Histology of the gut tube Flashcards
What are the 4 layers of the gut tube?
Mucosa
Submucosa
Muscularis propria
Serosa or adventitia
What are the 3 layers of mucosa?
Epithelium
Lamina propria
Muscularis mucosae
What does muscularis propria do?
Circular muscle
Longituinal muscle
What does the mucosa line?
The gut tube- It is exposed to the contents of the gut tube
Therefore, it needs to serve different purposes depending on location in the gut tube.
Where are the 4 basic mucosal types are found?
Protective – Oral cavity, pharynx, oesophagus & anal canal
Secretory – Seen only in the stomach
Absorptive – Typical of entire small intestine
Absorptive / Protective – Lines the whole of the large intestine
GI Tract mucosa undergoes abrupt transition from one form to another at 4 junctions:
Gastro -oesophageal junction
Gastro-duodenal junction
Ileo-cecal junction
Recto - anal junction
What kind of epithelium is this?
Surface epithelium
Stratified squamous
What is the red line?
Muscularis externa
What two orientations do the muscular layers sit in?
One circular and one longituinal layer
What do you notice about the thickness of the muscularis externa?
Thickest layer
What is the epithelial lining of the stomach?
Simple columnar epithelium
What are the large folds present in the wall of the stomach?
Rugae
Locate the gastric glands. What secretory cells are present in these
Muscous, parietal, chief and chief cells
What are the distinctive features of the small intestine?
Villi (finger like projection of the mucosa)
Columnar epithelium with striated borders
Goblet cells (like bowl shaped drinking cups with no handles)
Short tubular intestinal glands (Crypts of Leiberkuhn)
What appear to be ‘spaces’ can be seen scattered between the cells of the surface epithelium: these are actually the contents of secretory cells.
What are the cells called and what do they secrete?
Goblet cells which secrete mucus
What type of cells are present in the surface epithelium of the small intestine?
Enterocytes (absorptive cells) and enteroendocrine cells (as well as goblet cells)
Where, along the gut tube, do glands extend down beyond the muscularis mucosae (interna) into the submucosa?
Brunner’s glands in duodenum
The above images show two different sections of the small intestine. Which image is the duodenum?
Bottom image as there are lots of Brunner’s glands
What is the distinguishing structure shown that tells you that this is the duodenum?
Bruner’s glands
What is the function of these distinguishing structures?
To secrete bicarbonate ions to proctect the duodenum for acidic chyme
Can you see Peyer’s patches (lymph nodules) within the mucosa?
Yes
Jejunum
What is this?
What is the arrow pointing at?
What is the function of these?
Ileum
Peyers patch
These are gut associated lymphoid tissue. These cells are presented with ingested food molecules. This includes them being presented with antigens. The Peyer’s patch will then produce sensitised lymphocytes that are delivered to the gut lymph nodes
This amplifies the immune response
Activated lymphocytes are returned to the intestinal mucosa whereas plasma cells secrete antibodies
In the small duodenum
What is the villi?
What is the lymphocyte aggregration in lamina propria
Mucous glands in submucosa
Villi- Short, leaf shaped, abundant and closely packed of varying heights
Lymphcyte- None
Mucosa glands in submucosa- Present as a typical feature- Brunner’s glands
In the jejunum
What is the villi?
What is the lymphocyte aggregration in lamina propria
Mucous glands in submucosa
Villi- Tongue- Shaped with swollen ends, less abundant and of different heights
Lymphocyte- Absent or rare
Mucosa glands in submucosa- Absent
In the ileum
What is the villi?
What is the lymphocyte aggregration in lamina propria
Mucous glands in submucosa
Villi- Thin finger- shaped, less abundant with upper level variable
Lymphocyre- Prominent lymphoid aggregations known as Peter’s patches
Mucosa glands in submucosa- Absent
What is the predominant cell present in the surface epithelium?
Mucous secreting goblet cells
What do you notice about the muscularis externa?
Outer layer has changed to 3 longitudinal strips
Can you see the change in the epithelium in the last image?
What does the SS indicate?
What type of epithelium is present before and after the junction?
Stratified squamous epithelium
Before = Simple columnar epithelium
After = Stratified squamous epithelium
What does the villi, crypts, goblet cells and muscularis mucosa look like in the small intestine?
What does the villi, crypts, goblet cells and muscularis mucosa look like in the large intestine?
