A & P of Laryngeal System Flashcards
framework of larynx
musculo-cartilaginous structure located at top of trachea
adjacent to C4-C6 vertebrae
44 mm in males
36 mm in females
inner larynx
constricted tube with smooth surface
cartilage connected by ligaments and membranes
lined with wet,smooth mucous membrane
extrinsic ligaments
provide attachment between hyoid or trachea and cartilage of larynx
intrinsic ligaments
connect cartilages within larynx and form support structure for cavity of larynx and VF
glottis
space between true VF
most important for speech; valving to phonate
cartilages of larynx
3 unpaired: cricoid thyroid epiglottis 3 paired: arytenoids corniculates cuneiforms
cricoid cartilage
most inferior point of larynx - rests on trachea
ring-shaped
cricoid arch: low in front, allows VF to pass over
posterior quadrate lamina: point of arctic for arytenoids & thyroids
thyroid cartilage
largest laryngeal cartilage
anterior larynx
articulates with cricoid to allow it to rock back and forth
anterior point of attachment for VF
in posterior, inferior cornu artics with cricoid; superior cornu artics with hyoid
epiglottis
leaf-shaped
projects up beyond larynx and hyoid
protects larynx during swallowing
flops over larynx to divert food into esophagus
arytenoids
pyramid-shaped
sit on upper surface of cricoid
critical for normal phonation: provide attachment for VF & move them to midline
corniculates
sit on superior surface of arytenoids
prominent landmarks in aryepiglottic folds
cuneiforms
embedded in aryepiglottic folds above and anterior to corniculates
arytenoid landmarks
4 surfaces & 2 processes:
anterior surface: projects forward to form vocal process
lateral surface: surface for muscular process
medial surface: even surface for midline glottic closure
base: artics with cricoid
muscular process: attachment of LCA & PCA
vocal process: attachment of VF
hyoid bone
only bone in larynx
only bone in body that doesn’t artic with any other bone
U-shaped
link between tongue & larynx - extrinsic muscles attach via greater and lesser cornu and corpus
movement of the cartilages
cricothyroid joints: pitch adjustment
cricoarytenoid joints: VF abduction and adduction
structure of vocal folds
5 layers of tissue:
- epithelium
- superficial layer of lamina propria
- intermediate layer of lamina propria
- deep layer of lamina propria
- thyrovocalis muscle
epithelium
composed of nonkeratinizing stratified squamous epithelial cells (maintains hydration & protects during vibration)
most pliable layer of VF
glistening white appearance
Basement Membrane Zone (BMZ)
area between epithelium & SLLP
secures epithelium to lamina propria
most susceptible to injury due to vibration or shearing
leads to scars forming which may lead to nodules or benign tumor
Superficial Layer of Lamina Propria
elastin fibers in random orientation
can be extensively stretched during phonation
prone to swelling: Reinke’s Edema
Intermediate Layer of Lamina Propria
elastin fibers in A-P orientation
slightly less pliable than SLLP
Deep Layer of Lamina Propria
collagen fibers in A-P orientation
less elastic, provides more structure to VF
Thyroarytenoid Muscle (Vocalis Muscle)
makes up bulk of VF men: 17-21 mm women: 11-15 mm infants: 2.5-3 mm only active portion of VF moves to send other layers into vibration
Cover-Body Model
cover: epithelium + superficial layer of lamina propria
transition: intermediate + deep layers of lamina propria
body: vocalis muscle
intrinsic muscles of larynx
origins and insertions on laryngeal structures
responsible for: adduction, abduction, tensing, relaxing (fine movements)
extrinsic muscles of larynx
one attachment on larynx and one outside
important for safe swallowing
big movements - elevation & depression of larynx
rules about intrinsic laryngeal muscles
- All are paired EXCEPT transverse interarytenoid
- All are adductors EXCEPT posterior cricoarytenoid
- All are innervated by recurrent laryngeal nerve EXCEPT cricothyroid (superior laryngeal nerve)
laryngeal adductors
- Lateral cricoarytenoid
- Transverse arytenoid
- Oblique arytenoid
Lateral Cricoarytenoid (LCA)
origin: superior-lateral surface of cricoid
insertion: muscular process of arytenoid
function: adducts VF, increases medial compression
Transverse Arytenoid (TA)
origin: lateral margin of posterior arytenoid
insertion: lateral margin of posterior surface of opposite arytenoid
function: adducts VF
Oblique Arytenoid (OA)
origin: posterior base of muscular process
insertion; apex of opposite arytenoid
function: pulls apex medially
may be more important in swallowing or leftover from earlier in evolution
laryngeal abductor
Posterior Cricoarytenoid (PCA)
