Anatomy of the abdominal viscera: Esophagus and stomach

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Introduction0:00–0:31

Osmosis knows that anatomy can be overwhelming, but hopefully this video on the esophagus and stomach can make it a bit easier, so let's begin “digesting” this content together!
The esophagus and the stomach are part of the upper digestive tract and are involved in the first phases of digestion. We are going to use the pizza we ate for dinner last night as an example to help us explore the pathway of the esophagus and stomach.
Now, let’s start with the esophagus, which is a muscular tube that carries food from the pharynx to the stomach. We can think about the esophagus as a subway that our food travels in between these two structures.

Esophagus0:31–0:54

After the pizza we ate has been chewed and swallowed, the muscles of the esophagus help propel the bolus towards the stomach in a wave-like motion called peristalsis.

Esophagus - Layers0:54–1:29

The esophagus is made up of two muscular layers: an internal circular layer and an external longitudinal layer. In its proximal or superior third, the external layer consists of striated skeletal muscle, which is under voluntary control, while its distal or inferior third is made up of smooth muscle, which is under involuntary control.
And as you’d expect, the middle third is a transitional segment that consists of a mix of both types of muscle. The esophagus follows the curve of the vertebral column as it descends through the neck and into the mediastinum.

Esophagus - Path1:29–2:18

Once it reaches the diaphragm, it passes through the esophageal hiatus, just to the left of the median plane at the level of the T10 vertebra, where it becomes the abdominal esophagus.
The abdominal esophagus finishes its journey by becoming continuous with the stomach through the cardial orifice, which is surrounded by the cardiac sphincter.
It sits left of the midline at the level of the T11 vertebra and designates the esophagogastric junction, which is an important landmark where the mucosa abruptly changes from the stratified squamous epithelium of the esophagus to the simple columnar epithelium of the stomach.
The right border of the abdominal esophagus continues with the lesser curvature of the stomach, while its left border will eventually continue with the fundus of the stomach.
There are also important points along the length of the esophagus where there are natural constrictions. These constrictions of the esophagus are caused by four structures passing the esophagus as it descends in the cervical, thoracic and diaphragmatic regions.

Esophagus - Natural constrictions2:18–3:22

Now, to better visualize the esophagus and these constrictions, a barium swallow study can be performed which uses an x-ray imaging technique called fluoroscopy.
The cervical constriction, also known as the upper esophageal sphincter, is located at the pharyngoesophageal junction and is caused by the cricopharyngeus muscle.
The thoracic or the broncho-aortic constriction can occur at two points where the esophagus is first crossed by the arch of the aorta, and then where it’s crossed by the left main bronchus.
Lastly, the diaphragmatic constriction is where the esophagus passes through the esophageal hiatus of the diaphragm, with the diaphragm actually contributing to the lower esophageal sphincter.
These esophageal constrictions are areas where food can potentially get stuck. Now let’s talk about blood supply!

Esophagus - Arterial supply3:22–3:51

Proximally, the esophagus is supplied by branches of the inferior thyroid arteries. As we move distally, branches of the bronchial arteries and branches coming directly from the thoracic aorta supply the thoracic esophagus.
The arterial supply of the abdominal esophagus is provided by the left gastric artery which is a branch of the celiac trunk, and the left inferior phrenic artery.

Esophagus - Venous drainage3:51–4:13

The venous drainage of the thoracic esophagus occurs via the inferior thyroid vein and tributaries of the azygos vein. The venous drainage of the abdominal esophagus has two routes: to the hepatic portal venous system through the left gastric vein, and into the systemic venous system through esophageal veins entering the azygos vein.
The lymphatic drainage of the esophagus is divided into thirds; the superior third drains into deep cervical lymph nodes, the middle third into superior and posterior mediastinal lymph nodes, and the inferior third into the left gastric lymph nodes.

Esophagus - Lymphatic drainage4:13–4:28

Lastly, let’s discuss the innervation of the esophagus. It receives parasympathetic fibres from the right and left vagus nerves, and sympathetic fibers from the sympathetic trunks.

