Upper gastrointestinal Tract

Question 1

What is digestion?

Answer 1

Digestion is the process of breaking down macromolecules to allow absorption

Question 2

What is absorption?

Answer 2

Absorption is the process of moving nutrients & water across a membrane

Question 3

What is the basic plan of the gut wall?

Answer 3

1. Mucosa
   - epithelium
   - Lamina propri (loose connective tissue)
   - Musculsris mucosae
2. submucosa (connective tissue contain nerve plexus)
3. Muscularis: smooth muscle containing nerve plexus
4. Seroda/Adventitia: connective tissue +/- epithelium

Question 4

Describe the teeth

Answer 4

TEETH - 32 in total
•8 incisors
•4 canines
•8 premolars
•12 molars

Question 5

What are the muscles in the oral cavity?

Answer 5

•Masseter muscle – largest jaw muscle
- responsible for biting
•Several muscles control position of mandible

Question 6

What are the salivary glands?

Answer 6

•Food mixed with saliva (aqueous secretion & digestive enzymes)
•Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion

Question 7

What does the tongue do?

Answer 7

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

Question 8

What is the epithelium of the oesophagus like?

Answer 8

• Non-keratinising
• ‘Wear & Tear’ lining (extremes of temp. & texture)
• Lubrication – Mucus secreting glands (& saliva)

Question 9

What is the muscle like in oesophagus?

Answer 9

• Tonically active
• Swallowing centre
• Peristalsis
• Circular muscle

Question 10

What is the Gastro-oesphgeal junction?

Answer 10

• Reflux – prevented by diaphragm
• Epithelial transition
• Gastric folds - rugae

Question 11

What is stage 0 in swallowing?

Answer 11

• Stage 0: Oral phase
• Chewing & saliva prepare bolus
• Both oesophageal sphincters constricted

Question 12

What is stage 1 in swallowing?

Answer 12

• Stage 1: Pharyngeal phase
• Pharyngeal musculature guides food bolus towards oesophagus
• Both oesophageal sphincters open

Question 13

What is stage 2 in swallowing?

Answer 13

• Stage 2: Upper oesophageal phase
• Upper sphincter closes
• Superior circular muscle rings contract & inferior rings dilate
• Sequential contractions of longitudinal muscle

Question 14

What is stage 3 in swallowing?

Answer 14

• Stage 3: Lower oesophageal phase

* Lower sphincter closes as food passes through

Question 15

What are functions of stomach?

Answer 15

• Breaks food into smaller particles (acid & pepsin)
• Holds food, releasing it in controlled steady rate into duodenum
• Kills parasites & certain bacteria

Question 16

how does acid stop going up?

Answer 16

• Neg pressure in thorax
• Pos in abdomen
• Os in Abdominal in collapsed state
• Liagemtns

Question 17

When does epithelium change?

Answer 17

• Squamous excretory in stomach
• Protective in oesophagus
• Pink and red mucous meet
• When acid in, inflammation of oesophagus and red streaks and if persistent for years epithelium changes columnar epithelium protect.
• Metaplasai, displasai and then cancer

Question 18

When does epithelium change?

Answer 18

• Squamous excretory in stomach
• Protective in oesophagus
• Pink and red mucous meet
• When acid in, inflammation of oesophagus and red streaks and if persistent for years epithelium changes columnar epithelium protect.
• Metaplasia, displasai and then cancer

Question 19

What are the different sections of the stomach?

Answer 19

1. Cardia & Pyloric Region: Mucus only
2. Body & Fundus: Mucus, HCl, pepsinogen
3. Antrum: Gastrin
4. Invaginates into mucosa – Tubular glands

Question 20

What is special about stomach?

Answer 20

-Acid
•2L/day
•150mM H+ (3 mill x that in blood)
-Mucins = gel coating
•HCO3- trapped in mucus gel
-pH at:
•Epithelial surface = 6-7
•Lumen = 1-2

Question 21

What happens in peristalsis?

Answer 21

20% stomach contractions
•Propels chyme towards colon
•more powerful as moves from LOS to pyloric sphincter
•ANS essential

Question 22

What happens in segmentation?

Answer 22

80% stomach contractions
•Weaker.
• Fluid chyme towards Pyloric sphincter
•Solid chyme pushed back to body
•Stretching activates enteric NS

Question 23

What is the chief cell?

Answer 23

• Protein-secreting epithelial cell
• Abundant RER
• Golgi packaging and modifying for export
• Masses of apical secretion granules

Question 24

What does the chief cell secrete?

Answer 24

pepsinogen

HCL coverts to pepsin

Question 25

What is the parietal cell?

Answer 25

Resting: •Many mitochondria (requires lots of ATP) •Cytoplasmic tubulovesicles (contain H+/K+ ATPase) •Internal canaliculi (extend to apical surface) -Helps in formation of HCL

Question 26

How is HCL produced?

Answer 26

1. CO2 from capillaries goes into parietal cell 2, CO2 mixes with water with enzyme carbonic anhydroase 3. Potassium comes into cells from capillaries and gets secreted into gastric lumen 4. Na+ into capillaries 5. K+ gets ex changed with H+ via hydrogen potassium ATPase pump 6, Bicarbonate acid goes back into circulation 7. Hydrogen ion combines with chloride ion atP provides energy 8. H+ and K+ gets exchnaged 9. K+ ion goes into cells and H+ goes out of cell

Question 27

What is gastrin?

Answer 27

-Hormone secreted by G cells -Stimulates to partial cell to release HCL •Pyloric antrum •Local peptide hormones – Gastrin •Stimulate histamine release from chromaffin cells (lamina propia)

Question 28

What is the cephalic phase?

Answer 28

- Parietal cell needs stimulus 1. Neuro: through sight and smell: vagus nerve 2. Homronal local pancreatic: gastrin secreted by pancreas into bloodstream stimulating parietal cells, hormone 3. Local - Local reflexes, local neural response from nerves in stomach wall: different neural plexuses - Makes stomach secrete more HCL and more enzymes

Question 29

What is intestinal phase?

Answer 29

1. enterhormones: Signal from intestinal to brain come back via vagus nerve 2. Or small bowel secrete hormones: gastric inhibitory peptide, cholecystokinin and secretin (what are entergastrones)

Question 30

What are enterogastrones?

Answer 30

Enterogastric reflex either stimulates or surpasses secretion of HCL or eosin)

Question 31

What are excitatory intestinal phase?

Answer 31

Protein concentration in duodenum stimulates gastrin secretion

Question 32

How can you produce drugs to decrease acid secretion?

Answer 32

- G poteins - Histamine - Acetylcholine - Block gastrin secretion - Omeprazole: inhibit H+ and K+ Atpase - Ranitidine for histamine-2 blocker (reversible inhibitor if action of histamine at H2 histamine receptor in gastric pariatal cell)

Question 33

Which stimuli would be most likely to decrease acid secretion in stomach?

Answer 33

Chyme fatty acid content