DRE Flashcards
What is mastication?
chewing
function of mastication
-first step of digestion
-mash and crush food - small enough to swallow = bolus
-mix food with saliva
-increase surface area for enzymes
what is food called when it is small enough to swallow?
bolus
what does mastication involve?
-mandible up/down - incisors bite food
-molars side to side - crush food - bolus
tongue
what does chewing generate
saliva - necessary for digestive enzymes
what is the trigeminal nerve also known as?
suicide
what does a person feel if there is an issue with the trigeminal nerve
suicide nerve
muscles of mastication - jaw closing
-temporalis
-masserters
-medial pterygoid
muscles of mastication - jaw opening
-lateral pterygoid
-innervated by the 5th cranial nerve
what does deglutition mean
swallowing
what is the temporalis visible under
under fascia
what can you control chewing based on
the food you’re eating - learnt over the years as your brain figures it out
sends signals to the brain
what does the original theory to chewing state
can control mastication depending on the type of food eaten
control of bite - type of chewing modified by what
cortex - voluntary control
sensory feedback from dental/periodontal receptors
sensory feedback from dental/periodontal receptors function
-sends info to brain brainstem/CPG
-fine tune rhythmic jaw movements
-prevent excessive forces being applied to tooth
-if biting force INCREASES = inhibit jaw closing
-adapts to food type
where does voluntary control come from
the front of the brain
what happens in order for the muscle to control chewing
a message is sent to the chewing centre
central pattern generator is known as
chewing centre
what is chewing
repetitive and rhythmical motor activity (similar to locomotion and respiration) controlled by the ‘chewing centre’
control of mastication is not just an …..
involuntary reflex action
control of mastication can control JAW MOVEMENTS
explain
-jaw opening/jaw closing
-bought about by neuronal network in the brainstem
control of mastication can control BITE
explain
-great variability
-regulated by food type
-brought about by sensory feedback to the brainstem
what is deglutition
swallowing
give a brief overview of swallowing
-lasts only a few seconds
-coordinated by swallowing centre in medulla
-requires 25 different muscles
-three phases:
1.oral - voluntary
2.pharyngeal - involuntary
3.oesophageal - involuntary
-all-or-none reflex - one started can’t be stopped
what type of reflex is deglutition
all or none
name the 3 phases of deglutition and state whether they are involuntary or voluntary
1.oral - voluntary
2.pharyngeal - involuntary
3.oesophageal - involuntary
what phase is deglutition
pharyngeal phase
what happens if deglutition goes wrong
-can kill you
-swallowing centre also communicates with the breathing centre and respiration centre
pharyngeal phase - deglutition
explain
-lasts 1 second
-food activates pressure receptors in palate/pharynx
-impulses to swallowing centre in brain stem
impulses to swallowing centre - process
what is the epiglottis
flap that sits on the top of the trachea
-when swallowing epiglottis closes the opening of the glottis
where are the 3 places food can go
nose
trachea
oesophagus
oesophageal phase - deglutition explain
-lasts 8-20 seconds
-sphincters at both ends UOS/LOS
-muscular tube:
1.upper 1/3 - skeletal muscle
2.middle 1/3 - skeletal and smooth muscle
3.terminal 1/3 - smooth muscle
-peristaltic action pushes food down
-controlled by swallowing centre
-LOS opens to allow food into the stomach
what is peristalsis controlled by
-extrinsic vagal nerves
-intrinsic enteric nerves
oesophageal peristalsis is what type of muscle movement
wave-like smooth muscle contractions and relaxation
-response to wall distention by bolus
-contracts behind bolus
-relaxes in front of bolus
what is peristalsis
pushing food down
why is gravity not needed for food to go down into the stomach
peristalsis causes muscles to push the food down
functions of saliva
moistens and cleanses oral mucosa
cools food + aids chewing
lubrication by mucins
solubilises food
digestion
anti-bacterial
what is food called after it has been chewed/swallowed
bolus
describe lubrication by mucins
food is easier to swallow/chew
aids speed
protects oesophagus
why is lingual lipase important for babies
break down of lipids
milk = lipids
babies have a high lipid diet
why is saliva anti-bacterial
contains lysosomes, antibodies, lactoferrin
functions of saliva
buffer + minerals
why is saliva a buffer
alkaline buffer - HCO3-
neutralises acids in food/vomit
minerals - function of saliva
explain
mineralises teeth - high levels of calcium and phosphate
prevents enamel de-mineralisation by acids
secretes protective pellicle - protein rich coat - protects against acid
salivary hypofunction main causes
- head and neck cancer radiotherapy
- autoimmune diseases- sjogren’s, lupus, RA
- drug therapy
- reduced or totally absent saliva
- dry mouth- xerostomia
- difficulty swallowing dry foods
- loss of taste
- constant thirst
dental problems with salivary hypofunction
- oral bacteria/yeast overgrowth
- pH drops due to:
-lack of HCO3-
-bacteria producing acid
- bacteria cause caries formation
- acids causes enamel demineralisation
- periodontal disease
- difficulty wearing and injury due to dentures
symptoms of salivary hypofunction
- dry mouth
- burning mouth
- fissured lobulated tongue
- candida/oral yeast infection
- lichen planus - whitish streaks
- aphthous ulcers
- dental caries - tooth decay
what is the protein rich film on teeth stained by
tea/coffee/cigarettes
3 major parts salivary gland
parotids
submandibular
sublingual
secretion and % of parotids
25%
serous (watery) secretion
secretion and % of submandibular
mixed
serous and mucous secretion
70%
secretion and % of sublingual
mixed serous and mucous secretion
5%
sublingual saliva exp