Esophagus - Innervation4:28–5:00

The vagus nerves go on to form the esophageal plexus, which also contains sympathetic fibers mainly from the greater splanchnic nerves that arise from the sympathetic trunk at the T5 to T9 level.
Its fibers synapse along the aorta - including at the celiac ganglia - before contributing to the esophageal plexus. Let’s take a quick break and try to identify the four anatomical areas of constrictions in the esophagus.

Quiz5:00–5:10

Now, let’s move on to the stomach, the next stop for our bite of pizza after its journey through the esophagus. The stomach acts as a reservoir for ingested food like our piece of pizza, and prepares it for digestion with the help of enzymes and gastric juice which gradually converts solid food into a semiliquid mixture called chyme - we can think about the stomach as our own endogenous food blender.

Stomach5:10–6:02

Now, the size, shape and position of the stomach can vary from person to person and may change even in the same person during movements such as respiration and body position.
When lying supine, the stomach can occupy parts of the epigastric region, umbilical region, left hypochondriac region, and left lumbar region of the abdomen.
On the other hand, when sitting upright, the stomach will move slightly inferior. Now that we understand what the stomach does and its position within the body, let's dig into the external anatomical features of the stomach.

Stomach - Parts6:02–7:31

The stomach has four parts: the cardia, the fundus, the body and the pyloric part, along with two curvatures: the lesser curvature and the greater curvature.
The cardia is the part surrounding the cardial orifice which is the superior opening of the stomach and where the esophagus connects to the stomach.
The cardia is located at the level of the T11 vertebra. The fundus is the dilated superior portion of the stomach and is related to the left dome of the diaphragm.
Between the fundus and the esophagus, there’s a deep notch called the cardial notch. The body of the stomach comprises the major portion of the stomach and is located between the fundus and the pyloric antrum.
The pyloric portion of the stomach is a funnel-shaped region which has a wider part called the pyloric antrum and a narrow part called the pyloric canal.
Distally, it has a sphincteric region called the pylorus which is a marked thickening of the circular layer of smooth muscle that controls passage of the stomach contents through the pyloric orifice into the duodenum.
In a supine position, the pyloric part is located at the level of the transpyloric plane, located at the L1 vertebra midway between the jugular notch superiorly and the pubic crest inferiorly, while in a standing position, its location varies from the L2 through L4 vertebra.

Stomach - Curvatures7:31–7:57

The lesser curvature of the stomach forms the shorter concave right border of the stomach which is continuous with the right side of the esophagus superiorly.
The greater curvature forms the longer convex left border of the stomach, which passes inferiorly and curves medially to reach the pyloric antrum.
Because of the unequal lengths of the two curvatures, the stomach is shaped like the letter J. Let’s take another break and try to identify the parts of the stomach as well as the two curvatures.Now, let's talk about the internal features of the stomach.

Quiz7:57–8:09

The interior of the stomach is covered by a mucous layer that protects its surface from the gastric acid secreted by the stomach’s glands.

Stomach - Layers8:09–9:01

When the gastric mucosa contracts, it forms longitudinal wrinkles called gastric folds or gastric rugae, which are most obvious toward the pyloric part and along the greater curvature.
These gastric rugae will diminish and disappear when the stomach fills and distends, which is often the case when that one bite of pizza actually turns into eating the entire pizza.
Superficial to the gastric mucosa is the muscularis externa, which consists of 3 muscular sublayers. From internal to external, these are called the oblique layer, circular layer and longitudinal layer.
These layers of smooth muscle work together to cause movement and contractions within the stomach to help churn the stomach contents necessary to digest our piece of pizza.It is also important to understand the anatomical position of the stomach in relation to all of the other organs and structures that surround and cover it.

