MEDI7100 - The upper GI Tract (Mouth to Stomach) Anatomy PDF 2024

MEDI7100 – The upper GI (Mouth to Stomach) THE UNIVERSITY OF QUEENSLAND Faculty of Medicine, School of Biomedical Sciences (SBMS) Anatomy ©2024 MEDI7100 Anatomy Practical Clinical Science 1 The Upper GI Professor Mark Midwinter & A/Prof Frederik (Derik) Steyn, May 2024...

MEDI7100 – The upper GI (Mouth to Stomach) THE UNIVERSITY OF QUEENSLAND Faculty of Medicine, School of Biomedical Sciences (SBMS) Anatomy ©2024 MEDI7100 Anatomy Practical Clinical Science 1 The Upper GI Professor Mark Midwinter & A/Prof Frederik (Derik) Steyn, May 2024 i  MEDI7100 – The upper GI tract (Mouth to Stomach) Suggested reading/viewing: For those new to Anatomy, additional reading and viewing may be needed. There is some repetition between the different resources identified below – this is in recognition that different people will find different material useful. Consider the library resources below and focus on those that suit your learning style. All of these resources can be accessed by logging into and searching Clinical Key (https://www-clinicalkey-com-au.ezproxy.library.uq.edu.au ), or by following the links below: Gray’s anatomy for Students http://guides.library.uq.edu.au/anatomy/books Snell’s Clinical Anatomy by Systems https://search.library.uq.edu.au/primo- explore/fulldisplay?docid=61UQ_ALMA2176428360003131&context=L&vid=61UQ& search_scope=61UQ_All&tab=61uq_all&lang=en_US An@tomedia http://guides.library.uq.edu.au/anatomy under multimedia resources Ackland’s Video Atlas of Human Anatomy https://search.library.uq.edu.au/primo- explore/fulldisplay?docid=61UQ_ALMA61117003370003131&vid=61UQ&search_sc ope=61UQ_All&tab=61uq_all&lang=en_US&context=L ii  MEDI7100 – The upper GI tract (Mouth to Stomach) Table of Content Core Knowledge................................................................................... 1 1. Face, Mouth, and Mandible...................................................................................... 1 2. Teeth......................................................................................................................... 3 3. Hyoid, Muscles of Mastication, and Tongue............................................................ 4 4. Pharynx..................................................................................................................... 8 5. Salivary Glands...................................................................................................... 10 5. Oesophagus........................................................................................................... 11 6. Stomach.................................................................................................................. 15 7. Lymphatic drainage................................................................................................ 19 Detail Building on Core Knowledge..................................................... 22 1. The Soft Palate....................................................................................................... 22 2. The Tongue............................................................................................................ 24 3. The Oesophagus.................................................................................................... 25 Imaging Anatomy................................................................................ 28 1. Plain Radiography.................................................................................................. 28 2. Computed Tomography (CT)................................................................................. 30 3. Ultrasound.............................................................................................................. 32 4. Barium Swallow...................................................................................................... 33 5. Endoscopy.............................................................................................................. 34 6. Endoscopic Ultrasound.......................................................................................... 34 7. Imaging Protocols................................................................................................... 36 Applied Clinical Anatomy.................................................................... 37 1. Cancer of the Stomach........................................................................................... 37 2. Developmental Abnormalities................................................................................ 37 3. Hiatus hernia........................................................................................................... 37 4. Oesophageal Cancer............................................................................................. 38 5. Oral Health.............................................................................................................. 38 Cutting Edge Anatomy........................................................................ 39 iii  MEDI7100 – The upper GI (Mouth to Stomach) Core Knowledge Outline of this practical: These notes will examine the details of the mouth, including the skeleton (maxilla, mandible, palatine bones), the tongue, salivary glands, palate, and floor of the mouth. We will review the pharynx and observe how it progresses down to become the oesophagus. We will consider the oesophagus in the thorax and its relations to structures such as the aorta and thoracic duct. We will then examine the oesophageal hiatus in the diaphragm in detail, including its clinical relevance, before concentrating on the stomach itself. The stomach will be examined in detail, including its parts, blood supply, and innervation. 