![]() It contains motor fibers originating from the nucleus ambiguus in the medulla as well as afferents originating in the sensory nucleus of the trigeminal nerve 4,6. The pharyngeal branch of the vagus emerges from the upper part of the inferior vagal ganglion and passes forward between the internal and external carotid arteries parallel with and below the glossopharyngeal nerve to join the pharyngeal plexus at the upper border of the middle pharyngeal constrictor muscle 1,2,4. ![]() Parasympathetic fibers from the inferior salivary nucleus are also supplied to the mucous and serous glands of the oropharynx via the pharyngeal branches of the glossopharyngeal nerve 4. This component is afferent and supplies the mucous membrane of the oropharynx with common sensation and some taste fibers 3,4. ![]() It joins the pharyngeal branch of the vagus nerve which proceeds to join the pharyngeal plexus and pierce the middle constrictor muscle 3,4. The pharyngeal branch of the glossopharyngeal nerve arises prior to the glossopharyngeal nerve curving around the posterior border and lateral side of the stylopharyngeus 3,6. It is formed by the pharyngeal branches from the vagus and glossopharyngeal nerves and the cervical sympathetic 3-7. The pharyngeal plexus sends some branches between the middle and inferior constrictors and other branches between the superior and middle constrictors 4,6. It lies mainly over the middle pharyngeal constrictor muscle 4,5 although it spreads its branches over the dorsolateral surface of the both the superior and middle constrictors, and lower branches descend onto the inferior constrictor 6. The pharyngeal plexus lies within the external fascia of the pharynx 3 on the posterolateral wall of the pharynx in the retropharyngeal space 7. Relations: the pharyngeal plexus lies in the retropharyngeal space between the superior and middle constrictor muscles anteriorly and the longus capitus and colli muscles, prevertebral fascia, and bodies of the second and third cervical vertebrae posteriorly 7 and medial to the buccopharyngeal fascia 8 Supplies the superior, middle and inferior pharyngeal constrictor muscles, palatopharyngeus, salpingopharyngeus, levator veli palatini, palatoglossus and the muscle of the uvula 4,5 Origin and course: it is formed from the union of branches from the vagus nerve, glossopharyngeal nerve and cervical sympathetic nerves 4,5įilaments from the plexus ascend or descend external to the superior and inferior constrictors 5 before branching within the muscular layer and mucosa of the pharynx 4,5 If the eye is adducted by the medial rectus, the orbital axis runs almost perpendicular to the optical axis, so the inferior rectus no longer produces effective ocular depression, and instead produces external rotation and adduction.Location: within the external fascia of the pharynx 3, mainly over the middle pharyngeal constrictor on the posterolateral wall of the pharynx 4 Thus, when the physician testing eye movements first asks the patient to follow their finger laterally then inferiorly in the familiar H-shape, the inferior rectus muscle (and the oculomotor nerve that supplies it) are being directly tested. If the eye is abducted by the lateral rectus such that the optical axis lines up with the orbital axis, the inferior rectus produces ocular depression only, and is solely responsible for this movement. This means that the inferior rectus has secondary actions of adduction and external rotation (see figures 2 and 3). However, because the apex of the orbit is placed medially in the skull, the orbital axis that the inferior rectus runs in does not correspond with the optical axis of the eye in its neutral position. The primary action of the inferior rectus is to depress the eye (see figure 1) 1. Innervated by the oculomotor nerve, which also supplies medial rectus, superior rectus, and inferior oblique muscles. Inferior rectus is crossed by the inferior oblique muscle, which runs inferior to it as it crosses the floor of the orbit.īranches of the ophthalmic artery, itself a branch of the internal carotid artery. Inferior rectus runs anteriorly on the inferior surface of the eye and inserts into the inferior surface of the sclera just posterior to the junction of cornea and sclera 2. Inferior rectus, along with the other rectus muscles, arises from the annulus of Zinn, the common tendinous ring at the apex of the orbit that surrounds the optic canal 1. tertiary function: one of the three ocular adductors.secondary function: one of the two ocular external rotators.primary function: one of two ocular depressors.insertion: globe (anterior, inferior surface).origin: annulus of Zinn (tendinous ring). ![]()
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