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GIT Physiology > Mastication > Flashcards

Mastication Flashcards

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1
Q

What is mastication?

A

chewing - solid food is chewed, cut, torn and ground into smaller pieces

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2
Q

What structures are involved in chewing?

A
  1. upper and lower jaws with teeth 2. the striated mandibular muscles 3. the tongue and cheeks
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3
Q

Course of the food during mastication?

A

food is forced from oral cavity to the vestibule and back, crossing and recrossing the occlusional surfaces

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4
Q

Importance of chewing?

A
  1. exposing starches in food to salivary amylase
  2. increase surface area of ingested material for enzymatic attack
  3. Taste sensations are enhanced by mastication by dissolving or suspensions of solid components in the saliva
  4. prevent injury to the lining of the pharynx and eosophagus by reducing size of ingesta
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5
Q

What stimulates salivation?

A
  1. taste sensations - also stimulate gastric secretions 2. chewing
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6
Q

Centres integrating chewing lie where?

A
  1. lower brainstem in the basal ganglia

2. cerebral cortex

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7
Q

Function of the tongue after mastication and salivation?

A

the tongue compacts food into a bolus

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8
Q

What structures produce saliva?

A
  1. buccal glands
  2. 3 pairs of extrinsic salivary glands
    - produce 1 litre
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9
Q

Structure of extrinsic glands?

A

connected to oral cavity via ducts

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10
Q

Describe the kinds of saliva?

A
  1. serous - producing saliva rich in protein, water and electrolytes (parotid gland)
  2. mucous gland (sublingual gland) - produce mucus
  3. mucus + protein - submandibular gland
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11
Q

What is the composition of saliva?

A
  1. Constitutes 99% Water, hypoosmotic to plasma
  2. Electrolytes: Na+, K+ , Ca2+, Cl- and bicarbonate (HCO3-)
  3. Digestive enzymes: α-amylase, lysozymes
  4. Proteins: mucus (mucins), IgA and IgM
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12
Q

What are the functions of saliva?

A
  1. keeps mouth moist
  2. facilitates speaking
  3. health of the mouth
  4. facilitates swallowing
  5. digestion of starches
  6. facilitates food taste
  7. immunity
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13
Q

How does saliva maintain the health of the mouth?

A
  1. contains substances that limit and regulate bacterial growth 2. contains alkali that neutralises acid
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14
Q

How does saliva aid in the digestion of starch?

A
  1. Saliva contains salivary amylase (ptyalin or alpha-amylase) 2. Mediates starch digestion in the mouth
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15
Q

How does saliva ease swallowing?

A

Saliva moistens and lubricates food so that it can be broken down by chewing before being swallowed : 1. the water in the saliva moistens the food particles 2. salivary mucins bind masticated food into coherent and slippery bolus that can easily slide through the esophagus without damaging the mucosa

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16
Q

What regulates secretion of saliva?

A

autonomic nervous sytem - sympathetic + parasympathetic

17
Q

Sympathetic stimulation causes?

A

secretion of small amounts of viscous saliva

18
Q

Parasympathetic stimulation causes?

A

profuse secretion of watery saliva with a relatively low content of organic material

19
Q

Where does the parasympathetic outflow originate?

A

salivary nuclei of the medulla oblongota

20
Q

The salivary nuclei receives afferent signals from?

A
  1. mouth + palate - taste and touch 2. nose - smell 3. higher centres - brain stem nuclei
21
Q

What causes reflex secretion of saliva?

A
  1. food in the mouth 2. stimulation of the vagal afferent fibres at the gastric end of the oesophagus
22
Q

What accelerates salivary production?

A
  1. chewing with an empty mouth
  2. smell
  3. irritating stimuli
23
Q

What is swallowing/deglutition?

A

the movement of food from the mouth through oesophagus into the stomach - facilitated by saliva and mucus

24
Q

What structures are involved in swallowing?

A

mouth, pharynx + esophagus

25
Q

What are the 3 reflex stages involved in swallowing?

A
  1. oral 2. pharyngeal 3. oesophageal
26
Q

What is the oral (buccal) phase?

A

the voluntary phase where food is moved from mouth to pharynx

27
Q

Describe the oral stage?

A

food is compressed into a bolus against the hard palate by the tongue and the bolus is then moved backwards into the pharynx - once the bolus enters the oropharynx it stimulates touch receptors that initiate the swallowing reflex

28
Q

Describe the pharyngeal stage?

A

the upper oesophageal sphincter relaxes and it lasts less than a second - Elevation of the larynx and folding of the epiglottis direct the bolus over the closed glottis while the uvula and soft palate block passage back to the nasopharynx

29
Q

How do the swallowing reflexes begin?

A

as tactile receptors on the palatal arches and uvula are stimulated by the passage of the bolus

30
Q

Describe the swallowing reflex?

A
  1. The information is relayed to the swallowing centre of the medulla oblongata via the trigerminal and glossopharyngeal nerves
  2. Motor commands originating at this point cause the soft palate and uvula to close nasopharynx, and epiglottis to close opening to larynx
  3. During this period, the respiratory centres are inhibited, and breathing stops
31
Q

Describe the oesophageal stage?

A
  1. Food enters the oesophagus and initiates peristaltic wave that sweeps the bolus to the stomach in 5 to 6 seconds
  2. Once within the oesophagus, the bolus is pushed toward the stomach by a peristaltic wave
  3. The approach of the bolus triggers the opening of the lower oesophageal sphincter, and the bolus proceeds to the stomach
32
Q

Name the types of peristalsis in the oesophagus?

A
  1. primary 2. secondary
33
Q

Describe primary peristalsis?

A
  1. Initiated by swallowing and reflexely controlled by medullary swallowing centres 2. Coordinated by afferent and efferent fibres within the grossopharyngeal and vagus nerves
34
Q

Describe secondary peristalsis?

A
  1. Occurs in the absence of pharyngeal phase
  2. Sweeps the oesophagus clean of material left after previous swallow or refluxed from stomach
  3. Driven by local reflexes triggered by the stimulation of sensory receptors in the oesophageal walls
  4. May be caused by dry or poorly lubricated bolus
  5. These receptors relay information by way of the submucosal and myenteric plexus
35
Q

When can food enter the stomach?

A

when the lower oesophageal sphincter relaxes

GIT Physiology (5 decks)

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