, gently closing the eyelids during sleep or blinking. It provides finer control of the eyelids, with muscle fibers pulling the upper eyelids down and raising the lower ones. The deep palpebral or lacrimal part originates from the lateral surface and lacrimal crest of the lacrimal bone and inserts into the superior and inferior tarsi of the eyelids.
Treatment for facial paralysis of the eyes aims to protect the eye and keep it lubricated. In some cases, surgery may be considered to restore movement to the paralyzed side, including procedures such as nerve grafting or nerve transfers.
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Frequently asked questions
The orbicularis oculi muscle.
It is a sphincter-like muscle arranged concentrically around the upper and lower eyelids.
The main function of the orbicularis oculi muscle is to close the eyelids. It also assists with tear drainage and is important for facial expressions.
Loss of function of the orbicularis oculi muscle results in an inability to close the eyes. This may require the use of eye drops or, in extreme cases, surgical closure of the eye.
Yes, the orbicularis oculi muscle has two main parts: the orbital portion and the palpebral portion. The orbital portion is responsible for the forceful closure of the eyelids, while the palpebral portion acts involuntarily to close the eyelids gently during sleep or blinking.
