Histology of the gut tube

Question 1

What are the 4 layers of the gut tube?

Answer 1

Mucosa

Submucosa

Muscularis propria

Serosa or adventitia

Question 2

What are the 3 layers of mucosa?

Answer 2

Epithelium

Lamina propria

Muscularis mucosae

Question 3

What does muscularis propria do?

Answer 3

Circular muscle

Longituinal muscle

Question 4

What does the mucosa line?

Answer 4

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.

Question 5

Where are the 4 basic mucosal types are found?

Answer 5

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

Question 6

GI Tract mucosa undergoes abrupt transition from one form to another at 4 junctions:

Answer 6

Gastro -oesophageal junction

Gastro-duodenal junction

Ileo-cecal junction

Recto - anal junction

Question 7

Answer 7

Question 8

What kind of epithelium is this?

Answer 8

Surface epithelium

Stratified squamous

Question 9

What is the red line?

Answer 9

Muscularis externa

Question 10

What two orientations do the muscular layers sit in?

Answer 10

One circular and one longituinal layer

Question 11

What do you notice about the thickness of the muscularis externa?

Answer 11

Thickest layer

Question 12

Answer 12

Question 13

What is the epithelial lining of the stomach?

Answer 13

Simple columnar epithelium

Question 14

What are the large folds present in the wall of the stomach?

Answer 14

Rugae

Question 15

Locate the gastric glands. What secretory cells are present in these

Answer 15

Muscous, parietal, chief and chief cells

Question 16

Answer 16

Question 17

What are the distinctive features of the small intestine?

Answer 17

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) 


Question 18

Answer 18

Question 19

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?

Answer 19

Goblet cells which secrete mucus

Question 20

What type of cells are present in the surface epithelium of the small intestine?

Answer 20

Enterocytes (absorptive cells) and enteroendocrine cells (as well as goblet cells)

Question 21

Where, along the gut tube, do glands extend down beyond the muscularis mucosae (interna) into the submucosa?

Answer 21

Brunner’s glands in duodenum

Question 22

The above images show two different sections of the small intestine. Which image is the duodenum?

Answer 22

Bottom image as there are lots of Brunner’s glands

Question 23

What is the distinguishing structure shown that tells you that this is the duodenum?

Answer 23

Bruner’s glands

Question 24

What is the function of these distinguishing structures?

Answer 24

To secrete bicarbonate ions to proctect the duodenum for acidic chyme

Question 25

Can you see Peyer's patches (lymph nodules) within the mucosa?

Answer 25

Yes

Question 26

Answer 26

Jejunum

Question 27

What is this? What is the arrow pointing at? What is the function of these?

Answer 27

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

Question 28

In the small duodenum What is the villi? What is the lymphocyte aggregration in lamina propria Mucous glands in submucosa

Answer 28

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

Question 29

In the jejunum What is the villi? What is the lymphocyte aggregration in lamina propria Mucous glands in submucosa

Answer 29

Villi- Tongue- Shaped with swollen ends, less abundant and of different heights Lymphocyte- Absent or rare Mucosa glands in submucosa- Absent

Question 30

In the ileum What is the villi? What is the lymphocyte aggregration in lamina propria Mucous glands in submucosa

Answer 30

Villi- Thin finger- shaped, less abundant with upper level variable Lymphocyre- Prominent lymphoid aggregations known as Peter's patches Mucosa glands in submucosa- Absent

Question 31

What is the predominant cell present in the surface epithelium?

Answer 31

Mucous secreting goblet cells

Question 32

What do you notice about the muscularis externa?

Answer 32

Outer layer has changed to 3 longitudinal strips

Question 33

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?

Answer 33

Stratified squamous epithelium Before = Simple columnar epithelium After = Stratified squamous epithelium

Question 34

What does the villi, crypts, goblet cells and muscularis mucosa look like in the small intestine?

Answer 34

Question 35

What does the villi, crypts, goblet cells and muscularis mucosa look like in the large intestine?

Answer 35