1. Face, Mouth, and Mandible Using the following links from An@tomedia and Ackland’s Video atlas of anatomy, revisit the following points: o Zygoma (zygomatic bone) o Maxilla http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/17 http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/16 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528405 On the maxilla, note the two processes – frontal and zygomatic – which join with the bones of those names. Note also that the maxilla has a palatine process that extends horizontally to meet its fellow of the opposite side, to form the greater part of the skeleton of the hard palate. 1  MEDI7100 – The upper GI tract (Mouth to Stomach) The alveolar “process” is the rim of the maxilla that carries the teeth of the upper jaw. The main body of the maxilla is hollow – the maxillary sinus. Note the infraorbital foramen just below the orbital rim – this carries the infraorbital nerve and artery. The bony palate consists of the palatine processes of the maxillae, as seen above. Posteriorly, and adjoining these, are the two horizontal plates of the palatine bones. These meet in the midline, as well as joining with the palatine processes of the maxillae, and it is these four components that together make up the skeleton of the hard palate. Using the link below, consider the following parts and features: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/19 o Body of the mandible o Ramus of the mandible o Angle of the mandible o Mandibular notch o Condylar process, including the head and neck of the mandible o Coronoid process o Mandibular foramen on the medial aspect (the inside) of the ramus, guarded by a small tongue of bone, the lingula of the mandible o The mylohyoid line – a roughened, slightly raised ridge on the inside of the body of the mandible. The mylohyoid – the main muscle of the floor of the mouth – attaches here o The alveolar margin of the mandible – the part that carries the teeth of the lower jaw. o The mental foramen and mental symphysis 2  MEDI7100 – The upper GI tract (Mouth to Stomach) 2. Teeth Each tooth is composed of specialized connective tissue, the pulp, covered by three calcified tissues: dentine, enamel, and cementum. They are embedded in the alveolar processes of the maxilla and mandible and are surrounded by the gums (the gingivae). There are 20 primary teeth in a child, and 32 secondary or permanent, teeth in an adult. Using the links below, consider the teeth. They are divided into 4 quadrants, with 8 teeth in each in the adult: 2 incisors, 1 canine, 2 premolars, and 3 molars (note that the 3rd molar may erupt or not, known as the wisdom tooth) http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/20 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528437 3  MEDI7100 – The upper GI tract (Mouth to Stomach) 3. Hyoid, Muscles of Mastication, and Tongue The hyoid bone does not articulate with any other bone directly. It sits suspended from the styloid process of the skull by ligaments and lies in the front of the neck between the mandible and the larynx at the level of C3 vertebra approximately. Using the links below, consider the hyoid bone. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/neck/systems/07 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528421 The hyoid has a central body, and from this a pair of greater horns and a pair of lesser horns projects. Using the links below, identify the muscles attached to the hyoid bone, from above, behind, and below. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/neck/systems/14 http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/neck/systems/15 http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/30 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528421 o Geniohyoid o Stylohyoid o Thyrohyoid o Mylohyoid o Omohyoid o Middle constrictor of the o Digastric o Sternohyoid pharynx The muscles that lie anteriorly in the neck, in front of the thyroid gland and the larynx are known as the “strap muscles” that attach to the hyoid (except for the sternothyroid). 4  MEDI7100 – The upper GI tract (Mouth to Stomach) Consider the main facial muscles (supplied by CN VII) relevant to the upper GI, the group of muscles around the mouth: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/29 o The orbicularis oris acts as the “sphincter” of the mouth, controlling the opening and closure of the lips. o The buccinator is responsible for keeping food between the teeth while chewing, among other things. Using the links below, consider the muscles of mastication (supplied by CN Vc); these move the mandible, and identify the following: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/27 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528417 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528419 o Temporalis o Lateral pterygoid o Masseter o Medial pterygoid The two pterygoid muscles interleave at their attachments to the pterygoid process; the lateral pterygoid attaches to the head and neck of the mandible to pull it forward, while the medial pterygoid attaches to the medial surface of the angle of the mandible much lower down, and hence acts to elevate the mandible. 5  MEDI7100 – The upper GI tract (Mouth to Stomach) The muscles of the mouth and tongue include the tongue itself, which has intrinsic muscles, and the extrinsic muscles that attach the tongue to the mandible, hyoid, palate, and styloid process. The intrinsic muscles change the shape of the tongue, while the extrinsic muscles change the position of the tongue. Using the links below, note the extrinsic tongue muscles: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/31 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528425 o Genioglossus o Styloglossus o Hyoglossus o Palatoglossus 7  MEDI7100 – The upper GI (Mouth to Stomach) 4. Pharynx Using the link below, revise the structures of the pharynx, as introduced during your studies on the Upper Respiratory Tract https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528443 8  MEDI7100 – The upper GI tract (Mouth to Stomach) The pharynx consists of a muscular “tube” suspended from the base of the skull. Using the link below, note the three “circular” muscles: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/30 o Superior constrictor o Middle constrictor o Inferior constrictor They are all open anteriorly, so