Larynx Anatomy Flashcards
What makes up laryngeal skeleton
9 cartilages
What are the 9 cartilages of the laryngeal skeleton suspended from
Hyoid bone by fibrous membranes
What type of cartilage is the majority of the laryngeal skeleton
Hyaline cartilage
What is the exception to most of laryngeal skeleton being hyaline cartilage
epiglottis is elastic cartilage (E&E)
What muscle of the larynx is involved in forced inspiration
posterior cricoarytenoid
What is the role of of the posterior cricoarytenoid in forced inspiration
It causes lateral rotation at the cricoarytenoid joint which widens the rima glottidis (abducting the vocal cords) to allow passage of air
What are the two protective mechanisms of the larynx that reduce the potential for aspiration of unwanted items
Glottis closure (i.e. adduction of vocal cords) &
Cough reflex
What is the role of the larynx in phonation
The vocal cords (rima glottidis) generate vibrations in air to aid communication via the action of laryngeal muscles
Describe the steps of phonation
- Diaphragm &/ intercostal muscles contraction (inspiration)
- Volume of lungs decreases
- & so lung/ subglottal pressure increases
- The vocal cords vibrate
- & phonation is produced during controlled expiration
The greater the subglottal pressure the _______ the speech
E.g. whispering = __________ pressure
vs shouting = __________ pressure
The greater the subglottal pressure the louder the speech
E.g. whispering = lower pressure
vs shouting = greater pressure
What is the 3 regions of the (internal) larynx
- Laryngeal vestibule - below epiglottis & above ventricles
- Laryngeal ventricles - ‘sacks’ just above the vocal cords
- infra-glottic region - below the vocal cords
Vestibule & ventricles = supra-glottic region
What is the cricothyroid joint
Joint between the cricoid cartilage & thyroid cartilage
What is the cricoarytenoid joint
Joint between the cricoid cartilage & arytenoid cartilage
What are the main three types of cartilage of the larynx
Thyroid
Cricoid
Arytenoid
What are the two processes of the arytenoid cartilage
Vocal process
Muscular process
What is the role of the extrinsic muscles of the larynx
Move the larynx superiorly and inferiorly
What are the extrinsic muscles of the larynx
- 4 suprahyoid muscles
- 3 infrahyoid muscles
- Stylopharyngeus
What are the 4 suprahyoid muscles
Mylohoid
Geniohyoid
Stylohyoid
Digastric
What are the 3 infrahyoid muscles
Thyrohyoid
Sternothyroid
Omhyoid
Thyrohyoid attachments
Hyoid bone
Thyroid cartilage
Sternothyroid attachments
Thyroid cartilage
Sternum (manubrium)
Omohyoid attachments
Hyoid bone (Anterolateral to thyrohyoid attachement)
Scapula (near supra-scapular notch)
Mylohyoid attachment
Mandible (at mylohyoid line)
Hyoid bone
Geniohyoid attachment
Mandible (at inferior mental spine)
Hyoid bone
Digastric attachment
Mandible (at inferior mental spine, anterior to Geniohyoid)
Temporal bone
& intermediate tendon connects the anterior & posterior bodies & attaches to the hyoid bone
Stylohyoid attachment
Styloid process of temporal bone
Hyoid bone
Movement of what bone facilitates swallowing & speech
Hyoid bone
What is unique about the hyoid bone
- The hyoid bone is the only bone in the human body not directly connected to another bone
- It is held in place by a series of fibrous and muscular connections
What is the role of the intrinsic muscles of the larynx
They control the shape of the rima glottidis, and the length and tension of the vocal folds
What is the rima glottidis
Opening between the vocal folds and the arytenoid cartilages
What are the five intrinsic muscles of the larynx
Cricothyroid muscle
Thyroartenoid muscle
Lateral cricoarytenoid muscle
Posterior cricoarytenoid muscle
Arytenoid muscles (oblique and transverse)
Cricothyroid muscle function
Tenses vocal cords (high pitch)
Thyroartenoid muscle
Relaxes vocal cords (low pitch)
Lateral cricoarytenoid muscle function
Adducts vocal cords
Posterior cricoarytenoid muscle
Abducts vocal cords
Cricothyroid muscle attachements
- Proximal: anterolateral cricoid cartilage
- Distal: inferior horn of thyroid cartilage
Thyroartenoid muscle attachments
- Proximal: posterior thyroid cartilage
- Distal: anterior arytenoid cartilage
Lateral cricoarytenoid muscle attachments
- Proximal: muscular process of arytenoid
- Distal: anterior cricoid cartilage
Posterior cricoarytenoid muscle attachments
- Proximal: posterior cricoid cartilage
- Distal: muscular process of arytenoid cartilage
laryngeal ntrinsic muscles innervation
