anatomy and physiology of pharynx ( oro and naso and pharyngeal)

simple explanation

1. ANATOMY OF PHARYNX & ITS CONGENITAL ANOMALIES Presenters – Agraja & Ajith

2. Table of contents 01 02 Anatomy of pharynx Congenital anomalies

3. The pharynx is a cone-shaped fibromuscular tube forming the upper part of the air and food passages. 12-14 cm in length. Extends from the base of the skull to the lower border of the cricoid cartilage, where it becomes continuous with the oesophagus . The width of the pharynx is 3.5 cm at its base and this narrows to 1.5 cm at the pharyngo- oesophageal junction, which is the narrowest part of digestive tract apart from the appendix

4. Pharyngeal Spaces There are two potential spaces in relation to the pharynx where abscesses can form: 1. Retropharyngeal space , situated behind the pharynx and extending from the base of skull to the bifurcation of trachea. 2. Para pharyngeal space , situated on the side of pharynx. It contains carotid vessels, jugular vein, last four cranial nerves and cervical sympathetic chain .

5. STRUCTURE OF PHARYNGEAL WALL From within outwards it consists of four layers: 1. Mucous membrane 2. Pharyngeal aponeurosis ( pharyngobasilar fascia) 3. Muscular coat 4. Buccopharyngeal fascia

6. (a)Mucous Membrane Lines the pharyngeal cavity and is continuous with the mucous membrane of eustachian tubes, nasal cavities, mouth, larynx and oesophagus . Ciliated columnar epithelium in the nasopharynx and stratified squamous elsewhere. There are numerous mucous glands scattered in it.

7. Fibrous layer that lines the muscular coat and is particularly thick near the base of the skull but is thin and indistinct inferiorly. Fills up the gap left in the muscular coat near the base of the skull. (b)Pharyngeal Aponeurosis (Pharyngobasilar Fascia)

8. (c)Muscular coat It consists of two layers of muscles with three muscles in each layer: External layer: It contains superior, middle and inferior constrictor muscles. Internal layer: It contains stylopharyngeus, salpingopharyngeus and palatopharyngeus muscles.

9. (d) Buccopharyngeal fascia It covers the outer surface of the constrictor muscles. In the upper part, it is also prolonged forwards to cover the buccinator muscles. Above the upper border of the superior constrictor, it blends with pharyngeal aponeurosis.

10. KILLIAN’S DEHISCENCE Inferior constrictor muscle has two parts: thyropharyngeus with oblique fibres and cricopharyngeus with transverse fibres . 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 the site for herniation of pharyngeal mucosa in cases of pharyngeal pouch.

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12. WALDEYER’S RING Scattered throughout the pharynx in its sub-epithelial layer in the lymphoid tissue which is aggregated at places to form masses, collectively called Waldeyer’s ring. The masses are: 1. Nasopharyngeal tonsil or the adenoids 2. Palatine tonsils or simply the tonsils 3. Lingual tonsil 4. Tubal tonsils (in fossa of Rosenmüller ) 5. Lateral pharyngeal bands 6. Nodules (in posterior pharyngeal wall

13. The cavity of the pharynx can be divided into: 1.Nasopharynx 2.Oropharynx 3.Laryngopharynx

14. NASOPHARYNX Also called epipharynx . It lies behind the nasal cavities and extends from the base of skull to the soft palate or the level of the horizontal plane passing through the hard palate. Boundaries: Roof of the nasopharynx is formed by basisphenoid and basiocciput . Posterior wall is formed by arch of the atlas vertebra covered by prevertebral muscles and fascia. Both the roof and the posterior wall imperceptibly merge with each other.

15. NASOPHARYNX ( conti …) Floor is formed by the soft palate anteriorly but is deficient posteriorly. It is through this space, the nasopharyngeal isthmus , that the nasopharynx communicates with the oropharynx. Anterior wall is formed by posterior nasal apertures or choanae , separated from each other by the posterior border of the nasal septum. Posterior ends of nasal turbinates and meatuses are seen in this wall.

16. Lateral wall. Each lateral wall presents the pharyngeal opening of eustachian 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 the cartilage of the tube. Above and behind the tubal elevation is a recess called fossa of Rosenmüller , which is the commonest site for origin of carcino - ma (Figure 47.5). A ridge extends from the lower end of torus tubarius to the lateral pharyngeal wall and is called salpingopharyngeal fold It is raised by the corresponding muscle.

17. NASOPHARYNGEAL TONSIL (ADENOIDS) It is a sub-epithelial collection of lymphoid tissue at the junction of the roof and posterior wall of the nasopharynx and causes the overlying mucous membrane to be thrown into radiating folds. It increases in size up to the age of 6 years and then gradually atrophies.

18. NASOPHARYNGEAL BURSA It is an epithelial-lined median recess found within the adenoid mass and extends from pharyngeal mucosa to the periosteum of the basiocciput . It represents the attachment of notochord to the pharyngeal endoderm during embryonic life. When infected, it may be the cause of persistent postnasal discharge or crusting. Sometimes an abscess can form in the bursa ( Thornwaldt’s disease).

