Thread by @HistologyHome

GI System Histology: Tweetorial #3

Topic: Histology of the Stomach

Pop Quiz (poll in next tweet): How many layers of smooth muscle are present in the Muscularis Externa layer of the stomach?

#HistoHQ

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How many layers are found in the stomach Muscularis Externa?

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Today, we’ll focus our attention on the stomach! Similar to the esophagus (and the rest of the alimentary canal), the stomach possesses the four characteristic layers of the GI tract:

(1) Mucosa
(2) Submucosa
(3) Muscularis Externa
(4) Serosa/Adventitia

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The stomach has some general histologic trends!

Within the mucosa, simple columnar-lined gastric pits lead into gastric glands and occupy much of the Lamina Propria.

The Muscularis Externa is composed of 3 layers: Inner Oblique, Middle Circular, and Outer Longitudinal.

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The stomach is a complex organ with 4 anatomically distinct regions:

1. Cardia
2. Fundus
3. Body
4. Pylorus

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The cardia is a transitional zone between the esophagus and stomach that has a narrow lumen. This portion begins at the Z-line, which marks the change from esophageal stratified squamous to simple columnar epithelium. Its primary function is to produce mucus.

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The Fundus and Body are similar histologically! Their functions are to produce gastric acid, pepsinogen, and other secretory products. The glands are very pronounced and developed in these sections!

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Finally, the pylorus is very similar histologically to the cardia because its function is identical: to primarily produce mucus. This is a narrowing of the stomach immediately proximal to the pyloric sphincter.

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Now, let’s take some time to hone in on the gastric glands!

There are 4 main cell types:

1. Mucous Neck Cells - Not pictured here
2. Parietal Cells
3. Chief Cells
4. Enteroendocrine Cells

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This table summarizes the secretory products and relative locations of the cells!

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High yield points to remember about the stomach:

1. 3 layers of smooth muscle in the Muscularis Externa.

2. Cardia and Pylorus are primarily concerned with mucus production.

3. Body and Fundus are primarily concerned with gastric acid and pepsinogen.

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Let’s test what we’ve learned! Where are we located within the stomach with this section?

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What region of the stomach is shown in the image in the previous tweet?

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One more test! What cell type is responsible for the production of pepsinogen within the gastric glands?

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Thanks for sticking around for another week! This week’s #PathCorrelate is gastric ulcers. This is the pathological, focal loss of the mucosal layer of the stomach.

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A common presenting symptom is pain after meals. Risk factors include Helicobacter Pylori infection, excessive/prolonged NSAID use, and an imbalance of the local acidity within the stomach lumen.

#PathCorrelate

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Stay tuned for more GI System histology next week when we explore the small intestine!

#HistoHQ

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