Anatomical

Anatomical Position By TeachMeSeries Ltd (2018) Fig 1 – The oesophagusThe oesophagus originates in the neck, at the level of the sixth cervical vertebrae. It iscontinuous with the laryngeal part of the pharynx.It descends downward into the superior mediastinum of the thorax. Here, it is situatedbetween the trachea and the vertebral bodies T1 to T4. It then enters the abdomen bypiercing the muscular right crus of the diaphragm, through the oesophagealhiatus (simply, a hole in the diaphragm) at the T10 level.Anatomical StructureThe phrenoesophageal ligament connects the oesophagus to the border of theoesophageal hiatus. This permits independent movement of the oesophagus anddiaphragm during respiration and swallowing.The abdominal part of oesophagus is approximately 2cm long – it terminates by joiningthe cardiac orifice of the stomach at level of T11.Muscular layersThe oesophagus consists of an internal circular and external longitudinal layer ofmuscle. Furthermore, the external longitudinal layer is composed of different muscletypes in each third of the oesophagus: Superior third – voluntary striated muscle Middle third – voluntary striated and smooth muscle Inferior third – smooth muscleFood is transported through the oesophagus by peristalsis – a rhythmic contractions ofthe muscles, which propagates down the oesophagus. Hardening of these muscularlayers can interfere with peristalsis and cause dysphagia – difficulty in swallowing.

Anatomical RelationsThe oesophagus lies close to many structures in the thorax and abdomen: Anterior Posterior Right LeftThoracic part  Trachea  Thoracic  Pleura  Subclavian artery  Left recurrent  Vertebral  Terminal part laryngeal bodies of azygous  Aortic arch nerve vein  Thoracic duct  Thoracic duct  Pericardium  Pleura  Azygous veins  Descending aortaAbdominal  Left vagus  Right vagus part nerve nerve  Posterior  Left crus of surface of the the heart diaphragmOesophageal SphinctersThere are two sphincters present in the oesophagus, known as the upper and loweroesophageal sphincters. They act to prevent the entry of air and the reflux of gastriccontents respectively.Upper Oesophageal SphincterThe upper sphincter is an anatomical, striated muscle sphincter at the junction betweenthe pharynx and oesophagus. It is produced by the cricopharyngeus muscle. Normally,it is constricted to prevent the entrance of air into the oesophagus.Lower Oesophageal SphincterThe lower oesophageal sphincter is a physiological sphincter located in the gastro-oesophageal junction (junction between the stomach and oesophagus). The gastro-oesophageal junction is situated to the left of the T11 vertebra, and is marked by thechange from oesophageal to gastric mucosa.The sphincter is classified as a physiological (or functional) sphincter, as it does not haveany specific sphincteric muscle. Instead, the sphincter is formed from four phenomena: The oesophagus enters the stomach at an acute angle. The walls of the intra-abdominal section of the oesophagus are compressed when there is a positive intra-abdominal pressure.

 The folds of mucosa present aid in occluding the lumen at the gastro-oesophageal junction. The right crus of the diaphragm has a “pinch-cock” effect.During oesophageal peristalsis, the sphincter is relaxed to allow food to enter thestomach. Otherwise at rest, the function of this sphincter is to prevent the reflux of acidicgastric contents into the oesophagus.VasculatureIn respect to its arterial and venous supply, the oesophagus can be divided into itsthoracic and abdominal components. By TeachMeSeries Ltd (2018) Fig 2 – Posterior view of the oesophagus. Some of the thoracic vasculature is noted.ThoracicThe thoracic part of the oesophagus receives its arterial supply from the branches ofthe thoracic aorta and the inferior thyroid artery (a branch of the thyrocervical trunk).Venous drainage into the systemic circulation occurs via branches of the azygous veinsand the inferior thyroid vein.AbdominalThe abdominal oesophagus is supplied by the left gastric artery (a branch of the coeliactrunk) and left inferior phrenic artery. This part of the oesophagus has a mixed venousdrainage via two routes: To the portal circulation via left gastric vein To the systemic circulation via the azygous vein.

