Pharynx Complete detail only in one.pptx

Pharynx

1. Pharynx

2. As per: Competency based Undergraduate curriculum 1 AN36.3: Describe the boundaries and clinical significance of pyriform fossa. AN36.4: Describe the anatomical basis …, adenoids … AN36.5: Describe the clinical significance of Killian’s dehiscence. ( Note : Pyriform is also spelled as piriform.) Medical Council of India, Competency based Undergraduate curriculum for the Indian Medical Graduate, 2018. Vol. 1; pg 1-80. Human Anatomy/Yogesh Sontakke 2

3. • Pharynx is a wide, funnel-shaped musculomembranous tube ( pharynx = throat, in Latin). It is situated behind the nose, mouth and larynx. It extends vertically from the base of the skull to the esophagus. It acts as a common passage for food and air (Flowchart 30.1). Measurements • Length : 12–14 cm • Width : – About 3.5 cm (widest) in the uppermost part of pharynx (nasopharynx) – 1.5 cm (narrowest) at the pharyngoesophageal junction. Location • The pharynx is situated behind the nose, mouth, and larynx. The pharynx extends from the base of the skull to the lower border of cricoid cartilage (lower border of C6 vertebra) where it continues as esophagus. PHARYNX

4. Boundaries and External Relations Superiorly 1. Base of the skull 2. Posterior part of body of sphenoid 3. Basilar part of occipital bone Inferiorly 1. Esophagus Posteriorly 1. Prevertebral fascia 2. C1 to C6 cervical vertebrae Anteriorly 1. Communications with the nose, mouth and larynx. Laterally 1. Auditory tube 2. Styloid apparatus 3. Carotid arteries: Common, internal, and external 4. Last four cranial nerves. Subdivisions • The cavity of the pharynx is divided into three parts as follows (Fig. 30.1): 1. Nasopharynx – lies behind the nasal cavity 2. Oropharynx – lies behind the oral cavity 3. Laryngopharynx – lies behind the larynx. PHARYNX

5. • The nosopharynx or epipharynx is situated behind the nasal cavity and above the soft palate. Boundaries Roof • Body of sphenoid • Basilar part of occipital bone Floor • Soft palate • Pharyngeal isthmus (communication with oropharynx) Anterior wall • Posterior nasal aperture (communication with nasal cavity) Posterior wall • Anterior arch of C1 vertebra Lateral wall • Medial pterygoid palate of sphenoid • Note : Roof and posterior wall of pharynx form a continuous slope. NASOPHARYNX

6. Features The nasopharynx shows the following features (Figs 30.2 to 30.4, Flowchart 30.2): 1. Nasopharyngeal or pharyngeal tonsil ( adenoid ) : It is a median conical mass formed by aggregation of lymphoid tissue beneath the mucous membrane. It is prominent in children and atrophies in adults. It projects forward from the junction of roof and the posterior wall of pharynx. 2. Nasopharyngeal bursa ( pouch of Luschka ) : It is mucous diverticulum that extends upward into the substance of nasopharyngeal tonsil from its apex. [Hubert van Luschka, German anatomist, 1820–1875] . 3. Pharyngeal opening of auditory tube : It lies in the lateral wall of nasopharynx 1.25 cm behind the inferior nasal concha. It is a triangular opening. 4. Tubal tonsils : The upper and posterior margin of pharyngeal opening of auditory tube are elevated by aggregation of lymphatic follicles forming tubal tonsil. 5. Two mucous folds : There are two mucous folds that extend from tubal tonsil as follows: A. Salpingopharyngeal fold : It passes vertically downward on the lateral wall of pharynx. It contains salpingopharyngeus muscle . B. Salpingopalatine fold : It extends downward and forward to the soft palate. It contains the levator veli palatini muscle. • Pharyngeal recess ( fossa of Rosenmüller ) : It is a deep depression behind the tubal elevation. NASOPHARYNX

7. • The nasopharynx, similar to the nasal cavity, is lined by pseudostratified ciliated columnar epithelium. • The nasopharynx is the widest and noncollapsible part of the pharynx. Some Interesting Facts

8. Clinical Integration • Adenoid : Clinically, the enlarged pharyngeal tonsil is called adenoid . It may obstruct the airway passage at the nasopharynx that results in ‘ oral breathing ’. It may cause spread of infection to the middle ear through auditory tube (Fig. 30.5). • Adenoidectomy : It is a surgical removal of adenoid.

