upper GI Tract

Question 1

Give a brief definition of digestion

Answer 1

Process of breaking down macromolecules to allow absorption

Question 2

Absorption

Answer 2

Proves of moving water and nutrients across a membrane

Question 3

3 sections of GI tract

Answer 3

• Upper- oesophagus and foregut- stomach, pancreas, gall bladder
• Mid- midgut- small intestine and part of transverse colon large intestine
• Lower- hind gut- entire colon, rectum and anus

Question 4

4 layers of gut wall

Answer 4

Mucosa
Submucosa
Muscularis
Serous a/adventitia

Question 5

Mucosa

Answer 5

Made of - Epithelium
- Lamina propria (loose connective tissue)
- Muscularis mucosae

Question 6

Submucosa

Answer 6

connective tissue containing nerve plexus

Question 7

Muscularis

Answer 7

smooth muscle containing nerve plexus

Muscle layer is divided in 2- circular (inner layer) and longitudinal (outer layer)

Question 8

Serosa/adventitia

Answer 8

connective tissue with or without epithelium

Question 9

How many teeth do we have

Answer 9

32 in total

• 8 incisors
• 4 canine
• 8 premolars
• 12 molars

Question 10

Largest jaw muscle that is also in charge of biting

Answer 10

Masseter

Question 11

What muscles control chewing

Answer 11

• Masseter muscle- largest jaw muscle and responsible for biting
• Temporalis muscle
• Others control position of mandible

Question 12

What 3 salivary glands do we have and what 2 enzymes are in saliva?

Answer 12

• Parotid gland
• Sublingual
• Submandibular gland
• Enzymes are lingual lipase (fat digestion) and salivary amylase (carb digestion)

Question 13

What 2 groups of muscles are involved with tongue and what are their functions?

Answer 13

• Intrinsic muscles- fine motor control and moving food
• Extrinsic- gross movement of tongue (in, out, up, down) and assist mechanical digestion

Question 14

Oesophagus

Answer 14

Conduit for food, drink & swallowed secretions from pharynx to stomach

Question 15

Describe the structure of the oesophageal epithelium and how it relates to its function?

Answer 15

• Non-keratinising (stratified) squamous epithelium
• Wear and tear lining to protect from acid reflux
• Lubrication of food bolus- mucus secreting glands and saliva

Question 16

Describe the 2 oesophagus sphincters and describe what the Z line is?

Answer 16

• Tonically active
• Swallowing centre
• 2 sphincters- upper and lower

Question 17

Is the upper or lower oesophageal sphincter a true sphincter?

Answer 17

Upper

Lower has Z line where pale pink mucosa of squamous epithelium meets red mucosa of gastric epithelium

Question 18

What is the significance of this Z line in Barrett’s oesophagus?

Answer 18

Barrett’s oesophagus extends Z line upwards as loads of pink squamous epithelium (of the lower oesophagus) undergo metaplasia to become gastric columnar epithelium

Question 19

Describe the 2 muscle types and function of oesophagus

Answer 19

• Peristalsis
• Circular muscle- has segmental role- allows food to remain in certain parts of oesophagus for some time
• Longitudinal muscle- propagates food movement down oesophagus

Question 20

Is skeletal muscle found in the upper or lower oesophagus?

Answer 20

Both

Question 21

smooth muscle found in the upper or lower oesophagus?

Answer 21

Lower

Question 22

How does epithelial transition at the gastro-oesophageal junction occur and how does this develop to cancers?

Answer 22

Acid reflux means that the upper oesophagus is more acidic than normal

To cope with this, the squamous cells above the gastro-oesophageal junction become columnar epithelium

This change to columnar epithelium makes the cells unstable, leading to dysplasia and then becomes cancers

Question 23

How is acid reflux prevented by the diaphragm?

Answer 23

prevented by diaphragm by pinching lower oesophagus

Question 24

How does the anatomical orientation of the stomach to the oesophagus reduce the risk of acid reflux?

Answer 24

Stomach lies at an angle to the oesophagus

Other ligaments also suspend the gastro-oesophageal junction at an acute angle on the fringe oesophageal ligaments to prevent acid reflux

Question 25

There are gastric folds called rugae- what is their purpose?

Answer 25

So more digestion and absorption can occur To increase the surface area of the epithelium of the gastro intestinal tract so that more amount of digestion and more absorption can occur

Question 26

Describe the 4 stages of swallowing OPUL

Answer 26

- Stage 0- oral phase - Chewing and saliva **prepare bolus** - **Both** oesophageal **sphincters constricted** - Stage 1- pharyngeal phase - Pharyngeal muscles guide food bolus towards oesophagus - **Both sphincters open** - Stage 2- upper oesophageal phase - **Upper sphincter closes** - Superior circular muscle rings contract and inferior rings dilate - Sequential contractions of longitudinal muscle - Stage 3- lower oesophageal phase **Lower sphincter closes** as food passes through

Question 27

What are the stomach's 3 functions?