These two routes form a porto-systemic anastomosis, a connection between the portaland systemic venous systems.LymphaticsThe lymphatic drainage of the oesophagus is divided into thirds: Superior third – deep cervical lymph nodes. Middle third – superior and posterior mediastinal nodes. Lower third – left gastric and celiac nodes. Clinical Relevance: Disorders of the Oesophagus Barrett’s OesophagusBarrett’s oesophagus refers to the metaplasia (reversible change from one differentiatedcell type to another) of lower oesophageal squamous epithelium to gastric columnarepithelium. It is usually caused by chronic acid exposure as a result of a malfunctioninglower oesophageal sphincter. The acid irritates the oesophageal epithelium, leading to ametaplastic change.The most common symptom is a long-term burning sensation of indigestion.It can be detected via endoscopy of the oesophagus. Patients who are found to have itwill be monitored for any cancerous changes. Oesophageal CarcinomaAround 2% of malignancies in the UK are oesophageal carcinomas. The clinical featuresof this carcinoma are: Dysphagia – difficulty swallowing. It becomes progressively worse over time as the tumour increases in size, restricting the passage of food. Weight lossThere are two major types of oesophageal carcinomas: squamous cell carcinoma andadenocarcinoma. Squamous Cell Carcinoma – the most common subtype of oesophagus cancer. It can occur at any level of the oesophagus. Adenocarcinoma – only occurs in the inferior third of the oesophagus and is associated with Barrett’s oesophagus. It usually originates in the metaplastic epithelium of Barrett’s oesophagus. By TeachMeSeries Ltd (2018)

Fig 3 – Endoscopic view of oesophageal varices Oesophageal VaricesThe abdominal oesophagus drains into both the systemic and portal circulation, formingan anastomosis between the two.Oesophageal varices are abnormally dilated sub-mucosal veins (in the wall of theoesophagus) that lie within this anastomosis. They are usually produced when thepressure in the portal system increases beyond normal, a state known as portalhypertension. Portal hypertension most commonly occurs secondary to chronic liverdisease, such as cirrhosis or an obstruction in the portal vein.The varices are predisposed to bleeding, with most patients presentingwith haematemesis (vomiting of blood). Alcoholics are at a high risk of developingoesophageal varices.he stomach, part of the gastrointestinal tract, is a digestive organ located betweenthe oesophagus and the duodenum.It has a ‘J’ shape, and features a lesser and greater curvature. The anterior and posteriorsurfaces are smoothly rounded with a peritoneal covering.In this article, we shall look at the anatomy of the stomach – its position, structure andneurovascular supply.Anatomical PositionThe stomach is located in the superior aspect of the abdomen. It lies inthe epigastric and umbilical regions, mostly protected by the lower portion of the ribcage.The exact size, shape and position of the stomach can vary from person to person. Forexample, in thin individuals, it is not uncommon for the stomach to extend into the pelvicregion.Anatomical Structure By TeachMeSeries Ltd (2018)

Fig 1 – The parts of the stomach.The stomach has four main regions; the cardia, fundus, body and pylorus: Cardia – surrounds the superior opening of the stomach. Fundus – the rounded portion superior to and left of the cardia. Body – the large central portion inferior to the fundus. Pylorus – connects the stomach to the duodenum.Greater and Lesser CurvaturesThe medial and lateral borders of the stomach are curved, forming the lesser and greatercurvatures: Greater curvature – forms the long, convex, lateral border of the stomach. Arising at the cardiac orifice, it arches backwards and passes inferiorly to the left. It curves to the right as it continues medially to reach the pyloric antrum. The short gastric arteries and the right and left gastro-omental arteries supply branches to the greater curvature. Lesser curvature – forms the shorter, concave, medial surface of the stomach. The most inferior part of the lesser curvature, the angular notch, indicates the junction of the body and pyloric region. The lesser curvature gives attachment to the hepatogastric ligamentand is supplied by the left gastric artery and right gastric branch of the hepatic artery. By TeachMeSeries Ltd (2018)

Fig 2 – The greater and lesser curvatures of the stomachAnatomical RelationsThe anatomical relations of the stomach are given in the table below:Anatomical StructuresRelationSuperior Oesophagus, DiaphragmInferior Head and neck of pancreasAnterior Greater omentum, abdominal wall, left lobe of liver, gall bladderPosterior Lesser sac, left kidney, left adrenal gland, splenic artery, common bile duct, gastroduodenal arterySphincters of the StomachThere are two sphincters of the stomach, located at each orifice. They control the passageof material entering and exiting the stomach.Inferior Oesophageal SphincterThe inferior oesophageal sphincter is located between the oesophagus and thestomach (in contrast to the superior oesophageal sphincter, located in the pharynx).It is located to the left of the T11 vertebra. Situated immediately superior isthe oesophageal hiatus, an opening in the diaphragm through which the oesophagustravels. Histologically, the sphincter is marked by an abrupt change from stratifiedsquamous epithelium to simple columnar.The inferior oesophageal sphincter is termed a physiological (or functional) sphincter –it does not have any specific muscle (see the oesophagus for more on this).