19. RATHKE’S POUCH It is represented clinically by a dimple above the adenoids and is reminiscent of the buccal mucosal invagination, to form the anterior lobe of pituitary. A craniopharyngioma may arise from it.

20. TUBAL TONSIL It is a collection of sub-epithelial lymphoid tissue situated at the tubal elevation. It is continuous with adenoid tissue and forms a part of the Waldeyer’s ring . When enlarged due to infection, it causes eustachian tube occlusion.

21. SINUS OF MORGAGNI It is a space between the base of the skull and upper free border of superior constrictor muscle . Through it enters ( i ) the eustachian tube, (ii) the levator veli palatini, (iii) tensor veli palatini (iv) ascending palatine artery —a branch of the facial artery.

22. PASSAVANT’S RIDGE It is a mucosal ridge raised by fibers of palatopharyngeus . It encircles the posterior and lateral walls of nasopharyngeal isthmus. Soft palate, during its contraction, makes firm contact with this ridge to cut off nasopharynx from the oropharynx during the deglutition or speech.

23. EPITHELIAL LINING OF NASOPHARYNX Functionally, nasopharynx is the posterior extension of nasal cavity. It is lined by pseudostratified ciliated columnar epithelium .

24. Lymphatic Drainage of Nasopharynx Lymphatics of the nasopharynx, including those of the adenoids and 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 the posterior triangle of the neck. Lymphatics of the nasopharynx may also cross midline to drain into contralateral lymph nodes.

25. FUNCTIONS OF NASOPHARYNX Acts as a conduit for air. Through the eustachian tube, it ventilates the middle ear and equalizes air pressure on both sides of tympanic membrane.  Elevation of the soft palate against the posterior pharyngeal wall and the Passavant’s ridge helps to cut off the nasopharynx from the oropharynx. Acts as a resonating chamber during voice production. Acts as a drainage channel for the mucus secreted by nasal and nasopharyngeal glands.

26. OROPHARYNX Oropharynx extends from the plane of hard palate above to the plane of hyoid bone below. It lies opposite the oral cavity with which it communicates through oropharyngeal isthmus. The latter is bounded above, by the soft palate; below, by the upper surface of tongue; and on either side, by palatoglossal arch (anterior pillar).

27. BOUNDARIES OF OROPHARYNX 1. Posterior wall Posterior pharyngeal wall & lies opposite the second and upper part of the third cervical vertebrae. 2. Anterior wall It is deficient, where oropharynx communicates with the oral cavity, but below it presents: (a) Base of tongue, posterior to circumvallate papillae. (b) Lingual tonsils, one on either side, situated in the base of tongue. (c) Valleculae : They are cup-shaped depressions lying between the base of tongue and anterior surface of epiglottis. Each is bounded medially by the median glossoepiglottic fold and laterally by pharyngoepiglottic fold

28. 3. Lateral wall. It presents: (a) Palatine (faucial) tonsil (b) Anterior pillar (palatoglossal arch) formed by the palatoglossus muscle. (c)Posterior pillar (palatopharyngeal arch) formed by the palatopharyngeus muscle.

29. 3. Lateral wall. Both anterior and posterior pillars diverge from the soft palate and enclose a triangular depression called tonsillar fossa in which is situated the palatine tonsil. Boundary between oropharynx above and the hypopharynx below is formed by upper border of epiglottis and the pharyngoepiglottic folds.

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

31. FUNCTIONS OF OROPHARYNX 1. It serves as a conduit for passage of air and food. 2. Helps in the pharyngeal phase of deglutition. 3. Forms part of vocal tract for certain speech sounds. 4. Helps in appreciation of the taste. Taste buds are present in the base of tongue, soft palate, anterior pillars and posterior pharyngeal wall. 5. Provides local defense and immunity against harmful intruders into the air and food passages.

32. HYPOPHARYNX (LARYNGOPHARYNX) The lowest part of the pharynx lies behind and partly on the sides of the larynx. Superior limit: Plane passing from the body of hyoid bone to the posterior pharyngeal wall Inferior limit: Lower border of cricoid cartilage where hypopharynx becomes continuous with esophagus. Clinically, it is subdivided into three regions—the pyriform sinus, post cricoid region and the posterior pharyngeal wall.

33. Pharynx opened from behind showing structures related to nasopharynx, oropharynx and laryngopharynx

34. Pyriform sinus (fossa) It lies on either side of the larynx and extends from pharyngoepiglottic fold to the upper end of esophagus. It is bounded laterally by the thyrohyoid membrane and the thyroid cartilage and medially by the aryepiglottic fold, posterolateral surfaces of arytenoid and cricoid cartilages . It forms the lateral channel for food.

35. Post cricoid region It is the part of the anterior wall of laryngopharynx between the upper and lower borders of cricoid lamina. It is a common site for carcinoma in females suffering from Plummer–Vinson syndrome.

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37. FUNCTIONS OF HYPOPHARYNX Laryngopharynx, like oropharynx, is a common pathway for air and food , provides a vocal tract for resonance of certain speech sounds and helps in deglutition . There is coordination between contraction of pharyngeal muscles and relaxation of cricopharyngeal sphincter at the upper end of esophagus.

