Upper GIT Structure & Function Flashcards

1
Q

why do you need to chew

A

Prolong taste experience

prevents against respiratory failure

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2
Q

is chewing under voluntary or involuntary control

A

voluntary
Somatic nerves ⇒ skeletal muscles of mouth/jaw

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3
Q

what is the voluntary control of chewing

A

Somatic nerves ⇒ skeletal muscles of mouth/jaw

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4
Q

what makes up the chewing reflex

A

Contraction of jaw muscles

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5
Q

what does contraction of jaw muscles result in

A

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

inhibition of jaw muscles ⇒ reduced pressure ⇒ contraction

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6
Q

what makes up saliva

A

water

mucins

alpha amylase

electrolytes

lysozyme

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7
Q

water

A

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

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8
Q

mucins

A

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

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9
Q

alpha amylase

A

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

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10
Q

electrolytes

A

Tonicity/pH

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11
Q

lysozyme

A

Bacteriocidal - cleaves polysaccharide component of bacterial cell wall

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12
Q

what does mucous cells secrete

A

mucin

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13
Q

what do serous cells secrete

A

ezymes such as lipase

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14
Q

what controls salivary secretion

A

Controlled by parasympathetic and sympathetic NS

Both stimulatory

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15
Q

what controls the parasympathetic aspect of salivary secretion

A

Cranial nerves VII (facial) & IX (glossopharyngeal)

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16
Q

what does parasympathetic stimulate

A

profuse watery salivary secretion

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17
Q

what does sympathetic stimulate

A

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

18
Q

what are the four layers that make up the osophagus

A

Mucosa, submucosa, muscularis externa and adventitia

19
Q

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

A

stratified squamous epithelium (non-keratinised)

20
Q

Muscularis externa
upper 1/3 (superior)

A

skeletal muscle

21
Q

Muscularis externa
lower 2/3 (inferior)

A

smooth muscle

22
Q

whar regulates movement of material into and out of the oesophagus

A

Upper and lower oesophageal sphincters

23
Q

what is the oral phase of swallowing

A

Bolus pushed to back of mouth by tongue

24
Q

what is the pharyngeal phase of swallowing

A

Presence of bolus ⇒ sequence of reflex contractions of pharyngeal muscles

25
Q

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

A

swallowing centre (medulla)

26
Q

what does the soft palate close off

A

it is reflected backward and upward - closes off nasopharynx

27
Q

what occurs as bolus approached oesophagus after swallowing

A

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

28
Q

what happens once food has entered the oesophagus

A

UOS contracts (prevents food reflux)

29
Q

oesophageal phase

A

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

30
Q

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

A

10 seconds

31
Q

what occurs as bolus nears stomach

A

Lower oesophageal sphincter (LOS) relaxes ⇒ bolus enters stomach

32
Q

when is receptive relaxation of stomach

A

Initiated following relaxation of LOS and entry of bolus into stomach

33
Q

vagal reflexes

A

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

34
Q

what can the stomach volume range between

A

50ml ⇒ 1500ml (no change in pressure)

35
Q

what are the five different functions of the stomach

A

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)

36
Q

what are the anatomical structures a bolus meets in order

A

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

37
Q

Serosa

A

connective tissue outer layer

38
Q

Muscularis externae

A

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

39
Q

Submucosa and mucosa folded

A

(= rugae) when empty ⇒ stretch as stomach fills

40
Q

Mucus neck secrete

A

mucus

41
Q

Parietal secretes

A

HCL and IF

42
Q

Chief cells

A

secretes Pepsinogen