- composed of acini (cluster of cells) and ducts
- numerous small glands- lips, cheeks, palate, tongue
- saliva is a mixed secretion of all of these
composition of saliva
daily - 800-1500ml/day
H2O: >99%
ions: Na+, K+, HCO3-, Cl-, Ca2+, Mg2+, PO4^3-, I-
proteins: a-amylase, lipase, mucins, immunoglobins
p- 6.1-8.0 -depends on HCO3- content and flow rate
less ions than plasma
increase in salivary secretion = increase osmolality
basic pH to slightly acidic to basic
increase alkaline - increase HCO3-
composition of saliva MORE DETAIL
- daily secretion: 800-1500ml/day
- H2O : >99%
- ions : Na+, K+, HCO3-, Cl-, Ca2+, Mg2+, PO43-, I-
- proteins: a-amylase, lipase, mucins, immunoglobulins
- pH range: 6.1-8.0
- pH depends on HCO3- content and flow rate
- hypotonic compared to plasma - facilitates taste
- generally saliva has less ions in it than the plasma- but as more saliva required in mouth, more HCO3- added (eg. when eating)
- increase salivary secretion = increase osmolality (70% of plasma osmolality at maximal secretion rates)
- pH changes from being slightly acidic (at rest) to basic
- increase in alkalinity due to increase HCO3- in saliva
acinar cell secretion - saliva
ions from surrounding blood vessels move into acinus cells then lumen
primary saliva secretion like plasma - ISOTONIC SALIVA
H2O follows by osmosis from plasma into acinar lumen
ductal cell secretion - saliva
primary secretion moves down duct = modified
lots of ion channels in duct cell - remove Na+/Cl- and add K+/HCO3-
ducts impermeable to H2O - more solutes removed than H2O = HYPOTONIC SALIVA - lower solute conc than plasma
many ion channels involved - may be the target of drugs
MAY EXPLAIN WHY XEROSTOMIA IS A COMON SIDE EFFFECT OF DRUGS
describe salivary composition with varying flow rates basic
lower hydrostatic pressure in the surrounding capillaries forces LESS plasma into acini
higher hydrostatic pressure in the surrounding capillaries forces more plasma into acini
describe salivary composition with varying flow rates detailed
Na+/Cl- reabsorption very efficient and less in duct and mouth. K+/HCO3- added to duct but not a lot. More ions removed than added so saliva in mouth is HYPOTONIC relative to plasma
Na+/Cl- reabsorption very efficient and less in duct and mouth. K+/HCO3- added so more saliva in mouth is rich in these. More ions added than removed so saliva ALMOST isotonic relative to plasma but still hypotonic
describe how the secretion of saliva varies with flow rate
HCO3- valuable, don’t waste it
main purpose of un-stimulated saliva is to keep mouth lubrciated
-helps you talk
-don’t need lots of HCO3- unless eating as there isn’t much acid to neutralise
eating = stimulate salivary flow + produce HCDO3- saliva with buffering capacity
explain control of saliva secretion - detailed
- continuous
- low rate during sleep
-~0.05ml
-keeps mouth moist
-bacteria build up- dragon breath in morning
- increases in awake state
-~0.1-0.5ml/min when food not being eaten
- increases dramatically during meal
-~4ml/min
- pressure and chemoreceptors: chewing, taste, tactile stimulation
- input from cerebral cortex: thought, sight, smell of food
- exclusively under ANS control
- predominantly parasympathetic
- flow rate depends on type of stimulus
-sour taste/ endoscope can increase to 8ml/min
explain parasympathetic nerves in the control of saliva secretion
vasodilation - hyperemia
-increase transport into acinar cells
-increase transport of HCO3- from duct cells
-increase amylase
-increase extrusion of saliva from ducts
-increase secretion of H2O and ions, abundant watery saliva
describe sympathetic nerves in control of saliva secretion
decreases secretion
stress/fear etc
what is the overall function of the digestive system
cells require food for energy and synthetic processes
foods in the form of fats, proteins, carbs
break nutrients into smaller sub-units = small enough for the body to absorb
distribute via circulation to cells to use for energy, growth and repair
describe the components of the digestive system
continuous tube
alimentary tract: - oral cavity, teeth, tongue, salivary glands, pharynx, oesophagus, stomach, intestines
- mouth to oesophagus to stomach to anus
define gland
functional unit of cells that work together to create and release a product into duct or directly into bloodstream
ENDOCRINE/EXOCRINE GLANDS
where does an exocrine gland release into
into the duct
where does an endocrine gland release into
into blood
what type of gland is the pancreas
both endocrine and exocrine
define the physical functions of the GI tract
ingestion
mastication
deglutition
define motility
movement of food through GI tract
what is peristalsis
what is segmentation
no met movement
mixes food
in the small intestine - helps to churn and mix food
mechanical digestion
what type of digestion is segmentation
mechanical digestion
lots of smooth muscle in the walls that causes these to happen
what are the physical functions of the GI tract - DASS
digestion
absorption
secretion
storage and elimination
explain digestion in the GI tract
mechanical or chemical breakdown of carbs, proteins, and fats into sub-units small enough to cross gut wall
explain absorption in the GI tract
sub-units, water, ions all cross the epithelial lining of the small intestine and enter blood or lymph vessels
explain secretion of the GI tract
digestive organs secrete many substances to aid digestion and absorption
explain storage and elimination in the GI tract
temporary storage and elimination of indigestible food
adaptations of the GI tract
progressive increase in absorptive surface area - excellent design to increase absorptive capacity
long alimentary tract / small intestine
villi have microvilli = increase the surface area more
digestion - breaking
absorbing - bloodstream
proteases - exo glands
anything that isn’t used/broken down will be excreted
