Functional Anatomy of the Larynx Flashcards
1
Q
Describe the location of the larynx
A
- Larynx lies below the hyoid bone
- Part of the respiratory system - begins at laryngeal inlet and continues as the trachea (at C6/lower border of cricoid cartilage)
- Lies anterior to the laryngopharynx
2
Q
What is the main function of the larynx
A
Provide a protective sphincter for the lower respiratory tract
3
Q
Name the cartilages present in the larynx
A
- Thyroid cartilage contains the laryngeal prominence (Adam’s apple)
- Cricoid - only cartilage with a complete ring
- Thyroid cartilage and trachea do not have back
- Epiglottis - has ligaments attaching to thyroid cartilage
- Arytenoid cartilage moves vocal cords
4
Q
Describe the ligaments and membranes present in the larynx
A
- Thyrohyoid membrane - between thyroid cartilage and hyoid
- Cricothyroid ligament - between cricoid and thyroid cartilage
- Cricotracheal membrane - between cricoid and trachea
- Quadrangular membrane - epiglottis to arytenoid cartilage
5
Q
State where synovial joints are present within the larynx
A
- Between inferior horn of thyroid cartilage and cricoid
- Between cricoid and arytenoid cartilages
6
Q
Describe what the aryepiglottic fold is
A
- Aryepiglottic folds form margins of oval inlet of the larynx
- Lie over the epiglottis and quadrangular membrane
- Lined with mucous membrane - can be irritated leading to cough
7
Q
Describe the location of the two types of vocal cords
A
- Vestibular ligament/fold - false vocal cord
- Thickened lower border of quadrangular membrane
- Vocal ligament/fold - true vocal cord
- Thickened upper border of cricothyroid ligament
8
Q
Describe the 3 sections of the larynx
A
- Supraglottis - part of the larynx above vocal cords
- From epiglottis to vestibular folds
- Glottis - vocal folds
- Infraglottis - from vocal folds to cricoid cartilage
9
Q
What epithelium lines the larynx
A
- Larynx lined with pseudostratified ciliated columnar epithelium (part of respiratory tract)
- Apart from vocal cords, which are lined with stratified squamous epithelium due to constant abrasion from air
10
Q
Describe the laryngeal ventricle
A
- Between vestibular and vocal folds is a small recess (laryngeal ventricle) which leads laterally and upwards into the saccule of larynx
- Contains mucous glands that keep vocal folds moist
11
Q
What do the intrinsic muscles of the larynx do
A
- Act to alter the size and shape of the inlet or move position of vocal cords
- Act to close the larynx during swallowing, protecting the respiratory tract
- Act to open the larynx and allow movement of air during inspiration and expiration
- Controls movement of vocal cords in phonation and in cough reflex
12
Q
Describe the action of cricoarytenoid
A
- Act to open (abduct) the vocal cords, while other intrinsic muscles act to close (adduct) vocal cord
13
Q
Describe the innervation of the intrinsic muscles of the larynx
A
- All supplied by recurrent laryngeal nerve of vagus
- Except cricothyroid muscle which is supplied by external branch of superior laryngeal nerve
14
Q
Describe what the superior laryngeal nerve innervates within the larynx
A
- Internal branch provides sensation in supraglottis region
- External branch provides motor to cricothyroid muscle
15
Q
Describe the route of the recurrent laryngeal nerves
A
- Left nerve loops under arch of aorta and right loops under right subclavian artery
- Ascends in tracheo-oesophageal groove and has close relationship with inferior thyroid arteries supplying thyroid gland
16
Q
Describe what the recurrent laryngeal nerves innervate within the larynx
A
- Innervates all intrinsic muscles of larynx apart from cricothyroid
- Provides sensation to infraglottic region
17
Q
Describe the equipment used to endoscopically view the larynx
A
- Laryngoscope can be used to view vocal cords and allow for intubation (placement of a tube into subglottic region)
- Plastic tube has a inflatable cuff to prevent gastric contents from entering trachea
- Inflated after tube passes below the vocal cords
- Plastic tube has a inflatable cuff to prevent gastric contents from entering trachea
- Nasoendoscope - flexible endoscope inserted via nasal cavity and pharynx to visualize larynx
18
Q
How can you orientate yourself when viewing the larynx endoscopically
A
