Junebuggin'!

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The Seamless Gut by i-heart-histo

Each region of your digestive tract is histologically different.

Specialized in its own unique way to impart a specific function. When the different regions of these tubes work together they function as a seamless system that protects, absorbs and secretes. Ensuring that we digest the products we ingest, remove the nutrients that we need and dispose of those that we don’t.

Students of histology frequently meditate on the differences between these regions in an attempt to correlate structure with function and categorize regions based on appearance.

The seamless gut tube demonstrates these differences in a single image allowing junior histologists to compare and marvel in the functional specializations of each region.

1. Esophagus (middle third)

Non-keratinized stratified squamous epithelium provides protection against the abrasive forces encountered as the bolus is transmitted toward the stomach.

A muscularis externa composed of a unique smooth and skeletal muscle mix.

2. Stomach (fundus)

Large folds of mucosa and submucosa form rugae, which allow the stomach to distend as it fills with food.

Glandular epithelium composed of gastric pits opening into deep gastric glands. These contain numerous cells each with their own role to play in the digestion process through secretion of either hydrochloric acid, pepsinogen, mucous or hormones.

3. Duodenum

The mucosa becomes heavily folded to form villi, finger-like projections that increase the surface area across which absorption can occur.

Each simple columnar epithelial cell has a highly folded apical membrane forming microvilli, which still further increase the surface area for absorption.

The distinctive Brunner’s glands in the submucosa release a bicarbonate rich secretion into the duodenal lumen to neutralize the acidic contents released from the stomach and help prevent formation of a duodenal ulcer.

4. Jejunum

Villi, microvilli and plicae circulares (circular folds of the mucosa) are evident in the jejunum. It lacks any submucosal features which makes it easy to distinguish from duodenum and ileum.

5. Ileum

The final section of the small intestine also contains villi and epithelial cells with microvilli.

Large lymphoid aggregates known as Peyer’s patches reside in the submucosa, breach into the lamina propria and making this a clear feature of ileum.

6. Appendix

Surrounded by lymphoid nodules (similar to the ileum) but this vestigial region of gut tube has no villi or microvilli. Instead its mucosa contains deep crypts of Lieberkuhn lined by goblet cells that secret mucous.

7. Colon

Distinctive because of its large crypts of Lieberkuhn lined by goblet cells that produce large volumes of mucous. The mucous facilitates the passage of feces which become increasingly drier as more water is absorbed from them as they pass through the large intestine.

The muscularis mucosa has a distinctive arrangement in the colon also. The outer longitudinal layer of muscle no longer forms a sheet of smooth muscle around the tube, but is organized into three thin, evenly spaced bands called teniae coli.

Something to think about the next time you take a bite of your sandwich?

(via aspiringdoctors)

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