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+ CAPS 301: Respiratory, Renal, GI, Endocrinology, Reproduction > From Mouth to Stomach > Flashcards

From Mouth to Stomach Flashcards

1
Q

What are the structures within the mouth that contribute to GI processes? (5)

A
  • lips
  • tongue
  • palate
  • teeth
  • salivary glands
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2
Q

What do lips do?

A

help guide and retain food within oral cavity

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3
Q

What does tongue do?

A

important for guiding food during chewing (keeps food bolus under teeth) and during swallowing

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4
Q

What type of muscle is the tongue?

A

skeletal muscle

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5
Q

What is the palate? What does it allow?

A

forms roof of oral cavity, separating mouth from nasal passages

allows simultaneous breathing and chewing

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6
Q

What does the uvula do?

A

closes off nasal passages during swallowing

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7
Q

What is occlusion of teeth?

A

upper and lower teeth normally fit together – responsible for grinding food during chewing

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8
Q

Why do we chew?

A
  • breaks food into smaller pieces for swallowing
  • mixes food bolus with saliva
  • stimulates taste buds
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9
Q

Is chewing voluntary or reflexive?

A

initially voluntarily, then reflexive

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10
Q

What is reflexive skeletal muscle contraction (of jaw, lip, cheek, and tongue musculature) mediated by?

A

sensory afferents within oral cavity

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11
Q

What does taste bud simulation initiate?

A

long loop reflexive increases in salivary, gastric, pancreatic and bile secretions in anticipation of ingested nutrients

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12
Q

Secretion – Salivary Glands

What is saliva?

A

secretory product associated with mouth

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13
Q

Secretion – Salivary Glands

What is saliva composed of?

A
  1. 5% water

0. 5% electrolytes and protein (most important proteins are enzymes amylase and lysozyme, and mucus)

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14
Q

Secretion – Salivary Glands

What is saliva produced by?

A

three different pairs of salivary glands located outside oral cavity – parotid, submandibular and sublingual glands

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15
Q

Secretion – Salivary Glands

What is fluid?

A

important solvent for molecules

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16
Q

Secretion – Salivary Glands

What does fluid do? (3)

A
  • stimulates taste buds
  • aids in speech by moistening lips and tongue
  • keep mouth clean by flushing food residue away
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17
Q

Secretion – Salivary Glands

What is mucus?

A

thick and slippery glycoprotein

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18
Q

Secretion – Salivary Glands

What does mucus do? (2)

A
  • helps bind food together into a bolus

- lubricates this bolus as it travels toward stomach

19
Q

Secretion – Salivary Glands

What does amylase do?

A
  • breaks down polysaccharides into maltose (2-glucose molecule)

(marks initiation of carbohydrate digestion)

20
Q

Secretion – Salivary Glands

What does lysozyme do?

A

lyses cell wall of some bacteria, conferring some protection against infection

21
Q

Secretion – Salivary Glands

What does bicarbonate ion do?

A

neutralizes acid (acts as buffer)

  • acids from foods or bacteria in oral cavity
  • acidic environment = dental caries
22
Q

Secretion – Salivary Glands

What controls salivary secretions?

A
  • autonomic control (but saliva is continuously produced)

- tonic (background) parasympathetic activity

23
Q

Secretion – Salivary Glands

Can reflexive pathways initiate saliva production?

A

yes

conditioned reflex may activate salivary centre

24
Q

Secretion – Salivary Glands

Are the two branches of ANS on salivary glands antagonistic?

A

NO

  • parasympathetic: increases production of all secretions (ACh)
  • sympathetic: decreases fluid volume, but increases mucus production = dry, sticky mouth
25
Q

Motility – Swallowing

Is swallowing voluntary or reflexive?

A
  • initiation of swallowing is voluntary

- becomes reflexive

26
Q

Motility – Swallowing

What is the reflexive nature of swallowing coordinated by?

A

‘swallowing centre’ in medulla oblongata

27
Q

Motility – Swallowing

What are the 3 phases of swalling?

A
  1. oral phase
  2. pharyngeal phase
  3. esophageal phase
28
Q

Motility – Swallowing

Oral Phase

  • what occurs
  • structures required
A
  • pushing a food bolus toward the back of oral cavity and up against the palate
  • requires tongue
29
Q

Motility – Swallowing

Where is the pharynx?

A

posterior of oral cavity, at its junction with nasal passages

30
Q

Motility – Swallowing

Pharyngeal Phase
- what occurs

A
  • touch and pressure receptors in pharyngeal palate are activated by food bolus
  • info sent to medulla via trigeminal nerve (cranial nerve V)
  • initiates reflexive component of swallowing
31
Q

Motility – Swallowing

Esophageal Phase
- what occurs

A
  • swallowing centre relaxes pharyngoesophageal sphincter

- swallowing centre then initiates primary peristaltic waves by interacting with ENS

32
Q

Motility – Swallowing

What are the steps of the swallowing reflex?

A
  • swallowing center inhibits respiratory center in brainstem
  • contraction of pharyngeal wall behind bolus pushes food toward esophagus
  • t​ongue position during this phase prevents bolus from travelling back into mouth
  • uvula elevates to seal nasal passages, preventing food from entering
  • vocal cords contract and epiglottis closes over trachea, preventing bolus from entering trachea and bronchi
33
Q

Esophagus Motility – Peristalsis

What is the esophagus?

A

straight tube connecting pharynx with stomach

has large ring of circular muscle (sphincter) at each end that control entry and exit of GI luminal contents

34
Q

Esophagus Motility – Peristalsis

Why does the pharyngoesophageal sphincter remain closed (except during swallowing)?

A

to prevent air entering stomach

35
Q

Esophagus Motility – Peristalsis

What are the steps of primary peristalsis?

A
  • inner circular layer of muscularis externa contracts, pinching a ring
  • outer longitudinal muscle layer contracts in front of pinched ring, reducing length of tube
  • this sequence propagates along length of esophagus, pushing luminal contents toward stomach
  • primary peristaltic wave takes 5-9 seconds to travel from beginning to end of esophagus
36
Q

Esophagus Motility – Peristalsis

Is secondary peristalsis voluntary or reflexive?

A

reflexive

37
Q

Esophagus Motility – Peristalsis

Does secondary peristalsis involve the swallowing centre?

A

no

38
Q

Esophagus Motility – Peristalsis

When does secondary peristalsis occur?

A

when luminal contents become lodged – distension of GI wall activate stretch receptors, which stimulate ENS, and ENS coordinates strong peristaltic wave to dislodge luminal contents

39
Q

Esophagus Motility – Peristalsis

Describe the actions of the gastroesophageal sphincter (when it contracts/relaxes).

A
  • opens when peristaltic wave pushes food bolus against this region
  • reflexive relaxation, mediated by vagus nerve
  • sphincter then contracts again to prevent gastric reflux
40
Q

Digestion/Absorption

Digestion that occurs in mouth, pharynx and esophagus is a result of…

A

amylase in saliva

41
Q

Digestion/Absorption

How long does this process occur?

A

until luminal contents reaches stomach, and then stops because of gastric acid

42
Q

Digestion/Absorption

Do nutrients get absorbed?

A

there is no appreciable absorption of nutrients along this portion of GI tract

43
Q

Digestion/Absorption

How much digestion/absorption is there in the mouth?

A

minimal

+ CAPS 301: Respiratory, Renal, GI, Endocrinology, Reproduction (32 decks)

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