UNIT 4: Functions of the larynx and Vagus Nerve Flashcards
for breathing the airway must be open at all ____ valves …. which are:
3
vestibule, false vocal folds, and true vocal folds
during quiet respiration the true VFs are in what position?
intermediate/paramedial position - abducted approx 8mm
during forced respiration the true VFs are in what position?
lateral position - w physcial exertion abduction width doubles
swallowing is a ____ function
protective - failure to protect lungs during swallowing is life-threatening
what must the larynx prevent during swallowing?
the entrance of any substance into the airway, as it would be harmful to the lungs
how do different parts of the larynx prevent substances from entering the airway?
true vocal folds adduct
false vocal folds approximate
arytenoid cartilages are drawn toward the epiglottis
larynx is pulled up against the base of the tongue
epiglottis is deflected
sneezing, coughing, lifting, defecating, and childbirth all require…
build up of alveolar pressure
following inhalation sufficient pressure is generated by _______ and _______ at level of the larynx (laryngeal closure) …. this is called the ______ ______
compression of the thorax
airway resistance
vaslsalva maneurver
the valsalva maneuver increases _____ _____ and can impede _________
intrathoracic pressure
venous return of blood to the heart (pressure on inferior vena cava)
during the Valsalva maneuver the _____ becomes a rigid frame so the forces applied for lifting for ex can be translated to the legs…. if the ____ is not fixed, ____ is depressed by the muscle forces intended for lifting ex.
thorax
thorax, ribcage
what is a cough, how is it innervated?
response of respiratory tissue to an irritant or foreign object
CN X - somatosensory innervation to bronchial mucosa and motor innervation to trachealis muscle
describe how coughing is a violent, broadly-predictable behaviour
- deep inhalation thru widely abducted VFs
- tensing and tight adduction of VFs, elevation of larynx
- High Psub (relaxation pressure +m of expiration) blows VFs apart - maximal flow of air thru airway to clear irritant
If patients are coughing – what does this tell us?
something is going into their airway to stimulate this, we also know there is some preservation of sensory innervation, if they couldn’t feel it they couldn’t cough – even if swallow isnt working the best
chronic irritation from coughing leads to
vocal abuse due to excessive forces generated in coughing
we _____ the larynx for speech - biological functions of the larynx _____
borrow
take precedence
how do the VFs create phonation?
- VFs are masses that can be set into vibration
- VFs intrude into the airway (provides a source of turbulence in the vocal tract)
- vibration of VFs is achieved by placing and holding VFs in airstream so their physical qualities interact w airflow causing vibration
- VFs comprised of muscle and epithelial tissue that is capable of being moved when sufficient force is applied
bernoulli effect
given a constant volume of flow there will be a dec in pressure perpendicular to the flow and inc in velocity at a point of constriction in the flow
w the bernoulli effect, if the tube constricts the volume is the ____ and the velocity ____
same
increases
w the bernouli effect, if the rate of flow ____ at the point of constriction the pressure drops
increases
w the bernoulli effect, at the point of constriction the pressure will ____ and the velocity will ___ if volume is held constant
drop
increase
how does the bernoulli effect relate to vocal fold vibration
- trachea and larynx are the tube
- when the glottis is open and VFs are abducted, not sufficient construction
- adducting VFs produces constriction
- steady volume of air flow from lungs
- benoulli –> low pressure bw VFs so they will be sucked toward midline
what is happening at the glottis during the bernoulli effect?
inc velocity and dec pressure bw folds - folds suck together when pressure drops
as folds contact, instantaneous pressure above VFs drops, while pressure below VFs inc
transglottal pressure differential inc
folds blow apart, air flow begins again
what is the myoelastic aerodynamic theory of VF vibration?
air stream passes bw folds
vibrate as a result of elastic quality of tissue interacting w aerodynamic principles embodied in bernoulli effect
frequency of vibration varies according to VF tension, mass, and elasticity of tissue
how is the valve sys of the VFs used for voiceless consonants?
