upper GI tract

Question 1

what are the other names for the gastrointestinal system?

Answer 1

alimentary/ digestive system

Question 2

what is digestion?

Answer 2

break down of macromolecules to allow absorption

Question 3

what is absorption?

Answer 3

the process of moving nutrients and water across a membrane

Question 4

what are the components of the upper GI tract?

Answer 4

sublingual, sub mandibular and parotid glands, oesophagus and stomach

Question 5

what is the ‘full gut’?

Answer 5

the upper GI tract as well as the liver, pancreas, gall bladder and portion of duodenum

Question 6

what is the mid GI tract?

Answer 6

part of duodenum, jejunum, ileum, ascending colon, appendix and part of the transvers colon

Question 7

what is the lower GI tract?

Answer 7

transverse colon, descending colon, sigmoid colon, rectum and anus

Question 8

outline the gut wall structure?

Answer 8

mucosa- epithelium, lamina propria(loose connective tissue) and muscularis mucosae
submucosa- connective tissue containing nerve plexus
muscularis- smooth muscle(containing nerve plexus) 2 types - circular muscle (inner), longitudinal muscle (outer)
serosa/adventitia- connective tissue

Question 9

how many teeth are there?

Answer 9

32
8 incisors
4 canines
8 premolars
12 molars

Question 10

what muscles are there in the mouth?

Answer 10

masseter- responsible for biting
temporalis- responsible for biting
more for position of mandible

Question 11

what glands are in the oral cavity?

Answer 11

parotid, sublingual and submandibular

Question 12

what enzymes do the glands produce?

Answer 12

amylase and lipase

Question 13

what are the 2 main types of muscles of the tongue?

Answer 13

intrinsic- fine motor control and moving food

extrinsic- gross movement of tongue(in , out, up ,down), assists mechanical digestion

Question 14

what are the 2 ways of dividing the oesophagus?

Answer 14

location in body (cervical, thoracic, abdominal)
or
cm from incisors- upper third(up to 24cm), middle third(24-32cm), lower third(32-40cm)

Question 15

what is the function of the oesophagus?

Answer 15

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

Question 16

what is the epithelium of the oesophagus like, and how does each one support a function?

Answer 16

non-keratinizing- ‘wear and tear’ to wothstand temperature and textures
mucus secreting glands- lubrication

Question 17

what is the Z line?

Answer 17

a zigzag line separating pink mucosa and red mucosa of stomach meet

Question 18

what is Barret’s oesophagus?

Answer 18

epithelium of lower oesophagus turns into gastric mucosa (metaplasia)

Question 19

how is acid reflux prevented?

Answer 19

diaphragm presses it down

gastro-oesophageal position- lies at angle held by ligaments

Question 20

why are there folds in GI tract

Answer 20

increase surface area for absorption and secretion

Question 21

what does the circular muscle layer do?

Answer 21

segmental role

allows food to remain in segments

Question 22

what does the longitudinal muscle layer do?

Answer 22

propels food bolus forwards/ downwards

Question 23

outline the action of swallowing (stages0-3)

Answer 23

0 oral phase- chewing and saliva prepare bolus
both oesophageal sphincters are closed
1 pharyngeal phase- pharyngeal musculature guides food bolus towards oesophagus
both sphincters open
2 upper oesophageal phase- upper sphincter closes
superior circular muscle rings contract and inferior rings dilate
sequential contractions of long muscle
3 lower oesophageal phase- lower sphincter closes as food passes through

Question 24

what are the functions of the stomach?

Answer 24

breaks down food into smaller particles via acid and pepsin
holds food releasing it in a controlled steady rate into the duodenum
kills parasites and some bacteria

Question 25

what are the parts of the stomach (superior to inferior)

Answer 25

``` cardia(sits below gastro-oesophageal junction) fundus body antrum pyloric canal pylorus (sphincter) ```

Question 26

which regions of the stomach produce mucus only?

Answer 26

cardia and pyloric region

Question 27

which regions of the stomach produce mucus, HCL and pepsinogen (pepsin precursor)?

Answer 27

body and fundus

Question 28

which regions of the stomach produce gastrin?

Answer 28

antrum

Question 29

how much HCl is produced a day?

Answer 29

2L | has 150mM H 3 million times more than in blood

Question 30

what is in the mucins(gel coating)?

Answer 30

HCO3-

Question 31

what is the pH on the epithelial surface of stomach?

Answer 31

6-7

Question 32

what is the pH in the lumen of stomach?

Answer 32

1-2

Question 33

what are the functions of gastric muscle?

Answer 33

peristalsis (20% of stomach contractions)- propels chyme towards colon, more powerful, ANS is essential segmentation(80% of stomach contraction)- weaker, fluid chyme is pushed towards pyloric sphincter and solid chyme is pushed back to the body, enteric nervous system is activated by the stretching

Question 34

what is the gastric chief cell? and what are its characteristics?

Answer 34

``` protein-secreting epithelial cell abundant in rough ER golgi packaging and modifying for export masses of apical secretion granules secretes pepsinogen ```

Question 35

what is the stomach parietal cell and what are its characteristics?

Answer 35

secretes HCl many mitochondria cytoplasmic tubulovesicles (contain H+/K+ ATPase) internal canaliculi which extend to apical surface

Question 36

what changes when a parietal cell starts secreting?

Answer 36

tubulovesicles fuse with membrane | microvilli project into the canaliculi

Question 37

what does the secretion of HCl rely on?

Answer 37

K+ HCO3- (from CO2) and carbonic anhydrase H2 histamine receptors

Question 38

what is gastrin?

Answer 38

secreted from g cells in the antrum | stimulates histamine release from chromaffin cells (lamina propia)

Question 39

what are the phases of gastric secretion?

Answer 39

cephalic phase- though, sight, smell, taste of food etc vagus nerve stimulates parietal cell with acetylcholine gastric phase- food in stomach (stretch and chemo receptors) starts acid secretion intestinal phase- when food enters duodenum inhibition(via vagus nerve stimulating gastric inhibitory peptide, cholecystokinin and secretin) and stimulation of gastric acid

Question 40

what drugs are used to reduce acid secretion?

Answer 40

H2 blockers | proton pump inhibitors