Anatomy of the larynx and supralaryngeal vocal tract Flashcards
1
Q
What are the functions of the larynx
A
- It is a valve that protects the entrance to the Tracheobronchial Tree, notably during swallowing
- Here, the Vocal and Vestibular Folds adduct, the Epiglottis Moves down and the Larynx rises during swallowing
- If its protective role is ineffective, laryngeal incompetence can lead to food and fluid being aspirated into the Trachea
- Some activities required temporary closure of the Respiratory Tract to increase the pressure in the chest/abdomen such as coughing, lifting heavy weights or using increased abdominal pressure (defecation, micturition and child birth)
- It controls airflow through the respiratory tract during rest, exercise and phonation
2
Q
Describe the surface anatomy and topography of the larynx
A
- It is found inferior to the hyoid, anterior to the laryngopharynx and above the 1st cartilaginous tracheal ring
- The Thyroid Cartilage located in neck midline, below the 3rd to 4th cervical vertebrae
- The Thyroid Eminence of the Larynx is visible on the anterior surface of neck as “Adam’s apple” – often prominent in males
- It houses the vocal folds which run anteroposterior across the larynx
- They divide the laryngeal cavity into superior (= vestibule) and inferior (= atrium) regions
- The space/gap between the vocal folds is called the rima glottidis
3
Q
What are the components of the larynx
A
- It is comprised of 4 major cartilages, united by mobile synovial joints, with Ligaments and Membranes helping to fill the gaps between these cartilages
- Whilst the Hyoid bone is not part of the Larynx, it is the superior anchoring point for the Larynx
- The Cartilage skeleton provides support and mediates the key functions of the larynx
- The Epiglottis is made of Fibrocartilage
- Ligaments bind the cartilages together
- Intrinsic and Extrinsic Laryngeal Muscles move the cartilages of the Larynx relative to each other or move the Larynx as a whole respectively
- Most of the Larynx is lined with Respiratory Epithellium (Pseudostratified Ciliated Columnar) except for the Vocal Folds which are covered by Stratified Squamous Epithelium
- The Larynx has outer and inner walls, which arise from the Cricoid Ring inferiorly
4
Q
Describe the thyroid cartilage
A
- The Thyroid Cartillage is the largest cartilage ring of the Larynx and is formed of two Laminae which project anteromedially to meet in the Midline at an Angle (Laryngeal Prominence)
- This is found superior to the Cricoid Cartilage
- This may be seen and palpated in the midline of the neck as the Adam’s Apple (This can be seen anteriorly, predominantly in men as the angle between the Laminae becomes more acute at puberty, making the prominence sharper)
- A Superior Thyroid Notch is an indentation that can be palpated between the two laminae, superior to the Laryngeal Prominence
- The Posterior Margin of the Laminae of the Thyroid Cartilage is extended superiorly and inferiorly as slender Superior and Inferior Horns/Cornua
- The Oblique Line of the Thyroid Cartilage is found at the Posterior margin of the Lamina of the Thyroid Cartilage, extending anteroinferiorly from the Base of the Superior Cornu to halfway along the Inferior Border of the Lamina
5
Q
Describe cricoid cartilage
A
- It is the Shape of a Signet Ring, with the narrow/thinner part of the ring lying anteriorly and the thicker/wider section posteriorly
- The Anterior Aspect of the Cricoid Cartilage may be palpated in the neck, below the Thyroid Cartilage
- The Inferior Cornu of each Thyroid Lamina forms a synovial articulation with a facet on the Posterolateral Aspect of the Cricoid to form the Cricothyroid Joints
6
Q
What is the role of extrinsic ligaments of laryngeal cartilage
A
- The Thyrohyoid Membrane attaches to the Superior Border of the Lamina and Greater Horns of the Thyroid Cartilage inferiorly and the Inner Border of the Body and Greater Horns of the Hyoid Superiorly
- This closes the Gap between the Thyroid Cartilage and the Hyoid Bone
- The Cricothyroid Ligament/Membrane (Strong) attaches to the Inferomedial Border of the Thyroid Cartilage superiorly and the Medial Cricoid
- This closes the anterior gap between the Cricoid and Thyroid Cartilages superiorly and inferiorly respectively
