Anatomy of pharynx

This is a basic idea about pharynx that we need in dealing with clinical portion of throat in ENT

1. Anatomy Of Pharynx -6 th semester m.b.b.s Nischal shrestha

2. Soft palate Separates nasopharynx from oropharynx Has 2 surfaces –anterior & posterior ; 2 borders- superior & inferior Inferior border is free . From its middle, there hangs a conical projection called uvula ( latin = small grape) From each side of base of uvula, 2 curved folds of mucous membranes extend laterally & downwards. Anterior fold/ pillar contains palatoglossus muscle. Posterior fold/ pillar contains palatopharyngeus muscle. NOTE : Soft palate is a fold of mucous membrane that contains palatine aponeurosis which is flattened tendon of tensor veli palatine.

3. Muscles Of Soft Palate Tensor veli palatini Levator veli palatini Muscular uvula Palatoglossus Palatopharyngeus

4. Passavant’s Muscle Some of the upper fibres of palatopharyngeus pass circularly deep to mucous membrane of pharynx and form a sphincter that lies internal to superior constrictor. These fibres constitute passavant’s muscle. In mammals with acute sense of smell, epiglottis lies above soft palate and larynx lies at higher level than man. In man, larynx descends downwards and pull sphincter downwards . However, some fibres of sphincter are left behind and form a sphincter inner to superior constrictor at the level of hard palate. These fibres constitute Passavant’s muscle. This muscle is best developed in cases of cleft palate as this compensates to some extent for deficiency of palate.

5. Passavant’s Ridge Passavant’s muscle on contraction raises a ridge called the Passaavnt’s ridge on the posterior wall of nasopharynx. When soft palate is elevated it comes in contact with this ridge , the two together closing pharyngeal isthmus between nasopharynx and oropharynx so that food doesn’t enter nose. By varying degree of closure of this isthmus, voice quality can be modified.

6. Pharynx( latin =throat) Conical fibromucular tube forming upper part of air & food passage 12-14 cm long 3.5 cm at its base and 1.5 cm at pharyngo- oesopharyngeal junction( narrowest part of GI tract except for appendix) Extending from base of skull ( basiocciput & basisphenoid ) to lower border of cricoid cartilage anteriorly & inferior border of C6 vertebra posteriorly

7. Structure of Pharyngeal wall (from within outwards) Mucous membrane : lines pharyngeal cavity. Epithelium is ciliated columnar in nasopharynx and stratified squamous elsewhere. Pharyngobasilar Fascia : fills the gap left in muscular coat near base of skull. Muscular coat : consists of 2 layers of muscles with 3 muscles in each group Outer circular layer ; contains superior, middle & inferior constrictor muscles Inner longitudinal ; stylopharyngeus , salpingopharyngeus , palatopharyngeus 4 . Buccopharyngeal Fascia : covers outer surface of constrictor muscles & in upper part , it also prolongs forward to cover buccinators muscles.

8. Constrictor muscles 3 constrictors are so arranged that inferior overlaps middle which in turn overlaps superior. The fibres of superior constrictor reach the base of skull posteriorly in the midline. On the sides , there is a gap between base of skull and upper edge of constrictor. This gap is closed by upper strong part of pharyngobasilar fascia. The large gap is semilunar and called SINUS OF MORGAGNI . The structure passing through this gap are: Auditory tube Levator veli palatini The ascending palatine artery Palatine branch of ascending pharyngeal artery

9. Killian’s Dehiscence The inferior constrictor consists of 2 parts : one part thyropharyngeus with oblique fibres ,arises from thyroid cartilage and other with transverse fibres , cricopharygeus arises from cricoid cartilage. Between these two parts exists a potential gap called killian’s dehiscence . It is also called ‘gateway of tears’ as perforation can occur at this site during oesophagoscopy . This is also a site for herniation of pharyngeal mucosa in case of pharyngeal pouch k/a pharyngeal diverticula . Such diverticula are normal in pig. It is d/t neuromuscular incoordination which may b d/t fact different nerves supply 2 parts of inferior constrictor.

10. … Propulsive thyropharyngeus is supplied by pharyngeal plexus,& sphincteric cricopharyngeus by recurrent laryngeal nerve. If the cricopharyngeus fails to relax when thyropharyngeus contracts, bolus of food is pushed backwards, and tends to produce a diverticulum.

11. Longitudinal muscle coat Stylopharyngeus arises from styloid process and passes down through gap between superior & middle constrictors. Fibres of palatopharyngeus descend down from sides of palate. Salpingopharygeus descends from auditory tube .

12. Divisions Of Pharynx Anatomically , pharynx is divided into 3 parts: Nasopharynx (nasal part) / epipharynx ; extends from base of skull to soft palate or level of horizontal plane passing through hard palate Oropharynx (oral part) ; from hard palate to hyoid bone Laryngopharynx/ hypopharynx (laryngeal part) ; from upper border of epiglottis to lower border of cricoid cartilage

13. Why we study pharynx parts? There we find tonsils. They are passage of food and air NOTE : laryngopharynx is actually not hypopharynx. Laryngopharynx consists of larynx in front and hypopharynx behind so that trachea lies below larynx and esophagus lies below hypopharynx .

