Lecture 4 - 9/24 Flashcards
Primary Function of the Larynx
To protect the airway -Mechanically blocks foreign objects & food -Forcefully expels aspirated material
Secondary Function of the Larynx
-To produce voice
Brief and unspecific anatomy of Larynx and surroundings…
Larynx is suspended from hyoid bone Supports the tongue root Attaches to strap muscles –The suprahyoid & infrahyoid muscles – Elevate & lower larynx
KNOW THIS ANATOMY: (11)
Pharynx Tongue Jaw Epiglottis Hyoid bone Thyroid cartilage Cricoid cartilage Cricothyroid joint (control pitch) Arytenoid cartilages Cricoarytenoid joint (adduct & abduct VFs) Trachea
Innervation of Instrinsic Laryngeal Musculature
Vagus Nerve – Recurrent Laryngeal Branch -Thyroarytenoid muscle -Lateral cricoarytenoid muscle -Posterior cricoarytenoid -Interarytenoid muscles Vagus Nerve – Superior Laryngeal Branch -Cricothyroid muscle
Actions of Laryngeal Muscles
Adduct VFs -Thyroarytenoid muscle – Rotates arytenoid cartilages inward -Lateral cricoarytenoid muscle – Rotates arytenoid cartilages medially -Interarytenoid muscles – Approximates arytenoid cartilages Abduct VFs -Posterior cricoarytenoid muscle – Rotates the arytenoid cartilages laterally Shorten & Soften VFs -Thyroarytenoid muscle – Draws arytenoid cartilages toward thyroid to shorten the VFs Lengthen & Stiffen VFs -Cricothyroid muscle – Pulls thyroid & cricoid cartilages together to stiffen & elongate VFs
Extrinsic Musculature and Innervation
Elevators:
Trigeminal Nerve, CN V
-Digastric muscle, anterior belly
Facial Nerve, CN VII
- Digastric muscle, posterior belly
- Stylohyoid muscle
Glossopharyngeal Nerve, CN IX
-Stylopharyngeaus
Hypoglossal Nerve CN, XII
- Geniohyoid muscle
- Thyrohyoid muscle
Depressors:
Hypoglossal Nerve, C-1, C-2, & C-3
-Sternohyoid muscle
-Omohyoid muscle
-Sternothyoid muscle
-Cricothyroid muscle
Newborn Larynx
Newborn
-Larynx rides high in throat
-VFs are 2.5 -3 mm long
-Laryngeal cartilage is pliable
-Arytenoid cartilage including vocal process makes up ½ of length of VF
-The membranous portion of VFs is thick & uniform
-No evidence of vocal ligament
*The layered structure of lamina propria is not
developed
Development of Larynx and VT
Age 1-2 years
Immature thin vocal ligament develops
Age 3
Myelination of laryngeal nerves is complete
Age 4
Vocal tract lengthens as larynx descends
-Posterior 1/3 of tongue descends into pharynx
By age 5
-Larynx has adult configuration
By age 13 -15
-Vocal ligament has developed
-The three layers of lamina propria have developed
-Mutation of larynx occurs & fundamental frequency drops
in both males & females
-Mean male F0 drops from 226 Hz to 120 Hz
-Mean female F0 drops from 230 to 220 Hz
20-21 years of age
- Larynx reaches adult size
- Male VFs are 17-21 mm
- Female VFs are 11-15 mm
**Ossification of cartilage of larynx begins now & continues throughout entire life
Sex Specific Aging of Larynx
55+ Years Old
Males
- Thickening of deep layer of lamina propria
- Pitch elevates
Females
- Thinning of lamina propria
- Pitch lowers
- Increased roughness
- More vocal breakdowns
Aging of the Larynx (not sex specific)
80+ years old
Ossification of hyaline cartilage is almost complete
Heavier and less compliant
May have atrophy of the vocalis muscle
- Bowing of membranous portion of VFs
- Thinning of VF
May have stiffening of laryngeal joints
- Difficulty positioning arytenoid cartilage of VFs
- Glottal incompetency
- Increase in jitter & shimmer
Small bumps in the aryepiglottic fold
Two corniculate cartilages
Two cuneiform/arytenoid cartilages
Vocal process
Vocal Folds
Move quickly – Close glottis (to protect airway)
Delicate – Should not be pressed tightly together for prolonged periods
Myoelastic Aerodynamic Theory of Voice Production
Muller, 1843; van den Berg 1958
- Air passes through a narrow glottis
- Membranous portions of VFs are sucked together by Bernoulli effect
- Cartilaginous portion remains in phonation neutral position
- Air pressure builds below closed glottis
- Subglottal pressure exceeds 3-4 cm of H2O
- Membranous portions are blown apart
- Lateral excursion of membranous tissue
- Elasticity of membranous tissue is sufficient to snap VFs together & close glottis to create first glottal pulse (producing quiet phonation)
- Frequency of vibration is determined by length in relation to stiffness & mass of VF
Manner of Onset of Phonation
- Abrupt onset
- Full adduction of VFs (can lead to VF trauma) - Delayed onset of phonation – Voiceless initiation /hu/
- VFs partially abducted - Simultaneous onset of phonation – Voiced /mhm/
- VFs adducted to phonation neutral position - Abrupt Onset – Effortful Phonation
- Vocal folds hyperadducted
- Large excursions of VFs & high impact stress