they’re not complete circular muscles. Note where they attach anteriorly on either side of their openings. There are also three vertical muscles forming part of the pharynx: https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528449 o Stylopharyngeus o Palatopharyngeus o Salpingopharyngeus (from the auditory tube). The nerve supply to the pharynx is from the vagus and glossopharyngeal nerves (cranial nerves X and IX respectively), which form the pharyngeal plexus. This is best appreciated in the link below: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/66 9  MEDI7100 – The upper GI tract (Mouth to Stomach) 5. Salivary Glands The parotid gland is a salivary gland that occupies the space between the mastoid process and external acoustic meatus behind, and the ramus of the mandible in front. It is wrapped around the posterior edge of the ramus of the mandible. It is divided into two nominal parts (superficial and deep) by the facial nerve. The parotid duct runs forward from the superficial part of the gland to pierce the buccinator and enter the oral cavity adjacent to the upper 2nd molar tooth. This is best appreciated in the following video on the parotid gland and its surroundings: https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528433 The gland has a tough fibrous pseudocapsule, [this is one of the reasons that swelling of the gland, trying to stretch this capsule, can be so painful – e.g. in mumps; https://radiopaedia.org/articles/mumps]. Using the link below, consider the parotid gland http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/37 The submandibular gland (as its name would suggest) lies in the submandibular region and is “folded” over the posterior edge of the mylohyoid muscle, thus forming deep and superficial parts. The gland is closely related to the facial artery and vein. The deep part of the gland lies lateral to the hyoglossus muscle. Other structures in this region to note include the lingual nerve, the hypoglossal nerve (CNXII), and the submandibular duct running forward from the gland itself to enter the mouth just beside the frenulum of the tongue (the fold that “tethers” the tongue to the floor of the mouth). The sublingual gland is the smallest of the three paired salivary glands, and opens into the mouth via multiple small ducts, directly into the floor of the mouth. It lies above the mylohyoid, just beneath the mucous membrane of the floor of the mouth. 10  MEDI7100 – The upper GI tract (Mouth to Stomach) 5. Oesophagus Prof Midwinter prepared a short video on the Anatomy of the Oesophagus – please consider this before you study the notes below: https://www.youtube.com/watch?v=X2E3Sps-Aeg&list=PLvv_t6_cOJ78zkycowopf93M-aITT1wAD&index=7 As noted in this video, the oesophagus is a downward continuation of the pharynx, and the upper 20% of the oesophagus lies in the neck. The total length of the oesophagus is between 25-30cm, depending on the size of the person. Using the link below, consider the oesophagus http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/thorax/systems/22 It starts behind the cricoid cartilage of the larynx, and the encircling muscle fibres here are known as the cricopharyngeus muscle. It is actually the lowermost fibres of the inferior constrictor of the pharynx, and these act as a sphincter at the top of the oesophagus. They are skeletal muscle. Just above the cricopharyngeus, between it and the rest of the inferior constrictor proper, is a relatively weak spot (Killian’s dehiscence) and it is here that you may see a diverticulum (an outpouching) called a Zenker’s diverticulum, otherwise known as a pharyngeal pouch. This can collect food, cause dysphagia and is vulnerable to perforation in endoscopy. 11  MEDI7100 – The upper GI tract (Mouth to Stomach) The oesophagus has an inner circular muscle layer, and an outer longitudinal muscle layer, starting just below the cricopharyngeus muscle. The musculature of the oesophagus is skeletal muscle at the top, and smooth muscle at the lower end, with a gradual transition from one type to the other. The oesophagus descends into the thorax behind the trachea, and is closely related to the very thin, soft, posterior wall of the trachea. Below the tracheal bifurcation, the oesophagus is closely applied to the back of the left atrium of the heart. This is where the transducer is placed during a procedure called a transoesophageal echocardiogram, so that the ultrasonic view of the heart from behind is only looking through one wall of the oesophagus and the thin wall of the left atrium (https://radiopaedia.org/articles/transesophageal-echocardiography?lang=us). As the oesophagus descends through the posterior mediastinum, the descending aorta “swings” in behind it, so that the oesophagus is in front of the aorta: https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaid=10528599 The blood supply of the oesophagus is from 3 main sources: o branches of the inferior thyroid arteries in the root of the neck, o branches from the bronchial arteries, and direct oesophageal branches from the descending aorta in the thorax in the chest o branch of the left gastric artery supplies the lower oesophagus. 12  MEDI7100 – The upper GI tract (Mouth to Stomach) Recall that an anastomosis of the veins of the lower oesophagus with the left gastric vein is one of the important porto-systemic anastomoses, relevant in portal hypertension, when oesophageal varices can grow enormous and bleed profusely. Using the link below, revisit the portal venous system. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/systems/31 13  MEDI7100 – The upper GI tract (Mouth to Stomach) Using the link below, note the left and right vagus nerves as they approach the oesophagus from each side. These form a plexus on the surface of the oesophagus. At the level of the diaphragm, the plexus eventually merges into two vagal trunks. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/thorax/dissection/25 o The left vagus becomes the anterior vagal trunk as it passes through the diaphragm o The right vagus becomes the posterior vagal trunk. The oesophagus passes through the diaphragm at about the level of thoracic vertebra 10 (T10). Using the image and links below, note oesophageal hiatus, and also consider the crura (the diaphragm is a muscle of respiration, and so is discussed in context of breathing): http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/dissection/38 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528273 o The right crus arise from L1-L3 and their intervertebral discs. Some fibres from the right crus surround the oesophageal opening, acting as a physiological sphincter to prevent reflux of gastric contents into the oesophagus. o The left crus arise from L1-L2 and their intervertebral discs. Note the oesophageal hiatus is at the level of T10 vertebra. The abdominal oesophagus is 1–2.5 cm in length and is slightly broader at the cardiac orifice than at the diaphragmatic aperture. It lies to the left of the midline and enters the abdomen through the oesophageal aperture (formed by the two diaphragmatic crura). The hiatus is formed by looping fibres that arise from the crus of the diaphragm. This is an important structure that is repaired in antireflex surgery. 14  MEDI7100 – The upper GI tract (Mouth to Stomach) The junction of the oesophagus with the stomach is known as the gastro-oesophageal (or oesophago-gastric, OGJ) junction, (also by the much shorter name of the cardia). This is common site for oesophageal adenocarcinoma to originate. Squamous carcinoma tends to be more proximal in the oesophagus. There is no anatomic sphincteric muscle here in the oesophagus itself, but the looping fibres of the right crus of the diaphragm that form the oesophageal hiatus combined with the angulation (angle of His) at the OGJ, act as a physiological/functional sphincter to prevent gastro-oesophageal reflux. This can be defined in clinical manometric studies and fails to relax in a condition called achalasia leading to dysphagia. Idiopathic achalasia is a disease of unknown aetiology characterized by oesophageal aperistalsis and failure of lower oesophageal relaxation due to loss of inhibitory nitrinergic neurons in the oesophageal myenteric plexus (https://www.nature.com/subjects/achalasia). When this hiatus is too loose, the stomach can either slide up through the hiatus (a sliding hiatus hernia) or the fundus of the stomach can “roll” up beside the oesophagus – a para- oesophageal hiatus hernia. This latter type is potentially very dangerous, while the sliding type is more of a nuisance and can be very symptomatic due to the reflux. 6. Stomach Prof Midwinter prepared a short video on the Anatomy of the Stomach – please consider this before you study the notes below: https://www.youtube.com/watch?v=Lk3Kh-J3Kvk&list=PLvv_t6_cOJ78zkycowopf93M-aITT1wAD&index=3 Using the links below, note the general position of the stomach. It can vary in size and shape quite significantly from one to another. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/systems/13 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528593 Consider also the following parts of the stomach: o Fundus o Antrum and pylorus o Body o Greater and lesser curvatures 15  MEDI7100 – The upper GI (Mouth to Stomach) An empty stomach tends to keep much the same overall shape, but it flattens from front to back (that is, antero-posteriorly). When full, it assumes a much more globular shape, and there is usually a gas bubble of varying size in the fundus (when in the upright position). Using the following link to a gastroscopy, note the numerous folds in the gastric mucosa of the stomach – these are the rugae. Note also the pyloric sphincter, a thick circular muscle. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/imaging/54 The following arteries supply the stomach: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/systems/29 o Left gastric artery o Right Gastric artery o Right gastroepiploic artery o Left gastroepiploic artery o Short gastric arteries Left gastric artery, from the coeliac trunk, supplies mainly the lesser curvature from the upper part heading down and to the right. This joins with the right gastric artery, usually from the common hepatic artery, heading back around the lesser curve from right to left. This forms an arterial arc running around the lesser curve, with branches running from it onto the stomach. In a very similar way, there are two gastroepiploic arteries (“epiploic” refers to omentum) that form an arc running around the greater curvature. The left gastroepiploic artery arises from the splenic artery near or in the hilum of the spleen, and runs down and around to the right where it joins the right gastroepiploic artery that arises from the gastroduodenal artery. In addition to these four main arteries, there are some smaller arteries that arise from the splenic artery near the hilum of the spleen and run towards the right to supply mainly the fundus of the stomach. These are the short gastric arteries. 16  MEDI7100 – The upper GI tract (Mouth to Stomach) Using the links below, note the lesser omentum. It attaches to the stomach, and to the liver (this is also known as the gastrohepatic ligament). http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/dissection/22 https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528607 17  MEDI7100 – The upper GI tract (Mouth to Stomach) The greater omentum is essentially continuous around the greater curvature of the stomach. If you follow it round and up towards the fundus, it attaches to the spleen with two folds of peritoneum – the gastrosplenic ligament. This whole structure embryologically forms from the dorsal mesogastrium, with the spleen forming within the dorsal mesogastrium. The rest of the dorsal mesogastrium, between the spleen and the left kidney and diaphragm, is the lienorenal ligament (also known as the spleno-renal ligament. “Lieno” refers to the spleen). The omentum can be a difficult anatomical concepts to comprehend. One way to manage this, is by carefully considering its embryological origins. Before you proceed, we recommend that you consider the link below: https://aclandanatomy-com.ap1.proxy.openathens.net/MultimediaPlayer.aspx?multimediaId=10528605 Using the links below, consider also the peritoneal cavity and greater omentum http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/dissection/16 http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/dissection/17 Entry into the lesser sac is via the gastrocolic ligament (an important surgical manoeuvre), and the following picture shows this part of the greater omentum cut through, and the stomach reflected upwards to reveal the posterior abdominal wall structures, such as the pancreas. 