W3 - Upper GI tract

Question 1

What two types of epithelium do we tend to see in the GI?

Answer 1

Stratified squamous and simple columnar

Question 2

What two parts of the GI tract have stratified squamous epithelium and what is it’s function?

Answer 2

Oesophagus and rectum, it has a protective function

Question 3

What type of epithelium covers the majority of the GI tract and what is it’s function?

Answer 3

Simple columnar, secretion and absorption (can sometimes be protective - more immune cells in gut than anywhere else)

Question 4

What is difference between the squamous epithelium in the oesophagus and the skin?

Answer 4

It’s non-keratinised

Question 5

Which layer of the Oes contains oesophageal glands for lubrication and protection?

Answer 5

The submucosa

Question 6

What is different about the cells at the bottom of the Oes glands compared to the surface of the Oes?

Answer 6

They are columnar and not squamous

Question 7

Why is the highly proliferating basal layer of the Oes squamous epithelium at the bottom?

Answer 7

So they are protected and to not expose the lamina propria to infection

Question 8

What are the proliferative cells usually around in the Oes squamous epithelium?

Answer 8

The papillae

Question 9

Oesophageal glands produce mucin to aid movement of food from oes to stomach, where are these more typically located in this case?

Answer 9

Distal oesophagus

Question 10

Other than lubrication, what is the other function of oesophageal glands and why?

Answer 10

They produce antimicrobial peptides to help fight infection

Question 11

There are two parts to an oesophageal submucosal gland, the duct (connecting to gland) and the secretory part - gland, which is squamous and which is columnar?

Answer 11

Duct - squamous, Gland - columnar

Question 12

At the gastro-oesophageal junction what does the epithelium change from and to?

Answer 12

Protective to secretory

Question 13

Secretion of acids, digestive enzymes, mucous and lysozymes in the stomach are controlled by HMs but what triggers the release of these HMs?

Answer 13

The stretching of the rugae when food is ingested sends a signal to release HMs for digestion (switches off when food leaves stomach)

Question 14

What is the primary function of the rugae folds?

Answer 14

Allow for expansion of the stomach

Question 15

Foveolar cells in the cardia produce muc5AC, what is it’s very important function?

Answer 15

Stops the stomach acid and enzymes from digesting the stomach

Question 16

what do mucous secreting cells produce fro lubrication in the cardia?

Answer 16

Mucin6

Question 17

The body of the stomach have parietal cells within the gland, they produce HCl, how are the glands in the body more complex in structure than those in the cardia?

Answer 17

They are branched and are comprised of a base, a neck and an isthmus

Question 18

Unlike the stem cells in the oesophagus, where do the stem cells sit in the glands of the stomach’s body?

Answer 18

In the middle (isthmus)

Question 19

Foveolar cells are common to all parts of the stomach, what is a characteristic of these cells that makes sense considering they secrete muc5AC?

Answer 19

They are resistant to degradation

Question 20

In the glands in the body of the stomach, do all stem cells differentiate/migrate upwards?

Answer 20

No some up (foveolar) some down (parietal + chief)

Question 21

Mucous neck cells secrete trefoil factors and are protective, how are they found?

Answer 21

Clusters/single cells

Question 22

Parietal cells are large and round with eosinophilic cytoplasm, what do parietal cells have a lot of? (‘fried egg cells’)

Answer 22

Mitochondria and intracellular canaliculi

Question 23

Chief (zymogenic) cells or predominantly in the lower tubular gland in the stomach body, what do they secrete (other than lipids) and what does this convert to in the presence of an acid?

Answer 23

Pepsinogen (inactive enzyme), pepsin (active proteolytic enzyme)

Question 24

Zymogenic cells have a lot of rER, where is their nuclei positioned?

Answer 24

Base

Question 25

Neuroendocrine cells are found in the isthmus of the glands, what are the two HMs that they produce + what are their functions?

Answer 25

Gastrin by G cells (activates parietal cells to secrete HCl) and somatostatin by D cells (inhibits release of gastrin)

Question 26

What stimulates the release of gastrin and the release of somatostatin?

Answer 26

The parasympathetic signalling from rugae stretching (gastrin), presence of HCl (somatostatin)

Question 27

The gastric pits are larger in the pylorus than the body of the stomach, what does this mean about the HMs secreted?

Answer 27

There are more neuroendocrine cells and therefore more HMs secreted in the pylorus than the body

Question 28

What is another word for a gastric pit of a gland?

Answer 28

Foveolus

Question 29

Why are the gastric pits/foveoli in the pylorus deeper than the rest of the stomach?

Answer 29

Due to gravity, most of the food is at the base of the stomach so you need more of everything (especially muc5AC)