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Encyclopedia > Extraocular muscles

The extraocular muscles are the six muscles that control the movements of the eye. The actions of the extraocular muscles depend on the position of the eye at the time of muscle contraction. A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... Eye movements are the voluntary or involuntary movements of the eye. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Muscle Innervation Origin Insertion Primary function Secondary function Tertiary function
Superior rectus Oculomotor nerve Annulus of Zinn eye (anterior, superior surface) Elevation Intorsion Adduction
Inferior rectus Oculomotor nerve Annulus of Zinn eye (anterior, inferior surface) Depression Extorsion Adduction
Lateral rectus Abducens nerve Annulus of Zinn eye (anterior, lateral surface) Abduction . .
Medial rectus Oculomotor nerve Annulus of Zinn eye(anterior, medial surface) Adduction . .
Superior oblique Trochlear nerve Annulus of Zinn eye (posterior, superior, lateral surface) Intorsion Depression Abduction
Inferior oblique Oculomotor nerve Lacrimal bone eye (posterior, inferior, lateral surface) Extorsion Elevation Abduction


Five of the extraocular muscles have their origin in the back of the orbit in a fibrous ring called the annulus of Zinn. Four of these then course forward through the orbit and insert onto the globe on its anterior half (i.e., in front of the eye's equator). These muscles are named after their straight paths, and are called the four rectus muscles, or four recti. They insert on the globe at 12, 3, 6, and 9 o'clock, and are called the superior, lateral, inferior and medial rectus muscles. (Note that lateral and medial are relative to the subject, with lateral toward the side and medial toward the midline, thus the medial rectus is the muscle closest to the nose). The other two extraocular muscles follow more complicated paths. The superior oblique muscle originates at the back of the orbit and courses forward to a rigid pulley, called the trochlea, on the upper, nasal wall of the orbit. The muscle passes through the pulley, turning sharply across the orbit, and inserts on the lateral, posterior part of the globe. Thus, the superior oblique goes backward for the last part of its path, and because it goes over the top of the eye, it pulls it downward and lateralward. The last muscle is the inferior oblique, which originates at the lower front of the nasal orbital wall, and passes under the LR to insert on the lateral, posterior part of the globe. Thus, the inferior oblique pulls the eye upward and lateralward. [1][2] A nerve is an enclosed, cable-like bundle of nerve fibers or axons, which includes the glia that ensheath the axons in myelin. ... The superior rectus muscle is a muscle in the orbit that elevates, adducts, and rotates the eye medially. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The inferior rectus muscle is a muscle in the orbit that depresses, adducts, and rotates the eye laterally. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The lateral rectus muscle is a muscle in the orbit that abducts the eyeball (makes it move outwards). ... The sixth out of twelve cranial nerves, the abducens nerve controls the lateral rectus muscle - this means that the action of this nerve controls each eyes ability to look laterally (away from the midline). ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The medial rectus muscle is a muscle in the orbit that adducts the eyeball (makes it move inwards). ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The superior oblique muscle is a muscle in the orbit that causes the eye to look downwards when it is already directed medially (looking towards the nose). ... The fourth of twelve cranial nerves, the trochlear nerve controls the function of the superior oblique muscle, which rotates the eye towards the nose and also moves the eye downward. ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The inferior oblique muscle is a muscle in the orbit that adducts (medially rotates) and elevates the eyeball. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... The lacrimal bone (Os Lacrimale), the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit . ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The annulus of Zinn, also known as the annular tendon or common tendinous ring, is a ring of fibrous tissue surrounding the optic nerve at its entrance at the apex of the orbit. ...

Contents


Yoked muscles vs. antagnoistic muscles

Herrings law of equal innervation is used to explain the conjugacy of eye movements (saccades) in stereoptic animals. ...

Mnemonic

A good mnemonic to remember which muscles are innervated by what nerve is to paraphrase it as a molecular equation: LR6SO4R3.
Lateral Rectus - Cranial Nerve VI,
Superior Orbital - Cranial Nerve IV,
the Rest of the muscles - Cranial Nerve III.


