Anatomy of Pharynx

Anatomy of Pharynx

1. ANATOMY OF PHARYNX Dr Harjitpal Singh Assistant Professor(ENT), Dr RKGMC, Hamirpur

2. PHARYNX It is a musculo fascial half-cylinder that links the oral and nasal cavities in the head to the larynx and esophagus in the neck . It is 12–14 cm long. It is attached above to the base of skull and continuous below , approximately at the level of the sixth cervical vertebra , with the top of esophagus . The width of pharynx is 3.5 cm at its base and this narrows to 1.5 cm at pharyngo -oesophageal junction, which is the narrowest part of digestive tract apart from the appendix. The pharyngeal cavity is a common pathway for ‘air ’and ‘ food’. (common passages of respiratory systems and digestive systems )

3. BOUNDARIES Superiorly - Base of skull including posterior part of body of sphenoid and the basilar part of the occipital bone. Inferiorly -pharynx continues with oesophagus at the level of 6 th cervical vertebra/ lower border of cricoid cartilage. Posteriorly - Prevertebral fascia separating it from cervical spine Anteriorly -Communication with Nasal cavity, Oral cavity, and Larynx .

4. BOUNDARIES e. On each side - It is attached to the M edial pterygoid plate P terygo mandibular raphe M andible Tongue H yoid bone T hyroid and cricoid cartilages Communication with middle ear via eustachian tube Styloid process and muscles attached to it Common, Internal and External Carotid Artery

5. DIVISIONS OF PHARYNX

6. DIVISIONS OF PHARYNX

7. DIVISIONS OF PHARYNX 1. NASOPHARYNX/ EPIPHARYNX From the base of skull above to the level of soft palate/ palatal sphincter (C2 level). 2. OROPHARYNX From palatal sphincter to the level of tip of epiglottis (C4 level). 3. LARYNGOPHARYNX/ HYPOPHARYNX From tip of epiglottis to the lower border of cricoid cartilage (lower border of C6).

8. STRUCTURE OF PHARYNX From within outwards it consists of four layers: Mucous membrane - It is ciliated columnar in the nasopharynx and stratified squamous elsewhere. Pharyngeal aponeurosis / Pharyngobasilar fascia -it is a fibrous layer lining the muscular coat. Muscular coat -consist of- Outer Circular Layer consist of 3 muscles- > Superior constrictor > Middle constrictor > Inferior constrictor Inner Longitudinal Layer consist of 3 muscles- > Stylopharyngeus > Salpingopharyngeus > Palatopharyngeus Buccopharyngeal fascia -covers the outer surface of constrictor muscles and in the upper part, prolonged forwards to cover the buccinator muscles .

9. STRUCTURE OF PHARYNX Base of skull Eustachian tube Mucous membrane Sub mucosa Pharyngobasilar fascia Muscular coat Buccopharyngeal fascia c. Inferior Constrictor Superior Constrictor Venous Plexus Middle Constrictor Sinus of Mo rg ag ni

10. P H A R YNGEAL W A L L

11. P H A R YNGEAL W A L L Mu sc le Posterior A t t a c h m ent Anterior A t t a c h m e n t Innervation Function Superior Co n s t r i c t or P h a r y ngeal raphe P terygomandibular raphe and adjent bone on the mandibular and pterygoid hamulus Vagus Nerve Co n str i c t i on of pharynx ★ Constrictor muscles*: Middle Co n s t r i c t or P h a r y n g e al raphe Upper margin of greaterbhorn of hyoid bone and adjent margins of lesser horn and stylohyoid ligament Vagus Nerve Co n str i c t i on of pharynx Inferior Co n s t r i c t or P h a r y n g e al raphe Cricoid cartilage,oblique line of thyroid crtilage, and a ligament that spans between these attachments and crosses the crocothyroid muscle Vagus Nerve Con s tr i c t i on of pharynx

