Case 1 - Overview of the gastrointestinal tract

Question 1

what is the oral/buccal cavity lined with

Answer 1

lined by oral mucosa, a thick stratified squamous epithelium that is resistant to abrasion

Question 2

what does the mucosa produce

Answer 2

defensins to inhibit bacterial growth

Question 3

what type of teeth appear in the first 6-24 months of life

Answer 3

deciduous teeth (n=20) appear within the first months of life

Question 4

what are the deciduous teeth replaced by

Answer 4

gradually replaced in childhood as the permanent teeth erupt (finish by approx age 12)

Question 5

what is there lots of in saliva

Answer 5

IgA

Question 6

diagram showing the location of the different teeth

Answer 6

Question 7

how many incisors are there and what do they do

Answer 7

2 - slice and cut

Question 8

how many canines are there and what do they do

Answer 8

1 - tear and rip

Question 9

how many premolars are there and what do they do

Answer 9

2 - grind and crush

Question 10

how many molars are there and what do they do

Answer 10

3 - grind and crush (mostly grind)

Question 11

what is the formula used by dentists for each side of the mouth

Answer 11

formula used to show the 32 teeth in the mouth - 2 incisors in top left, right, bottom left and right and so on

Question 12

how much of saliva is water

Answer 12

approx 99%

Question 13

what are the different glands that produce saliva

Answer 13

parotid, sub lingual, and sub mandibular

Question 14

what lipases and amylases are in saliva

Answer 14

lingual lipases and alpha amylase

Question 15

is saliva slightly acidic or alkaline and why

Answer 15

slightly acidic (pH 6.75-7) to provide reasonably optimal conditions for enzyme funciton

Question 16

what act as lubricants in saliva

Answer 16

mucoproteins (mucin)

Question 17

what is the most abundant immunoglobulin in saliva

Answer 17

IgA

Question 18

what are included in saliva for dental repair

Answer 18

calcium and phosphate

Question 19

what is salivation controlled by

Answer 19

salivatory nuclei in the medulla and pons in the brainstem

Question 20

what stimulates the production of saliva with a high water content

Answer 20

mechanoreceptors and chemoreceptors in the mouth

Question 21

what is an important feature about mechanoreceptors

Answer 21

they are not food specific - non food objects induce saiation

Question 22

what can also induce salivation

Answer 22

inout from higher brain centres and lower digestive tract

Question 23

what are the two intrinsic nerve plexuses

Answer 23

myenteric nerve plexus
submucosal nerve plexus

Question 24

features of the ENS

Answer 24

the submucosal and myenteric plexuses are not simply nerve fibres from the CNS

they have their own neurones akin to the gut brain

the gut is influenced by the rest of the nervous system, but will function without any input from the brain or spinal cord

Question 25

what does contraction of the circular smooth muscle do

Answer 25

squeezes the gut contents

Question 26

what does contraction of the longitudinal muscle do

Answer 26

shortens that portion of the gut

Question 27

what cells have 'pacemaker' activity and what does this mean/do

Answer 27

interstitial cells of Cajal means that the smooth muscle layers in the gut are spontaneously active

Question 28

what does loss of the cells of Cajal lead to

Answer 28

gut motor dysfunction disorders

Question 29

how long is the oesophagus

Answer 29

25cm

Question 30

what does the submucosa contain

Answer 30

blood vessels, lymphatics, nerves, lymphoid tissue and mucus glands

Question 31

what is the oesophagus lined with

Answer 31

stratified squamous epithelium to resist abrasion

Question 32

what kind of muscle is found in the oesophagus

Answer 32

in the first third (voluntary) it is skeletal muscle in the last third (involuntary) it is smooth muscle the middle third is mixed

Question 33

what is the outer layer mostly made up of

Answer 33

adventita

Question 34

what is the last part beyond the diaphragm covered with

Answer 34

serosa

Question 35

what does the epithelium change to at the gastro-oesophageal junction

Answer 35

lining changes from squamous to columnar epithelium (glandular)

Question 36

what happens if there is metaplasia?

Answer 36

Barrett's oesophagus - change of epithelium from stratified squamous to gastric due to repeated damage form gastric reflux - precursor to oesophageal cancer

Question 37

diagram showing peristalsis in the stomach

Answer 37

Question 38

where is peristalsis confined to in the stomach

Answer 38

the lower part

Question 39

what valve opens and closes here and how is it regulated

Answer 39

the pyloric valve opens and closes and is tightly regulated

Question 40

what does the action of peristalsis and the pyloric valve result in

Answer 40

vigorous churning of contents and relatively slow gastric emptying

Question 41

what is the rate of gastric emptying controlled to some extent by

Answer 41

the caloric value of the contents of the duodenum

Question 42

what forms the numerous longitudinal folds (rugae)

Answer 42

thick mucosal and sub mucosal layers

Question 43

what happens after a meal in the small intestine

Answer 43

there are small irregular contractions of the small intestine

Question 44

what happens in the inter digestive state

Answer 44

the small intestine exhibits the migrating motor complex (MMC), which can take up to 2 hours to pass along the small intestine

