Chapter 4 - velopharyngeal-nasal structure and function

cranial bones

temporal (2), parietal (2), occipital (1), frontal (1), sphenoid (1), ethmoid (1)

facial bones

maxillary (2), palatine (2), vomer (1), inferior nasal conchae (2), lacrimal (2), nasal (2), zygomatic (2), mandible (1)

pharynx

oval tube, larger side to side than front to back

connective tissue predominates at the top, muscle predominates at the bottom

continuous with esophagus at lower end

3 cavities (nasopharynx, oropharynx, laryngopharynx)

nasopharynx

hard palate and above

contains auditory tubes and nasopharyngeal tonsil

oropharynx

hyoid bone to hard palate

opening is through the faucial isthmus (bounded by anterior faucial pillars)

contains the palatine tonsils and lingual tonsil

laryngopharynx

base of cricoid cartilage to hyoid bone

velopharyngeal port

always open at rest

closes for most speech sounds

velum

consists of the soft palate and uvula

covreed with connective tissue

muscle fibers are most numerous in middle portion; scarce at front and back

nasal cavities/fossae

two chambers separated by nasal septum

floor is hard palate

lateral walls are made up of conchae (curled and convoluted bones)

septum

cartilage at front, bone at back

passive forces

recoil of muscles, cartilages, and connective tissues

surface tension

gravity

aeromechanical forces

active forces

muscles of the pharynx, velum, and outer nose

superior, middle, and inferior constrictors; salpingopharyngeus, stylopharyngeus, palatopharyngeus

pull pharyngeal walls inward and forward to constrict the pharyngeal tube

muscles of the velum

palatal tensor, palatal levator, glossopalatine, pharyngopalatine, uvulus

muscles of the outer nose

levator labii superioris alaeque nasi, nasalis, anterior nasal dilator, posterior nasal dilator, depressor alae nasi

movements of the pharynx

lengthening/shortening by vertical movements of the larynx

inward/outward movements of lateral pharyngeal walls

forward/backward movements of posterior pharyngeal walls

forward/backward movements of velum, tongue, and epiglottis

movements of the velum

mainly upward/backward and downward/forward

becomes “hooked” when moving upward and backward

top of the hook is the velar eminence

undersurface of hook is the velar dimple

movements of the outer nose

anterior nares open most of the time for breathing

anterior nares can be dilated by nasal dilator muscles

anterior nares can be constricted by nasal constrictor muscles and aeromechanical forces

velopharyngeal-nasal control variables

velopharyngeal-nasal airway resistance

velopharyngeal sphincter compression

velopharyngeal-nasal acoustic impedance

velopharyngeal-nasal airway resistance

opposition to airflow through the velopharyngeal-nasal airway

can be altered by changes in cross-section/length of the velopharyngeal port, engorgement of the nasal cavities, and/or cross-section of the anterior nares

resistance also changes with the speed of airflow

velopharyngeal sphincter compression

the velopharynx can be closed with low compressive force (gently) or high compressive force (forcefully)

velopharyngeal muscles determine the level of this compressive force

different tasks require different levels of compressive force

velopharyngeal-nasal acoustic impedance

opposition to the flow of sound offered by the velopharyngeal-nasal apparatus

velopharyngeal port status (degree of opening) is the most important determinant of velopharyngeal-nasal impedance

ventilation

resting tidal breathing usually occurs through the nose (even though resistance is much higher than through the mouth(

advantages of nasal inspiration: incoming air is converted to body temperature, humidified, and filtered

advantage of nasal expiration: flow is slowed to enhance alveolar gas exchange