Answer 27

- Breaks food into smaller particles through acid and pepsin - Holds food and releases it in controlled steady rate into duodenum - **Kills parasites** and some bacteria

Question 28

What are the sections of the stomach?

Answer 28

- **Cardia** and **pyloric region**- secretes? secretes **mucus** only - **Body** and **fundus**- secretes? secrete **mucus, HCl and pepsinogen** - **Antrum**- what does it secrete? secretes **gastrin**

Question 29

What is the pH level of the stomach and how is the epithelium protected

Answer 29

pH of 1-2 in lumen- stomach produces 2L of acid a day with 150mM H+ Epithelial surface is protected by **mucus layer with HCO3- trapped in the mucus gel**

Question 30

Peristalsis

Answer 30

- 20% of stomach contractions - Propels chyme towards colon - More powerful as it moves from LOS to pyloric sphincter - ANS is essential

Question 31

Segmentation

Answer 31

- 80% of stomach contractions - Weaker - Fluid chyme towards pyloric sphincter - Solid chyme pushed back to body - Stretching activates enteric NS

Question 32

Which layer of muscle carries out segmentational contraction

Answer 32

Circular

Question 33

Which layer of muscle carries out peristalsis contraction

Answer 33

Longitudinal

Question 34

Is segmentation or peristalsis the stronger contraction

Answer 34

Peristalsis

Question 35

Which method of contraction occurs most often

Answer 35

Segmentation 80%

Question 36

- Where does peristalsis propel chyme to?t

Answer 36

Towards colon

Question 37

Where does segmentation move chyme to (2)?

Answer 37

Fluid chyme towards pyloric sphincter Solid chyme pushed back to the body

Question 38

Describe the nervous stimulation of peristalsis?

Answer 38

Activated by ans

Question 39

Describe the nervous stimulation of segmentation?

Answer 39

Stretching activated enteric nervous system

Question 40

What do gastric chief cells do secrete + how are they adapted (3)?

Answer 40

- **Secretes pepsinogen** - Protein secreting epithelial cell **rich in RER** - **Golgi packaging** and **modifying for export** - Masses of apical secretion granules

Question 41

What do parietal cells secrete and how are they adapted (3)?

Answer 41

- **Secretes HCl** - **Many mitochondria** (requires lots of ATP) - Has **cytoplasmic tubulovesicles** which contain HCl → the vesicles contain H+/K+ ATPase pump which pumps HCl into stomach lumen - Has **internal canaliculi** which extend to apical surface -

Question 42

Describe the process of HCl formation and secretion by parietal cells

Answer 42

1) Sodium-potassium pump brings K+ into parietal cell and Na+ out, then K+ moves into canaliculi (that have fused with the tubulovesicles) 2) CO2 taken up by parietal cells and reacts with H2O using carbonic anhydrase, forming carbonic acid which dissociates into H+ and HCO3-. 3) HCO3- transported out by AE1 antiporter and Cl transported into the parietal cell and then into cannaliculi 4) H+/K+ ATPase transports H+ into the canaliculi and moves K+ from the canaliculi back into the parietal cell 5) You get left with H+ and Cl- in canaliculi which combine to make HCl

Question 43

What triggers the production and secretion of HCl? (3 things, but one of the 3 is the main one)

Answer 43

**Histamine acting on (H2) histamine receptors on parietal cells** ACh Gastrin

Question 44

- What cells is gastrin produced by and what is the **direct** function of gastrin? -

Answer 44

- Made by **pyloric antrum** by **G cells** - Gastrin is a local peptide hormone - **Stimulates histamine release from chromaffin cells** (lamina propia), which triggers HCL secretion -stimulated by distention,small peptides and amino acids via vagus nerve

Question 45

What are the 3 phases of gastric secretion? CGI

Answer 45

- Cephalic phase, describe it The **thought, sight, smell** and taste of **food** **stimulates vagus nerve** which **stimulates parietal cell through ACh** which starts **formation of HCl** (ACh can also stimulate HCl secretion along with gastrin and histamine) - Gastric phase **Food reaches stomach**, **activation of stretch and chemoreceptors** This sends signals via **vagus nerve to brain** which **sends signals back through vagus nerve** to **activate HCl secretion** - Intestinal phase Chyme reaches duodenum. Signal comes via vagus nerve which inhibits gastric HCL and pepsin through inhibitory hormones

Question 46

How might you produce a useful drug to decrease acid secretion?

Answer 46

- Receptor blockers which block histamine receptor- cimetidine and **ranitidine**- block acid secretion - K+/H+ ATPase pump inhibitors prevent HCl formation (**omeprazole**) - a selective antimuscarinic, which blocks mAch receptor

Question 47

Which of the following stimuli would most likely decrease acid secretion in stomach?

Answer 47

Protein content in meal Chyme fatty acid content