18  MEDI7100 – The upper GI tract (Mouth to Stomach) The free edge of the lesser omentum is where the ventral mesogastrium finishes. The lesser sac, you will recall, lies behind the stomach, and in front of the pancreas. In the free edge of the lesser omentum note: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/regions/24 o Portal vein (posteriorly) o Bile duct o Hepatic artery Using the same link, also recognise the opening with these three structures in front, and the IVC, liver, right suprarenal gland, and perhaps the upper pole of the right kidney behind. This is the opening into the lesser sac of the peritoneal cavity – known as the epiploic foramen (also widely known by its eponym of the foramen of Winslow). In cases of severe bleeding from the liver, during abdominal surgery, there is a manoeuvre whereby a finger is placed through the epiploic foramen, and the structures in the free edge of the lesser omentum (portal vein, hepatic artery, and bile duct) are grasped between the thumb in front and the finger behind or by a clamp. This can control the bleeding significantly, and is known as the Pringle Manoeuvre. It is used to gain control of massive haemorrhage until a more definitive strategy can be applied. 7. Lymphatic Drainage Lymphatic drainage of the stomach tends to follow its arterial supply back, as is the case generally. So, a cancer of the stomach can spread to nodes in the spleen, the pancreas, greater omentum, and to the para-aortic nodes. Because of their importance in surgery for cancers of stomach and OGJ they are numbered as lymph node stations – this is illustrated below (this is for information only; you are not required to learn these at this stage). These allow staging of the disease and the appropriate treatment. We will cover this in greater detail next year, as we take a closer look at lymphatic drainage. 19  MEDI7100 – The upper GI tract (Mouth to Stomach) There is a collection system for the lymphatic drainage of the stomach and upper small intestine, lying just below the diaphragm, called the cisterna chyli. It is named this because the fatty substances absorbed from the upper bowel form a milky-white oily fluid called chyle. This accumulates in the cisterna chyli and then the thoracic duct drains upwards from this structure, to end in the major veins at the root of the neck, draining back into the venous circulation at that point. The cisterna chyli is indicated in the link below: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/thorax/systems/36 Using the link above, consider also the thoracic duct 20  MEDI7100 – The upper GI tract (Mouth to Stomach) Lymph and chyle together empty back into the venous circulation eventually. It is not hard to imagine how malignancies of the upper GI tract – particularly the stomach – can spread to the root of the neck and subsequently back into the venous system, and thence to anywhere. A Virchow's node is a left-sided supraclavicular lymph node. Virchow's nodes take their supply from lymph vessels in the abdominal cavity and are thus sentinel lymph nodes of cancer in the abdomen, particularly gastric cancer, ovarian cancer, testicular cancer and kidney cancer, that has spread through the lymph vessels. Such spread typically results in Troisier's sign, which is the finding of an enlarged, hard Virchow's node. 21  MEDI7100 – The upper GI tract (Mouth to Stomach) Detail Building on Core Knowledge 1. The Soft Palate In relation to the soft palate, consider the skull from below. Imagine how the soft palate “hangs” from the back of the bony hard palate. The control of the soft palate is vital for coordinated swallowing, the gag reflex, and speech. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/regions/26 The soft palate consists of a sheet of fibrous aponeurosis with muscles inserted into it, and hence can be tensed and elevated. These muscles include: o The tensor veli palatini o The levator veli palatini o The musculus uvuale Using the image below, consider the tensor palati. It arises from the fossa between the pterygoid plates, and has a tendon that hooks around the pterygoid hamulus on the medial pterygoid plate, and enters the soft palate from the side. It thus pulls sideways against its opposite number, tensing the soft palate. The levator palati, arises from the inferior surface of the petrous temporal bone and the cartilaginous part of the auditory tube, and inserts into the palatine aponeurosis. As this muscle is pulling from more posteriorly, it elevates the free edge of the palate, as opposed to tensing it. Note also the palatoglossus, and the palatopharyngeus. These run downwards from the lateral part of the soft palate, forming two “arches” on the side wall of the pharynx near the back of the tongue. It is between these two folds that the palatine tonsils lie. These are indicated on the link below: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/72 22  MEDI7100 – The upper GI tract (Mouth to Stomach) The palatine tonsils are masses of lymphoid tissue, and generally called simply “the tonsils”. But the muscles that make up the two arches are also active in closing off the oral cavity from the pharynx (by moving together with the corresponding muscles on the opposite side) and moving the soft palate down like a trapdoor. The control and function of the soft palate is vital. And due to the complexity of its operation, it is one of the control mechanisms that fails in conditions such as stroke, for example. 