38. 3 Pairs of Pharyngeal Constrictor Muscles

39. The arteries supplying the pharynx are almost the same as those supplying the tonsil. These are as follows: Ascending pharyngeal branch of the external carotid artery. Ascending palatine and tonsillar branches of the facial artery. 3. Dorsal lingual branches of the lingual artery. 4. The greater palatine, pharyngeal and pterygoid branches of the maxillary artery. The veins form a plexus on the posterolateral aspect of the pharynx. The plexus receives blood from the pharynx, the soft palate and the prevertebral region. It drains into the internal jugular and facial veins. BLOOD SUPPLY OF PHARYNX

40. The Relationship of the Pharynx to the Vertebral Column The pharynx is suspended from the base of the skull, is surprisingly free from the cervical column. This is reasonable, since the pharynx has no muscular attachments to the vertebrae. The mechanism responsible for velopharyngeal closure plays an extremely important role in speech production, and we ought to become familiar with it.

41. NASOPHARYNGEAL ANOMALIES   The nasopharynx is the embryonic intersection of the neural axis, alimentary, and respiratory tracts and is subject to a variety of congenital malformations. 1.Cystic lesions   Squamous-lined cysts in the midline of the nasopharynx are thought to arise from rests of Rathke pouch. Thornwaldt cysts  — Thornwaldt cysts are midline nasopharyngeal cysts that are thought to arise from obstruction at the Thornwaldt bursa , at the junction of the remnants of the notochord and the pharyngeal ectoderm.

42. First branchial pouch cysts : The first branchial pouch arises in the pharynx and extends laterally and cephalad to contact the first branchial cleft, forming the Eustachian tube. First branchial pouch cysts, resulting from errors in embryogenesis, may present in the lateral wall of the nasopharynx. Teratomas : Nasopharyngeal teratomas are principally solid masses composed of tissues derived from embryonic ectoderm, mesoderm, and endoderm. They can be benign or malignant. Teratomas that protrude from the mouth may be diagnosed on prenatal ultrasound and can cause upper airway obstruction in the neonate.

43. Heterotopic brain: Heterotopic brain can be located in the nasopharynx, even in the absence of an encephalocele. Surgical removal, usually by a trans palatal route, has been advocated for diagnosis and relief of upper airway obstruction. Ectopic pituitary : Rarely, functional pituitary tissue may present in the nasopharynx associated with failed closure of the craniopharyngeal canal. A small sella turcica and persistent craniopharyngeal canal can be demonstrated on T1-weighted MRI. MRI usually provides sufficient information to make the diagnosis, and biopsy generally should be avoided in this setting.

44. PHARYNGEAL ANOMALIES Second branchial pouch : Second branchial cleft and pouch anomalies are the most common branchial defects. The second branchial pouch originates in the oropharynx. Second branchial pouch anomalies typically present as masses in the oropharynx, which is the site of the palatine tonsils and the embryologic origin of the second branchial pouch. Cysts, sinuses, and fistulae of the second branchial cleft often can be tracked to the inferior tonsillar pole during resection. Pharyngeal and pharyngolaryngeal bands are a rare cause of obstruction of the upper aerodigestive tract. The associated lack of tonsillar and adenoid tissue in patients with these anomalies suggests that the anomalies may be caused by failed formation of the second branchial arch.

45. Third and fourth branchial arch  : The hypopharynx is the source for the third and fourth branchial pouches each arising in the pyriform sinus. Cysts of third or fourth branchial origin present as recurrent abscesses in the neck or simulate suppurative thyroiditis. Preoperative barium esophagography or direct laryngoscopy may reveal an outpouching of the pyriform apex. Failure to follow the tract all the way to the pyriform sinus may result in recurrent cervical infection.

46. In the newborn, adenoidal tissue is very sparse but by 3 month of age a half centimeter or so of tissue thickness is usually present. Thereafter, it increases even more, but there is considerable variability. If adenoidal tissue is not visualized after 6 months of age, the possibility of hypogammaglobulinemia should be considered. In some patients, the adenoidal tissue may extend into the retropharyngeal space, Such extensions may be nodular or smooth and may at first suggest a retropharyngeal mass or abscess.

47. References: Dhingra, P. L. (2013). Diseases of Ear, Nose and Throat. Chennai, Elsevier. • Hazarika, P., Nayak, D. R., Balakrishnan, R. (2010). Textbook of Ear, Nose, Throat and Head and Neck Surgery. New Delhi, CBS Publishers & Distributors. BD Chaurasia’s Human Anatomy, Regional and Applied Dissection and Clinical Volume 3 & Volume 4. Eighth Edition. CBS Publishers & Distributors. Willard R. Zemlin. Speech and Hearing Science, Anatomy & Physiology. Third Edition.Englewood Cliffs, New Jersey. Ann W.Kummer. Cleft Palate and Craniofacial Conditions. A Comprehensive Guide to Clinical Management. Fourth Edition. Jones & Barlett Learning. Congenital anomalies of the jaw, mouth, oral cavity, and pharynx (medilib.ir)