Another way to remember which nerves innervate which muscles is to understand the meaning behind all of the Latin words. The fourth cranial nerve, the trochlear, is so named because the muscle it innervates, the superior oblique, runs through a little fascial pulley that changes its direction of pull. This pulley exists in the superiomedial corner of each orbit, and "trochl-" is Latin for "pulley." The sixth cranial nerve, the abducens, is so named because it controls the lateral rectus, which abducts the eye (rotates it laterally) upon contraction. All of the other muscles are controlled by the third cranial nerve, the oculomotor, which is so named because it is in charge of the movement (motor) of the eye (oculo-).


References

  1. ^  Roger H.S. Carpenter (1988); Movements of the Eyes (2nd ed.). Pion Ltd, London. ISBN: 0850861098.
  2. ^  Westheimer Gerald, McKee Suzanne P (1975); "Visual acuity in the presence of retinal-image motion". Journal of the Optical Society of America 65(7), 847-50.

External links

  • eMedicine - Extraocular Muscles, Actions
Muscles of the Head -- Neck -- Trunk -- Upper limb -- Lower limb -- LIST OF ALL MUSCLES

facial expression: auricularis anterior - buccinator - corrugator supercilii - depressor anguli oris - depressor labii inferioris - depressor septi nasi - levator anguli oris - levator labii superioris - levator labii superioris alaeque nasi - levator palpebrae superioris - mentalis - nasalis - occipitofrontalis (occipitalis, frontalis) - orbicularis oculi - orbicularis oris - platysma - procerus - risorius - zygomatic (major, minor) A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... This is a list of muscles of the human anatomy. ... Photographs from the 1862 book Mécanisme de la Physionomie Humaine by Guillaume Duchenne. ... The muscles of the auricula. ... Buccinator The buccinator is a muscle of which the bulk of is located in the cheeks. ... Left obicularis oculi notice the corrugator muscle at the top The Corrugator supercilii is a small, narrow, pyramidal muscle, placed at the medial end of the eyebrow, beneath the Frontalis and Orbicularis oculi. ... The Depressor anguli oris is a muscle of the human body. ... The Depressor labii is part of a small quadrilateral muscle. ... The Depressor septi nasi is a muscle of the human body, in the nose. ... The Levator anguli oris is a muscle of the human body. ... The Levator labii superioris is a muscle of the human body used in facial expression. ... The levator labii superioris alaeque nasi muscle is, translated from Latin, the lifter of the upper lip and of the wing of the nose. It is the muscle with the longest name in the human body. ... The levator palpebrae superioris muscle is a muscle in the orbit that elevates the superior (upper) eyelid. ... The Mentalis is a muscle of the human body. ... The Nasalis (Compressor naris) is a sphincter-like muscle of the nose whose function is to compress the nasal cartilege. ... The Occipitofrontalis is a term used by some to describe a muscle of the human body, with two parts: the occipital part/belly, and the frontal part/belly. ... The Occipitalis muscle is a muscle of the human body. ... The Frontalis is a muscle of the human body. ... The Orbicularis oculi is a muscle of the human body. ... The orbicularis oris is the sphincter muscle around the mouth. ... The platysma is a superficial muscle that stretches from the clavicle to the mandible overlapping the sternocleidomastoid. ... Procerus muscle Origin/Proximal Attatchment: From fascia over the lower of the nasal bone Insertion/Distal Attatchment: Into the skin of the lower part of the forehead between the eyebrows Action/Relevance: Draws down the medial angle of the eyebrow giving expressions of frowning Innervation: Buccal branch of the facial... The Risorius is a muscle of the human body. ... The Zygomatic major is a muscle of the human body. ... The Zygomaticus minor is a muscle of the human body. ...


mastication: masseter - pterygoid (lateral, medial) - temporalis - stylopharyngeus Mastication or chewing is the process by which food is torn and/or crushed by teeth. ... In human anatomy, the masseter is one of the muscles of mastication. ... The lateral pterygoid is a muscle of mastication with two heads. ... The medial pterygoid is a muscle of mastication with two heads. ... The temporalis muscle is one of the muscles of mastication. ... The Stylopharyngeus muscle is a muscle of the human body. ...