Stomach - Anatomical position9:01–10:36

The stomach is mostly covered by visceral peritoneum. The lesser omentum, which is a small double-layered peritoneal fold extending from the lesser curvature of the stomach and proximal duodenum to the liver.
The greater omentum is actually a 4-layered peritoneal fold that extends from the greater curvature of the stomach and hangs down covering the intestines like a blanket.
Now, the anterior surface of the stomach is in close proximity to the diaphragm, the left lobe of the liver and the anterior abdominal wall, where the posterior surface of the stomach is in close proximity to the pancreas inferiorly, the spleen laterally, and the transverse colon inferolaterally, which runs along the greater curvature to the left colic flexure.
Furthermore, the stomach can also be used as a division between the two main compartments of the peritoneal cavity, the greater sac and the lesser sac, the latter of which is also known as the omental bursa.
The greater sac is the larger compartment of the peritoneal cavity and lies anterior to the stomach, whereas the lesser sac lies posterior to the stomach and lesser omentum and is a sac-like cavity that allows movement of the stomach over the structures posterior to it.
Also remember, the greater sac and lesser sac communicate with each other through the omental foramen, and opening posterior to the free edge of the lesser omentum.
Ok, let’s move on to the arterial supply of the stomach which is provided by branches of the celiac trunk. The lesser curvature is supplied by the left gastric artery and right gastric artery, and the greater curvature is supplied by the left and right gastro-omental or gastroepiploic arteries.

Stomach - Arterial supply10:36–11:10

Along these curvatures, the two gastric arteries and the two gastro-omental arteries will form anastomoses with each other.
The fundus and the upper body are supplied by the short gastric arteries and posterior gastric arteries. Now the veins are easy to remember as they mirror the arteries of the stomach.

Stomach - Venous drainage11:10–11:41

All of the venous blood from the stomach ultimately drains into the hepatic portal vein: The left gastric vein and the right gastric vein drain directly into the hepatic portal vein, while the short gastric veins and the left gastro-omental vein drain into the splenic vein that joins with the superior mesenteric vein to form the hepatic portal vein.
The right gastro-omental vein also drains directly into the superior mesenteric vein. Lymph from the stomach mainly drains to the nodes located along the lesser and greater curvature and can be organized as coming from the upper two thirds and lower third of the stomach.

Stomach - Lymphatic drainage11:41–12:22

Most of the upper two thirds of the stomach drains to the gastric lymph nodes, with lymph from the fundus and superior part of the body of the stomach also draining to the pancreaticosplenic nodes.
Lymph from the lower third closer to the lesser curvature drain to the pyloric nodes, where the inferior third closer to the greater curvature drain to the pancreaticoduodenal lymph nodes.
The lymph from all these nodes will mainly drain to the celiac nodes. Time for another break!

Quiz12:22–12:30

Try to identify the arteries of the stomach.Now, let’s talk about the innervation of the stomach! The parasympathetic innervation of the stomach is from the anterior vagal trunk and posterior vagal trunk and their branches.

Stomach - Innervation12:30–13:18

The anterior vagal trunk sends branches to the anterior surface of the stomach, liver, and duodenum. It emerges from the esophageal plexus and is formed mainly by the left vagus nerve.
The posterior vagal trunk sends branches to the posterior surface of the stomach. It emerges from the esophageal plexus and is formed mainly by the right vagus nerve.
The sympathetic innervation of the stomach is provided from the T6 to T9 segments of the spinal cord with fibers travelling to the abdomen within the greater splanchnic nerves to synapse in the celiac ganglia before they go on to innervate the stomach.
Alright, let’s finish up with a quick recap. The esophagus is a muscular tube that carries food from the pharynx to the stomach.

Review13:18–14:48

It has two layers of muscles: an internal circular layer and an external longitudinal layer. The esophagus has four anatomical constrictions where food is more likely to become stuck: one cervical constriction, two thoracic constrictions, and one diaphragmatic constriction.
The stomach is an important part of the digestive tract, located between the esophagus and the small intestine. It has four parts: the cardia, the fundus, the body and the pyloric part, along with two curvatures: the lesser curvature and the greater curvature.
The arterial supply of the stomach is provided by the celiac trunk and its branches such as the left gastric artery and right gastric artery, the left and right gastro-omental arteries, the short gastric arteries and the posterior gastric arteries.
The venous drainage is provided by the left gastric vein and right gastric vein, the short gastric veins, the left gastro-omental vein and right gastro-omental vein.
The parasympathetic innervation of the stomach is provided by branches of the anterior and posterior vagal trunks, while the sympathetic innervation of the stomach is through the greater splanchnic nerves from the T6 to T9 spinal cord
Anatomy of the abdominal viscera: Esophagus and stomach | Osmosis