23  MEDI7100 – The upper GI tract (Mouth to Stomach) 2. The Tongue Using the link below, consider the tongue and its muscles. http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/31 As mentioned earlier, the intrinsic muscles change the SHAPE of the tongue, while the extrinsic muscles change the POSITION of the tongue. And all of these except the palatoglossus are innervated by the hypoglossal nerve (cranial nerve XII). 24  MEDI7100 – The upper GI tract (Mouth to Stomach) Using the link above, note also the genioglossus - it is attached anteriorly to the genial tubercles on the posterior surface of the mental process of the mandible (the chin). It protrudes the tongue. If a patient has a lesion of the hypoglossal nerve, so that the muscles of the tongue on one side are paralysed, and if you ask that patient to poke out their tongue it will deviate towards the damaged side. Note from the picture below that the intrinsic muscles are in 3 dimensions – longitudinal, transverse, and vertical. Revisit the link from An@tomedia and again consider the muscles of the tongue (the intrinsic and extrinsic muscles of the tongue); what are their functions? http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/head/systems/31 3. The Oesophagus What is unusual about the nerve supply and muscle of the oesophagus? http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/thorax/systems/22 The nerve supply of the oesophagus is worth mentioning, particularly as the muscular coat of the oesophagus (inner circular and outer longitudinal) is skeletal muscle in the upper third (so-called “voluntary” muscle), smooth muscle in the lower third, and mixed in the middle third. It forms a gradual transition from top to bottom. So, the nerve supply is interesting. Special motor fibres in the vagus supply the skeletal muscle in the upper oesophagus. Parasympathetic preganglionic fibres also from the vagus enter the smooth muscle in the lower part, with these fibres synapsing in the wall of the oesophagus with very short postganglionic fibres then supplying the smooth muscle. 25  MEDI7100 – The upper GI tract (Mouth to Stomach) The vagus is not JUST a parasympathetic nerve, although that is its major function. It supplies skeletal muscle (oesophagus, and you will recall that it also supplies most of the skeletal muscle of the pharynx, and larynx too). This is an example of so-called “voluntary” skeletal muscle acting in an involuntary way, innervated by the vagus – although swallowing, speech etc can be initiated voluntarily, the actual muscle functions are largely autonomous once initiated. It is hard to stop a swallow once it is under way. There is also sympathetic innervation of the oesophagus, both directly from the sympathetic trunk and via branches from the splanchnic nerves (all as postganglionic fibres). These are thought to act contrary to the parasympathetic fibres, causing relaxation of the oesophagus to allow bolus passage. Pain from the oesophagus is also mediated via these sympathetic connections back to the sympathetic trunks. This is the pain that is commonly referred to as “heartburn” as it is burning in nature and situated just behind the lower sternum, and is usually caused by acid reflux from the stomach. Using the link below, note the splanchnic nerves: http://www.anatomediaonline.com.ap1.proxy.openathens.net/amedia/app/#!/content/abdo/dissection/35 o Greater splanchnic nerves o Lesser splanchnic nerves o Least splanchnic nerves Three thoracic splanchnic nerves pass from sympathetic ganglia along the sympathetic trunk in the thorax to the prevertebral plexus and ganglia associated with the abdominal aorta in the abdomen. The greater splanchnic nerve arises from the fifth to the ninth (or tenth) thoracic ganglia and descends obliquely on the vertebral bodies, supplies branches to the descending thoracic aorta, and perforates the ipsilateral diaphragmatic crus to end mainly in the coeliac but partly in the aorticorenal ganglion and suprarenal (adrenal) gland. 26  MEDI7100 – The upper GI tract (Mouth to Stomach) The lesser splanchnic nerve arises from the ninth and tenth (or tenth and eleventh) thoracic ganglia and pierces the diaphragm with the greater splanchnic nerve and joins the aorticorenal ganglion. The least splanchnic nerve, when present, arises from the twelfth thoracic ganglion and travels to the renal plexus. 27  MEDI7100 – The upper GI tract (Mouth to Stomach) Imaging Anatomy 1. Plain Radiography Abdominal radiography (AXR) can be useful in many settings. Before the advent of computed tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology and often allowed indirect evaluation of other abdominal viscera. Consider the detailed discussion of AXR at the case below: https://radiopaedia.org/articles/abdominal-radiography?lang=gb. Case courtesy of Amanda Er, Radiopaedia.org, rID: 38094. Normal AXR cases are available at the links below. Normal AXR. The large bowel (red), small bowel (blue), kidneys (yellow) and liver (blue) are demonstrated. Note that a normal liver variant (Riedel lobe) is visible on image C. In most cases the inferior margin of the liver does not extend below the lower pole of the right kidney (as shown in D). From: https://radiopaedia.org/cases/normal- abdominal-x-ray-2?lang=gb (Case courtesy of Dr Jeremy Jones, Radiopaedia.org, rID: 34071). In the acute setting AP supine (AXR), PA erect (AXR) and an erect chest (CXR) is obtained. These projections allow assessment of intestinal distension and air fluid levels. The erect CXR allows detection of pneumoperitoneum, as free gas accumulates under the hemidiaphragm. Pneumoperitoneum. Free gas under the right hemidiaphragm and central tendon. Distended bowel loops are also seen. In this case the pneumoperitoneum occurred following bowel infarction and perforation. From: https://radiopaedia.org/cases/pneumoperitoneum-26?lang=gb (Case courtesy of Dr Varun Babu, Radiopaedia.org, rID: 19474) 28  MEDI7100 – The upper GI tract (Mouth to Stomach) As with other