Upper GI Tract Structure and Function

Question 1

why do we chew?

Answer 1

prolong the taste experience

defense against respiratory failure

Question 2

how is chewing controlled?

Answer 2

voluntary- somatic nerves- skeletal muscle of mouth/jaw

reflex- contraction of jaw muscles- pressure of food against gums

Question 3

what glands secrete saliva?

Answer 3

parotid, submandibular, sublingual

Question 4

what is in saliva and why?

Answer 4

Water: 99% of secreted fluid. Softens, moistens, dilutes particles. Solvent

Mucins: Major protein component. Mucins + water = mucus. Viscous solution - lubricant function

-Amylase: Catalyses breakdown of polysaccharide (starch, glycogen) into disaccharide (maltose) + glucose

Electrolytes: Tonicity/pH

Lysozyme: Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

Question 5

what controls salivary secretion

Answer 5

controlled by parasympathetic and sympathetic NS

both stimulatory

Question 6

in what way does the parasympathetic NS effect salivary secretion?

Answer 6

Cranial nerves VII (facial) & IX (glossopharyngeal)

Stimulation profuse watery salivery secretion

Question 7

in what way does the sympathetic NS effect salivary secretion?

Answer 7

Stimulation  small volume, viscous salivary secretion
High mucus content (a1 adrenoceptors)
High amylase content (b2 adrenoceptors)

Question 8

in what way does reflex control effect salivary secretion?

Answer 8

prescence of food in the mouth- chemoreceptors/pressure receptors

Question 9

what is the oesophagus?

Answer 9

conduit between pharynx and stomach

Question 10

what size is the oesophagus?

Answer 10

25cm

Question 11

what are the layers of the oesophagus?

Answer 11

mucosa, submucosa, muscularis externa and adventitia

Question 12

what type of epithelium is the mucosa of the oesophagus?

Answer 12

stratified squamous

Question 13

what is significant about the submucosa?

Answer 13

mucous glands are present and they have ducts which secrete lubrication

Question 14

what type of muscle is the upper 1/3 of the muscularis externa?

Answer 14

skeletal muscle

Question 15

what type of muscle is the lower 2/3 of the muscularis externa?

Answer 15

smooth muscle

Question 16

is the oral phase of swallowing voluntary or involuntary?

Answer 16

voluntary

Question 17

what pushes the bolus to the back of the mouth?

Answer 17

tongue

Question 18

what is a bolus?

Answer 18

ball-like mixture of food and saliva that forms in the mouth during the process of chewing

Question 19

what happens when bolus approaches the oesophagus?

Answer 19

Upper oseophageal sphincter (UOS) relaxes and epiglottis covers opening to larynx (prevents food entering trachea)

Question 20

what happens when food has entered oesophagus?

Answer 20

upper oesophageal sphincter contracts

Question 21

how long does it take to get from oesophagus to stomach?

Answer 21

10 seconds

Question 22

what happens when bolus nears stomach?

Answer 22

lower oesophageal sphincter relaxes- bolus enters stomach

Question 23

functions of the stomach

Answer 23

Temporary store of ingested material

Dissolve food particles and initiate digestive process

Control delivery of contents to small intestine

Sterilise ingested material

Produce intrinsic factor (Vitamin B12 absorption)

Question 24

what type of tissue is in the serosa of the stomach?

Answer 24

connective tissue outer layer

Question 25

what are the layers of the muscularis externae?

Answer 25

three layers:
longitudinal (outer),
circular (middle),
oblique (inner)

Question 26

what happens to mucosa and submucosa i the stomach?

Answer 26

Submucosa and mucosa folded (= rugae) when empty stretch as stomach fills