14. Mucosal layer importance As this layer comes into direct contact with food , air etc. so it must be good defensive layer. So we get MALT (mucosa associated lymphoid tissue ) in digestive tract, aggregated lymphoid nodules ( peyer’s patches & appendix) in small intestine. In the same way we do have tonsils in our pharyngeal wall.( 5 sets ) >1 pharyngeal tonsil >2 palatine tonsil > 2 lingual tonsil

15. Nasopharynx Roof is formed by basisphenoid and basiocciput Posterior wall is formed by arch of atlas covered by prevertebral muscles and fascia Floor is formed by soft palate anteriorly but is deficient posteriorly Anterior wall is formed by posterior nasal aperture or choana

16. Lateral wall of nasopharynx Each lateral wall presents the pharyngeal opening of E ustachian tube situated 1.25 cm behind the posterior end of inferior turbinate . It is bounded above and behind by an elevation called TORUS TUBARIUS raised by cartilage of tube. Above and behind the tubal elevation is a recess called FOSSA OF ROSENMULLER , which is commonest site for origin of carcinoma . A ridge extends from lower end of lateral pharyngeal wall & is called SALPINGOPHARYNGEAL FOLD . It is raised by corresponding muscle.

17. Nasopharyngeal tonsil (Adenoids) Is a subepithelial collection of lymphoid tissue at the junction of roof & posterior wall of nasopharynx Radiating folds seen Increases in size upto age of 6 and then gradually atrophies upto 10 may be

18. Nasopharyngeal Bursa Is epithelial- lined median recess found within adenoids and extends from pharyngeal mucosa to periosteum of basiocciput . It represents the attachment of notochord to pharyngeal endoderm during embryonic life When infected, it may be cause of persistent postnasal discharge or crusting Sometimes an abscess can form in the bursa ( THORNWALDT’S DISEASE )

19. Rathke’s Pouch Represented clinically by a dimple above the adenoids and is remnascent of buccal mucosa invagination, to form anterior lobe of pituitary. A craniopharyngioma may arise from it.

20. Tubal Tonsil Collection of subepithelial lymphoid tissue situated at tubal elevation When enlarged due to infection , it causes occlusion of Eustachian tube.

21. Epithelial lining of Nasopharynx Lined by pseudostratified ciliated columnar epithelium

22. Lymphatic Drainage Lymphatics of nasopharynx including adenoids & pharyngeal end of Eustachian tube drain into upper deep cervical jugular nodes either directly or indirectly through retropharyngeal and parapharyngeal lymph nodes. They also drain into spinal accessory chain of nodes in posterior triangle of neck Lymphatics may also cross midline to drain into contralateral lymph node

23. Lymphatic Drainage Lymphatics of nasopharynx including adenoids & pharyngeal end of Eustachian tube drain into upper deep cervical jugular nodes either directly or indirectly through retropharyngeal and parapharyngeal lymph nodes. They also drain into spinal accessory chain of nodes in posterior triangle of neck Lymphatics may also cross midline to drain into contralateral lymph node

24. Pharyngeal Spaces Retropharyngeal Space : situated behind pharynx and extending from base of skull to bifurcation of trachea Parapharyngeal Space: situated on the side of pharynx. It contains carotid vessels, jugular vein, last 4 cranial nerves and cervical sympathetic chain.

25. Oropharynx Oropharyngeal isthmus is bounded above by soft palate, below by upper surface of tongue and on either side by palatoglossal arch ( anterior pillar) Boundaries Posterior wall : related to retropharyngeal space and lies opposite the second and upper part of 3 rd cervical vertebrate. Anterior wall : deficient above where it communicates with oral cavity, but below it presents; Base of tongue , posterior to circumvallate papillae Lingual tonsil, 1 on either side , situated in base of tongue Vallecula ; cup shaped depressions lying between base of tongue and anterior surface of epiglottis. They are seat of retention cysts.

26. Lateral Wall It presents Palatine ( faucial ) tonsil Anterior pillar ( palatoglossal arch) formed by palatoglossal muscle Posterior pillar ( palatopharyngeal arch) formed by palatopharyngeus muscle Both diverge from soft palate and enclose a triangular depression called tonsillar fossa which contains palatine tonsil Boundary between oropharynx above and hypopharynx below is formed by upper border of epiglottis and pharyngoepiglottic folds.

27. Lymphatic Drainage Drain into upper jugular chain particularly the jugulodigastric ( tonsillar) node . The soft palate , lateral and posterior pharyngeal walls and base of tongue also drain into retropharyngeal and parapharyngeal nodes and from there to jugulodigastric and posterior cervical group.

28. Hypopharynx (laryngopharynx) Anterior wall Inlet of larynx Posterior surfaces of cricoid and arytenoid cartilages Posterior wall is supported mainly by 4 th and 5 th cervical vertebrae & partly by 3 rd and 6 th . In this region post. Wall is formed by superior, middle & inferior constrictors Lateral wall produces a depression called piriform fossa , on each side of inlet of larynx Clinically subdivided into 3 regions- pyriform sinus, postcricoid region and posterior pharyngeal wall

29. Piriform Fossa/Sinus/Recess (smuggler’s fossa) Bounded medially by aryepiglottic fold, posterolateral surfaces of arytenoid & cricoid cartilages Laterally by thyroid cartilage & thyrohyoid membrane Piriform= pear shaped In submucosa of fossa lies internal laryngeal nerve branch of superior laryngeal nerve & thus is accessible for local anaesthesia . Also removal of foreign bodies from fossa may damage nerve leading to anesthesia in supraglottic part of larynx Pooling of saliva occurs if there is any obstruction in food passage (Jackson’s sign) It is a hidden area. Any malignancy in this area will initially cause fewer symptoms & has tendency to present late Area is rich in lymphatics  drain into upper deep cervical group of lymph node . Malignancy here has tendency for distant metastasis

30. Postcricoid Region Part of anterior wall of laryngopharynx between upper & lower borders of cricoid lamina. Common site for carcinoma in female suffering from Plummer-Vinson syndrome

31. Posterior Pharyngeal Wall Extends from level of hyoid bone to level of cricoarytenoid joint