week 7 L2- upper GI tract

Question 1

define digestion

Answer 1

process of breaking down macromolecules to allow absorption

Question 2

define absorption

Answer 2

process of moving nutrients and water across a membrane

Question 3

name the process within the gastrointestinal system

Answer 3

ingestion, digestion absorption and excretion

Question 4

describe the structures and function of each gut wall components

Answer 4

mucosa-epithelium, lamina propria and muscularis mucosa for absorptive and secretory function
submucosa- connective tissue for nerve innervation
muscularis- smooth muscle for peristalsis
serosa/adventia- connective tissue

Question 5

role of oral cavity in digestion

Answer 5

test break down of food, muscles masseter muscles responsible for biting
salivary glands- parotid, sublingual and submaxillary secretes saliva containing lingual lipase and amylase
tongue-intrinsic muscles for fine control and extrinsic for gross movement to propagate food down pharynx

Question 6

where does the oesophagus start and finish?

Answer 6

starts at C5 and finish at T10

pass through the e neck, thorax and abdomen

Question 7

function of the oesophagus

Answer 7

conduit for food, drinks and swallowed secretions from pharynx to stomach

Question 8

structure of the oesophagus

Answer 8

squamous epithelium cells
non-keratinised, having protective function v/s wear and tear and secrete mucus for lubricating functions
tonically active muscles and swallowing centre

Question 9

difference between lining of oesophagus at the stomach entrance

Answer 9

presence of columnar epithelial cells secreting mucus compared to squamous lining the oesophagus at the neck

Question 10

function of sphincters in the stomach

Answer 10

control rate at which food gradually moves along the digestive tract

Question 11

describe the gastrointestinal reflux disease

Answer 11

inflammation of the oesophagus due to stomach acid into the oesophagus
squamous epithelium lining changed to columnar secreting mucus aka Barrette’s oesophagus
example of metaplasia-dysplasia and eventually cancer

Question 12

types of muscles in the oesophagus

Answer 12

circular and longitudinal

Question 13

describe the feature of Gastro-oesophageal junction

Answer 13

reflux-prevented by diaphragm which pinches the walls of the oesophagus to prevent acid reflux
epithelial transition- from squamous to columnar to secrete mucus as protective layer
gastric folds- rugae that allows surface area for stretch when large food quantity enters the stomach and recoil when less food comes in to occupy less space
thorax is -ve pressure whereas the abdomen is +ve pressure
preventing acid reflux

Question 14

hiatus hernia

Answer 14

part of the stomach goes into the chest-causing acid reflux

due to lower oesophageal sphincters pressure

Question 15

swallowing description

Answer 15

stage 0-3
oral stage- chewing and saliva prepare bolus, both oesophageal sphincters closed
pharyngeal stage- pharyngeal muscles guide bolus to oesophagus, both oesophageal sphincters open
upper oesophageal stage-upper sphincter close and peristalsis starts
lower oesophageal stage- lower sphincter close as food pass through

Question 16

functions of the stomach

Answer 16

breaks down food using acid and pepsin
holds and gradually release food into the duodenum
kills certain bacteria and parasite

Question 17

structures of the stomach

Answer 17

cardia and pyloric region-mucus only
body and fundus- mucus, HCL and pepsinogen
antrum- Gastrin

Question 18

what invaginate into the mucosa

Answer 18

tubular glands

Question 19

volume acid secreted by stomach

Answer 19

2L/day

150mM H+

Question 20

what is mucin

Answer 20

gel coating the stomach that contain HCO3- that protects the stomach from the acidity

Question 21

pH of stomach

Answer 21

epithelial surface 6-7

lumen 1-2

Question 22

stomach moment

Answer 22

peristalsis and segmentation

Question 23

peristalsis

Answer 23

20% stomach contraction propel chyme towards the colon

ANS control

Question 24

segmentation

Answer 24

80% stomach contraction
stretching activates the enteric NS
weaker moving chyme towards pyloric sphincters while solid chyme pushed back to body

Question 25

describe the role of chief cells

Answer 25

protein secreting cells- link to organelles

secretes pepsinogen

Question 26

describe the role of parietal cells

Answer 26

resting, mitochondria rich, presence of cannaliculi

production of HCL to activate the pepsinogen

Question 27

mechanism of HCL production in parietal cells

Answer 27

inwards CO2 transport followed by carbonic anhydrase reaction
HCO3- exchanged for chloride ion which moves to cannaliculi
K+ exchanged for Na+ which moves into the cannaliculi
using ATP K+ moves back in and H+ transported to cannaliculi through H+/K+ ATPase

Question 28

describe the role of gastrin

Answer 28

found in pyloric antrum, secrete gastrin which stimulates release of histamine from chromatin cells

Question 29

phases of gastric secretion

Answer 29

Cephalic phase, Gastric phase and intestinal phase

Question 30

describe the cephalic phase

Answer 30

conditioning through thought sight and smell stimulates the vagal nerve and PNS
increase in acid secretion and pepsin production

Question 31

describe the gastric phase

Answer 31

stimulus of food in stomach causing stretch and chemo-receptors activation
PNS response along with vagal nerve, LOCAL reflex to increase acid secretion

Question 32

describe the intestinal phase

Answer 32

3 part response- switch off the stomach
A-nervous response by afferent nerves to the brain
B-endocrine response to secrete enterogastrones in response to chyme, gastric inhibitory peptide cholecystokinin secretin
C- local response to stop HCL and Pepsin production

Question 33

how might you produce useful drug to reduce acid secretion

Answer 33

ranitidine-anti-histamine antagonist

omeprazole- proton pump inhibitor

Question 34

stimuli most likely to reduce acid secretion in stomach

Answer 34

chyme fatty acid content