laryngeal valve opened so that air may flow unobstructed into pharynx and oral cavity (where it is manipulated by articulators)
how is the valving of the VFs used for whispering?
edges of VFs of membranous glottis are stiffened, positioned apart to prevent vibration
vocal processes of arytenoids are toed in (LCA m)
cartilaginous glottis is separated posteriorly to form glottal chink (whisper triangle)
this glottal adjustment allows for air to flow thru the glottis into oral cavity w/o setting VFs into vibration
phonation can occur when the VFs are brought ______ _____ aka _______
brought together medially
aka adduction
phonation is the product of
repeated opening and closing of the glottis (i.e. repeated glottal cycles)
phonation is NOT the product of
repetitive adductions of the VFs
process of drawing the VFs apart to end phonation is
abduction
actual vibration of the VFs is the product of _____ interacting with ____ in the absence of ______
airflow
tissue
repetitive muscle contraction
general somatic afferent
pain, temp, mechanical stimulation of skin, muscles or joints
special somatic afferent
vision and hearing
general visceral afferent
sensation within viscera (ex. abdominal organs)
special visceral afferent
taste and smell
general visceral efferent
motor to glands, viscera
general somatic efferent
motor to skeletal muscle (only CN XII)
special visceral efferent (aka branchial motor)
muscles of branchial arch origin (larynx, pharynx, soft palate, face, jaw)
what are the 5 fibre types in the vagus nerve CN X?
special visceral efferent (branchial motor)
general visceral efferent
general visceral afferent
special visceral afferent
general somatic afferent
CN X special visceral efferent provides _____ innervation to …..
motor innervation to muscles in the pharynx and larynx
what are the 3 major functions of CN X special visceral efferent fibers?
velopharyngeal port (need this to close or else we’d only have nasal sounds, liquids could also go into nasal cavity)
cross-sectional volume of the pharynx
positioning and tension of VFs
for the SVE fibers of CNX the lower motor neuron has cell bodies where? where does the LMN receive info from?
nucleus ambiguus in medulla
receives info from motor cortex of both R and L hemispheres (Bilateral innervation)
describe the intra-cranial pathway of SVE of CNX
axons leave nucleus ambiguus, exit medulla as 8-10 rootlets
all rootlets exit the skull thru jugular foramen to reach muscles of the palate, pharynx, and intrinsic muscles of the larynx
describe the extra-cranial pathway of SVE of CN X
after emerging from the jugular foramen the vagus gives off…..
pharyngeal nerve, superior laryngeal nerve, recurrent laryngeal nerve
pharyngeal nerve (Xph)
divides into pharyngeal plexus to supply muscles of soft palate and pharynx
superior laryngeal nerve (SLN)
descends adjacent to pharynx; divides into internal (afferent) and external (efferent) SLNs; eSLN supplies cricothryoid muscle
recurrent laryngeal nerve (RLN)
takes diff path on right and left sides of the body
describe the two pathways of the recurrent laryngeal nerve - left and right
RIGHT: RLN branches from vagus anterior to subclavian artery … hooks under the subclavian artery and ascends posterior to it, in a groover bw trachea and esophagus
LEFT: RLN branches from vagus anterior to aortic arch …. hooks under arch abd ascends thru superior mediastinum to reach groover bw trachea and esophagus
describe the intra-cranial pathway of general visceral efferent CN X fibers
cell bodies in dorsal motor nucleus (DMNX; gut, lungs, liver, pancreas) and medial nucleus ambiguus (cardiac plexus) in medulla –> fibres exit skull via jugular foramen
the intra-cranial pathway of general visceral efferent CNX fibres are influenced by input from….
hypothalamus, olfactory sys, reticular formation, nucleus tractus solitarius (NTS)
describe the extra-cranial pathway of CN X GVE (for pharynx and larynx/ thorax and abdomen)
Pharynx and larynx: axons are distributed to the pharyngeal plexus thru the pharyngeal and SLN branches –> secretomotor activation of glands in pharyngeal and laryngeal mucosa
thorax abdomen: secretomotor activation of glands and smooth muscle (esophagus, lungs, heart, stomach, liver etc)
general visceral afferent fibres of CN X receive sensation from the ….
pharynx/larynx, trachea (caudal), esophagus, and thoracic and abdominal viscera
CNX GVA: sensations from true VFs and below is in the ….
