Ans. is `b' i.e., Nasopharynx Nasopharynx It is the pa of pharynx which lies behind the nose, above the level of soft palate. It differs from the oral (oropharynx) and laryngeal pa (hypopharynx) in that its cavity always remains patent. Boundaries of nasopharynx are : Roof:- Basisphenoid & basiocciput Floor :- Soft palate anteriorly; deficient posteriorly (nasopharyngeal isthmus) through which nasopharynx communicate with aropharynx. Posterior wall :- C 1 veebra with preveebral muscles and fascia. Anterior wall :- Choanae Lateral wall :- Pharyngeal opening of Eustachian tube is situated 1.25 cm behind the posterior end of inferior turbinate. It is bounded above and behind by an elevation called torus tubaris, behind which is a recess called fossa of rosenmullar. Shape and contents of nasopharynx Nasopharynx can be divided into two sections or chambers :- Upper chamber :- Large rectangular or ovoid (oval)"184) Lower chamber :- Tubular Contents of nasopharynx are :? Adenoids / Nasopharyngeal tonsil : Subepithelial collection of lymphoid tissue at the junction of roof and posterior wall of nasopharynx. Nasopharyngeal Bursa : Epithelial lined median recess extending from pharyngeal mucosa to the periosteum of basiocciput. Represents attachment of notochord to pharyngeal endoderm during embryonic life. Abscess of this bursa is called as Thornwald's disease. Rathke pouch : Reminiscent of buccal mucosal invagination to form the anterior lobe of pituitary. Represented by a dimple above adenoids. Sinus of Morgagni : Space between base of skull and upper border of superior constrictor muscle. Through this pass auditory tube, levator palati muscle and ascending palatine aery.