- All = inferior laryngeal nerve/ recurrent laryngeal nerve (branch of CN X)
- Except cricothyroid muscle = external branch of the superior laryngeal nerve (branch of CN X)
What joint do the intrinsic laryngeal muscles work on
All = cricoarytenoid joint
Except cricothyroid muscle = cricothyroid joint ‘nodding’
Arytenoid muscle attachments
- Proximal: one arytenoid cartilage
- Distal: another arytenoid cartilage
Arytenoid muscles function
Adducts the vocal ligaments (assists the lateral cricoarytenoid muscle)
What is the lining of the internal larynx
Respiratory mucosa
Laryngeal mucosa innervation
- Mucosa above the vocal folds = internal laryngeal nerve
- Mucosa below the vocal folds = inferior laryngeal nerve
Inferior laryngeal nerve vs recurrent laryngeal nerve
Recurrent laryngeal nerve becomes inferior laryngeal nerve at the cricothyroid joint
Summarise the origin & path of the superior laryngeal nerve
Superior laryngeal nerve branches off from the vagus nerve (CN X) just above the carotid bifurcation
It then splits into the external & internal laryngeal nerve at the level of the hyoid bone
The internal laryngeal nerve pierces through the thyrohyoid membrane & it carries sensory fibers to the laryngeal mucosa superior to the vocal cords
The external laryngeal nerve carries motor fibres to the cricothyroid muscle
Summarise the origin & path of the recurrent laryngeal nerve
Recurrent laryngeal nerve brancehs off from the vagus nerve (CN X) in the mediastinum
The right RLN loops around the right subclavian artery & the left RLN loops under the aortic arch
The RLN(s) travel up the neck alongside the trachea & pass behind the thyroid gland
The RLN(s) pass behind the cricothyroid joint where they become the inferior laryngeal nerve
The inferior laryngeal nerve carries sensory fibers to the laryngeal mucosa inferior to the vocal cords
The inferior laryngeal nerve also carries sensory fibres to the intrinsic muscles of the larynx
Summarise the innervation of the internal larynx mucosa & intrinsic muscles
- Cricothyroid muscle = external laryngeal nerve
(branch of superior laryngeal nerve of vagus nerve) - All muscles except cricothyroid = inferior laryngeal nerve
(Continuation of RLN which is a branch of vagus nerve) - Mucosa above the vocal folds = internal laryngeal nerve (branch of superior laryngeal nerve of vagus nerve)
- Mucosa below the vocal folds = inferior laryngeal nerve
(Continuation of RLN which is a branch of vagus nerve)
Summarise the steps involved in generating voice once the air enters the larynx
Using the laryngeal musculature, air can be forced through the rima glottidis, which in turn vibrates the vocal cords forming sound. This is amplified by the pharynx, oral cavity, nose & sinuses to generate voice
- Tension of the vocal cords ________ pitch
- Relaxation of the vocal cords ________ pitch
- Adduction of the vocal cords makes sound _______
- Abduction of the vocal cords makes sound _______
- Tension of the vocal cords increases pitch
- Relaxation of the vocal cords decreases pitch
- Adduction of the vocal cords makes sound quieter
- Abduction of the vocal cords makes sound louder
What happens to the soft palpate in order for air to go through the oral cavity & what two cranial nerves are involved in this
Soft palate tenses (CN V3) and elevates (CN X) to close off entrance into nasopharynx
What happens to the soft palpate in order for air to go through the nasal cavity & what two cranial nerves are involved in this
Soft palate depresses (CN V3) and descends (CN X) to open entrance into nasopharynx
The tongue is involved in generating voice. What cranial nerve controls this?
CN XII
The teeth & lips are involved in generating voice. What cranial nerve controls this?
CN VII
What sounds require air to flow through the nasal cavity
‘m’, ‘n’, ‘ing’
What cranial nerve is key in the cough reflex
CN X
Describe the cough reflex
- Sensory stimuli in the supraglottis conveyed to brainstem via internal branch of superior laryngeal nerve (CN X)
- Glottic closure (rima gluttidus adduction) by lateral cricoarytenoid and arytenoid muscles via CN X
- Internal and innermost intercostal muscles and the diaphragm musculature contract to increase body cavity pressure
- Glottic release of high pressure air jet
Where should the laryngoscope be placed during laryngoscopy
The tip of the curved laryngoscope blade should be located within the vallecula, a mucosal lined space between the base of the tongue and the anterior aspect of the epiglottis