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13. P H A R YNGEAL W A L L ★ Longitudinal muscles: Muscle O rigin Insertion Innervation Function Stylopharyngeus M iddle side of base of styloid process P haryngeal wall G l o s s o pha r y n geal nerve [ Ⅸ ] Elevation of the pharynx S a l p i ng p p h a r y nge u s I nferior aspect of pharyn- geal end of pharyngo- tympanic tube P haryngeal wall Va gus nerve [ Ⅹ ] Elevation of pharynx P a l a t o p ha r y n geus U pper surface of palatine aponeurosis P haryngeal wall Va gus nerve [ Ⅹ ] Elevation of phary- nx, and closure of the oropharyngeal isthmus

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15. FASC I A The pharyngeal fascia is separated into two layers: Buccopharyngeal Fascia : a thin layer, coats the outside of the muscular part of the wall. Pharyngobasilar Fascia : a much thicker layer, lines the inner surface

16. PHARYNGEAL SPACES There are two potential spaces in relation to the pharynx where abscesses can form. Retropharyngeal space , situated behind the pharynx. Parapharyngeal space , situated on the side of pharynx.

17. RETROPHARYNGEAL SPACE Between the buccopharyngeal fascia and prevertebral fascia, which extends from skull base to the upper part of posterior mediastinum (T 1 ,T 2 ), the bifurcation of trachea . Anteriorly by the posterior pharyngeal wall and buccopharyngeal fascia. Posteriorly by the cervical vertebra their muscles and fascia. One on each side, and separated from parapharyngeal space. It contains retropharyngeal lymph nodes and connective tissue.

18. RETROPHARYNGEAL SPACE

19. PARAPHARYNGEAL SPACE Situated on the side of pharynx. It is an inverted cone-shaped potential space that extends from the hyoid bone to the base of the skull. It’s occupied by the carotid vessels, Internal jugular vein, Deep cervical lymph nodes, The last four cranial nerves and Cervical sympathetic trunk.

20. 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- zenker’s diverticulum .

21. KILLIAN’S DEHISCENCE

22. WALDEYER’S RING Scattered throughout the pharynx in its subepithelial layer is the lymphoid tissue which is aggregated at places to form masses, collectively called Waldeyer’s ring. It has no afferents and efferents drain into cervical lymph nodes. 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).

23. WALDEYER’S RING

24. LYMPHATIC DRAINAGE Nasopharyngeal tonsil and some drainage from tubal tonsil is to Retropharyngeal nodes Oropharynx- Into Upper Jugular chain particularly Jugulodigastric ( tonsillar ) node. Soft palate, Lateral and Posterior pharyngeal walls and base of tongue- into retropharyngeal and parapharyngeal nodes.

25. LYMPHATIC DRAINAGE

26. BLOOD SUPPLY OF PHARYNX Ascending pharyngeal branch of external carotid Ascending palatine branch of facial (branch of external carotid) Greater palatine branch of maxillary. Venous drainage through plexus which drains to: superiorly : pterygoid plexus in the infratemporal fossa. inferiorly : the facial and internal jugular veins

27. NERVE SUPPLY OF PHARYNX Nerve supply is by pharyngeal plexus of nerves, which is formed by: • Branch of vagus (X nerve): Motor supply • Branches of glossopharyngeal (IX nerve): Sensory supply • Sympathetic plexus.

28. FUNCTIONS OF PHARYNX • Pharynx helps to provide immunity and formation of antibodies • It protects the lower respiratory tract • It forms plasma cells and lymphocytes • Acts as a warning to the body against infectious agents in air and food.

29. DIVISIONS OF PHARYNX

30. NASOPHARYNX (EPIPHARYNX) Nasopharynx is the uppermost part of the pharynx and therefore, also called epipharynx . It is also called third chamber of nose, which lies behind the nose and above the soft palate. Dimensions of nasopharynx are: 4 cm (height) × 4 cm (width) × 3 cm (length). Roof and posterior wall form a continuous sloping surface, which is formed mainly by the basilar part of occipital bone and to some extent, by body of sphenoid and arch of altas vertebra

31. NASOPHARYNX (EPIPHARYNX) 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.

32. NASOPHARYNX (EPIPHARYNX) Lateral wall has the eustachian tube opening, 1 to 1.25 cm (equidistant from all walls), behind and little below the posterior end of inferior turbinate. The opening is triangular in shape, bounded above and behind by tubal cartilage. Two folds of mucous membrane— salpingopharyngeal and salpingopalatine stretch from the opening of eustachian tube to the walls of pharynx and palate.

