Week 2.1 - physiology of the mouth (workbook) Flashcards
what is the mouth a way into?
the GI tract
what is the function of the mouth?
disrupts food stuffs and mix with saliva to form boluses to be swallowed
what is the oral mucosa and teeth vulnerable to?
physical and chemical damage, & infection
what is a major function of saliva in the oral environment?
ensuring a moist, chemically appropriate environment with a healthy bacterial flora
what is physical disruption of food by?
mastication (chewing)
what is mastication carried out by?
powerful muscles - mainly the masseter muscle
generate huge forces
what is the masseter muscle innervated by?
branch of trigeminal nerve
how is the force transmitted to food?
via teeth
what d the incisors and molars do?
incisors cut food into pieces
molars crush food and mix with saliva to form paste (to be swallowed)
what happens to the bolus?
moistened and lubricated by saliva
how much saliva do we produce each day from what?
1.5 litres of saliva from 3 pairs of salivary glands
what is the function of saliva?
moistens and lubricates food for swallowing and also contains enzymes which begin the digestion of (particularly) carbohydrates
what is a much more significant role of saliva?
protection of oral environment
mucosa and saliva
mucosa is not cornified and must be kept wet (by saliva)
what are teeth constantly at risk from?
from bacterial acid, which needs to be neutralised, and the bacterial ecology of the mouth needs to be maintained by mild bactericidal action
what is zerostomia?
no saliva secretion in the mouth
what happens in zerostomia?
we can eat without saliva, but if there is no secretion, the mouth very rapidly deteriorates
what type of solution is saliva?
a hypotonic solution
what is a hypotonic solution?
excess water over the other body fluids) with relatively low concentrations of Na+ & Cl-, but with excess concentrations of K+ and HCO3-
how is resting saliva like? what can happen to it?
resting saliva is neutral, once stimulated, it becomes alkaline
what does saliva contain aside from enzymes?
significant mucus
where is saliva secreted from?
3 pairs of salivary glands
what are the 3 pair of salivary glands?
parotid glands
sub lingual glands
sub maxillary glands
how much of the saliva is secreted by the parotid glands? and what type of saliva?
25% of saliva by volume
serous secretion with a mixture of water, electrolytes and enzymes
how much of the saliva is secreted by the sub lingual glands (under tongue)? what type of saliva?
5% of saliva (don’t want too much mucous)
saliva is rich in mucus - known as mucous saliva
how much of the saliva is secreted by the sub maxillary glands (behind & inferior tongue)? type of saliva?
about 70% saliva
secretes both serous and mucous components
what are salivary glands composed of?
numerous blind ended tubes, with acini (secretory component of ducts) at blind end and ducts converging to outlets in the mouth
are serous acini and mucus acini the same?
no, different in structure
what type of acini does the sub maxillary gland contain?
mixture of both as it secretes both serous and mucus acini
what is saliva made from and how does it compare?
made from plasma, but always hyPOtonic to plasma
how is hypotonicity of saliva achieved?
NOT by directly pumping water
by first secreting an isotonic solution (same ionic component as plasma), then removing ions from it (less ions than plasma)
what do acinar cells secrete?
an isotonic fluid containing enzymes
what do duct cells do?
remove Na+ & Cl- (salt) and add HCO3-
how are the gap between ducts cells like? why?
tight, so water doesn’t follow the resulting osmotic gradient, and saliva remains hyPOtonic
what happens at low flow rates of saliva out of acinar cells?
duct cells remove most of the Na+, so saliva is VERY hypotonic
what is the capacity of the duct cells to modify saliva? what does this mean?
very limited, so at high flow rates, a smaller fraction is removed, and saliva becomes less hypotonic (still lots of NaCl and not enough HCO3-, more isotonic)
what happens to the stimulus to secrete by duct cells at high flow rates?
promote HCO3- secretion, so saliva becomes more alkaline, although not enough NaCl removed (not hypotonic)
what does high flow rate (stimulated) result in, in terms of volume, hypotonicity, alkalinity & enzyme content)?
high volume, low hypotonicity, high alkalinity (duct cells secrete HCO3-), high enzyme content (more saliva = more enzymes)
what is salivary secretion mostly controlled by?
the ANS (involuntary)
what stimulates the acinar cells? to produce what?
parasympathetic nerves (rest & digest) from the otic ganglion stimulate acinar cells to produce primary secretion (of isotonic saliva)
what stimulates the duct cells? to do what?
also parasympathetic nerves from the otic ganglion (same as acinar cells) to add extra HCO3- to saliva
what does salivary volume depend on?
ANS control - controlling amount secreted from acinar cells
how is ANS outflow coordinated?
from the brain stem in response to afferent stimuli (entering brain stem)
what are afferent stimuli that can affect antonomic outflow?
smell & taste of food & conditioned reflexes (e.g. pavlov’s dog)
what does sympathetic nervous activity do to salivary glands?
reduces blood flow to the salivary glands (vasoconstrict), which limits salivary flow, producing the typical dry mouth of anxiety - need blood for outflow of saliva
what is the rate of ductal recovery of Na+ increased by (taking Na+ away - produce hypotonic saliva)?
hormone aldosterone from adrenal cortex (zona glumerulosa - outermost layer)
what happens once saliva is mixed with chewed food?
forms bolus, it must be swallowed
how is swallowing carried out?
in 3 phases:
- voluntary phase
- pharyngeal phase
- oesophageal phase
what is the main purpose of the voluntary phase?
a bolus is moved onto the pharynx
what happens in the pharyngeal phase?
afferent information from receptors in the pharynx reaches the swallowing centre in the brain stem
what happens when afferent information from pharynx receptors reaches swallowing centre in brain stem? (pharyngeal phase)
triggers a set of movements, including:
- inhibition of breathing - prevent aspiration
- raising of larynx (to meet epiglottis)
- closure of glottis (airways) - by epiglottis
- opening of entrance to oesophagus (to travel to stomach)
what type of muscle is in the upper 1/3 of the oesophagus?
voluntary straited
what type of control is the muscle of the upper 1/3 of the oesophagus under?
somatic nerves (voluntary) - as opposed to automonic, so upper 1/3 is an active movement we choose to carry out
what type of muscle is in the lower 2/3 of the oesophagus?
smooth muscle
what type of control is the muscle of the lower 2/3 of the oesophagus under?
parasympathetic nervous system (part of ANS, involuntary), rest & digest
what happens in the oesophageal phase?
a wave of peristalsis sweeps down the oesophagus, propelling the bolus to the stomach in about 9 seconds
what are the oropharynx and the oesophagus essentially?
highways concerned with passing ingested food to the stomach and intestines for digestion (& absorption)
what are the oropharynx and the oesophagus open to?
potentially hazardous environment & are potentially under threat of attack from a number of directions
