1a. Anatomy, Neuroanatomy, and Physiology of the Speech Mechanism

Question 1

Muscles of Respiration: 2 Categories

Answer 1

Thoracic muscles of inspiration

Abdominal muscles of expiration

Question 2

Larynx (aka voice box; houses VFs)

Answer 2

• Air (from lungs) flows upward through the trachea and comes toward larynx, which lies on top of trachea.
• Larynx is a valving mechanism that opens and closes.
• Major structures: hyoid bone, thyroid cartilage, cricoid cartilage, tracheal ring

Question 3

Larynx: Biological Functions (in addition to producing sound needed for speech)

Answer 3

• Closure of the trachea so that food and other substances do not enter lungs
• Production of cough reflex to expel foreign substances that accidentally enter trachea
• Closure of the VFs to build subglottic pressure necessary for physical tasks, such as excretion and lifting heavy items

Question 4

Laryngeal Structures and Cartilages

Answer 4

• Larynx is suspended from hyoid
• Epiglottis, a protective leaf-shaped cartilage, drops to cover the orifice of the larynx during swallowing
• Key cartilages of the larynx: thyroid, cricoid, and arytenoid cartilages

Question 5

Laryngeal Cartilages Cont’d

Answer 5

• Thyroid: forms anterior and lateral walls of larynx; protects larynx
• Cricoid: “uppermost tracheal ring”; linked w/ thyroid and paired arytenoid cartilages; completely surrounds the trachea
• Arytenoid: small, pyramidal-shaped; connected to cricoid via cricoarytenoid joint, which permits sliding and circular movements
• Corniculate cartilages: small, cone-shaped; sit on apex of arytenoids; assist in reducing laryngeal opening when swallowing
• Cuneiform cartilages…

Question 6

Intrinsic Laryngeal Muscles (6)
(Both attachments within larynx)

Note: Primarily responsible for controlling sound production

Answer 6

Thyroarytenoid
Lateral cricoarytenoid
Transverse arytenoid
Oblique arytenoid
Cricothyroid 
Posterior cricoarytenoid

Question 7

Intrinsic Laryngeal Muscles: Individual Roles

Answer 7

• *Thyroarytenoid (Internal and External TA): Internal= aka VFs/vocalis muscle; portion of TA that vibrates and produces sound
• Lateral cricoarytenoid: Adducts VFs; increases medial compression
• Transverse arytenoid: Adducts VFs
• Oblique arytenoid: Pulls apex of arytenoids in a medial direction
• *Cricothyroid: Lengthens and tenses VFs
• Posterior cricoarytenoid: Abducts VFs

Question 8

Extrinsic Laryngeal Muscles: Attachment/Role

Note: Primarily responsible for supporting the larynx and fixing its position

Answer 8

• Have one attachment to a structure w/in larynx and one attachment outside
• All extrinsic muscles are attached to the hyoid bone and lower or raise the position of the larynx w/in neck

Question 9

Extrinsic Laryngeal Muscles: Elevators aka Suprahyoid Muscles (6)

Answer 9

Digastric (V, VII)
Geniohyoid (XII, C1)
Mylohyoid (V)
Stylohyoid (VII) 
Hyoglossus (XII)
Genioglossus (XII)

Question 10

Extrinsic Laryngeal Muscles: Depressors aka Infrahyoid Muscles (4)

Answer 10

Thyrohyoid (XII, C1)
Omohyoid (C1-C3)
Sternothyroid (C1-C3)
Sternohyoid (C1-C3)

Question 11

Vocal Folds: 3 Layers

Answer 11

• Epithelium (outer cover)
• Lamina propria (middle layer; has 3 layers)
• Vocalis muscle (body; VF stability and mass)

Question 12

Vocal Folds: 2 Other Pairs of Folds

Answer 12

• Aryepiglottic folds: composed of a ring of connective tissue and muscle extending from arytenoid tips to larynx; separate laryngeal vestibule from pharynx and helps preserve airway
• Ventricular/false VFs: vibrate only at very low F0s and usually not during phonation in a normal speaker; compress during coughing and lifting heavy items