origin: posterior cricoid lamina
insertion: posterior aspect of muscular process of arytenoid cartilage
laryngeal tensors
- cricothyroid
2. thyrovocalis
cricothyroid (CT)
pars recta
pars oblique
depresses thyroid in relation to cricoid & tenses VF
thyrovocalis
tenses VF
laryngeal relaxers
- Thyromuscularis
2. Superior Thyroarytenoid
cortical areas involved in phonation
- Frontal lobe: movement
- primary motor cortex (laryngeal/phonatory area)
- premotor/supplementary areas
- Broca’s - Parietal lobe: sensory processing
- Temporal lobe: language processing
- Wernicke’s
- auditory cortex
- auditory association area
pyramidal tract
voluntary vocalization
- sensory/motor cortexes, bilaterally
- project via corticospinal corticobulbar pathways
corticobulbar pathway
important for voice
- CN V (trigeminal)
- CN VII (facial)
- CN X (vagus)
- CN XII (hypoglossus)
extrapyramidal tract
extends from cortex to brainstem or spinal cord via basal ganglia (inhibitory) & cerebellum
cerebellum
- integration and control over movement
- background tone
- feedback mechanism
thalamus
integrating station between outgoing and incoming stimuli
Periaqueductal Gray (PAG)
- surrounds cerebral aqueduct
- connected to many areas in cortex, medulla and pons, esp Nucleus retroambiguus (NRA)
- coordinates breathing, laryngeal motor patterns
- expression of emotion
- damage to PAG = mutism or ventilator dependent
Nucleus retroambiguus (NRA)
gives rise to cranial nerves
Nucleus ambiguus (NA)
- houses motor neurons of CN X
- direct connection from cortex to NA unique in humans; allows for purposeful speech
- motor pathway to limbic, PAG & NA: emotional vocalization (laughing, crying, screaming, coughing)
CN X: Vagus
Innervates:
- intrinsic muscles of larynx (except CT)
- pharynx
- palate
- trachea
- bronchi
- lungs
- heart
- external ear
- parts of GI tract
superior laryngeal nerve
internal branch = sensory (upper larynx)
*important for swallowing
external branch = motor (CT muscle)
recurrent laryngeal nerve
susceptible to injury from heart surgery, thyroid, lungs
laryngeal reflexes
Receptors in mucosa highly sensitive to: -touch -movement -vibration -changes in air pressure -chemicals React by initiating reflexive closure of larynx Also aid in proprioceptive sense of larynx to control phonation.
glottis
space between VF
anterior 3/5 is membranous
posterior 2/5 is cartilaginous
changes shape during breathing and phonation
Myoelastic-Aerodynamic Theory of Phonation
- describes one cycle of VF vibration as interaction of muscle forces, elastic recoil forces and aerodynamic forces
- muscle forces = medial compression of LCA & IA that adduct VF
- elastic recoil = VF displaced from adducted position
- aerodynamics = positive & negative air pressures (positive opens glottis; negative closes it)
Bernoulli Effect
when molecules flow thru a tube, pressures are constant. At point of constriction, speed of molecules increases and pressure decreases.
Bernoulli Effect of Vocal Folds
- air passing thru trachea
- encounters constriction at VF
- so molecules speed up
- therefore air pressure drops
- then VF sucked together
- this conserves energy so muscles don’t have to continually contract and relax. muscles only have to initiate cycle by adducting; Bernoulli keeps them together.
cycle of vibration
one opening and one closing of glottis "duty cycle" sustained as long as there's sufficient medial compression: muscle action & Bernoulli FO = rate of vibes/sec men = 90-130 Hz women = 180-230 Hz kids = 250-300 Hz infants = 500 Hz
mucosal wave
vibration is very complex; rippling, wave-like motion
pliability of cover vs. stiffness of ligament/body
vertical phase difference: time lag between top and bottom of VF
longitudinal phase difference: time lag between posterior/anterior; zipper-like
Phonation Threshold Pressure(PTP)
amount of subglottic pressure required to blow apart VF measured as cmH20 3-8 cmH20 minmum for normal convo higher for higher pitch level affected by hydration and fatigue
changing pitch
VF -length -density -tension Muscles involved synergistically -CT: fine tunes FO -TA: at loud and low FO -Suprahyoid: aids higher FO -Subhyoid: aids in lower FO
Changing loudness
intensity measured in dB
interaction between respiration and laryngeal musculature
-degree of subglottal pressure
-fullness of medial compression
the greater the pressure, the higher the intensity
vocal registers
particular range of vocal FO
- Pulse (glottal fry): lowest register; 30-80 Hz; duty cycle = 90% closed/10% open
- Falsetto (loft): highest; >300 Hz; duty cycle = never completely closed
- Modal (middle):
- male = 80-150 Hz
- female = 170-230 Hz
- child = 220-300 Hz
