Practical 4 Functional anatomy of esophagus and stomach

Objectives By the end of the session the students should be able to: a. Describe the functional anatomy of the esophagus and stomach, sphincters and their key relations to other abdominal organs b. Identify blood supply, lymphatic drainage and nerve supply of esophagus and stomach c. Identify clinical application

Esophagus It is muscular, collapsable tube about 25cm long joining the pharynx to the stomach. Commences at the lower border of the cricoid cartilage.(C6) Descends along the front of the spine, through the posterior mediastinum, Enters the abdomen through an opening in the right crus of the diaphragm at the level of T10 at 7 th left costal cartilage, terminates at the cardiac orifice of the stomach, opposite the (T11)

Relations of the esophagus In the Neck( cervical part of esophagus) Anteriorly- trachea, and in the lower part of the neck it is related to the thyroid gland and thoracic duct Posteiorly- the vertebral column and longus colli muscle Laterally- lobes of the thyroid gland

Relations of the esophagus In Thorax Anteriorly- Trachea, Left recurrent laryngeal nerve, Left principal bronchus, Pericardium, Left atrium, Left atrium. Posteriorly-Bodies of the thoracic vertebrae, Thoracic duct, Azygos vein, Right posterior intercostal arteries, Descending thoracic aorta (at the lower end)

On the Right side: Right mediastinal pleura, Terminal part of the azygos vein. On the Left side: Left mediastinal pleura Left subclavian artery Aortic arch Thoracic duct

Relations of esophagus In the Abdomen Anteriorly - Posterior surface of the left lobe of the Liver Posteriorly - Left crus of the Diaphragm The left and the right Vagus nerve lie on the anterior and posterior surfaces respectively.

ESOPHAGEAL CONSTRICTIONS The esophagus has 3 anatomic constrictions. The first is at the junction with the pharynx(pharyngeoesophageal junction). 15 cm from incisor teeth. The second is at the crossing with the aortic arch (22.5 cm) and the left main bronchus (27.5 cm) The third is at the junction with the stomach (40 cm). They have a considerable clinical importance. Why?

They may cause difficulties in passing an esophagoscope. In case of swallowing of caustic liquids (mostly in children), this is where the burning is the worst and strictures develop. The esophageal strictures are a common sites of the development of esophageal carcinoma. In this picture what is the importance of the scale?

Blood supply of esophagus Arterial supply- arterial supply to the esophagus in the upper third is by Inferior thyroid artery, middle third is by thoracic aorta and lower third is by the branches of the left gastric artery. Venous drainage- venous blood from the upper third of esophagus drains into inferior thyroid vein, from middle third into azygous vein and lower third into the left gastric vein which is the tributary of portal vein.

Lymph Drainage The upper third is drained into the deep cervical nodes. The middle third is drained into the superior and inferior mediastinal nodes. The lower third is drained in the celiac lymph nodes in the abdomen. 11

Nerve Supply It is supplied by sympathetic fibers from the sympathetic trunks. The parasympathetic supply comes form the vagus nerves. Inferior to the roots of the lungs, the vagus nerves join the sympathetic nerves to form the esophageal plexus. The left vagus lies anterior to the esophagus. The right vagus lies posterior to it. 12

Gastroesophageal sphincter No anatomical sphincter exist in the junction of the esophagus with the stomach. Physiologically sphincter action is produced by the circular muscles of the region The closure of the sphincter is under vagal control, and this can be augmented by the hormone gastrin and reduced in response to secretin, cholecystokinin, and glucagon. GERD, Achalasia of the cardia

Location The stomach is a dilated part of the alimentary canal. It is located in the upper part of the abdomen. It extends from beneath the left costal margin into the epigastric and umbilical regions. Most of the stomach is protected by the lower ribs. It is roughly J-shaped. 14 STOMACH

PARTS 2 Orifices: Cardiac orifice Pyloric orifice 2 Borders: Greater curvature Lesser curvature 2 Surfaces: Anterior surface Posterior surface 3 Parts: Fundus Body Pylorus: The pylorus is formed of 3 parts Pyloric antrum Pyloric canal Pyloric sphincter 15

Cardiac Orifice It is the site of the gastro- esophageal sphincter. It is a physiological rather than an anatomical, sphincter. Consists of a circular layer of smooth muscle (under vagal and hormonal control). Function: Prevents (GER) regurgitation (reflux) NB. Notice the abrupt mucosal transition from esophagus to stomach (Z- line) 16

