Gastrointestinal System Module - 2023-2024 Anatomy of Oral Cavity, Pharynx & Oesophagus PDF

Gastrointestinal System Module Functional & Applied Anatomy of Oral Cavity, Pharynx & Oesophagus MUHAMMAD ALBAHADILI 2023-2024  Objectives At end of the lecture, we were able to Describe the anatomy of the inner part of the mouth, pharynx and oesopha...

Gastrointestinal System Module Functional & Applied Anatomy of Oral Cavity, Pharynx & Oesophagus MUHAMMAD ALBAHADILI 2023-2024  Objectives At end of the lecture, we were able to Describe the anatomy of the inner part of the mouth, pharynx and oesophagus Differentiate the types of cells that formed the mucosa of the mouth, pharynx and oesophagus, Describe the action of pharyngeal muscles in swallowing Differentiate the action of intrinsic ms from extrinsic ms of the tongue Numerate the factors that prevent the reflux of gastric content into the oesophagus Numerate the portal-systemic anastomosis sites  The Oral Cavity Vestibule proper Vestibule Vestibule – space bounded by the lips & cheeks anteriorly and laterally; internal boundary formed by dental arches  Ducts of the parotid glands discharge their secretions into the vestibule; opposite the upper 2nd maxillary molar Oral Cavity Proper  Oral Cavity Proper : Space posterior & medial to the dental arches  The roof is formed by the hard and soft palate  Soft palate continuous with the wall of the pharynx & is joined with the tongue by two arches (palatoglossal & palatopharyngeal) formed by muscles covered by a mucous membrane; palatine tonsil lies in between  Communicates posteriorly with the oropharynx  Tongue lies inferiorly inside   Beneath and medial to the lower teeth is the floor of the mouth  The tongue is connected to the floor of the oral cavity by a midline fold of mucosa (lingual frenulum) The frenulum allows the anterior part of the tongue to move freely Tongue tie  Ducts of the submandibular salivary glands open at the base of the frenulum; the ducts of the sublingual glands also open alongside the frenulum Oral Mucosa the lining epithelium is stratified squamous (nonkeratinized) the exception in areas (gums, hard palate & dorsal surface of the tongue) that are subjected to abrasive forces (masticatory mucosa) is stratified squamous keratinised.  Mastication muscles Primary Masseter Temporalis Medial pterygoid Lateral pterygoid Mastication muscles Accessory muscles Anterior belly of digastric Mylohyoid Geniohyoid buccinator  Nerve muscle origin insertion function supply Digastric mandible mylohyoi Mandibular Mandible d Hyoid Depresses of the bone C1-C2 via mandible geniohyoi mandible hypoglossal d CN Compression of buccinat Outer surface of Facial cheeks & lips or maxilla & mandible against teeth The Tongue – General Anatomy  Mobile muscular (skeletal) organ capable of assuming a variety of shapes & positions  Composed of a root, body, an apex, curved dorsal surface & an inferior surface   A V-shaped dorsal groove (sulcus terminalis) marks the boundary between anterior (body) & posterior parts (base) Posterior 1/3rd Anterior 2/3rd  its covered by a mucosa which is rough (keratinised s. s.) on the dorsal surface  but thin and transparent on the inferior (sublingual) surface (non- keratinised s. s.) Mucous Membrane Of the anterior 2/3rd - Contains lingual papillae - four types of lingual papillae (filiform, fungiform, foliate & vallate) - Filiform (most numerous) are conical, highly keratinised & contain afferent nerve endings sensitive to touch - Fungiform are scattered, keratinised; most numerous near the apex & margins of the tongue; appear as red spots (vascular core) - Vallate lie anterior to the sulcus and are large, nonkeratinised & surrounded by deep trenches; walls contain taste buds (function in the four primary taste sensations – salty, sweet, bitter & sour) - Foliate are located just in front of V of vallate p. they are clustered in tow groups on iether side of the tongue, content taste buds Mucous Membrane of (posterior 1/3rd) - No lingual papillae - Cobblestone surface because of the presence of lymphoid nodules (lingual tonsil)  Taste buds: Areas of specialised epithelia (specialised mucosa) where intraepithelial structures (taste buds) function for taste perception (gustation); most taste buds on the dorsal surface of the tongue What is about the water?  