Killian's dehisence is seen in -

Ans. is 'c' i.e., Cricopharynx o Inferior constrictor muscle has two parts(i) Thyropharyngeous with oblique fibres, and (ii) Cricopharyngeous with transverse fibres.o Between these two parts of inferior constrictor exists a potential gap called Killan's dehiscence. It is also called the gateway to tear as perforation can occur at this site during esophagoscopy. It is also the site for herniation of pharyngeal mucosa in case of pharyngeal pouch.