9. • The oropharynx lies behind the oral cavity. It extends from the pharyngeal isthmus above to the upper border of epiglottis below. Boundaries Roof 1. Soft palate 2. Pharyngeal isthmus through which oropharynx communicates with the nasopharynx Floor 1. Posterior one-third of tongue 2. Interval between tongue and epiglottis Anteriorly 1. Oropharyngeal isthmus through which oropharynx communicates with oral cavity 2. Posterior one-third of tongue Posteriorly 1. Bodies of C2 and C3 vertebrae Lateral wall 1. Pterygomandibular raphe 2. Mandible 3. Tongue 4. Hyoid bone. OROPHARYNX

10. The oropharynx presents the following features (Figs 30.2 and 30.3): 1. Palatine tonsils : There is one palatine tonsil on each side in the lateral wall of oropharynx. It is located into a tonsillar fossa . 2. Tonsillar fossa : It is a triangular depression in the lateral wall of oropharynx. It lodges palatine tonsil. Boundaries of tonsillar fossa: Anterior : Palatoglossal arch Posterior : Palatopharyngeal arch Inferiorly : Posterior one-third of tongue Apex : Meeting point of anterior and posterior margins at the soft palate. 3. Palatoglossal arch : It is a mucosal fold that runs downward and forward from the palate to the lateral margins of the tongue. It contains palatoglossus muscle. 4. Palatopharyngeal arch : It is a mucosal fold that runs downward and backward to the pharyngeal wall. It contains palatopharyngeus muscle. 5. Lingual tonsils : These are mucosal aggregation of lymphoid follicles on the dorsum of posterior onethird of tongue. 6. Median and lateral glossoepiglottic folds connect the anterior surface and edges of epiglottis, respectively, to the tongue. 7. Epiglottic valleculae are shallow fossae between the median and lateral glossoepiglottic folds. OROPHARYNX

11. Box 30.1: Oropharyngeal isthmus • It is an arched opening between two palatoglossal folds through which the oral cavity communicates with the oropharynx. Boundaries (Fig. 30.6) Superiorly : Soft palate Inferiorly : Dorsal surface of posterior one-third of tongue Laterally : Palatoglossal arch one on each side. Functions • The oropharyngeal isthmus closes during deglutition to prevent the regurgitation of food from oropharynx to mouth.

12. • The laryngopharynx lies behind the laryngeal inlet . It extends from the upper border of epiglottis to the lower border of cricoid cartilage. Boundaries Superiorly : Oropharynx Inferiorly : Esophagus Anteriorly : 1. Laryngeal inlet 2. Posterior surface of larynx Posteriorly : Bodies C3–C5 vertebrae Laterally : Thyroid cartilage and thyrohyoid membrane. Features The laryngopharynx presents the following features (Figs 30.2 and 30.3): 1. Laryngeal inlet : Inferiorly, the laryngopharynx communicates with the laryngeal cavity through laryngeal inlet. It is bounded superiorly by upper margin of epiglottis, below and behind by interarytenoid mucous folds, and on each side by aryepiglottic fold . 2. Piriform fossa : See Box 30.2. LARYNGOPHARYNX

13. Box 30.2: Piriform (pyriform) fossa Q. Write a short note on piriform fossa. • It is also called piriform sinus or smuggler’s fossa . • It is a depression in the lateral wall of laryngopharynx, one on each side of laryngeal inlet (Fig. 30.7). Boundaries Medially : Aryepiglottic fold Laterally : Mucosa covering the medial surface of lamina of thyroid cartilage and thyrohyoid membrane. Above : Lateral glossoepiglottic folds separate the piriform fossa from vallecula. Relations • Internal laryngeal nerve and superior laryngeal vessels pierce the thyrohyoid membrane and transverse underneath the mucous membranes of the floor of piriform fossa. Morphology • The piriform fossa is deep in ruminating animals, and it acts as a lateral food channel to convey the bolus of food during deglutition by the side of closed laryngeal inlet.