Intrinsi c The Muscles Of The Tongue Extrinsi c  Intrinsic (confined) muscles permit changes in the shape of the tongue:  Longitudinal  Transvers  Vertical Extrinsic muscles of the tongue allow for movement and changes in position; Styloglossus: create a trough for swallowing, retracting the tongue. Hyoglossus: depresses and retracts the tongue, making the dorsum more convex. Palatoglossus: elevation of the posterior part of the tongue Genioglossus: protruding the tongue and deviating it towards the opposite side. When acting together, the muscles depress the center of the  nerve supply: anterior 2/3 of the tongue originated from 1st pharyngeal arch & posterior 1/3 from 3rd pharyngeal arch. Sensory: general sensation for anterior 2/3 is lingual (branch of CN V) &Taste fibres (special innervation) derived from the facial (CN VII) nerve (Chorda tympani) But for posterior 1/3 glossopharyngeal (CN IX) nerves for both general sensation & teste Motor: all the muscles of the tongue is innervated by Hypoglossal (XII CN) except palatoglossus is pharyngeal branch of Vagus (X CN)  The Tongue – Clinical Correlates Gag reflex The gag reflex, (pharyngeal reflex), is an involuntary reflex involving bilateral pharyngeal muscle contraction and elevation of the soft palate. This reflex may be evoked by stimulation of the posterior pharyngeal wall, tonsillar area, or base of the tongue. afferent (sensory) IX CN & efferent (motor) X CX.  The Tongue – Clinical Correlates Paralysis of genioglossus (forms the bulk of tongue mass) obstructing the airway with a risk of suffocation; during general anaesthesia, the muscle relaxes and thus the tongue of the patient is prevented from a backward move. by inserting an airway Protection of the airway The Tongue – Clinical Correlates Any cause lead to injury of CN XII leading to atrophy of same side of the tongue > the tongue deviates to the paralysed side? Thin mucous membrane on the inferior side of the tongue allows for quick absorption of drugs into the deep lingual veins  Salivary Glands Salivary Glands Major minor Parotid >800 glands Submandibula r lingual  Minor salivary glands These lie just under mucosa. Distributed over lips, cheeks, palate, floor of mouth & retro- molar area. Also appear in upper aerodigestive tract Contribute 10% of total salivary volume.  Sublingual Salivary glands This is the smallest of the major salivary glands. The sublingual glands are a paired set of salivary glands lying in the anterior part of the floor of the mouth between the mucous membrane above , the mylohyoid muscle below and the body of the mandible close to the mental symphysis anteriorly. Sublingual gland has no true fascial capsule.  The gland has a head portion that drains by numerous excretory ducts (Ducts of Rivinus) directly into the oral cavity and the tail that drains into the submandibular duct or directly into the mouth Submandibular Gland This gland lies in the submandibular triangle formed by the anterior and posterior bellies of the Digastric muscle and the inferior margin of the mandible.  The gland forms a ‘C’shape around the posterior margin of the Mylohyoid muscle, which divides the gland into a superficial (large) and deep (small) lobe. The gland is surrounded by a well-defined capsule that is derived from the deep cervical fascia which splits to enclose it  Submandibular Gland…… Wharton’s duct empties lateral to the lingual frenulum on the anterior floor of mouth Submandibular Gland…… Important anatomical relations include: the anterior facial vein and artery hyoglossus muscle lingual nerve hypoglossal nerve. Parotid Gland The parotid gland represents the largest salivary gland The gland lies in a recess bounded by the ramus of the mandible, base of skull and the mastoid process. its lies on carotid sheath and extended over the masseter ms. Parotid Gland…… 80% of the gland overlies the Masseter and mandible. The remaining 20% of the gland (the retromandibular portion  Structures through gland: Fascial N Terminal branches of ex. Carotid A. Retromandibular vein Intra-parotid LNs. Divided into 80% superficial and 20% deep to facial N.  Parotid Gland…… Stensen’s duct arises from the anterior border of the Parotid and parallels the Zygomatic arch, 1.5 cm inferior to the inferior margin of the arch. It runs superficial to the masseter muscle, then turns medially 90 degrees to pierce the Buccinator muscle at the level of the second maxillary molar where it opens onto the oral cavity.  Facial N. & parotid After exiting the foramen, it turns anterior to enter the gland at its posterior margin. The nerve then branches approximately 1.3 cm from the stylomastoid foramen. The nerve then gives rise to 2 divisions: 1)Temporofacial (upper) 2)Cervicofacial (lower) Facial CN & parotid gland Facial CN Temporofaci Cervicofacia al l Temporal Buccal zygomatic Marginal cervical Facial nerve palsy is the diminished function of the facial nerve or one of its branches. Bell’s palsy, which results in the complete inability to move one side of the face, is the most common cause of facial nerve palsy. This condition completely or partially improves within a few months. Symptoms Sudden paralysis on one side of the face, including the