Question 13

Myoelastic-Aerodynamic Theory
and Bernoulli Effect

(Mucosal Wave: Critical to VF vibration)

Answer 13

• VFs vibrate b/c forces and pressure of air and elasticity of VFs
• Air flow (from lungs) is stopped by closed VFs–>build-up of subglottal pressure–>blows VFs apart–>vibration–>air moves w/ increased velocity through glottal opening–>pressure between VF edges decreases and VFs get sucked together

*Bernoulli effect is the “sucking” motion of the VFs toward one another, caused by increased speed of air passing bet. VFs

Question 14

Neuroanatomy of the Vocal Mechanism:

The primary Cortical Areas involved in speech-motor control, including phonation, are:

Answer 14

• Area 4 (Primary motor cortex)
• Area 44 (Broca’s area)
• Areas 3, 1, 2 (Somatosensory cortex)
• Area 6 (Supplementary motor cortex)

Question 15

Cerebellum: Function

Answer 15

Regulate motor movement; critical in the control of speech movement; key to coordination of the laryngeal muscles for adequate phonation; key to the effective functioning of other speech systems such as respiration

Question 16

Cranial Nerves

Answer 16

• VII (facial) = innervates posterior belly of digastric muscle
• X (vagus) = includes the following primary branches, which innervate the larynx: superior laryngeal nerve (SLN) and right laryngeal nerve (RLN)

Question 17

SLN and RLN: Functions

Answer 17

SLN: Internal branch provides all sensory info to larynx; external branch supplies motor innervation solely to the cricothyroid muscle

RLN: Supplies all motor innervation to the interarytenoid, posterior cricoarytenoid, thyroarytenoid and lateral cricoarytenoid muscles; It supplies all sensory info below the VFs

Question 18

Articulation: Key Structures Involved

and CNs Mostly Involved w/ Innervating Muscles of Articulation

Answer 18

Pharynx, soft palate, hard palate, mandible, teeth, tongue, lips, and cheeks

V (trigeminal), VII (facial), X (vagus), XI (spinal accessory), XII (hypoglossal)

Question 19

Resonators (3)

Answer 19

The resonators that serve to modify laryngeal tone are the pharynx, the nasal cavity, and the oral cavity

Question 20

Pharynx: Pharyngeal Muscles are Innervated by which CNs?

Answer 20

• All pharyngeal muscles (except for stylopharyngeus) are innervated by X, XI
• Stylopharyngeus is innervated by IX

Question 21

Velum/Soft Palate: Muscles and Functions

Answer 21

• Levator veli palatini (X, XI): primary elevator of the velum
• Tensor veli palatini (V): tenses velum, dilates eustachian tube
• Palatoglossus (X, XI): elevates and depresses velum
• Palatopharyngeus (X, XI): narrows pharyngeal cavity, lowers velum, may assist in elevating larynx

Question 22

Mandible: Muscles and Innervation (8)

Elevators (elevates/protrudes)

Answer 22

Masseter (V)
Temporalis (V)
Medial (internal) pterygoid (V)
Lateral (external) pterygoid (V)

Question 23

Mandible: Muscles and Innervation (8)

Depressors (all depress mandible)

Answer 23

Anterior belly of digastric (V): pulls hyoid forward
Posterior belly of digastric (VII): pulls hyoid back
Geniohyoid (XII, C1)
Mylohyoid (V)

Question 24

Parts of the tongue (4)

Answer 24

• Tip: thinnest, most flexible; imp. for artic.
• Blade
• Dorsum: largest area; lies in contact w/ hard and soft palate
• Root: very back and bottom portion

Question 25

Tongue Muscles (XII): Intrinsic (4)

Answer 25

Superior longitudinal muscle
Inferior longitudinal muscle
Transverse Muscles
Vertical Muscles

Question 26

Tongue Muscles (XII): Extrinsic (5)

Answer 26

Genioglossus (bulk; allows it to move freely) 
Styloglossus
Hyoglossus
Chondroglossus
Palatoglossus

Question 27

Lips and Cheeks: Primary muscle for each

Answer 27

Lips: Orbicularis oris
Cheeks: Buccinator