Salivary Glands, Oesophagus and Stomach Microanatomy

Question 1

What are the layers of the gut wall?

Answer 1

Mucosa; Submucosa; Musclularis externa; Serosa/adventitia

Question 2

What are the layers of the mucosa?

Answer 2

Epithelium: protection, secretion, absorption
Lamina Propria: Support (CT and BVs/nerves)
Muscularis mucosa: movement independent of peristalsis

Question 3

What are the two nerve plexi of the gut ad where are they?

Answer 3

Submucosal nerve plexus in submucosa

Myenteric nerve plexus in muscularis externa

Question 4

What are the three salivary glands, what are their secretions?

Answer 4

Parotid- Serous (25%)
Submandibular- Mixed (70%)
Sublingual- Mixed (5%)

Question 5

What are the three different cell types of the glands?

Answer 5

Serous acinus
Mucous acinus
Striated duct

Question 6

What is the structure of a serous acinus?

Answer 6

Central nuclei; darkly stained due to zymogin granules (amylase); surrounding myoepithelial cells which contract

Question 7

What is the structure of a mucous acinus?

Answer 7

Peripheral nuclei; light colour due to mucous granules

Question 8

What is the structure of a striated duct cell and what do they do?

Answer 8

Fenestrated with many mitochondria on the outside.

Metabolically active and controls flows on ions on secretions, particularly bicarbonate

Question 9

What does mucous do in saliva?

Answer 9

Lubricates and prevents bacterial adhesion.

Question 10

How do bicarbonate ions; lysozyme; lactoferrin and IgA protect saliva?

Answer 10

Bicarbonate: protects against bacterial secretions and acidic things i.e vomit.
Lysozyme: bacterial cell walls
Lactoferrin: iron dep. bacteria
IgA: bacteria and viruses.

Question 11

How do amylase; lipases and kallikrein aid digestion?

Answer 11

Amylase: breaks down CHO at pH 4-11
Lipase at pH 4
Kallikrein: causes an increase in blood supply to the glands, meaning more saliva (PSNS)

Question 12

How are salivary glands controlled by the ANS?

Answer 12

SNS: less, viscous saliva, dry mouth, high enzyme concentrate.
PSNS: More watery saliva, increased blood flow, myoepithelial cells contract.

Question 13

What do the three different stomach glands secrete?

Answer 13

Cardia- mucous
Fundus- HCl, intrinsic facor, pepsinogen, somatostatin
Pylorus- Mucuous, pepsinogen, gastrin, somatostatin

Question 14

What are the different stomach cell types?

Answer 14

Simple columnar mucuous cells; mucuous neck cells; undiff. stem cells; parietal cells; chief cells; enteroendocrine cells

Question 15

What are the features of simple columnar mucous cells and what can affect them?

Answer 15

They secrete an insoluble, alkaline mucous coat that will trap HCO3-. Also have a dense layer of phospholipids. Both these are stimulated to be made by PROSTAGLANDIN E2.
Helicobacter pylori converts urea to ammonia by urease, damaging the mucuous coat, as well as toxins (ulcerogens) harm the cell.

Question 16

What do mucous neck cells secrete?

Answer 16

Soluble acidic mucous.

Question 17

What do parietals cells secrete and how are these important?

Answer 17

HCL: provide the acidic environemnt for pepsinogen to be converted to pepsin, and to sterilise food. Decreased HCl can cause a decrease in digestion (less pepsin) and/or not all bacteria are killed, causing potentially gastroenteritis.

Intrinsic factor: aids vitmain B12 absorption, which is important in RBC haemopoiesis. Decreased IF can causes pernicious anaemia.

Question 18

What do chief cells produce?

Answer 18

pepsinogen

Question 19

How do enteroendorcine cells work?

note that they secrete hormones int blood stream of LP

Answer 19

G cells will secret gastrin, which stimulates all stomach cells and ECL cells to secrete histamine.
Histamine will stimulate PARIETAL cells and D cells to secrete somatostatin.
Somatostatin inhibits G cells and ECL cells secreting gastrin and histamine.

Prostaglandin E2 will inhibit G cells and ECL cells, meaning decrease gastrin etc. NB PE2 can be inhibited by NSAIDs such as aspirin.