muscles of the forehead Difficulty in closing eyelids and smiling Drooling A decrease in the ability to taste Difficulty in chewing Pain or numbness behind the ears Salivary Glands Functions Saliva: It’s a clear, viscous fluid 98% water plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (amylase, lipase) antimicrobial agents (IgA, and lysozymes). Keeps the mucous membrane of the oral cavity moist Lubricates the food during mastication Begins digestion of carbohydrates Serves as a mouthwash Role in the prevention of tooth decay Facilitates taste Facilitates speech  Salivary Gland – Histology Parotid Sublingual Submandibular - Mainly serous - Mostly mucus - Serous/mucus Mucous acini Mucous acini Serous acini Serous acini High content of Mucins Weak amylase & amylase Lysozyme  Secretion of saliva  The afferent is in response to stimulation centrally or stimulation of taste bud receptors; nerves from taste buds in the anterior tongue pass in the chorda tympani (branch of Facial Nerve - CVII) & from the posterior tongue pass in the glossopharyngeal nerve (CIX) Salivary Glands – Functional Correlates  Parasympathetic secretomotor fibres to the submandibular & sublingual glands are conveyed via the chorda tympani which joins the lingual nerve (branch of Trigeminal Nerve – CV3) to reach the glands  Parasympathetic secretomotor fibres to the parotid gland first pass into the glossopharyngeal nerve and then join the auriculotemporal nerve (branch of CV3) to reach the gland Salivary secretion Both parasympathetic & sympathetic ANS stimulate the secretion of saliva Parasympathetic: large volume, watery & rich with enzymes, when? Sympathetic: small vol. rich in mucus, when?  Secretions from the gland acini into a duct system; striated duct > excretory duct > collecting duct  – cells lining the striated & excretory ducts modify the composition of the saliva, how? Salivary Glands – Clinical Correlates Sialography: radiographic examination of major ducts & secretory units of the parotid & submandibular gland by injection of contrast medium for diagnosis of stricture, stone cause obstruction Blockage of submandibular duct by calculi (stones) Salivary Glands – Clinical Correlates Majority of salivary gland tumours occur in the parotid gland; most of the tumours are benign. parotidectomy presents surgical challenges because the facial nerve & its branches are embedded in the gland so: Superficial parotidectomy For benign or low-grade malignancy Radical parotidectomy for high-grade malignancy  Salivary Glands – Clinical Correlates Viral infection of the parotid gland (mumps) causes inflammation (parotiditis); parotid gland capsule & cervical fascia limit swelling and thus cause severe pain – pain in the auricle, external acoustic meatus, temporal region & temporomandibular joint because of common nerve supply via the auriculotemporal nerve (branch of CV3) (sensory branch)  Gums & Teeth Gums (gingivae) are composed of fibrous tissue covered with mucosa; the attached portion to the jaws & necks of the teeth is covered by SSKE – unattached is NKSSE Gums & Teeth  Improper oral hygiene results in food & bacterial deposits in gum crevices > cause gum inflammation (gingivitis); if left untreated > supporting structures & alveolar bone affected causing periodontitis (inflammation & destruction of bone & periodontium) > dental abscesses Gum & teeth  Teeth set in tooth sockets are used in mastication & assist in speech; deciduous (primary) or permanent (secondary); children (20 deciduous), adults (32 permanent)  Decay of teeth results in dental caries (‘cavities’ ) > eventually invade the pulp cavity > pulpitis – cavity is small & rigid & swelling cause intense pain (toothache)  Abscesses from maxillary molar teeth may extend into the maxillary air sinus causing sinusitis  The Palate Consists of a bony part (hard palate) and a muscular part (soft palate)  Hard palate Consist of four layers, a bony skeleton of palatine processes of maxillae and horizontal plates of palatine bones Submucosa relatively dense containing minor salivary glands Lamina propria densely collagenous cover with KSSE Separates the oral cavity from the nasal cavity & nasopharynx The soft Palate  Composed of musculoaponeurotic tissue attached anteriorly to the hard palate, posteriorly free mobile, on either side bound to tongue and pharynx by palatoglossus & palatopharyngeus MMS.  