HNS33 Swallowing And Speech Flashcards
Stages of swallowing
- Oral stage
- Pharyngeal stage
- Esophageal stage
Oral stage
Chewing (voluntary)
—> Integrity of hard palate (e.g. cleft palate: food can go into nose)
—> Tongue mobility
—> Food bolus loaded onto tongue
—> **Palatoglossal arch closed (Posterior oral cavity is closed)
—> Tongue push bolus backward to oropharynx
—> **Palatoglossal arch opened
—> **Closure of nasopharynx by soft palate (pump theory: prevent leakage of pressure into nasal cavity)
—> **Elevation of larynx (+ forward)
—> Mechanoreceptors activated
—> Pharyngeal plexus (CN9, 10)
—> Swallowing reflex
Pharyngeal stage
- Involuntary
- Shortest stage (~seconds)
- Complex muscle contractions
—> Soft palate and Posterior pharynx appose tongue
—> Food bolus enter pharynx
Components:
1. Pharyngeal contractions: Suprahyoid muscles
—> ***Larynx move upward + forward
—> Forced into epiglottis
- Epiglottis pushed down by base of tongue base (pushing back —> Major pump)
—> ***Folding of epiglottis over airway - ***Closure of vocal cords / glottis
- Suprahyoid muscle pulled larynx upward and outward
—> ***Upper esophageal sphincter opened at the same time - Food enter pharyngeal wall
—> Contraction of constrictor muscles (accessory muscle)
—> Pharyngeal peristalsis begins
Esophageal stage
- Involuntary (don’t aware of it happening)
- Continuation of esophageal peristalsis
—> UES remains open until bolus completely passes into esophagus
—> Food bolus empties into esophagus
—> UES closes
—> Peristalsis of esophagus to push food down
—> LES relaxes + Airway re-opens + Larynx down
***Neural control of swallowing
Oral stage:
- Mastication (CNV3)
- Tongue movement (CN12 + Pharyngeal plexus)
- Sensation (CNV2, CNV3, CN9)
- Special sensation (CN7, CN9)
Oropharyngeal stage:
- Tongue movement (CN12 + Pharyngeal plexus)
- Sensation (CN9)
- Soft palate movement (CNV3 (Tensor veli palatini), CN10 Pharyngeal plexus (Others))
Pharyngeal stage:
1. Sensation
—> Superior (CN9)
—> Hypopharynx (CN10 Superior laryngeal nerve)
- Laryngeal elevation
—> **Geniohyoid (C1 via CN12 / Cervical plexus (Ansa cervicalis) via CN12)
—> **Stylohyoid (CN7)
—> **Mylohyoid, Anterior belly of digastric (CNV3)
—> **Palatopharyngeus (Pharyngeal plexus) - Closure of glottis / vocal cords (CN10 Recurrent laryngeal nerve)
- Opening of UES / Cricopharyngeus: (CN10 Pharyngeal plexus)
***Prevention of aspiration
- Elevation of larynx + Folding of epiglottis —> close Laryngeal inlet
- Closure of false cords (Most important mechanism)
- Closure of glottis / true cords (Most important mechanism)
- vocal cord palsies —> aspiration - Generation of positive subglottic pressure (exhale a bit against closed glottis during swallowing)
Clinical significance of swallowing
Symptoms
- Globus (lump in throat)
- Dysphagia
- Choking
- Cough
- Silent aspiration due to sensation deficit —> recurrent aspiration pneumonia
- Pneumonia
Causes
- Intra-luminal (tumour)
- Intra-mural (muscle problem)
- Extra-luminal (thyroid tumour)
- CNS pathologies
Investigations
- Endoscopy
- VFSS (videofluoroscopic swallowing study)
- Manometry (measurement of pressure within various parts of the gastrointestinal tract —> see if muscles working properly)
2 Components of Speech
- Phonation
- generation of sound by forcing ***air through larynx —> cause vocal fold to vibrate - Articulation
- change of quality of sound
- generation of sound by movements of ***mandible, lips, larynx, soft palate, tongue
***Intrinsic muscles of larynx
- Adductors —> Close glottis (move cord towards midline)
- Lateral Cricoarytenoid
- Transverse + Oblique Arytenoid - Abductors —> Open glottis
- ***Posterior Cricoarytenoid (ONLY abductor that open airway for inspiration, 2 vocal cords normally closed due to tension of ligaments) - Shortening of vocal cord —> Thicken cord —> Lower pitch
- Thyroarytenoid / Vocalis muscle - Lengthening of vocal cord —> Pull thyroid cartilage anteriorly —> Increase tension of cord —> Higher pitch
- Cricothyroid (supplied by ***Superior laryngeal nerve)
Superior laryngeal nerve vs Recurrent laryngeal nerve
ALL laryngeal muscles: Recurrent laryngeal nerve (branch of CN10)
EXCEPT
Cricothyroid muscle: External laryngeal nerve (branch of Superior laryngeal nerve —> branch of CN10)
Histology of vocal cord
- Mucosal layer
- **Pseudostratified squamous epithelium (superior + inferiorly)
- **Non-keratinising squamous epithelium (contact surface of medial cord) - Lamina propria / Subepithelial tissue
- 3 layers
- Superficial layer (**Superficial lamina propria / **Reinke’s space)
—> **Loose areolar tissue
—> allow vocal cord epithelium to vibrate freely
—> pathology at this place —> impede vibration of epithelium —> hoarseness
- Intermediate layer + Deep layer —> **Vocal ligament - Vocalis and Thyroarytenoid muscle
Phonation
Action of intrinsic **Adductor laryngeal muscles (Lateral Cricoarytenoid, Transverse + Oblique Arytenoid)
—> Adduct / close vocal cord
—> Exhale
—> **Generate subglottic pressure
—> Pressure >3-5 cm H2O
—> Force vocal cords apart
—> Immediate falling of subglottic pressure
—> Vocal cords close again
—> Quick repetition
—> Vibration of vocal folds generate sounds
—> Male - 120Hz, Female - 230Hz
Loudness and Pitch
Loudness
- Force of expiration
- Lung function, Respiratory muscles
Pitch
1. Tension, “Dimentions” / Length of vocal folds (by Intrinsic laryngeal muscle)
—> higher pitch: longer and thinner vocal folds
—> lower pitch: shorter and thicker vocal folds
2. Size of larynx
Clinical significance of phonation
Symptoms
1. Hoarseness
Causes
- Air: COPD (air generation —> force generation)
- Neurological: Recurrent laryngeal nerve palsy (surgical complication, neurological problem) —> cannot close cord tightly
- Structure: Vocal cord pathologies (Polyps, Cancer, Scarring of SLP)
Investigations
- Cross-sectional imaging (CT, MRI)
- Endoscopy
Articulation
Change in shape of **upper aero digestive tract
—> Change **resonance chamber
—> Generate **modification of tone
—> Different **harmonics of tone e.g. nasal speech
- Mandible (CN5)
- Lips (CN7)
- Larynx (CN10)
- Soft palate (CN10)
- Tongue (CN12)
Pathologies:
- ***Higher centre —> poor coordination of muscles —> poor articulation e.g. Cerebellum dysfunction —> Scanning speech
- Tongue-tie —> Dysarthria (痴脷筋)