Pyloric SphincterThe pyloric sphincter lies between the pylorus and the duodenum. It controls of the exitof chyme (food and gastric acid mixture) from the stomach.In contrast to the inferior oesophageal sphincter, this is an anatomical sphincter. Itcontains smooth muscle, which constricts to limit the discharge of stomach contentsthrough the orifice.Emptying of the stomach occurs intermittently when intragastric pressure overcomesthe resistance of the pylorus. The pylorus is normally contracted so that the orifice is smalland food can stay in the stomach for a suitable period. Gastric peristalsis pushes thechyme through the pyloric canal into the duodenum for further digestion. By TeachMeSeries Ltd (2018) Fig 3 – The peristaltic ejection waves of the stomachGreater and Lesser OmentaWithin the abdominal cavity, the organs are covered in a double layered membrane,called the peritoneum. It supports the viscera, and attaches them the abdominal wall.The greater and lesser omenta are two structures that consist of peritoneum folded overitself (two layers of peritoneum – four membrane layers). Both omenta attach tothe stomach, and are useful anatomical landmarks: Greater omentum – hangs down from the greater curvature of the stomach. It drapes over the transverse colon and folds back upon itself before reaching the posterior abdominal wall. It features many lymph nodes, which contain macrophages to help combat infections of the GI tract. Lesser omentum – continuous with peritoneal layers of the stomach and duodenum. These two layers combine at the lesser curvature, and ascend to attach to the liver. The main function of the lesser omentum is to attach the stomach and duodenum to the liver.Together, the greater and lesser omenta divide the abdominal cavity into two; the greaterand lesser sac. The stomach lies immediately anterior to the lesser sac. The greater andlesser sacs communicate via the epiploic foramen, a hole in the lesser omentum. By TeachMeSeries Ltd (2018)

Fig 4 – The greater and lesser omenta.Neurovascular SupplyThe arterial supply to the stomach comes from the coeliac trunk and itsbranches. Anastomoses form along the lesser curvature by the right and left gastricarteriesand along the greater curvature by the right and left gastro-omental arteries: Right gastric – branch of the common hepatic artery, which arises from the coeliac trunk. Left gastric – arises directly from the coeliac trunk. Right gastro-omental – terminal branch of the gastroduodenal artery, which arises from the common hepatic artery. Left gastro-omental – branch of the splenic artery, which arises from the coeliac trunk.The veins of the stomach run parallel to the arteries. The right and left gastric veins draininto the hepatic portal vein. The short gastric vein, left and right gastro-omental veinsultimately drain into the superior mesenteric vein. By TeachMeSeries Ltd (2018)

Fig 5 – Arterial supply to the stomachInnervationThe stomach receives innervation from the autonomic nervous system: Parasympathetic nerve supply comes from the posterior vagal trunks, derived from the vagus nerve. Sympathetic nerve supply from the T6-T9 spinal cord segments pass to the coeliac plexus. It also carries some pain transmitting fibres.LymphaticsThe gastric lymphatic vessels travel with the arteries along the greater and lessercurvatures of the stomach. Lymph fluid drains into the gastric and gastro-omental lymphnodes found at the curvatures.Efferent lymphatic vessels from these nodes connect to the coeliac lymph nodes,located on the posterior abdominal wall. Clinical Relevance: Disorders of the Stomach Gastro-Oesophageal Reflux DiseaseThis is a digestive disorder affecting the lower oesophageal sphincter. It refers to themovement of gastric acid and food into the oesophagus.GORD is a common condition, affecting 5-7% of the population. Symptomsinclude dyspepsia, dysphagia, and an unpleasant sour taste in the mouth.There are three main causes of reflux disease: Dysfunction of the lower oesophageal sphincter Delayed gastric emptying Hiatal hernia (see below)

Treatment involves lifestyle changes, medication such as a PPI to reduce stomach acid,and as a last resort, surgery. Hiatus HerniaA hiatus hernia occurs when a part of the stomach protrudes into the chest throughthe oesophageal hiatus in the diaphragm. There are two main types of hiatal hernias,sliding and rolling: Sliding hiatus hernia – The lower oesophageal sphincter slides superiorly. Reflux is a common complication, as the diaphragm is no longer reinforcing the sphincter. Rolling Hiatus Hernia – The lower oesophageal sphincter remains in place, but a part of the stomach herniates into the chest next to it. By TeachMeSeries Ltd (2018) Fig 6 – Classifications of hiatus hernias. A is the normal anatomy, B is a pre-stage, C is a sliding hiatal hernia, and D is a rolling type.Rate This Article