Which condition is characterized by a diverticulum in the pharynx?

Zenker's diverticulum is a condition characterized by the development of a pharyngeal diverticulum, which is an outpouching that occurs just above the upper esophageal sphincter at the level of the cricopharyngeus muscle. This diverticulum is a result of an imbalance between the pressure in the esophagus and muscle relaxation, leading to the herniation of the mucosal layer through the muscle wall.

Patients with Zenker's diverticulum often present with symptoms such as difficulty swallowing (dysphagia), regurgitation of undigested food, halitosis (bad breath) due to food decomposition in the diverticulum, and sometimes aspiration pneumonia due to regurgitation.

In contrast, other options listed refer to diverticula located in different parts of the gastrointestinal tract. Meckel's diverticulum occurs in the ileum and is a remnant of the omphalomesenteric duct, gastric diverticulum refers to outpouchings in the stomach wall, while a rectal diverticulum would be associated with diverticula in the lower gastrointestinal tract. Therefore, the unique anatomical location and formation mechanism of Zenker's diverticulum distinctly identify it as the correct answer in this context.