The soft palate has two actions,  becomes tense against elevated tongue (CV3)  Elevation during swallowing prevents the passage of food into the nasal cavity & nasopharynx (CX) Soft palate muscles Cleft palate: Failure of fusion of palatal processes during development > cleft palate; feeding problems & food in the nasal cavity > aspiration of food into the respiratory system   Pharynx – expanded Pharynx portion of digestive system posterior to the oral cavity  Divided into nasopharynx, oropharynx & Nasopharynx laryngopharynx Oropharynx Laryngopharynx   Pharynx wall – The muscles of the pharynx voluntary muscle (external circular & inner longitudinal) Sty cle mu  External muscle lop s layer – three ha r pharyngeal ngey constrictors us Sa uscl  Internal muscle m lpi e layer – three other ng op muscles ha ry n ge u Pala cle s s toph a ry nge us Pharyngeal Muscles The outer circular layer includes: superior constrictor muscle Middle constrictor muscle inferior constrictor muscle  Pharyngeal Muscles The inner longitudinal layer includes: Stylopharyngeus muscle Salpingopharynge us muscle Palatopharyngeus muscle Pharyngeal Muscles are innervated by the pharyngeal branch of the Vagus nerve (CN X) except for the stylopharyngeus muscle which is innervated by the glossopharyngeal nerve (CN IX). what is the epithelial cells that lining the pharynx ? pharyngeal pouch; (Zenker’s diverticulum) The inferior pharyngeal constrictor consists of two parts; thyropharyngeal and cricopharyngeal. The thyropharyngeal part is located superiorly and it comprises most of the muscle. The specific orientation of muscle fibers defines a triangular gap between the thyropharyngeal and cricopharyngeal parts of the muscle called Killian’s dehiscence (or triangle). This is a weak spot of the pharyngeal wall through which the pharyngeal diverticulum may prolapse. The Oesophagus 25 cm long muscular tube; upper part contains striated muscle, middle part contains striated & smooth muscle & lower part contains smooth muscle; under vagus nerve control Has three regional location – cervical, thoracic & abdominal  Relations of esophagus in the neck Located anterior to the vertebral column Posterior to the trachea On either side of the thyroid, recurrent laryngeal NNs & carotid sheath Esophageal relations in the chest Anterior
Posterior Right Left Thoracic Trachea vertebral Subclavian Left bodies Pleura artery recurrent Thoracic Terminal Aortic arch laryngeal duct part of Thoracic nerve Azygous azygous duct Pericardiu veins vein Pleura m Descending aorta
Right Left vagus vagus nerve nerve Abdominal Right crus Left crus of the of the diaphragm diaphragm  Anatomical Relations The anatomical relations of the esophagus give rise to four physiological constrictions in its lumen – it is these areas where food/foreign objects are most likely to become impacted. They can be remembered using the acronym ‘ABCD‘: Arch of aorta Bronchus (left main stem) Cricoid cartilage Diaphragmatic hiatus  SITES OF CONSTRICTION IN THE ESOPHAGUS Site of constriction

Distance from
Vertebral level upper incisor teeth At the pharyngo-esophageal C6 6 inches (15 cm) junction (cervical constriction) At crossing of arch of aorta T4 9 inches (22 cm) (aortic constriction) At crossing of left principal T6 11 inches (27 cm) bronchus (bronchial constriction) At the opening in the T10 15 inches (40 cm) diaphragm (diaphragmatic constriction) Esophagus: histology Has two sphincters – Upper fibres of inferior constrictor muscle called the cricopharyngeus muscle) - lower oesophageal sphincter (not an ‘anatomical sphincter’)  factors that prevent reflux of gastric contents into oesophagus: - angle of entry of oesophagus into the stomach - right crus of the diaphragm - location of the fundus - mucosal flap in the cardiac region of the stomach - intra-abdominal pressure NERVE SUPPLY The esophagus is supplied by both parasympathetic and sympathetic fibres. The parasympathetic fibres are originated from recurrent laryngeal nerves and esophageal plexuses created by vagus nerves. They supply sensory, motor, and secretomotor supply to the esophagus. The sympathetic fibres are originated from T5-T9 spinal segments are sensory and vasomotor.  The Oesophagus – Blood Supply  Three arterial sources :  inferior thyroid for (cervical region),  aorta (thorax)  & left gastric artery (abdomen) Venous drainage: Inferior thyroid, azygos system & left gastric vein (into the portal system) naturally occurring venous communications between tributaries of the portal venous system and tributaries of the systemic venous system. Oesophagus – Clinical Correlates  Narrowing at three points – at its commencement, where it is crossed by the left bronchus and at its entry into stomach  Portal hypertension – oesophageal varices > may rupture > haemoptysis  Metaplasia in the oseophageal mucosa due to continual gastric reflux (GORD) Left  Mitral stenosis > left atrial hypertroph Bronchus y > displacement of oesophagus  Dysphagia – swallowing difficulties  Achalasia – motor disorder, failure of the ‘lower oesophageal sphincter’ to relax & abnormality of function of the Oesophagus smooth muscle in lower oesophagus