Fundus Dome-shaped Located to the left of the cardiac orifice Usually full of gas. In X-Ray film it appears black 17

Body Extends from: The level of the fundus to The level of Incisura Angularis: A constant notch on the lesser curvature 18

Lesser Curvature Forms the right border of the stomach. Extends from the cardiac orifice to the pylorus. Attached to the liver by the lesser omentum. 19

Greater Curvature Forms the left border of the stomach. Extends from the cardiac orifice to the pylorus. Its upper part is attached to the spleen by gastrosplenic ligament Its lower part is attached to the transverse colon by the greater omentum. 20

PYLORIC ANTRUM AND PYLORUS The pyloric antrum extends from Incisura angularis to the pylorus The pylorus is a tubular part of the stomach It lies in the transpyloric plane It has a thick muscular end called pyloric sphincter. The cavity of the pylorus is the pyloric canal. 21

Anterior Relations Anterior abdominal wall Left costal margin Left pleura & lung Diaphragm Left lobe of the liver 22

Posterior Relations mach Bed: Peritoneum (Lesser sac) Left crus of diaphragm Left suprarenal gland Part of left kidney Spleen Splenic artery Pancreas Transverse mesocolon They are separated from the stomach by Peritoneum (Lesser sac except the spleen) 23

The bed of the stomach, on which the stomach rests in the supine position, is formed by the structures forming the posterior wall of the omental bursa. From superior to inferior, the bed of the stomach is formed by the left dome of the diaphragm, spleen, left kidney and suprarenal gland, splenic artery, pancreas, and transverse mesocolon

Arteries 5 arteries: As it is derived from the foregut all are branches of the celiac trunk 1- Left gastric artery: It is a branch of celiac artery. Runs along the lesser curvature. 2- Right gastric artery: From the hepatic of celiac. Runs to the left along the lesser curvature. 25

Arteries 3-Short gastric arteries – arise from the splenic artery. Pass in the gastrosplenic ligament. 4- Left gastroepiploic artery: from splenic artery Pass in the gastrosplenic ligament, along the greater curvature 5- Right gastroepiploic artery: from the gastroduodenal artery of hepatic. Passes to the left along the greater curvature. 26

Veins All of them drain into the portal circulation. The right and left gastric veins drain directly into the portal vein. The short gastric veins and the left gastroepiploic vein join the splenic vein which joins superior mesenteric vein to form portal vein. The right gastroepiploic vein drain in the superior mesenteric vein. 28

Lymph Drainage The lymph vessels follow the arteries. They first drain to the: Left and right gastric nodes Left and right gastroepiploic nodes and the Short gastric nodes Ultimately, all the lymph from the stomach is collected at the celiac nodes. 29

Nerve Supply 30

NERVE SUPPLY OF STOMACH There are two types of nerve supply of the stomach; sympathetic and parasympathetic. The sympathetic constricts the sphincters, however the parasympathetic is a secreto-motor and stimulate smooth muscles for peristaltic movement and induce evacuation. Therefore, to empty the pylorus, the sympathetic stimulation must be inhibited and the parasympathetic excited. Distribution of the vagus innervation to the stomach; the right vagus nerve innervates the posterior portion of the stomach while the left vagus supplies the anterior part of the stomach.

Parasymathetic innervation of the stomach I-The anterior gastric nerve(left vagus): 1. mainly supplies the anterior portion of the body, 2. it also innervates the liver(hepatic branch), 3. nerve to the pylorus 4. duodenal branch 5. anterior gastric branch II-The posterior gastric nerve(right vagus): 1. innervates a small portion of the anterior body, 2. a main fiber innervates the posterior body with posterior gastric branch, 3. and another celiac branch which innervates all the small intestines, up until the lateral third of the transverse colon(innervates the medial two thirds), along with the pancreas.

Sympathetic innervation of the stomach Those fibers are mainly derived from T5-T9 spinal cords, and supply their targets by the splanchnic chain, which is a branch from the thorax ganglia that penetrates the diaphragm to the abdomen. They synapse in the celiac ganglia, or the superior mesenteric ganglia, which incapsulates the blood vessels(the post ganglionic fibers pass the myenteric plexus without synapsing with it).

Gastric ulcer Gastric pain Cancers of stomach Gastroscopy Nasogastric intubation

References Clinical Anatomy by Region 9th Edition, PAGE 168 –172 Gray’s anatomy- the anatomical basis of clinical practice, 14 th edition, chapter 65, Abdominal esophagus and stomach