33. NASOPHARYNX (EPIPHARYNX) Torus tubarius is a mucosal elevation in the lateral aspect of the nasopharynx, formed by the underlying pharyngeal end of the cartilaginous portion of the Eustachian tube. The opening of the Eustachian tube is anterior to the torus tobarius . Above and behind the tubal elevation is a recess called fossa of Rosenmüller , which is the commonest site for origin of carcinoma.

34. FOSSA OF ROSENMÜLLER

35. NASOPHARYNX (EPIPHARYNX) Rathke’s pouch is seen as a dimple in the roof of nasopharynx. It is reminiscent of the buccal mucosal invagination, to form the anterior lobe of pituitary. A craniopharyngioma may arise from it.

36. RATHKE’S POUCH

37. NASOPHARYNX (EPIPHARYNX) Sinus of Morgagni : It is an interval between upper border of superior constrictor and base of skull and many structures pass upward from the pharynx. Structures passing through this gap- - Levator veli palatini -Ascending palatine artery -Tensor veli palatini -Eustachian tube Passavant ridge is an elevation formed by fibers of superior constrictor and palatopharyngeus , which helps in closing the nasopharynx from oropharynx with the posterior border of soft palate. It encircles the posterior and lateral walls of nasopharyngeal isthmus

38. NASOPHARYNGEAL TONSIL (ADENOIDS) It is a subepithelial collection of lymphoid tissue at the junction of roof and posterior wall of nasopharynx. It 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 by age of 11-12 years. No feeding blood vessel, supplied by adjacent plexus only. It has no capsule.

39. NASOPHARYNGEAL BURSA It is an epithelial-lined median recess found within the adenoid mass. It 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).

40. FUNCTIONS OF NASOPHARYNX Acts as a conduit for air, which has been warmed, humidified in the nose, towards its passage to the larynx and trachea. 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 posterior pharyngeal wall and the Passavant’s ridge helps to cut off nasopharynx from oropharynx. This function is important during swallowing, vomiting, gagging and speech. Acts as a resonating chamber during voice production. Voice disorders are seen in nasopharyngeal obstruction and velopharyngeal incompetence Acts as a drainage channel for the mucus secreted by nasal and nasopharyngeal glands.

41. OROPHARYNX

42. OROPHARYNX

43. OROPHARYNX

44. OROPHARYNX Anterior wall: upper part- deficient, communicates with oral cavity through Oropharyngeal isthmus/ Isthmus of Fauces . lower part - Base of tongue Lingual tonsils Valleculae Oropharyngeal isthmus: It is bounded by following structures: i. Above: Soft palate ii. Inferior: Dorsal surface of tongue iii. Lateral: On either side, by palatoglossal arch (anterior tonsillar pillar )

45. OROPHARYNX Base of tongue: It lies posterior to circumvallate papillae and insertion of palatoglossal muscle. Lingual tonsils: They are situated in the base of tongue. Valleculae : These cup-shaped spaces, one on each side, lie between the base of tongue and anterior surface of epiglottis . The median glossoepiglottic fold separates the two valleculae . Laterally they are bounded by the pharyngoepiglottic fold that is the upper limit of pyriform sinus of laryngopharynx .

46. OROPHARYNX Posterior wall: Body of second cervical and upper part of 3rd cervical vertebra . Lateral wall: - Palatine/ Faucial tonsil - Anterior pillar ( Palatoglossus muscle) - Posterior pillar( Palatopharyngeus muscle) 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

47. OROPHARYNX Superior : Anteriorly soft palate makes the roof of oropharynx . Posteriorly it communicates with nasopharynx through nasopharyngeal isthmus at the plane of hard palate and atlas vertebra . Inferior : It communicates with laryngopharynx at the plane of upper border of epiglottis and the pharyngoepiglottic folds and third cervical vertebra.