- Rima glottidis is the gap between the vocal folds
- Point anteriorly
19
Q
Describe the position of the vocal cords during inspiration and expiration
A
The vocal cords abduct
20
Q
Describe the position of the vocal cords during phonation
A
- True vocal cords adduct
- Expired air is forced through closely adducted vocal cords to vibrate a column of air
- Position of arytenoid on cricoid cartilage determine position of true vocal cords and therefore size of aperture
21
Q
Describe how the cough reflex occurs in the larynx
A
- During a cough, vocal cords powerfully adducted
- Intrathoracic pressure builds, then cords suddenly abduct
22
Q
How can pitch be altered by vocal cords
A
- Pitch of sound can be altered by tension and length of true vocal cords
- High-pitched sounds - vocal cords taut
- Low-pitched sounds - vocal cords relaxed
- Bilateral contraction of cricothyroid muscle increases length and tension in vocal cords
- Tilts thyroid cartilage
- Allows production of high pitched sounds
- Tilts thyroid cartilage
23
Q
What muscles of the larynx aid swallowing
A
- Protects airways from food/fluid during swallowing
- Contraction of aryepiglottic muscles act to narrow laryngeal inlet and pull epiglottis down
- Assisted by elevation of larynx (through pharyngeal muscles and suprahyoid muscles)
- Closure of vocal cords (glottis)
24
Q
Explain what a cricothyroidotomy is
A
- Emergency access to provide patent airway
- If a patient cannot be ventilated, such as anaesthetized or unconsciousness, access can be gained through cricothyroid membrane
25
How can recurrent laryngeal nerves be damaged
- Recurrent laryngeal nerves closely associated with inferior thyroid artery
- Potentially injured during thyroid surgery
- Also can be injured from aortic arch aneurysm, cancer involving apex of lung or disease/surgery involving larynx, oesophagus or thyroid
26
Describe the presentation of a unilateral vocal cord palsy
- Paralysed vocal cord assumes a paramedian position
- Between fully abducted and fully adducted
- Unilateral palsy may lead to hoarseness of voice and ineffective cough
- Often contralateral side compensates in time
27
Describe the presentation of the bilateral vocal cord palsy
- Both vocal cords paralysed in paramedian position
- Narrow glottis
- Significant airway obstruction
- Require emergency surgical airway such as crocothyroidotomy or tracheostomy
28
Describe the presentation of an injury to the superior laryngeal nerve
- Injury to superior laryngeal nerve leads to hoarseness of voice, especially when attempting high pitched sounds
- Failure to innervate cricothyroid muscle
29
How do conditions causing swelling of the larynx present
Patients present with stridor, raised respiratory rate, distress, hypoxia with possible cyanosis
30
Give examples of conditions which could cause swelling of the larynx
- Laryngitis
- Laryngeal nodules
- Laryngeal cancer
- Croup - inflammation of upper respiratory tract due to viral infection
- Epiglottitis - could lead to complete airway blockage
- Laryngeal oedema - such as through allergic reaction
31
What is the cervical plexus
- Network of nerve fibres that supplies innervation to some of the structures of the neck and trunk
- Located in the posterior triangle in the neck
- Plexus is formed form the anterior rami of C1-C4 cervical nerves
32
Describe the muscular and sensory branches from the cervical plexus
- Muscular branches are located deep to the sensory branches
- Supply muscles of the neck, back and diaphragm
- Phrenic nerve arises from C3-C5 and innervates the diaphragm
- Ansa cervicalis - loop of nerves formed by C1-C3
- Gives off branches that supply 4 infrahyoid muscles including the omohyoid
- Depress the hyoid bone - important in speech and swallowing
- Sensory branches supply the skin of the neck, upper thorax, scalp and ear
- These nerves enter the skin at Erb's point (middle of the posterior border of the sternocleidomastoid)
33
Outline the relationship between the blood supply of the thyroid and the nerves supplying the larynx
- Recurrent laryngeal nerves run behind the thyroid gland to innervate the larynx
- Can be damaged in thyroid enlargement or thyroid surgery
- Runs closely with the inferior thyroid artery
- External laryngeal nerve runs alongside the superior thyroid artery