Question 45

what is the signal to stop this inter digestive activity

Answer 45

ingestion of food, and this can be mimicked by gastrin and by cholecystokinin (CCK) which are released from the stomach and intestine, respectively

Question 46

what is CCK

Answer 46

is a potent inhibitor of gastric emptying in response to high caloric value in the duodenum, an example of local integration of activity to meet demand

Question 47

how active is the colon

Answer 47

active almost continuously, although increased activity can be elicited by particular stimuli

Question 48

how long is transit time in the colon

Answer 48

2-3 days

Question 49

what is the major component in terms of transit time (dehydration and storage)

Answer 49

the transverse colon is the major component

Question 50

what do contractions of the circular muscle cause

Answer 50

haustra - not like peristalsis

Question 51

what happens as one haustrum fills

Answer 51

as one haustrum fills and distends, this induces contractions that push food into the next

Question 52

what is the gastrocolic reflex

Answer 52

powerful, propulsive contractions can be elicited by the introduction of food to the stomach

Question 53

what is the function of the stomach

Answer 53

mixes food acts as a reservoir

Question 54

what starts disgestion

Answer 54

the stomach - proteins, nucleic acids

Question 55

what is the pH of the stomach and what does this do

Answer 55

pH 1-2 and this activates some enzymes

Question 56

what is the only truly essential function of the stomach

Answer 56

absorbing vitamin B12 using intrinsic factor

Question 57

what does the stomach absorb

Answer 57

alcohol some water some vitamin B12

Question 58

what produce gastrin

Answer 58

mucous cells and enteroendocrine cells produce gastrin. these are tightly coiled

Question 59

what are the exocrine gastric secretions

Answer 59

hydrochloric acid mucus pepsinogen intrinsic factor

Question 60

what are the endocrine secretions

Answer 60

gastrin somatostatin

Question 61

what are the main cells of the stomach

Answer 61

goblet cells mucous cells parietal cells chief cells G cells D cells

Question 62

what do goblet cells do

Answer 62

secrete an alkaline mucus

Question 63

what do mucous cells do

Answer 63

secrete mucus and pepsinogens

Question 64

what do parietal cells do

Answer 64

secrete gastric acid and intrinsic factor

Question 65

what do chief cells do

Answer 65

secrete pepsin and gastric lipase

Question 66

what do G cells produce

Answer 66

gastrin

Question 67

what do D cells produce and where are they found

Answer 67

found in antrum and produce somatostatin

Question 68

what does hydrochloric acid do

Answer 68

acidifies the lumen, produces pepsin from pepsinogen

Question 69

what does mucus do

Answer 69

protects mucosal surface being damaged by HCL

Question 70

what does pepsinogen do

Answer 70

precursor of pepsin (which acts as an endopeptidase)

Question 71

what does intrinsic factor do

Answer 71

important in the absorption of Vit B12 and erythropoeisis

Question 72

what does gastrin do

Answer 72

stimulates acid production

Question 73

what does somatostatin do

Answer 73

inhibits release of gastrin

Question 74

what stimulates the release of pepsinogen

Answer 74

acetylcholine i.e vagal input

Question 75

what controls and stimulates HCL

Answer 75

acetylcholine i.e vagal input gastrin (from G cells) histamine (from enterochromaffin cells) other hormones

Question 76

what is gastric acid secretion inhibited by

Answer 76

somatostatin (via decreased gastrin release) secretin (via decreased gastrin secretion) gastric inhibitory peptide and other enterogastrones (directly on parietal cells)

Question 77

what are the 3 phases of gastric secretion

Answer 77

cephalic phase gastric phase intestinal phase

Question 78

what is the cephalic stage

Answer 78

through smell, sight, taste of food releases ACh, stimulating the parietal cells and also the G cells - vagally mediated, about 40% of gastric acid secretion occurs here

Question 79

what is the gastric phase

Answer 79

distension and reflex activation of enteric neurones and vagal outflow stimulate the parietal cells and G cells. digested proteins in the stomach also stimulate the G cells - about 50% of gastric acid secretion occurs here

Question 80

what is the intestinal phase

Answer 80

amino acids present in the bloodstream (products of protein digestion) directly stimulate the parietal cells - about 10% of gastric acid secretions occurs here

Question 81

what is the gastric mechanism for the inhibition of gastric secretion

Answer 81

if proteins are present in the stomach, they act as buffers to keep luminal pH>3 as the stomach empties, therefore, the luminal pH falls below 3. D cells release somatostatin to inhibit gastrin release and thereby reduce acid secretion

Question 82

what is the duodenal mechanism of gastric secretion

Answer 82

acidification of the duodenal lumen releases secretin, which inhibits gastrin secretion acidification of the duodenal lumen and the presence of fatty acids and salt in the duodenum release gastric inhibitory peptide, which acts directly on parietal cells to inhibit HCL secretion

Question 83

main GI hormones - where are they produced and their major actions

Answer 83

Question 84

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Answer 84

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