main purpose of cephalic phase of digestion
anticipatory in preparing the stomach before food arrives
what does the cephalic phase of digestion start with
thought, sight, smell of food
- stimulates cerebral cortex and other appetite centres in brain
– activates parasympathetic NS and signal from vagus nerve to stomach causes gastric secretions
plate
- roof of oral cavity
- separates it from nasal cavity
- permits breathing while chewing
structures in oral cavity
- plate
- tongue
- pharynx
- teeth
tongue
floor of oral cavity
- made of voluntary controlled skeletal muscle
- movement of tongue is important for chewing, swallowing and speech
- state buds are on tongue
pharynx
- cavity behind nose and mouth connecting them to esophagus
- common for both digestive system and respiratory system
teeth
external bones embedded in jaw bone
- used mastication/chewing and mixing food w/ saliva
saliva
secretions from salivary glands
how many salivary glands are there and where are they?
3
- located outside oral cavity but secrete into mouth
how much saliva is secreted daily?
1-1.5L
composition of saliva
99.5% water and 0.5% electrolytes, enzymes and other proteins
major salivary proteins
amylase, mucous and lysozyme
6 primary functions of saliva
1) amylase breaks down carbs in mouth
- breaks down polysaccharides -> disaccharide maltose
2) mucus moistens food to help w/ swallowing
3) lysozyme is ani-bacterial and destroys bacteria
4) saliva is important for taste since only molecules dissolved in saliva will activate state buds
5) plays a role in speech to lubricate tongue and lips
6) has bicarbonate buffers to neutralize acids from food and bacteria in mouth
what makes salivary glands unique?
sympathetic and parasympathetic NS work together to increase salivary secretion
parasympathetic NS saliva vs sympathetic saliva
parasympathetic- fast flow that’s watery rich in enzymes
sympathetic- smaller volume thats thicker and rich in mucus
**thats why we get a dry mouth when stressed
salivary secretion reflexes
1) simple salivary reflexes
2) conditional salivary reflexes
simple salivary reflexes
- occur when chemoreceptors and mechanoreceptors in oral cavity respond to presence of food
- activation sends info to salivary center in medulla
– then sends impulses via extrinsic autonomic nerves to salivary glands to increase salivation
conditional salivary reflexes
- the “mouth watering” reflex that happens when we think, see, smell, or hear prep of food
- learned response
– pleasure of eating activates cerebral cortex to stim salivary centre
is swallowing voluntary?
- yes
- it’s initiated when bolus or liquid is forced to back of mouth by tongue
- when bolus exerts pressure on pharynx a compleicated reflex is triggered that is involuntary response coordinated by 25 pairs of muscles
what is important to note abt swallowing?
its an all or none event
- meaning although it starts as voluntary, once started, it can’t be stopped
phase 1 of swallowing
- oropharyngeal stage
- very rapid (~1second)
- bolus enters pharynx and must be directed to esophagus to prevent it from going to other openings
how the mouth stops the blolus from entering other areas
tongue is positioned at back of palate to keep food from coming back into the mouth
how the nasal passages stop the blolus from entering other areas
uvula elevates and blocks nasal passages
how the respiratory passages stop the blolus from entering other areas
- respiratory center in brain stem is inhibited so there’s no movement of air
- also larynx elevates and vocal folds tighten to prevent food from entering trachea
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Module 5: Section 115
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Module 6: Section 146
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