1. Laryngeal Anatomy

2. Development of the voice
Birth:
-larynx has higher anatomical position
-6th level of the cervical region
-pitch of neonate= 700 Hz
2 years:
-soft cartilage's & lax ligaments (susceptible to collapse)
-ossification of hyoid cartilage's

3. 5 years:
-larynx assumes position C7
-pitch decreases
20 years:
-hardening of the cricoid
30 years:
-hardening of the arytenoid
65 years:
-ossification of all cartilage's except the cuneiform & corniculate

4. Four voicing signals in the neonate
Birth Signal-
-short duration (1 sec.)- vowel pattern
Pain Signal-
-long in duration, high-pitched
-strained harsh quality
Hunger signal-
-rising & falling of pitch; glottal signal
Pleasure Signal-
-more nasal, pitch variability, glottal quality

5. Differences: Female & Male Voices
Prepubescent-
-minimal, similar pitch
Puberty-
-male v.f.’s enlarge 8-10mm & females 4mm
-thyroid angle is 90 ° in males and 120 °in females.
-v.f.’s enlarge in both female & male
-epiglottis flattens
-v.f. mucosa becomes less transparent
-tonsils & adenoids atrophy

6. Geriatric vocal folds
deterioration in pitch, loudness range,& endurance
v.f.’s appear thin & bowed
“aging larynx”= Presbylaryngeus
breakdown of collagenous & elastic fibers
intermediate layers of v.f.’s are looser & thinner
bowed appearance during glottal closure
thickening of superficial layer of lamina propria.

7. Vocal Fold Microstructure
Membranous portion of v.f.’s is intricate & layered,
There are 5 histologically discrete layers,
Layers vary in composition and mechanical properties,

8. Histologic Layers
5 histologic layers from most superficial to most deep are:
Epithelium
Lamina propria (3 layers)
-superficial layer
-intermediate layer
-deep layer
Vocalis muscle

9. Vocal Ligament Vocalis Muscle Epithelium Lamina Propria
superficial layer
intermediate layer
deep layer
Vocalis Muscle

10. Frontal section through membranous portion
epithelium
lamina propria
superficial
intermediate
deep
vocalis muscle
conus elasticus

11. Epithelium thin mucosal covering of squamous cells
wraps around internal contents of v.f.’s
no mass, totally compliant
needs thin layer of mucous lubrication to oscillate best.

12. Lamina Propria Consists of three layers: 1) Superficial layer-
-composed of loose fibrous matrix (known as Reinke’s space)
-composition described as soft gelatin
2) Intermediate layer-
-composed of elastic fibers and has slightly more mass

13. -denser still, composed of collagenous fibers
3) Deep layer-
-denser still, composed of collagenous fibers
Tissues of 3rd & 4th layers together are known as the vocal ligament
The vocal ligament develops throughout childhood until the larynx reaches full maturity (puberty)

14. Vocalis Muscle Fifth layer Main body of the vocal fold
Provides stability and mass

15. 5 layers
As layers change from superficial to deep, mass gradually changes & compliance for vibration
Epithelial; most elastic
Subsequent layers form a complex transition
Finally, stiff deep muscle tissue

16. The Body-Cover Model Theory developed by Hirano (1974)
Model attempts to explain the extreme variability in voice production
Model explained:
-Cover :(epithelium & superficial layer of the lamina propria)
-Transition:(intermediate and deep layer of the lamina propria)
-Body : (vocalis muscle)

17. Cover:
1) epithelium
2) lamina propria
-superficial
Transition
1) intermediate
2) deep
Body
vocalis muscle

18. More on Body-Cover Characteristics of v.f. vibration are dependent on:
-length
-elastic properties
-mass distribution
Body contraction/ vocalis contraction= the cover becomes shortened and thicker giving more mass to the length unit
Cover is entirely passive; longitudinal state is specified by its length & lateral displacement depends on the thickness of its body.

19. Some clinical observations
When CT and vocalis activity are weak: movement of body & cover are identical,
When vocalis activity is strong and the CT is weak: movement is greater for the cover rather than body,
When CT is active and vocalis is relaxed: both the body & cover are equally stiffened, movement is minimal (e.g.. Falsetto).

20. Histology Cartilage's are made up of two different types of tissue
-Thyroid & Cricoid= Hyaline cartilage
-Epiglottis, cuneiform & corniculate= elastic cartilage
Hyaline: thin, dense collagenous fiber (protein based)
Elastic: elastic fibers

21. Histological differences between structures
v.f. layered structure varies along its length
How does the membranous portion of the v.f. connect to the cartilaginous framework?
-at anterior end of v.f.’s :
*macula flava (a mass of elastic fibers, attached to ant. commissure)
-at posterior end of v.f.’s:
*post. macula flava (attached directly to arytenoid cartilage

22. Function of Macula Flava
Hypothesized to protect the membranous portion of the vocal folds during vibration from mechanical damage.

23. Structure in Newborns Epithelium is similar to adults
Major difference: lamina propria is thick relative to its v.f. length (adult’s thinner)
No vocal ligament

24. Trends in Vocal Fold Growth
immature macula flava in newborns (more susceptible to damage),
immature vocal ligament appears at 4 years (still very thin & does not contact vocalis muscle),
3 layers of lamina propria don’t exist until the ages 6-12,
thickness of cover and lamina propria increase with age,
intermediate lamina propria gets thinner with age,
deep layer of lamina propria gets thicker.

25. Summary regarding thickness
1) Cover thickest at midportion
2) Lamina propria thinnest at midportion
lamina propria thickest at the two ends, ant. & post. macula flava
4) Vocalis muscle thicker than mucosa- thinner in the ant. end & thicker at post. end
5) Vocalis muscle thicker than mucosa- thinner in the anterior end, thicker at the posterior end.

26. Changes with age
1) Cover gets thicker with age- not in epithelium but superficial layer of lamina propria,
2) Superficial layer of lamina propria becomes swollen with age,
3) Elastic fibers become looser with aging, especially in males 40 years and older
4) Great individual differences in changes of v.f. structure as a function of aging.

27. Reading
Seikel: Pgs (If you already read chapter from last lecture, disregard)