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SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
All the muscles of the tongue are supplied by the hypoglossal or 12th cranial nerve, with the exception of the palatoglossus muscle which is supplied by the pharyngeal plexus of nerves (IX, X, and sympathetics). The hypoglossal nerve may be injured in a carotid endarterectomy or submandibular gland procedures. The most important muscle to know about is the genioglossus muscle, which serves to protrude the tongue. When genioglossal muscle tone is lost, as in someone with a decreased level of consciousness, or a fractured mandible (where the genioglossus muscle arises), the tongue falls back and obstructs the airway, rapidly resulting in hypoxia and death if basic life support measures are not quickly instigated.
Anatomy and Embryology of the Mouth and Dentition
Published in John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford, Head & Neck Surgery Plastic Surgery, 2018
The genioglossus muscle brings about the forward traction of the tongue to protrude its apex from the mouth. Acting bilaterally, the two muscles depress the central part of the tongue, making it concave from side to side. Acting unilaterally, the muscle helps move the tongue to the opposite side. Genioglossus receives its motor innervation from the hypoglossal nerve. Its blood supply is derived from the lingual artery (sublingual branch) and the facial artery (submental branch).
The Crucial Role of Craniofacial Growth on Airway, Sleep, and the Temporomandibular Joint
Published in Aruna Bakhru, Nutrition and Integrative Medicine, 2018
Certain physiological and anatomical factors that cause the nocturnal respiratory problems persist when the patients are awake. Studies have determined significant differences in craniofacial, upper airway, and related structures between awake OSA patients and controls. Furthermore, several studies have demonstrated that the neuromuscular properties of pharyngeal and genioglossus muscles are also compromised in awake OSA patients when compared with controls. These anatomical and physiological characteristics of the upper airway and related structures in OSA patients may trigger the chain of interactions between the muscles of the craniomandibular complex (including the pharyngeal and post-cervical muscles) resulting in a CCE and FHP.
Obstructive sleep apnea: personalizing CPAP alternative therapies to individual physiology
Published in Expert Review of Respiratory Medicine, 2022
Brandon Nokes, Jessica Cooper, Michelle Cao
Under normal circumstances, diaphragmatic inspiratory efforts are preceded by efforts of the upper airway dilators ~50-100 ms beforehand. There are muscle groups with differing actions that work in tandem to coordinate the upper airway behavior to ventilatory demands. Genioglossus is the best studied of these muscles and is both necessary and sufficient to dilate the upper airway [44]. During NREM sleep, the loss of cortical drive necessitates that the upper airway muscles be able to respond to chemoreceptive and mechanical cues to maintain airway patency. During REM sleep, there is a relative but not complete atonia of the upper airway, in addition to a reduced ventilatory drive, which makes upper airway collapse more likely. Cues for upper airway dilator firing are 1) mechanoreceptive – negative inspiratory pressure as well as supine sleep positioning increase upper airway dilator activity; 2) chemoresponsiveness – elevated PaCO2 for instance; and 3) state-dependent neural drive. Each of these cues overlay to create a propensity for upper airway dilatory efforts to occur [10,13,44–46].
Noninvasive electrical stimulation of oropharyngeal muscles in obstructive sleep apnea
Published in Expert Review of Respiratory Medicine, 2021
Juan Luis Rodríguez Hermosa, Myriam Calle, Ina Guerassimova, Baldomero Fernández, Víctor Javier Montero, José Luis Álvarez-Sala
The upper airways lack rigid bony support to perform these important functions, and the muscles surrounding them are responsible for their patency; therefore, the upper airways are susceptible to collapse. There are at least 20 dilator muscles, and among them, the genioglossus muscle (GG) plays a very important role in upper airway patency during sleep [13]. It is the principal tongue protrusor and various studies have shown that its contraction is more important in reducing pharyngeal resistance and collapsability in comparison with other upper airway dilators [14,15,16,17]. The contraction of the genioglossus muscle stabilizes and lengthens the upper section of the upper airways; this section is the most vulnerable to collapse (Figure 1). The moment the genioglossus, geniohyoid, and palatal veil-tensor muscles relax, the probability of apnea episodes occurring during sleep is greater. This is the reason for the continuing attempts of GG stimulation. Different approaches have been used: transcutaneous, intraoral and intramuscular electrodes placement and, lately, the direct hypoglossal nerve stimulation (HNS) via implantable devices. Despite the extensive work done by the HNS researchers and the promising first results, there is still insufficient evidence for consistent recommendation. It is also asurgical procedure requiring general anesthesia and risks and complications of the procedure have been documented.
The pharmacotherapeutic management of obstructive sleep apnea
Published in Expert Opinion on Pharmacotherapy, 2019
Stefano Marra, Dario Arnaldi, Lino Nobili
During sleep there is a physiological muscle hypotonia. The reduction of dilatory muscle activity increases the risk of airway collapse. Normally, this risk is counteracted by arousals and increased central respiratory drive induced by mild hypercapnia. The upper airway muscles have complex patterns of neuronal activation. The genioglossus, which is the most important pharyngeal dilatory muscle, receives up to six different patterns of drive [25]. The genioglossus receives inputs by the central nervous system from the brainstem and reflex inputs from pharyngeal mechanoreceptors and chemoreceptors. This eventually leads to a phasic pattern of muscle activation, being more evident during inspiration and less during expiration. Muscle activities are reduced at sleep onset [26] and vary between sleep stages [27]. In OSA patients, the combination of a loss in central drive and poor reflex input to the muscles, causes a poor and ineffective response of the genioglossus to the reduced width of the airway, eventually leading to OSA events.