standard imaging, a systematic approach to interpretation of AXR is useful. The ABDO X mnemonic provides one such approach. Consider the following links before you proceed: https://radiopaedia.org/articles/abdominal-x-ray-review-abdo-x?lang=gb. Case courtesy of Dr Jeremy Jones, Radiopaedia.org, rID: 56824. https://medicine-program.uq.edu.au/radiology-resources/video-tutorials-how-series. Radiology Resources is found through the medicine subject guide on the UQ library, this resources contains many short lectures on image interpretation and diagnostic case examples. The diagnosis of free peritoneal gas is an important finding. On AXR, Rigler’s sign, gas is seen on both sides of the bowel wall: within the bowel's lumen and within the peritoneal cavity, outlining the wall. Pneumoperitoneum (https://radiopaedia.org/articles/pneumoperitoneum) with Rigler sign (annotated image; https://radiopaedia.org/articles/rigler-sign-bowel). Caecal perforation was confirmed operatively. Case courtesy of Dr Jeremy Jones, Radiopaedia.org, rID: 8041 It is important to be aware of pitfalls and the importance of the clinical context as always. One of these is Chilaiditi syndrome, with interposed colon between the diaphragm and the liver mimicking a pneumoperitoneum on plain CXR. 29  MEDI7100 – The upper GI tract (Mouth to Stomach) Chilaiditi syndrome: colonic loops are noted between the right hemidiaphragm and the liver. From: https://radiopaedia.org/articles/chilaiditi-syndrome (Case courtesy of Maen K H, Radiopaedia.org, rID: 36447). 2. Computed Tomography (CT) The features of the facial skeleton (particularly the zygomatic, maxillary and palatine bones) as relevant to the gastrointestinal tract are demonstrated on the labelled images below. Examine the labelled imaging cases and identify the bony features discussed above. https://radiopaedia.org/cases/ct-facial-bonesorbits-axial-labelling-questions?lang=gb. Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 62714. https://radiopaedia.org/cases/ct-facial-bonesorbits-coronal-labelling-questions?lang=gb. Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 62758. Coronal CT (bone window) demonstrating the zygomaticomaxillary suture (38) and the zygomatic arch (74). From: https://radiopaedia.org/cases/ct-facial-bonesorbits-coronal-labelling-questions?lang=gb (Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 62758) 30  MEDI7100 – The upper GI tract (Mouth to Stomach) Examine the axial CT neck below and identify the oesophagus (differentiating it from the trachea). The lymphatic levels of the neck are also considered in this case. https://radiopaedia.org/cases/ct-neck-with-annotated-scrollable-images-1?lang=gb. Case courtesy of Dr. Tabby A. Kennedy, Radiopaedia.org, rID: 74853. Axial CT demonstrating the course of the oesophagus. From: https://radiopaedia.org/cases/ct-neck-with- annotated-scrollable-images-1?lang=gb (Case courtesy of Dr. Tabby A. Kennedy, Radiopaedia.org, rID: 74853). The CT studies at the cases below demonstrate the normal appearance of the stomach. Note the key anatomical regions of the stomach: the fundus, cardia, curvatures (greater and lesser), antrum and pylorus. Examine the coronal images also, these demonstrate the curvatures of the stomach and the anatomy of the duodenum. Axial CT (portal phase) demonstrating the key anatomical features of the stomach: fundus (9), gastroesophageal junction (13), body (30), antrum (47), pylorus (51). Also note the mucosa of the stomach forms large folds – rugae. These images are ordered from most superior to inferior (A-E). From: https://radiopaedia.org/cases/ct- abdomenpelvis-upper-axial-labelling-questions?lang=gb (Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 64044) 31  MEDI7100 – The upper GI tract (Mouth to Stomach) The epiploic foramen and its relations are demonstrated on axial CT below. Axial CT (portal phase) demonstrating the epiploic foramen. The portal vein (37) (with hepatic artery and bile duct) form the portal triad and are found within the hepatoduodenal ligament (free edge of the lesser omentum). The inferior vena cava (39) (with overlying peritoneum) forms the posterior wall of the epiploic foramen (38). From: https://radiopaedia.org/cases/ct-abdomenpelvis-upper-axial-labelling-questions?lang=gb (Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 64044) 3. Ultrasound Upper abdominal ultrasound is used to investigate acute abdominal pain at the bedside. It is useful for the assessment of solid organs and fluid filled structures. Consider the following article as a summary: https://radiopaedia.org/articles/us-abdomen-summary?lang=gb. Case courtesy of Dr Patrick J Rock, Radiopaedia.org, rID: 47462. The case below demonstrates the normal appearance of the upper abdominal structures on ultrasound. Abdominal ultrasound will be further covered in the practical sessions and subsequent notes relating to the liver, spleen and pancreas. https://radiopaedia.org/cases/normal-upper-abdominal-ultrasound-male-adult-1. Case courtesy of Dr Henry Knipe, Radiopaedia.org, rID: 48019. 32  MEDI7100 – The upper GI tract (Mouth to Stomach) Normal appearance of the liver (A), gallbladder (B), bile duct (C) and spleen (D) on ultrasound. From: https://radiopaedia.org/cases/normal-upper-abdominal-ultrasound-male-adult-1 (Case courtesy of Dr Henry Knipe, Radiopaedia.org, rID: 48019). 4. Barium Swallow Barium swallow imaging can be used to investigate dysphagia. In this study, the upright patient swallows a bolus of high-density barium. A discussion of this study, with a list of indications and contraindications can be found at the case below: https://radiopaedia.org/articles/barium-swallow?lang=gb. Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 6471. A normal barium study is shown at below. Note the patency of the oesophagus, and the presence of several normal contours from surrounding structures. Normal barium swallow. https://radiopaedia.org/cases/normal-barium-swallow?lang=gb (Case courtesy of Dr Ian Bickle, Radiopaedia.org, rID: 53859) 33  MEDI7100 – The upper GI tract (Mouth to Stomach) Oesophageal motility disorders are demonstrable on barium fluoroscopy. Inability to relax the lower oesophagus occurs in achalasia. The bird beak sign on barium swallow is characterstic. Consider the bird's beak sign of the oesophagus in the case below: https://radiopaedia.org/articles/bird-beak-sign-oesophagus?lang=gb (Case courtesy of Dr Yuranga Weerakkody and A/Prof Frank Gaillard, Radiopaedia.org, rID: 5996). The bird beak sign on barium swallow in a patient with achalasia. Dilation of the upper oesophagus and tapering of the gastroesophageal junction. From: https://radiopaedia.org/cases/achalasia-49?lang=gb (Case courtesy of Dr Mohammad Taghi Niknejad, Radiopaedia.org, rID: 89229) 5. Endoscopy Upper GI endoscopy is used to examine the oesophagus and proximal stomach. A video demonstrating technique and normal findings is provided in the applied anatomy section. The following Australian Family Physician article may also be of interest. https://www.racgp.org.au/download/Documents/AFP/2015/October/october_focus-walker.pdf. Walker M, Harris A, Edwards G, Talley N. A GP primer for understanding upper gastrointestinal tract biopsy reports. Australian Family Physician. 2015;44:706-11. 6. Endoscopic Ultrasound Endoscopic ultrasound (EUS) combines the range of endoscopy with the diagnostic abilities of ultrasound. https://radiopaedia.org/articles/endoscopic-ultrasound. The ultrasound probe being positioned on the end of the endoscope allows higher frequencies to be used as less penetration is required, and hence higher resolution of the wall of the gut tube and surrounding structures. EUS is used in the imaging of the upper GI tract and surrounding structures, including lymph nodes and blood vessels. This allows more accurate tumour staging and even guided fine needle aspiration of lymph nodes for cytology. 34  MEDI7100 – The upper GI tract (Mouth to Stomach) http://educationaldimensions.com/eLearn/aspirationandbiopsy/eusterm.php https://www.hopkinsmedicine.org/gastroenterology_hepatology/_pdfs/esophagus_stomach/esophageal_cancer.p df The utility of EUS in biliary and pancreatic disease will be covered in the hepatobiliary and pancreatic notes. 35  MEDI7100 – The upper GI tract (Mouth to Stomach) 7. Imaging Protocols Aetiology for upper gastrointestinal presentations is wide ranging. It is hence important that indications for the various imaging studies are understood. The imaging pathways presented at http://www.imagingpathways.health.wa.gov.au/ assist with this. Shown below is an example pathway for the patient presenting with dysphagia. Imaging pathway for investigation of dysphagia. From: http://www.imagingpathways.health.wa.gov.au/index.php/imaging- pathways/gastrointestinal/gastrointestinal/dysphagia#pathway 36  MEDI7100 – The upper GI tract (Mouth to Stomach) Applied Clinical Anatomy 1. Cancer of the Stomach To appreciate the significance of cancer of the stomach you need to understand the anatomy of the condition itself – e.g. where is it likely to spread via either the lymph nodes or via the venous return – but also the anatomy of the surgery that may need to be performed. In your clinical rotations you will see endoscopies performed, looking down into the stomach and duodenum. Consider this video for an explanation of upper GI endoscopy: https://www.sciencedirect.com/science/article/pii/S2212097113700852 2. Developmental Abnormalities The various developmental anomalies mentioned earlier in these notes and in the lectures, such as trachea-oesophageal fistula or oesophageal atresia are particular problems in infants, and unless treated, can be incompatible with life. You will encounter some of these during your pathology studies. Types of Tracheoesophageal Fistulas. Contributed by FreeEd Net & The US Army. From: https://www.ncbi.nlm.nih.gov/books/NBK535376/ 3. Hiatus hernia Hiatus hernia is a very common problem but we don’t really know why – is it diet-related? Obesity? Is there any geographical difference in the incidence? (something for you to research). But it is important that you know the anatomy of the condition, and also to understand why a sliding hiatus hernia can be very symptomatic but rarely acutely dangerous, whereas a “rolling” (para-oesophageal) hiatus hernia has the potential for very acute life-threatening complications. 37  MEDI7100 – The upper GI tract (Mouth to Stomach) 4. Oesophageal Cancer Cancer of the oesophagus is an awful condition, related to smoking (but also occurring in non-smokers). The oesophagus is lined by non-keratinising squamous epithelium, so tumours of the main part of the oesophagus tend to be squamous cell carcinomas. Tumours close to the oesophago-gastric junction (the cardia) tend to involve the glandular gastric-type epithelium and therefore are more commonly adenocarcinomas. Treatment of oesophageal cancer is an area that can be particularly demanding, and depending on the stage at which the tumour is diagnosed, the results of treatment can range from very good to very poor. Complications of treatment are common, whether the treatment is surgical, or chemo-radiation, or both. But the anatomy of the oesophagus and the applied anatomy of the surgical options to treat this devastating condition is obviously very important. 5. Oral Health Problems involving the mouth are everyday common problems that are seen by GPs, emergency doctors, dentists, pharmacists, nurses, and a whole range of other specialties. These problems can range from fungal infections (Candidiasis, for example) that can severely impact on the ability to eat properly, problems with the teeth, problems with the tongue, palate, pharynx (e.g., pharyngeal pouch), all the way through to major malignant tumours involving the mandible, maxilla, tongue, lips, or even half the face. These can be a real challenge in terms of being able to work with the anatomy to provide airway, ability to drink and eat, and drain salivary secretions. We will see more potential problems as we study the rest of the GIT. 38  MEDI7100 – The upper GI tract (Mouth to Stomach) Cutting Edge Anatomy 39