1a. Anatomy, Neuroanatomy, and Physiology of the Speech Mechanism Flashcards
Muscles of Respiration: 2 Categories
Thoracic muscles of inspiration
Abdominal muscles of expiration
Larynx (aka voice box; houses VFs)
- 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
Larynx: Biological Functions (in addition to producing sound needed for speech)
- 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
Laryngeal Structures and Cartilages
- 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
Laryngeal Cartilages Cont’d
- 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…
Intrinsic Laryngeal Muscles (6)
(Both attachments within larynx)
Note: Primarily responsible for controlling sound production
Thyroarytenoid Lateral cricoarytenoid Transverse arytenoid Oblique arytenoid Cricothyroid Posterior cricoarytenoid
Intrinsic Laryngeal Muscles: Individual Roles
- *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
Extrinsic Laryngeal Muscles: Attachment/Role
Note: Primarily responsible for supporting the larynx and fixing its position
- 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
Extrinsic Laryngeal Muscles: Elevators aka Suprahyoid Muscles (6)
Digastric (V, VII) Geniohyoid (XII, C1) Mylohyoid (V) Stylohyoid (VII) Hyoglossus (XII) Genioglossus (XII)
Extrinsic Laryngeal Muscles: Depressors aka Infrahyoid Muscles (4)
Thyrohyoid (XII, C1)
Omohyoid (C1-C3)
Sternothyroid (C1-C3)
Sternohyoid (C1-C3)
Vocal Folds: 3 Layers
- Epithelium (outer cover)
- Lamina propria (middle layer; has 3 layers)
- Vocalis muscle (body; VF stability and mass)
Vocal Folds: 2 Other Pairs of Folds
- 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
Myoelastic-Aerodynamic Theory
and Bernoulli Effect
(Mucosal Wave: Critical to VF vibration)
- 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
Neuroanatomy of the Vocal Mechanism:
The primary Cortical Areas involved in speech-motor control, including phonation, are:
- Area 4 (Primary motor cortex)
- Area 44 (Broca’s area)
- Areas 3, 1, 2 (Somatosensory cortex)
- Area 6 (Supplementary motor cortex)
Cerebellum: Function
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
Cranial Nerves
- 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)
SLN and RLN: Functions
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
Articulation: Key Structures Involved
and CNs Mostly Involved w/ Innervating Muscles of Articulation
Pharynx, soft palate, hard palate, mandible, teeth, tongue, lips, and cheeks
V (trigeminal), VII (facial), X (vagus), XI (spinal accessory), XII (hypoglossal)
Resonators (3)
The resonators that serve to modify laryngeal tone are the pharynx, the nasal cavity, and the oral cavity
Pharynx: Pharyngeal Muscles are Innervated by which CNs?
- All pharyngeal muscles (except for stylopharyngeus) are innervated by X, XI
- Stylopharyngeus is innervated by IX
Velum/Soft Palate: Muscles and Functions
- 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
Mandible: Muscles and Innervation (8)
Elevators (elevates/protrudes)
Masseter (V)
Temporalis (V)
Medial (internal) pterygoid (V)
Lateral (external) pterygoid (V)
Mandible: Muscles and Innervation (8)
Depressors (all depress mandible)
Anterior belly of digastric (V): pulls hyoid forward
Posterior belly of digastric (VII): pulls hyoid back
Geniohyoid (XII, C1)
Mylohyoid (V)
Parts of the tongue (4)
- 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
Tongue Muscles (XII): Intrinsic (4)
Superior longitudinal muscle
Inferior longitudinal muscle
Transverse Muscles
Vertical Muscles
Tongue Muscles (XII): Extrinsic (5)
Genioglossus (bulk; allows it to move freely) Styloglossus Hyoglossus Chondroglossus Palatoglossus
Lips and Cheeks: Primary muscle for each
Lips: Orbicularis oris
Cheeks: Buccinator
