Upper GIT Structure & Function

Question 1

why do you need to chew

Answer 1

Prolong taste experience

prevents against respiratory failure

Question 2

is chewing under voluntary or involuntary control

Answer 2

voluntary
Somatic nerves ⇒ skeletal muscles of mouth/jaw

Question 3

what is the voluntary control of chewing

Answer 3

Somatic nerves ⇒ skeletal muscles of mouth/jaw

Question 4

what makes up the chewing reflex

Answer 4

Contraction of jaw muscles

Question 5

what does contraction of jaw muscles result in

Answer 5

pressure of food against gums, hard palate and tongue ⇒ mechanoreceptors

inhibition of jaw muscles ⇒ reduced pressure ⇒ contraction

Question 6

what makes up saliva

Answer 6

water

mucins

alpha amylase

electrolytes

lysozyme

Question 7

water

Answer 7

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

Question 8

mucins

Answer 8

Major glycoprotein component. Mucins + water = mucus. Viscous solution - lubricant function in GI tract

Question 9

alpha amylase

Answer 9

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

Question 10

electrolytes

Answer 10

Tonicity/pH

Question 11

lysozyme

Answer 11

Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

Question 12

what does mucous cells secrete

Answer 12

mucin

Question 13

what do serous cells secrete

Answer 13

ezymes such as lipase

Question 14

what controls salivary secretion

Answer 14

Controlled by parasympathetic and sympathetic NS

Both stimulatory

Question 15

what controls the parasympathetic aspect of salivary secretion

Answer 15

Cranial nerves VII (facial) & IX (glossopharyngeal)

Question 16

what does parasympathetic stimulate

Answer 16

profuse watery salivary secretion

Question 17

what does sympathetic stimulate

Answer 17

small volume of saliva, viscous salivary secretion

High mucus content (α1 adrenoceptors) norepinephrine and sympathetic (more mucins to be converted to mucus)

High amylase content (β2 adrenoceptors) mainly in serous alveoli or alveoli cells

Question 18

what are the four layers that make up the osophagus

Answer 18

Mucosa, submucosa, muscularis externa and adventitia

Question 19

what type of epithelium is osophagus, mouth and anal mucosa lined by

Answer 19

stratified squamous epithelium (non-keratinised)

Question 20

Muscularis externa
upper 1/3 (superior)

Answer 20

skeletal muscle

Question 21

Muscularis externa
lower 2/3 (inferior)

Answer 21

smooth muscle

Question 22

whar regulates movement of material into and out of the oesophagus

Answer 22

Upper and lower oesophageal sphincters

Question 23

what is the oral phase of swallowing

Answer 23

Bolus pushed to back of mouth by tongue

Question 24

what is the pharyngeal phase of swallowing

Answer 24

Presence of bolus ⇒ sequence of reflex contractions of pharyngeal muscles

Question 25

what are the sequence of reflex contractions of pharyngeal muscles coordinated by

Answer 25

swallowing centre (medulla)

Question 26

what does the soft palate close off

Answer 26

it is reflected backward and upward - closes off nasopharynx

Question 27

what occurs as bolus approached oesophagus after swallowing

Answer 27

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

Question 28

what happens once food has entered the oesophagus

Answer 28

UOS contracts (prevents food reflux)

Question 29

oesophageal phase

Answer 29

Propulsion of bolus to stomach aided by peristaltic wave - sweeps along entire oesophagus

Question 30

how long does it take to propel bolus from oesophagus to stomach

Answer 30

10 seconds

Question 31

what occurs as bolus nears stomach

Answer 31

Lower oesophageal sphincter (LOS) relaxes ⇒ bolus enters stomach

Question 32

when is receptive relaxation of stomach

Answer 32

Initiated following relaxation of LOS and entry of bolus into stomach

Question 33

vagal reflexes

Answer 33

relaxation of thin, elastic smooth muscle of gastric fundus and body

Question 34

what can the stomach volume range between

Answer 34

50ml ⇒ 1500ml (no change in pressure)

Question 35

what are the five different functions of the stomach

Answer 35

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 36

what are the anatomical structures a bolus meets in order

Answer 36

Oesophagus ⇒ gastroesophageal (cardiac) opening (lower oesophageal (cardiac) sphincter) ⇒ cardiac region ⇒ fundus ⇒ body (greater and lesser curvature) ⇒pyloric region ⇒ pyloric opening (pyloric sphincter)

Question 37

Serosa

Answer 37

connective tissue outer layer

Question 38

Muscularis externae

Answer 38

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

Question 39

Submucosa and mucosa folded

Answer 39

(= rugae) when empty ⇒ stretch as stomach fills

Question 40

Mucus neck secrete

Answer 40

mucus

Question 41

Parietal secretes

Answer 41

HCL and IF

Question 42

Chief cells

Answer 42

secretes Pepsinogen