14. 1. Smugglers fossa : Sometimes, the piriform fossa is artificially deepened by smugglers and used to hide diamonds. 2. Perforation : Piriform fossa may get perforated during endoscopy. 3. Damage to internal laryngeal nerve : Accidently, ingested foreign bodies may get lodged into piriform fossa. During their removable, the internal laryngeal nerve may get damaged. Clinical Integration

15. STRUCTURE OF PHARYNX • The wall of pharynx consists of the following layers from within outward (Fig. 30.8): 1. Mucosa 2. Submucosa 3. Pharyngobasilar fascia or pharyngeal aponeurosis 4. Muscle coat 5. Buccopharyngeal fascia or loose areolar sheath.

16. • Mucous membrane of pharynx : It contains considerable amount of elastic fibers. The pharynx is lined by non-keratinized stratified epithelium except nasopharynx which is lined by pseudostratified ciliated columnar epithelium . • Tonsils : The subepithelial collections of lymphoid follicles produce Waldeyer’s ring that has pharyngeal tonsil, tubal tonsil, palatine tonsils, and lingual tonsils. • Submucosa : In the upper part of pharynx, it condenses to form pharyngobasilar fascia . • Pharyngobasilar fascia or pharyngeal aponeurosis : It is a fibrous thickening of pharyngeal submucosa. It lines the pharyngeal muscles internally. It is thicker near the base of skull where it fills the gap between the skull and upper border of superior constrictor muscles. This gap is called sinus of Morgagni . Posteriorly, the pharyngobasilar fascia forms pharyngeal raphe . • Muscle coat : The pharynx consists of two layers of striated muscle. a. Outer layer of three pairs of constrictor muscles. b. Inner layer of three pairs of longitudinal muscles. • Buccopharyngeal fascia : It is a layer of loose areolar tissue. It covers the outer surface of pharynx. Anteriorly, it merges with buccopharyngeal fascia.In the upper part of pharynx, it merges with the pharyngobasilar fascia and closes sinus of Morgagni. Some Interesting Facts

17. • The pharynx consists of the striated muscles which are arranged in two layers as follows (Figs 30.9 and 30.10, Flowchart 30.3): 1. Outer circular layer: It consists of three pairs of constrictor muscles: Superior, middle, and inferior. 2. Inner longitudinal layer: It consists of three pairs of muscle—stylopharyngeus, palatopharyngeus , and salpingopharyngeus . Constrictors of Pharynx • The constrictors of pharynx form the lateral and posterior wall of the pharynx. They originate anteriorly and pass posteromedially to get inserted on midline fibrous pharyngeal raphe . • Arrangements : The constrictors are arranged in a specific manner so that the lower fibers of superior constrictor are overlapped by upper fibers of middle constrictor and lower fibers of middle constrictor are overlapped by the upper fibers of inferior constrictor muscle. • There are four gaps related to the constrictors: 1. Above the superior constrictor 2. In between superior and middle constrictor 3. In between middle and inferior constrictors 4. Below the inferior constrictor. • These gaps give passage to the structures mentioned in Box 30.3. • Embryology : The constrictors of pharynx develop from 4th and 6th pharyngeal arches, hence supplied by cranial part of accessory nerve through the vagus. • The detail of the constrictors are given in Table 30.1. • Actions of constrictors : All the constrictor muscles help in deglutination. • Nerve supply : All the constrictors of pharynx are supplied by fibers from cranial part of accessory through pharyngeal branch of vagus. Note : Thyropharyngeus is supplied by pharyngeal plexus and external laryngeal branch of vagus nerve and cricopharyngeus is supplied by recurrent laryngeal branch of vagus nerve. MUSCLES OF PHARYNX

18. Table 30.1: Constrictor muscles of pharynx Muscle Origin Insertion Superior constrictor Pterygoid hamulus Pterygomandibular raphe Medial surface of mandible at the posterior end of mylohyoid line Side of posterior part of the tongue Pharyngeal tubercle on the base of skull Median fibrous raphe Middle constrictor Lower part of stylohyoid ligament Lesser cornua of hyoid bone Upper border of greater cornua of hyoid bone Median fibrous raphe Inferior constrictor 1. Thyropharyngeus 2. Cricopharyngeus Oblique line on lamina of thyroid cartilage Tendinous band between inferior tubercle of thyroid cartilage and cricoid cartilage Cricoid cartilage Median fibrous raphe Median fibrous raphe

19. Box 30.3: Gaps in pharyngeal wall • There are gaps in the constrictor muscles of pharyngeal wall as follows (Figs 30.11 and 30.12): Gap Structures passing through them 1. Gap between the base of skull and upper border of superior constrictor [called sinus of Morgagni] 1. Auditory tube 2. Levator veli palatini 3. Ascending palatine artery 4. Palatine branch of ascending pharyngeal artery 2. Between superior and middle constrictors 1. Stylopharyngeus muscle 2. Glossopharyngeal nerve 3. Between middle and inferior constrictor 1. Internal laryngeal nerve 2. Superior laryngeal vessels 4. Between the lower border of inferior constrictor and esophagus 1. Recurrent laryngeal nerve 2. Inferior laryngeal vessels

20. Box 30.4: Killian Dehiscence and Zenker’s diverticulum • Zenker’s diverticulum ( hypopharyngeal diverticulum ) or pharyngeal pouch is a diverticulum of pharyngeal mucosa, just above the cricopharyngeus muscle [Friedrich Albert von Zenker, German Pathologist, 1825–1898] (Fig. 30.13, Flowchart 30.4). • Killian dehiscence is a weak posterior part of the pharyngeal wall that lies between cricopharyngeus and thyropharyngeus parts of the inferior constrictor of pharynx. • In case of the excessive pressure within the lower part of pharynx, the mucosa of the pharyngeal wall balloon out through the Killian dehiscence to form Zenker’s diverticulum [Gustav Killian, German laryngologist, 1860–1921]. It may result due to neuromuscular incoordination or spasm of cricopharyngeus muscle. It occurs because the two parts of the inferior constrictor have different nerve supplies. The propulsive thyropharyngeus is supplied by the pharyngeal plexus and the sphincteric cricopharyngeus is supplied by the recurrent laryngeal nerve. In neuromuscular incoordination, if the cricopharyngeus fails to relax when the thyropharyngeus contracts, the bolus of food is pushed backward and tends to produce a diverticulum. • Signs and symptoms of Zenker’s diverticulum: 1. Asymptomatic 2. Dysphagia (difficulty in swallowing) 3. Regurgitation of food 4. Cough. • Diagnosis 1. Barium swallow radiography 2. Endoscopy.

21. Longitudinal Muscles of Pharynx • The wall of pharynx has three pairs of longitudinal muscles (Fig. 30.14, Flowchart 30.5): 1. Stylopharyngeus 2. Palatopharyngeus 3. Salpingopharyngeus . • All these muscles are inserted on the posterior border of lamina of thyroid cartilage . • These muscles elevate the larynx and shorten the pharynx during swallowing. Their details are listed in Table 30.2.

22. Table 12.1: Muscles of mastication Muscle Origin Insertion Nerve supply Stylopharyngeus Styloid process Posterior border of lamina of thyroid cartilage Glossopharyngeal nerve Palatopharyngeus Arises by two fasciculi (anterior and posterior) from upper surface of palatine aponeurosis Posterior border of lamina of thyroid cartilage Few fibers run posteriorly to form Passavant’s ridge Cranial root of 11th cranial nerve Salpingopharyngeus Lower part of the cartilage of auditory tube Posterior border of lamina of thyroid cartilage Cranial root of 11th cranial nerve

23. Nerve supply • The pharynx is supplied by pharyngeal plexus which is formed by 1. Pharyngeal branch of vagus carrying fibers of the cranial accessory nerve 2. Pharyngeal branches of glossopharyngeal nerve 3. Pharyngeal branches of superior cervical sympathetic ganglion. • Motor supply : All the muscles of the pharynx are supplied by cranial root of accessory nerve through vagus nerve except stylopharyngeus which is supplied by glossopharyngeal nerve. Note : Inferior constrictor receives additional supply from recurrent laryngeal nerve. • Sensory supply : 1. Glossopharyngeal nerve 2. Vagus 3. Pterygopalatine ganglion (maxillary nerve) 4. Lesser palatine nerves. • Taste sensation from vallecula and epiglottis is carried by internal laryngeal branch of vagus. • Secretomotor supply : Parasympathetic fibers from lesser palatine branches of pterygopalatine ganglion are secretomotor for the mucous glands of pharynx. Arterial supply • Pharynx is supplied by the following arteries: 1. Ascending pharyngeal branches of external carotid artery 2. Ascending palatine and tonsillar branches of facial artery 3. Dorsal lingual branches of lingual artery 4. Greater palatine and pharyngeal branches of maxillary artery. Venous drainage • Pharyngeal venous plexus : It drains the venous blood from the pharynx. It is situated on the posterolateral aspect of the pharynx over the middle constrictor. Pharyngeal plexus drains into the internal jugular and facial veins. Lymphatic drainage • The lymphatics from the pharynx drain into the retropharyngeal and deep cervical nodes. NERVE SUPPLY, BLOOD SUPPLY AND LYMPHATIC DRAINAGE OF PHARYNX

24. Q. Write a short note on deglutition or swallowing. • Definition : Deglutition is a coordinated process by which the food is transferred from the mouth to the stomach. Stages of deglutition • There are three stages of deglutition as follows: 1. First stage – in the mouth – voluntary 2. Second stage – in the pharynx – involuntary 3. Third stage – in the esophagus – involuntary. First stage • It is voluntary stage that involves the transfer of food bolus from the oral cavity to the oropharynx. • Mechanism In this stage, the mouth is closed  anterior part of tongue is raised and pressed against the hard palate by intrinsic muscles of tongue  this movement pushes the food bolus into the posterior part of oral cavity  soft palate closes down onto the back of tongue  approximation of palatoglossal arches and upward movement of hyoid bone  food bolus pushes through oropharyngeal isthmus into the oropharynx. Second stage • It is involuntary stage that involves the transfer of food bolus from oropharynx to esophagus. • Mechanism Contraction of levator veli palatini and tensor veli palatini  elevation of soft palate  closure of nasopharyngeal isthmus (prevents entry of food into the nose)  approximation of aryepiglottic folds  closure of laryngeal inlet (prevents entry of food into larynx)  contraction of longitudinal muscles of pharynx  elevation of larynx and pharynx  food bolus pushed downward over the epiglottis  contraction of superior and middle constrictors and palatopharyngeus  food bolus pushed further downward into the esophagus . Box 30.5: Deglutition (swallowing)

25. Third stage • It is involuntary stage that involves the transfer of food bolus from esophagus to stomach. • Mechanism Contraction of thyropharyngeus and relaxation of cricopharyngeus push food downward (prevent regurgitation of food)  peristaltic movement of esophagus  relaxation of lower esophageal sphincter  entry of bolus into the stomach. Clinical integration • Dysphagia : It is difficulty in swallowing. Causes : Carcinoma of esophagus, cardiospasm (cardiac achalasia). • Achalasia cardia : It is a failure of lower esophageal sphincter due to congenital absence of ganglion cells in myenteric plexus of esophageal wall. It causes accumulation of food in esophagus. Box 30.5: Deglutition (swallowing)

26. • There are three spaces located around the constriction of pharynx, one retropharyngeal space and two lateral pharyngeal or parapharyngeal spaces. For details, see Chapter 8, Fig. 8.18, and Flowchart 8.4. PHARYNGEAL SPACES

27. Thank you…