48. OROPHARYNX Lymphatic Drainage: 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

49. OROPHARYNX Functions of Oropharynx: „A common conduit for the passage of both air and food . Oropharyngeal phase of deglutition . Vocal tract for certain speech sounds . Taste : The base of tongue, soft palate, anterior pillars and posterior pharyngeal wall contain taste buds. „ Local defence and immunity.

50. PALATINE (FAUCIAL) TONSILS These are two masses of lymphoid tissue situated in the lateral wall of oropharynx. Each tonsil is placed between palatoglossal (anterior pillar) and palatopharyngeal fold (posterior pillar). Its medial surface is free and projects into the pharynx. Inferiorly , it extends into dorsum of tongue. Superiorly , it invades the soft palate. Plica triangularis is a free fold of mucous membrane extending from palatoglossal arch to the anteroinferior part of tonsil. Upper part of tonsil contains a deep cleft called crypta magna or intratonsillar cleft. Medial surface presents 12 to 15 orifices termed tonsillar crypts or pits, which extend into the whole substance of tonsil, branching inside the tonsil. These help in increasing the surface area.

51. PALATINE (FAUCIAL) TONSILS Lateral surface is covered by fibrous capsule separated from muscular wall formed by superior constrictor with styloglossus muscle on its lateral side. At antero inferior part, the capsule is firmly attached in the side of tongue. Tonsillar branch of facial artery with two veins enters the tonsil at this point. Paratonsillar veins descend from the soft palate onto the lateral aspect of capsule of tonsil and it is this vessel, which is responsible for massive bleeding, if injured during operation. Internal carotid artery lies 2.5 cm behind and lateral to the tonsil .

52. PALATINE (FAUCIAL) TONSILS The tonsillolingual sulcus, which separates the tonsil from tongue, is a common site for carcinoma . Supratonsillar fossa: The medial surface of tonsillar upper pole has a semi-lunar fold, which extends between anterior and posterior pillars. This pole encloses a potential space called supratonsillar fossa . Anterior tonsillar space: At the lower pole, which is attached to the tongue, a triangular fold of mucous membrane extends from anterior pillar to the anteroinferior part of tonsil and encloses a space called anterior tonsillar space.

53. PALATINE (FAUCIAL) TONSILS Tonsillar Crypts: The nonkeratinizing stratified squamous epithelium on medial surface of tonsil dips into the tonsillar mass and forms crypts (12–15). Openings of crypts can be seen on the medial surface of the tonsil . „ Crypta magna or intratonsillar cleft: It is situated near the upper part of tonsil. It is very large and deep and represents the ventral part of second pharyngeal pouch. Secondary crypts: They arise from the main crypts within the substance of tonsil. „ Content : Crypts may be filled with cheesy material, which consists of epithelial cells, bacteria and food debris and can be expressed out with pressure over the anterior tonsillar pillar .

54. PALATINE (FAUCIAL) TONSILS Capsule: Lateral surface of tonsil is covered by a well- defined fibrous capsule, which is separated from the bed of tonsil by loose areolar tissue that allows easy dissection in this plane during tonsillectomy . In this same plane occurs the peritonsillar abscess . Some fibers of palatoglossus and palatopharyngeus muscles are attached to tonsillar capsule.

55. PALATINE (FAUCIAL) TONSILS Blood Supply: Arterial supply: The main artery of tonsil is tonsillar branch of facial artery, which arises from external carotid artery. The other vessels, which supply the tonsil include: - Ascending pharyngeal artery from external carotid . - Ascending palatine , a branch of facial artery. - Dorsal lingual branch of lingual artery. - Descending palatine branch of maxillary artery.

56. PALATINE (FAUCIAL) TONSILS Blood Supply: The ascending pharyngeal, facial, lingual and maxillary arteries are all branches of external carotid artery that may need to be ligated in cases of refractory bleeding after tonsillectomy. Venous drainage: Veins from the tonsils drain into paratonsillar veins, which are present on lateral surface of tonsil and drain into the common facial vein and pharyngeal venous plexus.

