Final answer:
The muscles involved in the opening of the pharyngoesophageal segment include the pharyngeal constrictors and the cricopharyngeus muscle, with innervation primarily from the vagus nerve. This muscle relaxation, along with pharyngeal constrictions and laryngeal elevation, facilitates the passage of food from the pharynx into the esophagus, controlled by the medulla oblongata.
Step-by-step explanation:
The opening of the pharyngoesophageal segment, also known as the upper esophageal sphincter, is a critical event during swallowing or deglutition. This opening allows the passage of food from the pharynx to the esophagus. The musculature involved primarily includes the inferior pharyngeal constrictor muscle, particularly the cricopharyngeus part, that relaxes to open the sphincter. The innervation of these muscles is provided by branches of the vagus nerve, specifically the pharyngeal plexus for the superior, middle, and inferior pharyngeal constrictors, and the recurrent laryngeal nerve for the cricopharyngeus muscle.
The muscles of the pharynx that play a role in swallowing include the superior, middle, and inferior pharyngeal constrictor muscles. The action initiated by these muscles constricts the pharynx to push the food bolus towards the esophagus. In addition to muscle contraction, the opening of the upper esophageal sphincter is facilitated by the elevation of the larynx and the relaxation of the cricopharyngeus muscle.
Secretions from esophageal mucosa glands aid in lubricating the food bolus, minimizing friction and easing its passage through the esophagus. The intricate coordination of these actions is managed by the medulla oblongata, which controls this complex neuromuscular activity.