tongue: extrinsic (genioglossus - hyoglossus - styloglossus - palatoglossus) intrinsic (superior longitudinal - inferior longitudinal - verticalis - transversus) Many animals have longer and more flexible tongues than humans. ... The Genioglossus is a muscle of the human body. ... The Hyoglossus is a muscle of the human body. ... The Styloglossus is a muscle of the human body. ... The Palatoglossus is a muscle of the human body. ... The Superior longitudinal muscle is a muscle of the human body. ... The Inferior longitudinal muscle is a muscle of the human body. ... The Verticalis muscle is a muscle of the human body. ... The Transversus muscle is a muscle of the human body. ...


palate, Eustachian tube, and pharynx: palatopharyngeus - salpingopharyngeus - stapedius - tensor tympani - tensor veli palatini - levator veli palatini - pharyngeal constrictor (superior, middle, inferior) The palate is the roof of the mouth in humans and vertebrate animals. ... Anatomy of the human ear. ... The pharynx is the part of the digestive system and respiratory system of many animals immediately behind the mouth and in front of the esophagus. ... The Palatopharyngeus muscle is a muscle of the human body. ... The Salpingopharyngeus muscle is a muscle of the human body. ... The stapedius is the smallest striated muscle in the human body. ... The tensor tympani muscle arises from the auditory tube and inserts onto the handle of the malleus, damping down vibration in the ossicles and so reducing the amplitude of sounds. ... The Tensor veli palatini muscle (or Tensor palati) is a muscle of the human body. ... The Levator veli palatini is a muscle of the human body. ... The Superior pharyngeal constrictor muscle is a muscle of the human body. ... The Middle pharyngeal constrictor muscle is a muscle of the human body. ... The Inferior pharyngeal constrictor muscle is a muscle of the human body. ...


extraocular: rectus (inferior, superior, lateral, medial) - oblique (inferior, superior) The inferior rectus muscle is a muscle in the orbit that depresses, adducts, and rotates the eye laterally. ... The superior rectus muscle is a muscle in the orbit that elevates, adducts, and rotates the eye medially. ... The lateral rectus muscle is a muscle in the orbit that abducts the eyeball (makes it move outwards). ... The medial rectus muscle is a muscle in the orbit that adducts the eyeball (makes it move inwards). ... The inferior oblique muscle is a muscle in the orbit that adducts (medially rotates) and elevates the eyeball. ... The superior oblique muscle is a muscle in the orbit that causes the eye to look downwards when it is already directed medially (looking towards the nose). ...


intraocular: ciliary body - iris dilator - iris sphincter To meet Wikipedias quality standards, this article or section may require cleanup. ... There are two sets of ciliary muscles in the eye. ... The Iris dilator muscle is a muscle of the human body. ... The Iris sphincter muscle is a muscle of the human body. ...


larynx: posterior cricoarytenoid - lateral cricoarytenoid - interarytenoid - thyroarytenoid - cricothyroid - aryepiglottic - thyroepiglotticus The larynx (plural larynges), or voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. ... The posterior cricoarytenoid muscles allow the rima glottidis to be opened; they therefore have the opposite effect to the lateral cricoarytenoid muscles. ... The lateral cricoarytenoid muscles allow the rima glottidis to be closed, protecting the airway; they therefore have the opposite effect to the posterior cricoarytenoid muscles. ... The cricothyroid muscle attaches to the anterolateral aspect of the cricoid and the inferior cornu and lower lamina of the thyroid cartilage, tilting the thyroid forwards and lengthening the vocal cords. ...


  Results from FactBites:
 
Eye muscles - 2 (399 words)
Extraocular muscles are the eye muscles outside the eyeball.
The muscles of the iris are in the form of smooth muscle bundles, which are in concentric circles.
The muscles of the iris are sphincter pupillae and dilator pupillae.
  More results at FactBites »

 
 

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