[Physiology] Upper GI Tract Structure & Function

Question 1

why do we need to chew

Answer 1

Prolong taste experience
Defence against respiratory failure

Question 2

how is chewing controlled

Answer 2

Somatic nerves ⇒ skeletal muscles of mouth/jaw

Question 3

what is the chewing reflex action

Answer 3

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

⇒ inhibition of jaw muscles ⇒ reduced pressure ⇒ contraction

Question 4

water

Answer 4

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

Question 5

what makes up saliva

Answer 5

water
mucins
alpha amylase
electrolytes
lysozymes

Question 6

mucins

Answer 6

Major protein component.

Mucins + water = mucus. Viscous solution - lubricant function

Question 7

alpha amylase

Answer 7

alpha 14glycosidicbonds Catalyses breakdown of polysaccharide (starch, glycogen) into disaccharide (maltose) + glucose

Question 8

electrolytes

Answer 8

tonicity / ph control

Question 9

lysozyme

Answer 9

bacteriocidal
kill bacteria by breaking down the polysacaride component within the cell wall rendering it unviable

Question 10

dumping syndrome

Answer 10

a group of symptoms, such as diarrhea, nausea, and feeling light-headed or tired after a meal, that are caused by rapid gastric emptying. Rapid gastric emptying is a condition in which food moves too quickly from your stomach to your duodenum.

Question 11

why is it important to control ph

Answer 11

if ph is too low dental enamel in your teeth is soluble at low ph

if ph is too high tartar is formed

Question 12

parotid gland

Answer 12

takes up a substantial chunk of the side of your face. And it drains into the mouth through the palate irrigates oral cavity

Question 13

parotid duct

Answer 13

The parotid gland wraps around the back of your lower jaw. From there, saliva travels through a tube called the parotid duct.

Question 14

sublingul gland

Answer 14

irrigates mouth from below

Question 15

Submandibular gland

Answer 15

irrigates mouth from back of the mouth and below

Question 16

exocrine glands

Answer 16

glands that secrete substances on to an epithelial surface by way of a duct

lead outside of your body, also found in pancreas

Question 17

what is salivary secretion controlled by

Answer 17

both parasympathetic and sympathetic NS which are both stimulatory

Question 18

parasympathetic action on salivary glands

Answer 18

Stimulation ⇒ profuse watery salivery secretion

Question 19

what controls the parasympathetic ascpect of salivary secretion

Answer 19

Cranial nerves VII (facial) & IX (glossopharyngeal)

Question 20

sympathetic action on salivary secretion

Answer 20

Stimulation ⇒ small volume, viscous salivary secretion

Question 21

what does sympathetic salivary secretion contain high amounts of

Answer 21

High mucus content (α1 adrenoceptors)
High amylase content (β2 adrenoceptors)

Question 22

what effect would cutting the vagus nerve have on salivary secretion

Answer 22

no effect

Question 23

what is the osophagous

Answer 23

Conduit between pharynx and stomach (25cm)

Question 24

what are the four layers the osophagous contains

Answer 24

Mucosa (innermost), submucosa, muscularis externa and adventitia

Question 25

what is the mucosa in the osophagous lined with

Answer 25

stratified squamous epithelium (non-keratinised)

Question 26

what does submucosa contain

Answer 26

glands, ducts causing lubrication

Question 27

what is within the muscularis externa

Answer 27

upper 1/3 (superior) = skeletal muscle

lower 2/3 (inferior) = smooth muscle

Question 28

what regulates movement of material into and out of oesophagus

Answer 28

Upper and lower oesophageal sphincters

Question 29

skeletal muscle in the upper third of the osphagous is responsible for what

Answer 29

swallowing reflex

Question 30

smooth muscle in the lower third of the osphagous is responsible for what

Answer 30

teeth movement

Question 31

what is the oral phase of swallowing

Answer 31

Bolus pushed to back of mouth by tongue

Question 32

pharyngeal phase of swallowing

Answer 32

Presence of bolus ⇒ sequence of reflex contractions of pharyngeal muscles

Co-ordinated by swallowing centre (medulla)

Soft palate reflected backward and upward (closes off nasopharynx)

Question 33

what happens when bolus approaches the osophagous

Answer 33

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

Question 34

what happens once food has entered the osophagous

Answer 34

UOS contracts (prevents food reflux)

Question 35

Oesophageal Phase of swallowing

Answer 35

Propulsion of bolus to stomach
Peristaltic wave sweeps along entire oesophagus
Propelled to stomach in ~10 secs

Question 36

what happens as bolus nears stomach

Answer 36

Lower oesophageal sphincter (LOS) relaxes ⇒ bolus enters stomach

Question 37

Receptive relaxation of stomach

Answer 37

Initiated following relaxation of LOS and entry of bolus into stomach
Vagal reflexes ⇒ relaxation of thin, elastic smooth muscle of gastric fundus and body
Stomach volume: 50ml ⇒ 1500ml (no change in pressure)

Question 38

serosa

Answer 38

connective tissue outer layer

Question 39

Muscularis externae

Answer 39

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

Question 40

Submucosa and mucosa folded

Answer 40

(= rugae) when empty ⇒ stretch as stomach fills