[004] Larynx Flashcards
What is the preferred method for gaining and maintain access to airways
Endotracheal intubation
If intubation is not possible (eg obstructions such as trauma to or carcinoma of mouth and face, swelling of larynx and pharynx, fractures to cervical spine)
Or where a long term solution is needed, airways can be accessed via …
- the cricothyroid membrane (chricothyrotomy)
- directly via trachea (tracheostomy)
Cricothyrotomy vs tracheostomy
Cricothyrotomy
- access through cricothyroid ligament between cricoid and thyroid cartilages of the larynx
- ligament can be palpated in midline
- usually only small blood vessels, connective tissue and skin (although occasionally, pyramidal lobe) overlying it
Tracheostomy
- route of entry complicated because large veins and part of thyroid gland overlie this region
Components of the larynx
- cartilaginous skeleton: provides support and mediates key functions of larynx
- ligaments: bind cartilages together
- muscles (intrinsic and extrinsic): move cartilages relative to each other or move the larynx as a whole
- mucous membrane: most of larynx lined with respiratory epithelium (ciliated, columnar)
Exception: vocal folds are covered by protective stratified squamous epithelium
Cartilage of the larynx
- Three large unpaired cartilages (cricoid, thyroid, and epiglottis)
- Three pairs of smaller cartilages (arytenoid, corniculate, and cuneiform)
Functions of the larynx
- protects airways — particularly during swallowing. Vocal and vestibular folds adduct, epiglottis moves down and larynx rises during swallowing
- some activities require temporary closure of respiratory tract to increase pressure in chest and abdomen (eg coughing, lifting heavy weights and other uses of increased abdominal pressure (defecation and micturition, child birth))
- controls airflow through respiratory tract eg during rest or exercise
- controls airflow during phonation (singing, speaking, shouting)
What level is the thyroid cartilage at
C4/5
What is the rima glottidis
Space between vocal folds
What is the general role of extrinsic ligaments of the larynx
Binds the cartilages together
What are the extrinsic ligaments of the larynx
- thyrohyoid membrane
Connects hyoid (greater horns and body) with thyroid cartilage (superior rim and horns) - cricothyroid membrane (closes anterior gap between cricoid and thyroid cartilages)
- cricotracheal ligament (connects cricoid with first cartilage of trachea)
What are the intrinsic ligaments of the larynx?
Intrinsic ligaments line the inside of the larynx:
- quadrangular membrane connect lateral margins of epiglottis to arytenoid and thyroid cartilages
- inside, their lower borders form the vestibular ligaments - Conus elasticus (cricovocal membrane) connects cricoid to vocal process of arytenoid and thyroid cartilage.
- Free superior border is thickened to form vocal ligament
Functions of intrinsic laryngeal muscles
- Control of inlet to larynx: sphincter action on inlet is used to resist high intra-thoracic/ abdominal pressures (eg coughing, lifting heavy objects ) and is important in swallowing
- Control of size of Rima glottidis: controlling airflow, protection of airways in swallowing and phonation
- Control tension/ length of vocal folds: in phonation to control pitch of sound
(All intrinsic muscles are involved in all of these functions as they work as a unit)
Which muscles are important in controlling the laryngeal inlet
- closing
- opening
Closing sphincter of larynx: aryepiglottic muscle, oblique arytenoid muscles
(Both narrow the laryngeal inlet)
Opening — pulling epiglottis forward
- thyroepiglottic muscles
What happens when you relax vocal folds
Relax vocal folds, slow down vibrations, open rima glottidis
What muscle is important in tensing vocal folds
Thyroarytenoid
What muscles tense vocal folds, and thereby increase vibrations
Cricothyroid muscles
- forward and downward rotation of the thyroid cartilage at the cricothyroid joint
Vocalis muscles
- adjusts tension in vocal folds
Muscles important in vocal fold abduction and abduction
Posterior cricoarytenoids
- abduction and external rotation
Lateral cricoarytenoids
- adduction and internal rotation
Transverse arytenoids
- adduction and internal rotation
What are the extrinsic muscles of the larynx and what do they do
Extrinsic muscles can act on larynx to elevate or depress it
Mostly effected via supra- and infra-hypod muscles as larynx is connected to hydroid
Suprahyoid muscle — raise hyoid
- digastric, stylohyoid, mylohyoid, geniohyoid, styloglossus
Infrahyoid muscle — depress hyoid
- Sternohyoid, Sternothyroid, thyrohyoid, omohyoid
Nerve supply to larynx
From two branches of vagus nerve (X)
- superior laryngeal nerve split into motor and sensory branch)
- recurrent laryngeal nerve (mixed sensorimotor nerves)
Blood supply to larynx
Blood supply to larynx via external carotid arteries and thyrocervical trunk
- superior laryngeal arteries (branch of superior thyroid arteries)
- inferior laryngeal arteries (branch of inferior thyroid arteries)
What is the dividing plane for arterial blood supply in larynx
Vocal folds
Venous drainage of larynx
Superior laryngeal veins drain into superior thyroid veins, which in turn drain into internal jugular veins
Inferior laryngeal veins drain into inferior thyroid veins, which drain into left brachiocephalic vein
Lymphatics of larynx
Lymphatic vessels drain directly to the deep cervical nodes, mostly anterior to internal jugular veins
Lymphatics drain regions above and below vocal folds
- those above vocal folds follow superior laryngeal artery and terminate in deep cervical nodes associated with bifurcation of common carotid artery
- those below vocal folds drain into deep nodes associated with inferior thyroid artery or with nodes associated with the front of cricothyroid ligament or upper trachea
Source and filter theory of speech production
Source of acoustic energy: air stream from lungs, shaped by vocal folds
Acoustic energy is then modulated by filter: supralaryngeal vocal tract
Into speech elements (eg vowels, consonants)
To produce different speech elements, the filter is adjusted (eg changes in length or shape/ diameter of supralaryngeal vocal tract)