57. BLOOD SUPPLY OF TONSIL

58. PALATINE (FAUCIAL) TONSILS Nerve Supply: Lesser palatine branches from sphenopalatine ganglion of maxillary division of trigeminal nerve (CN V2). „ Glossopharyngeal nerve (CN IX).

59. BED OF TONSIL

60. BED OF TONSIL The pharyngobasilar fascia, superior constrictor, buccopharyngeal fascia, glossopharyngeal nerve and styloglossus muscle form the bed of tonsil. Lateral to the superior constrictor muscles lies facial artery , submandibular salivary gland, posterior belly of digastric muscle, medial pterygoid muscle and the angle of mandible. Styloid process: The styloid process when enlarged may be palpated intraorally in the lower part of tonsillar fossa. The glossopharyngeal nerve and styloid process can be approached through the tonsil bed after tonsillectomy.

61. HYPOPHARYNX Hypopharynx extends from the tip of epiglottis or plane of hyoid bone to the lower border of cricoid cartilage, from 3rd to 6th cervical vertebrae. Clinically, it is subdivided into three regions: Pyriform sinus, Post cricoid region and Posterior pharyngeal wall.

62. HYPOPHARYNX

63. HYPOPHARYNX Inferior: It becomes continuous with esophagus at the level of lower border of cricoid cartilage and 6th cervical vertebra. Anterior: It communicates with larynx through the laryngeal inlet, which is bounded by the epiglottis , aryepiglottic folds and arytenoids . Inlet of larynx: i . Posterior surface of arytenoid cartilage ii . Posterior aspect of cricoid cartilage. Pyriform sinus lies on each side of laryngeal orifice.

64. HYPOPHARYNX Pyriform sinus (Fossa): Each pyriform fossa, which lies on either side of the larynx, forms the lateral channel for food . Foreign bodies may lodge in the pyriform fossa . Boundaries: Lateral : Thyrohyoid membrane and the thyroid cartilage . Medial : Aryepiglottic fold, posterolateral surface of arytenoid and cricoid cartilages. Superior : Pharyngoepiglottic fold separates it from vallecula . Inferior : It opens into the esophagus at the level of lower border of cricoid cartilage.

65. HYPOPHARYNX Pyriform sinus (Fossa): Internal laryngeal nerve runs submucosally in the lateral wall of the sinus and thus is easily accessible for local anaesthesia . It is also through this nerve that pain is referred to the ear in carcinoma of the pyriform sinus . It is most richly supplied by lymphatics , which come out of thyrohyoid membrane to end in upper deep cervical group of lymph nodes.

66. HYPOPHARYNX Post cricoid region: This anterior wall of laryngopharynx ( pharyngoesophageal junction) extends between the level of arytenoids and lower border of cricoid lamina. Post cricoid region is a common site for carcinoma , which usually develops from Plummer-Vinson syndrome especially in females . The sensory supply is the internal laryngeal nerve, a branch of the superior laryngeal nerve „.

67. HYPOPHARYNX Post cricoid region: A rich venous plexus in this region drains into superior laryngeal veins.  It is more prominent in infants and engorges during crying, known as the " postcricoid cushion " on laryngoscopy, perhaps as protection against emesis.

68. HYPOPHARYNX Posterior pharyngeal wall: Posterior pharyngeal wall extends from hyoid bone to the cricoarytenoid joint, between the apices of pyriform fosse.

69. FUNCTIONS OF HYPOPHARYNX Common pathway for air and food. „ Provides a vocal tract for resonance of certain speech sounds . „ Helps in deglutition. There is coordination between contraction of pharyngeal muscles and relaxation of cricopharyngeal sphincter at the upper end of oesophagus. Lack of this coordination, i.e. failure of cricopharyngeal sphincter to relax when pharyngeal muscles are contracting causes hypopharyngeal diverticulum.