RLN
CNX GVA: sensations from Larynx above the true VFs (ex. laryngeal vestibule, false VFs) is from the….
internal SLN (iSLN)
CNX GVA: sensations from pharynx is in the ….
Xph
CNX GVA also has sensation that drives 2 reflexes
gag reflex and cough reflex
CN X GVA: describe the extra-cranial pathway of RLN
VFs and lower larynx –> cell bodies in inferior vagal ganglion
CN X GVA: describe the extra-cranial pathway of iSLN
pharynx and upper larynx (above VFs) –> pierces thru the thyrohyoid membrane –> joins w eSLN to fomr SLN; SLN joins w RLN to form vagus –> cell bodies in inferior vagal ganglion
CN X GVA: describe the extra-cranial pathway of Pharyngeal nerve
soft palate; joins SLN –> cell bodies in inferior vagal ganglion
CN X GVA: describe the extra-cranial pathway of sensory fibres of vagus
pass into cranium via jugular foramen
describe the intra-cranial course of CN X GVA
primary neurons synapse w secondary neurons in nucleus tractus solitarius in medulla
some secondary neurons synapse in hypothalamus, reticular formation and DMNX for parasympathetic reflexes (w visceral motor pathway)
CN X special visceral afferent receives sensation from…
stretch receptors in walls of aortic arch, chemoreceptors in aortic bodies adjacent to aorta
taste receptors from pharynx, epiglottis, and laryngeal aditus
describe the extra-cranial course for CN X SVA fibres
sensory fibres from heart converge w pharyngeal plexus
gustatory fibres from pharynx, epiglottis, and larynx converge w pharyngeal plexus
cell bodies of primary neurons are in inferior vagal ganglion
axons enter cranium thru jugular foramen
describe the CN X SVA intra-cranial course (taste)
secondary neuron from NTS to thalamus
tertiary neuron from thalamus to insula
CN X general somatic afferent carry what info
cutaneous sensations from skin at back of the ear and in the external auditory meatus, external surface of tympanic membrane
describe the extra-cranial pathway of CN X GSA
primary neuron has cell bodies in superior vagal ganglion
describe the intra-cranial pathway of CN X GSA (primary, secondary, tertiary neurons)
primary neuron –> axonal fibres travel to the CN V sensory sys
secondary neuron –> cell bodies in nucleus of spinal tract; axons ascend to contralateral thalamus
tertiary neuron –> cell bodies in thalamus axons tracel thru internal capsule to primary somatosensory cortex
remember w embryogenic dev: 4th arch is _____ externally, 5th and 6th are _____, and 5th _____ in humans
visible
underdeveloped
disappears
the Xph and SLN of the vagus comes from which arch?
4th
the RLN of the vagus comes from which arch?
6th
muscles of the palate/pharynx, and cricothyroid muscle comes from which arch?
4th
intrinsic muscles of the larynx comes from which arch?
6th
what skeletal and vasculature components come from the 4th to 6th arches?
skeletal - thyroid, triticial, arytenoids, cricoid, corniculate, cuneiform, epiglottis
vasculature - arch of aorta, pulmonary arteries
what are the two things that need to be tested clinically for CN X?
velopharyngeal movement
laryngeal function
how can you test velopharyngeal movement?
“ah” = look for symmetry and range of movement
asymeetry, uvula deviates on movement, swings toward the strong/intact side
gag reflex (sensory is Xph and CN IX; motor is Xph)
how can you test laryngeal function?
“ah” max phonation time = perceptual judgement of hoarseness, breathiness, pitch breaks
cough (voluntary vs reflexive)
