![]() ![]() It is activated when swallowing which is why swallowing helps relieve the pressure buildup in the ear when changing altitude especially noticeable when flying. When contracted it has two effects: it tenses the palatal aponeurosis which anchors other muscles, so it acts as a synergist to their actions and importantly also helps open the eustachian tube to equalize the pressure in the middle ear. It inserts on a band of connective tissue that runs along the posterior edge of the hard palate. All of these reflexes and responses and the passive elastic properties of the CP may contribute to the generation of tone in the CP and UES.This paired muscle, the tensor veli palatini originates over an area that includes the medial pterygoid plate of the sphenoid, the spine of the sphenoid and importantly on the lateral surface of the cartilage that forms the eustachian (auditory) tube. The UES or CP also contracts with arousal or with changes in posture. The pharyngo-UES and pulmonary-UES reflexes may generate the respiratory rhythm often observed on UES pressure or electromyographic activity. Inflation of the lungs causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. Pressure on the pharyngeal mucosa contracts the CP and UES and is mediated by a glossopharyngo-vagal reflex. Distension of the esophagus causes contraction of the CP and UES, which is mediated by a vago-vagal reflex. Various reflexes control the tone of the CP. Therefore, the CP motoneurons may not generate CP tone. Pharyngeal motoneurons often have a respiratory rhythm, but not a spontaneous background discharge. These motoneurons are topographically organized with other pharyngeal and laryngeal muscles and the striated muscle esophagus. The motoneurons of the CP are found in the nucleus ambiguus, and the innervation is ipsilateral for animal species in which the CP has a median raphe. ![]() Parasympathetic ganglia and various peptides (galanin, cGRP, VIP, neuropeptide Y, substance P, tyrosine hydroxylase) have been found in the CP, but their role in control of the CP is unknown. The GLN may be sensory the sympathetics may innervate the mucosa, blood vessels, and glands but no functional innervation by the RLN has been identified. Only the PE and SLN provide motor fibers to the CP. The CP is innervated by branches of the vagus nerves: pharyngoesophageal (PE), superior laryngeal (SLN), and recurrent laryngeal (RLN) glossopharyngeal (GPN) and cervical sympathetics. The high compliance of the CP allows it to be opened by distraction of other muscles (e.g., geniohyoideus) or increased intraluminal pressure. A passive tone in the CP is present and increases through all degrees of stretch. The optimum length of the CP for development of active tension is about 1.7 times resting length therefore, in some respects the CP acts more like cardiac than striated muscle. In humans and rats, but not other animals, the CP has no median raphe. The fibers may attach to the connective tissue framework, forming a muscular net. The CP is a striated muscle composed of variable-sized small (25-35 microm) muscle fibers that are primarily type I (slow twitch), highly oxidative, and contain abundant (40%) endomysial elastic connective tissue. ![]() All 3 muscles may at times function to maintain tone in the UES, but only the CP contracts and relaxes in all physiologic states consistent with the UES. The upper esophageal sphincter (UES) is composed of the cricopharyngeus (CP), thyropharyngeus (TP inferior pharyngeal constrictor in humans), and cranial cervical esophagus.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |