Pharynx & Esophagus Lecture 3 PDF

Pharynx Objectives Extent, communications Parts - boundaries and their features Pharyngeal lymphatic ring Muscles of pharynx Blood supply, lymphatic drainage and nerve supply Pharynx Nasal cavity Nasopharynx Pharyngeal isthmus Oral cavity Oropharynx Epiglottis Laryngo pharynx Esophagus Larynx Cricoi...

Pharynx Objectives Extent, communications Parts - boundaries and their features Pharyngeal lymphatic ring Muscles of pharynx Blood supply, lymphatic drainage and nerve supply Pharynx Nasal cavity Nasopharynx Pharyngeal isthmus Oral cavity Oropharynx Epiglottis Laryngo pharynx Esophagus Larynx Cricoid cartilage Trachea Wide muscular tube, about 12 cm long, situated behind the nose, mouth and larynx Superiorly it extends till the base of the skull Inferiorly it continues as esophagus at the level of 6th cervical vertebra Upper part is wide and lower part is narrow Located anterior to upper 6 cervical vertebrae Communications of pharynx: Anteriorly with nasal cavity, oral cavity and larynx On each side with middle ear through auditory tube Parts of pharynx: Cavity of the pharynx is divided into 3 parts Nasopharynx – nasal part Oropharynx – oral part Laryngopharynx – laryngeal part Pharynx Nasopharynx Pharyngeal isthmus Oropharynx Laryngopharynx Oral cavity Larynx Esophagus Nasopharynx (nasal part): Upper most part of pharynx situated behind the nose and above the soft palate Respiratory in function – lined by ciliated columnar epithelium Anteriorly it communicates with nasal cavity through posterior nasal apertures (choanae) Inferiorly it extends till the lower border of soft palate and communicates with oropharynx through pharyngeal isthmus Supplied by the branches of maxillary nerve Boundaries of nasopharynx: Roof, floor, posterior wall and 2 lateral walls Roof: Contains body of sphenoid bone and basilar part of occipital bone Contains pharyngeal tonsil (collection of lymphoid tissue) – adenoids Floor: Mobile and formed by the soft palate Has pharyngeal isthmus communicates with oropharynx Posterior wall: Contains anterior arch of atlas (1st cervical vertebra) Note: The pharyngeal tonsil is an aggregate of lymphoid tissue lying in the midline along the roof and posterior wall of the nasopharynx, at the level of the sphenoid and occipital bones. Body of sphenoid Basilar part of occipital bone Soft palate Anterior arch of atlas Lateral wall presents: Opening of auditory tube – connects the nasopharynx to the middle ear cavity Tubal elevation - formed by the cartilage of auditory tube (also contains tubal tonsil – lymphoid aggregation) Salpingopharyngeal fold – begins from the posterior end of tubal elevation (contains salpingopharyngeus muscle) Pharyngeal recess (fossa of Rosenmuller) – groove situated behind the tubal elevation and salpingopharyngeal fold Salpingopalatine fold – mucosal fold extending from the anterior end of tubal elevation to the soft palate Fold of levator palati – triangular elevation below the opening of auditory tube (formed by the levator palati muscle) Nasopharynx and oropharynx Opening of auditory tube Salpingopalatine fold Fold of levator palati Tubal elevation Pharyngeal tonsil Pharyngeal recess Salpingopharyngeal fold Soft palate Oral cavity Anterior arch of atlas Pharyngeal isthmus Oropharynx Oropharynx (oral part): Middle part of pharynx, located behind the oral cavity Extent - lower border of soft palate to upper border of epiglottis Above it communicates with nasopharynx through pharyngeal isthmus Anteriorly it communicates with oral cavity through oropharyngeal isthmus Below it is continuous with laryngopharynx at the upper border of epiglottis It lies in front of 2nd (axis) and 3rd cervical vertebrae Supplied by - glossopharyngeal nerve Its lateral wall contains: – Palatoglossal fold or arch (produced by palatoglossus muscle) – Palatopharyngeal fold or arch (produced by palatopharyngeus muscle) – Palatine tonsil (collection of lymphoid follicles located between the arches) Oropharynx Nasopharynx Soft palate Pharyngeal isthmus Oropharynx Oral cavity Bodies of 2nd (axis) and 3rd cervical vertebrae Palatopharyngeal fold Palatoglossal fold Palatine tonsil Epiglottis Laryngopharynx (laryngeal part): Is the lower part of pharynx, situated behind the larynx It is situated in front of 3rd, 4th, 5th and 6th cervical vertebrae Extends from the upper border of epiglottis to 6th cervical vertebra (lower border of cricoid cartilage) Continues inferiorly as esophagus Supplied by the branches of vagus nerve Anterior wall presents – inlet of larynx in the upper part and cricoid and arytenoid cartilages of larynx in the lower part – piriform fossa (small depression on either side of inlet of larynx) Laryngopharynx Oropharynx Laryngopharynx Esophagus Larynx Piriform fossa: Lateral boundary is formed by the thyrohyoid membrane and lamina of thyroid cartilage Medial boundary is formed by the aryepiglottic fold (which separates it from the inlet of larynx) Internal laryngeal nerve and superior laryngeal vessels - deep to the mucous membrane Ingested food particles such as fish bone may get impacted in the fossa. If care is not taken while removing the foreign particle, internal laryngeal nerve may be injured causing loss of sensations from the upper part of larynx which leads to loss of protective cough reflex Inlet of larynx Aryepiglottic fold Piriform fossa Pharyngeal (Waldeyer’s) lymphatic ring Formed by - palatine, tubal, lingual and pharyngeal tonsils Incomplete circular band of lymphoid tissue around the superior part of the pharynx Anteroinferior part of the ring - lingual tonsil Lateral parts of the ring - palatine and tubal tonsils Posterior and superior parts of the ring - pharyngeal tonsil Acts as a first line of defense against microbes that enters the body via the nasal and oral routes Structure of pharynx Wall of the pharynx is composed of following layers from within outwards Mucosa Submucosa Pharyngobasilar fascia – thin sheet of connective tissue, forms pharyngeal raphe on the posterior aspect Muscular coat – containing – Inner longitudinal layer – made up of stylopharyngeus, salpingopharyngeus and palatopharyngeus muscles – Outer circular layer – made up of 3 pharyngeal constrictors Buccopharyngeal fascia (connective tissue layer) Muscles of pharynx: – Superior, middle and inferior constrictor muscles – Palatopharyngeus muscle – Stylopharyngeus muscle – Salpingopharyngeus muscle Constrictor muscle are situated at the outer part of pharynx (constrictors contract involuntarily so that contraction takes place sequentially from the superior to the inferior end of the pharynx, propelling food into the esophagus) Palatopharyngeus, stylopharyngeus and salpingopharyngeus muscles are located at the inner part of pharynx (these elevate the larynx and shorten the pharynx during swallowing and speaking) Nerve supply to muscles: Stylopharyngeus - glossopharyngeal nerve All other muscles of pharynx - pharyngeal branch of vagus nerve via pharyngeal plexus of nerves (inferior constrictor also supplied by external and recurrent laryngeal nerves) Muscles of pharynx Superior constrictor Stylo pharyngeus Middle constrictor Inferior constrictor Esophagus Trachea Inferior constrictor has 2 parts – thyropharyngeus and cricopharyngeus parts Pharyngeal constrictors (Posterior view) Pharyngeal raphe Pharyngobasilar fascia Esophagus Structures passing between pharyngeal constrictors The overlapping of the constrictor muscles leaves four gaps in the musculature for structures to enter or leave the pharynx The levator palati, auditory tube, and ascending palatine artery - between superior constrictor and the skull Stylopharyngeus muscle and glossopharyngeal nerve between the superior and middle constrictors Internal laryngeal nerve and superior laryngeal artery and vein - between the middle and inferior constrictors Recurrent laryngeal nerve and inferior laryngeal artery pass through a gap inferior to the inferior constrictor Killian’s dehiscence and pharyngeal diverticulum Killian’s dehiscence is a potential gap which exists between 2 parts of inferior constrictor muscle – thyropharyngeus and cricopharyngeus Seen as a dimple in the mucosa at this region Pharyngeal diverticulum may develop through this week area in case of neuromuscular incoordination i.e. if cricopharyngeus fails to relax following contraction of thyropharyngeus part Increased pressure forces the mucosa and submucosa posteriorly through the Killian’s dehiscence Nerve supply of pharynx: Pharynx is supplied by pharyngeal plexus of nerves formed by the pharyngeal branches of glossopharyngeal, vagus and superior cervical sympathetic ganglion Pharyngeal plexuses are located on the middle constrictor Blood supply of pharynx: Arterial supply: Ascending pharyngeal artery of external carotid artery Ascending palatine and tonsillar arteries of facial artery Palatine, pharyngeal branches of maxillary artery Venous drainage: Veins of pharynx terminate at the internal jugular vein and facial vein Lymphatic drainage: Retropharyngeal and deep cervical lymph nodes Esophagus Objectives Origin, course and termination Parts and their relations Constrictions of esophagus Blood supply, nerve supply and lymphatic drainage Applied anatomy Esophagus Muscular tube, 10 inches in length Origin: Continuation of pharynx (pharyngoesophageal junction) at the level of C6 vertebra Course: Runs down in the lower part of neck Enters thorax by passing through thoracic inlet Descends in the superior mediastinum and then in the posterior mediastinum Passes through esophageal opening of diaphragm (T10 vertebra) Enters abdomen Termination: Joins the cardiac end of stomach (T11 Diaphragm vertebra) Esophagus Stomach Esophagus (cervical part) Left recurrent laryngeal nerve Parts: cervical, thoracic and abdominal Relations: Cervical part: Anterior – trachea, recurrent laryngeal nerves Posterior – vertebral column Lateral – carotid sheath, lobe of thyroid gland Trachea Esophagus (thoracic part) Diaphragm Esophagus (abdominal part) Stomach Neck – cross section Relations of esophagus – thoracic part Pharynx Trachea Arch of aorta Left Principal bronchus Esophagus Left subclavian artery Vertebral column Heart Esophagus (thoracic part) Diaphragm Esophagus (abdominal part) Descending thoracic aorta Anterior relations trachea, left principal bronchus, pericardium, heart Posterior relations vertebral column Right relations - right lung, right pleura, arch of azygos vein Left relations – left lung, left pleura, arch of aorta, descending thoracic aorta Esophagus (cervical part) Trachea Arch of aorta Abdominal part relations: Anterior – left lobe of Left pleura liver Posterior – diaphragm Left subclavian artery Arch of azygos vein Left principal bronchus Left vagus Esophagus (thoracic part) Diaphragm Esophagus (abdominal part) Descending thoracic aorta Constrictions of esophagus 1st 2nd 3rd 4th Normally shows 4 constrictions First constriction – at its beginning (15 cm from incisor teeth) cuased by cricopharyngeus muscle (inferior constrictor) Second constriction – where it is crossed by arch of aorta (22.5 cm from incisor teeth) Third constriction – where it is crossed by left principal bronchus (27.5 cm from incisor teeth) Fourth constriction – where it pierces diaphragm (40 cm from incisor teeth) No constrictions are visible in the empty esophagus. As it expands during filling, the structures mentioned above compress its walls Blood supply: Cervical part – inferior thyroid artery and vein Thoracic part –descending thoracic aorta, azygos, hemiazygos and accessory hemiazygos veins Abdominal part – left gastric artery and vein Nerve supply: Parasympathetic nerves - vagus, recurrent laryngeal nerve Sympathetic nerves – middle cervical sympathetic ganglia and upper 4 thoracic sympathetic ganglia Lymphatic drainage: Cervical part – deep cervical lymph nodes Thoracic part – mediastinal lymph nodes Abdominal part – celiac lymph nodes Blood supply of esophagus Inferior thyroid Inferior thyroid veins Accessory Hemiazygos vein Descending Thoracic aorta Left Gastric artery Hemiazygos vein Azygos vein Portal vein Left Gastric vein Applied anatomy Awareness of constrictions of esophagus is important when passing instruments through the esophagus into the stomach, and when viewing radiographs of patients who are experiencing dysphagia (inability to swallow) Foreign object swallowed into the GIT may get impacted at the areas where the esophagus is compressed/constricted Scarring/stricture of the mucosa may also occur at these sites if a corrosive/caustic liquid is swallowed Achalasia cardia : results from spasm of sphincter/ inability of the lower esophageal sphincter to relax (it fails to open up) during swallowing. It causes dysphagia (leads to a backup of food within esophagus) Esophageal Varices Dilated submucosal veins in the lower esophagus due to portal hypertension Submucosal veins of the lower esophagus drain to both the portal (left gastric vein) and systemic venous systems (azygos vein), they constitute a portosystemic anastomosis. In portal hypertension (cirrhosis of liver), blood is unable to pass through the liver via the hepatic portal vein, causing a reversal of flow in the esophageal tributary Large volume of blood causes the submucosal veins to enlarge, forming esophageal varices These may rupture and cause severe hemorrhage that is life-threatening Pyrosis (heartburn) Most common type of esophageal discomfort or substernal pain. This burning sensation in the abdominal part of the esophagus is usually the result of regurgitation of small amounts of food or gastric fluid into the lower esophagus (gastroesophageal reflux disorder; GERD).