Upper GI Tract Structure and Function

Question 1

5 main constituents of saliva

Answer 1

1. water
2. mucins
3. alpha-amylase
4. electrolytes
5. lysozymes

Question 2

what is the purpose of water in saliva

Answer 2

to soften the food and dilute it

Question 3

purpose of mucins in saliva

Answer 3

create mucousy consistency which acts as a lubricant

Question 4

purpose of alpha-amylase in saliva

Answer 4

to breakdown polysaccharides

Question 5

purpose of electrolytes in saliva

Answer 5

to maintain tonicity and pH

Question 6

purpose of lysozymes in saliva

Answer 6

to kill bacteria by cleaving polysaccharides from their cell wall

Question 7

3 pairs of glands of saliva secretion

Answer 7

parotid, submandibular and sublingual

Question 8

what parasympathetic nerves stimulate salivation

Answer 8

facial and glossopharyngeal (VII and IX)

Question 9

which nervous systems saliva is more watery

Answer 9

parasympathetic

Question 10

which nervous systems saliva has a higher mucus content

Answer 10

sympathetic

Question 11

which nervous systems saliva has a lower amylase content

Answer 11

parasympathetic

Question 12

which nervous system produces a higher volume of mucus

Answer 12

parasympathetic

Question 13

what stimulus acts on the para/symp systems for salivation

Answer 13

food in the mouth acting on chemoreceptors and pressure receptors

Question 14

roughly how long is the oesophagus

Answer 14

25cm

Question 15

four layers of oesophagus wall

Answer 15

mucosa, submucosa, muscularis externa and adventitia

Question 16

what section of the oesophagus has no adventitia

Answer 16

abdominal (i.e. below diaphragm)

Question 17

what type of epithelium in the oesophagus

Answer 17

stratified squamous

Question 18

how does the muscle of the oesophagus change from top to bottom

Answer 18

skeletal in the top 1/3

smooth in the bottom 2/3

Question 19

where is the swallowing control centre

Answer 19

in the medulla, close to the respiratory control centre

Question 20

describe the process of swallowing

Answer 20

bolus pushed to back of throat by tongue –> pharyngeal reflex triggered –> pharyngeal muscles contract –> nasopharynx close off by soft palate moving up and back –> upper oesophageal spinchter relaxes –> epiglottis covers trachea –> UOS contracts –> perstaltic wave moves bolus through oesophagus –> LOS relaxes –> bolus enters stomach

Question 21

what is the voluntary action of swallowing

Answer 21

pushing the bolus to the back of the throat by the tongue

Question 22

what happens to the stomach when the bolus enters it

Answer 22

vagal reflexes triggered by the LOS relaxing causes the stomach to relax its smooth muscle

Question 23

how long does the oesophageal phase of swallowing last

Answer 23

about 10 seconds

Question 24

how can the stomach change volume without changing pressure

Answer 24

because it unpleats its folds in wall (rugae)

Question 25

what is the pH of the stomach

Answer 25

~2

Question 26

additional muscle layer of stomach

Answer 26

oblique

Question 27

how does the oblique muscle layer aid digestion

Answer 27

by ‘ringing out’ the contents to create more mixing

Question 28

stomach anatomy from top to bottom

Answer 28

LOS –> cardiac region –> fundus –> body –> pyloric region –> pyloric sphincter

Question 29

innermost stomach muscle layer

Answer 29

oblique

Question 30

outermost stomach muscle layer

Answer 30

longitudinal