Stomach 1 + 2

Question 1

What are the functions of the stomach?

Answer 1

Stores food
Starts digestion of protein
Innate defence (acidic)
Little bit of car and fat digestion

Question 2

What is the term given to the digested food leaving the stomach entering into the duodenum?

Is it acidic or alkaline?

Answer 2

Chyme

Acidic

Question 3

What are the 3 general parts of the stomach?

Answer 3

Fundus

Body

Antrum

Question 4

What is the name of the point where the oesophageal tissue becomes stomach tissue? (The first part of the stomach the oesophagus leads into?)

Answer 4

Cardia

Question 5

How does the type of cell change as it goes from the oesophageal tissue to the stomach tissue (cardia)?

Answer 5

Lower oesophagus = stratified squamous

Stomach/cardia = simple columnar

Question 6

What are the 2 sphincters helping controlling the movement of contents through the stomach?

Answer 6

Lower oesophageal sphincter

Pyloric sphincter

Question 7

What are sphincters made out of?

Answer 7

Smooth muscle rings

Question 8

What is the function of the lower oesophageal sphincter?

Answer 8

Prevent reflux of stomach contents to oesophagus

Question 9

What is the function of the pyloric sphincter?

Answer 9

Controls release of chyme into the duodenum from the stomach

Question 10

What aids the lower oesophageal sphincter to remain closed?

Answer 10

Right crus of the diaphragm wraps around it
Acute angle

Question 11

What part of the stomach is the Fundus?

What part of the stomach is the body?

What part of the stomach is the antrum?

Answer 11

Fundus = upper 1/3

Body = middle 1/3

Antrum = lower 1/3

Question 12

Go to the last slide of Stomach 1 and label the stomach:

Answer 12

1 = pyloric sphincter
2 = antrum
3 = body
4 = Fundus
5 = right crus of diaphragm
6 = lower oesophageal sphincter

Question 13

What is the function of the Rugae in the stomach?

Answer 13

They are numerous folds in the walls of the stomach which can allow the stomach to expand

Question 14

What is receptive relaxation?

Answer 14

The peristalsis of food through the oesophagus towards the stomach leads to the reflex relexation of the proximal stomach (Fundus distends) so stomach can fill without a significant rise in pressure

Question 15

What are the 3 layers of muscle in the stomach from innermost to outwards?

Answer 15

Oblique
Circular
Longitudinal

Question 16

How does the thickeners of the muscle wall change as you move from proximal to distal?

Answer 16

Thinner proximal
Thicker more muscular distal

Question 17

What is the significance of the thickness of the muscular walls of the stomach getting thicker as you go from proximal to distal?

Answer 17

Food moves faster as it descends

Meaning smaller parts can advance on but larger bits of food remain to be further digested

Question 18

What cells line the entire surface of the stomach?

Answer 18

Surface mucus cells

Question 19

What is the importance of surface mucus cells lining the entire surface of the stomach?

Answer 19

Produce a protective layer of mucus to protect underlying epithelia

Question 20

What are gastric pits?

Answer 20

Invaginations of the epithelium of the stomach

Question 21

What do the gastric pits lead to in the stomach?

Answer 21

Gastric glands

Question 22

What cells are found in the gastric glands?

Answer 22

Parietal cells

Chief cells

Enteroendocrine cells (like G cells)

Question 23

What is the function of parietal cells?

Answer 23

Produce stomach acid

Question 24

What is the function of chief cells?

Answer 24

Release pepsinogen = inactive form of pepsin (is a protease)

Question 25

Where are the majority of parietal cells located?

Answer 25

Body of stomach

Question 26

Where are the majority of G cells located? What are there function?

Answer 26

Antrum Produce Gastrin

Question 27

What are some protective mechanisms of the stomach?

Answer 27

Produce bicarbonate on the epithelial membrane to help keep layer neutral Stomach cells regularly replaced Prostaglandins made to support mucosal blood flow which supports the protective mucus layer

Question 28

What is the important pump that gets put on the apical membrane of a parietal cell when it needs to produce stomach acid?

Answer 28

Proton pump = H+/K+ ATPase

Question 29

What are the 2 states a parietal cell can be in?

Answer 29

Resting state Active state

Question 30

What is a parietal cell like in the resting state?

Answer 30

Normal apical membrane Proton pumps contained within tubulovesicles within the parietal cell

Question 31

What happens to a parietal cell when it becomes activated?

Answer 31

Apical membrane invaginates forming canaliculi+microvilli to make its SA large Tubulovesicles fuse with canaliculi so proton pumps can pump into the stomach lumen

Question 32

What are the 3 phases of digestion?

Answer 32

Cephalic phase Gastric phase Intestinal phase

Question 33

What are some sensory triggers that lead to the cephalic phase of digestion/acid production?

Answer 33

Smell Sight Taste

Question 34

What are some gastric triggers that lead to the production of acid? gastric phase of digestion

Answer 34

Stretch Presence of amino acids and small peptides Food acts as a buffer higher pH

Question 35

What are some intestinal triggers leading to the production of HCl?

Answer 35

Chyme in duodenum/ presence of partially digested proteins

Question 36

What are the 3 receptors that can be activated to stimulate a parietal cell?

Answer 36

Gastrin receptors Histamine receptors Muscarinic receptors

Question 37

What simulates G cells to produce Gastrin?

Answer 37

Peptides in stomach lumen

Question 38

What type of receptors does Gastrin bind to on a parietal cell?

Answer 38

Cholecystokinin receptors

Question 39

How is acid production stimulated by vagal stimulation?

Answer 39

ACh can bind to receptors on the G cell leading to Gastrin production ACh can bind directly to Muscarinic receptors directly on the parietal cell

Question 40

How does Histamine stimulate acid production?

Answer 40

Entero-chromaffin like cell (ECL) makes histamine which binds to H2 receptors on Parietal cell making it produce HCl ECL also has a Muscarinic ACh receptor

Question 41

What cell inhibits acid production in the stomach?

Answer 41

D cell

Question 42

What hormone do D cells produce to inhibit acid production?

Answer 42

Somatostatin

Question 43

When do D cells secrete somatostatin?

Answer 43

When the pH in the stomach is very low (too acidic)

Question 44

What is the brief process of HCl being produced by the parietal cells?

Answer 44

Water + CO2 makes carbonic acid Carbonic acid dissociates to H+ and HCO3- (carbonic acid catalyses) H+ pumped out into stomach lumen across H+/K+ ATPase (apical membrane) Bicarbonate ions pumped into venous blood antiport with Cl-

Question 45

What is the alkaline tide?

Answer 45

The venous blood leaving the stomach is more alkaline due to the anions antiporter on the basal membrane exchanging HCO3- with Cl- in the parietal cell

Question 46

What substances stimulate parietal cells to produce stomach acid?

Answer 46

Gastrin (CCK receptors) ACh (Muscarinic receptors) Histamine (H2 receptors)

Question 47

Look at last slide of Stomach 2, label the parietal cell

Answer 47

1 = H2O 2 = CO2 3 = carbonic anhydrase 4 = H+ 5 = H+/K+ ATPase 6 = Cl-