- The Cricoid Superiorly is attaches to the 1st ring of the Tracheal Cartilage by the Cricotracheal Ligament
7
Q
What is the role of intrinsic ligaments of laryngeal cartilage
A
- The Inner wall of the Larynx is completed by a fibroelastic membrane that extends from the Lateral Sides of the Epiglottis superiorly to the Arytenoids posteroinferiorly and down to the Lower Aspect of the Thyroid Cartilage
- The Region of this membrane found between the Lateral Sides of the Epiglottis anteriorly, the Arytenoids Posteriorly and Thyroid Cartilages laterally is the Quadrangular Membrane and is less well developed (Fibroelastic Membrane here is replaced by muscle fibres)
- The Quadrangular Membrane ends inferiorly at a sharp free border that runs between the Arytenoid posteriorly and the Thyroid Lamina anteriorly (Vestibular Ligament)
- When these Vestibular Ligaments are covered with Mucosa, they form the Vestibular Folds (False Vocal Cords)
- There is a slit-like gap inferior to the Vestibular Ligament and superior to the Vocal Ligament, known as the Vestibular Recess - This contains a blind-ended sac containing Mucous Secreting Glands which lubricate the Vocal and Vestibular Folds
- Beneath this gap is the Conus Elasticus/Cricovocal membrane, with the superficial part of the Conus elasticus in the midline anteriorly forming the Cricothyroid Ligament between the Cricoid Cartilage and Thyroid Cartilage
- The Conus Elasticus arises from the Upper Margin of the Cricoid Cartilage inferiorly and attaches to the Vocal Process of the Arytenoid Cartilages posteriorly and the Thyroid Cartilage anteriorly.
- It has a free margin that is thickened and runs from the Vocal/Anterior Process on the Base of the Arytenoid Cartilage (found posteriorly) to the Posterior Surface of the Midline of the Two Thyroid Laminae (found anteriorly). This is called the Vocal Ligament
- This forms the Inferior Border of the Slit in the Inner Wall of the Larynx whilst the Vestibular Ligament form the Superior Border of this Slit
- When the Vocal Ligament is covered with Mucous Membrane, it is called the Vocal Fold
- The Aryepiglottic Fold is a triangular fold of the Mucous Membrane of the Larynx which extends from the Lateral Borders of the Epiglottis Superiorly to the Arytenoid Inferiorly, covering the Free Superior Edge of the Quadrangular Membrane
- They are found superior to and enclose the Aryepiglottic Muscle
8
Q
What is a coniostomy/cricothyrotomy and why is it done
A
- The Most common Airway Obstruction results from objects becoming lodged in the Laryngeal Inlet alongside a reflex spasm of the Laryngeal Muscles
- Usually, the obstruction can be used dislodged by coughing, manually removing it with the fingers or via Abdominal Thrusts/Heimlich Manoeuvre
- When this cannot be done in an emergency situation (E.g Obstructions, Carcinoma of the Mouth and Face, Inflammation of the Larynx and Pharynx or Fractures to the Cervical Spine), an incision can be made through the Cricothyroid Membrane in the Midline, found below the Vocal Folds at the entrance to the Trachea
Small items that are swallowed with difficulty tend to get stuck in the Piriform Fossa and sometimes need to be removed
9
Q
What is tracheostomy
A
- This is an elective procedure to reduce the dead space in the airway of a weak patient or to facilitate prolonged artificial ventilation of patients
- This is often done when long term access and management of the airways is needed
- A transverse incision is made in the neck through the Skin and Platysma (In the same direction that the skin creases upon Neck Flexion), midway between the Cricoid Cartilage and the Suprasternal Notch
- The Infrahyoid Muscles are then retracted to each side and the Isthmus of the Thyroid Gland is identified
- This is extremely vascular and so, is clamped, ligated and divided (Taking care as to not damage the External Laryngeal and Recurrent Laryngeal Nerves)
- The Trachea deep to the Thyroid is opened below the First Tracheal Ring and a flap is created by cutting inferiorly at both ends of the transverse incision, and reflecting the flat inferiorly
- This flat is then sewn to the skin superficial to the flat to ensure clear access to the airway
10
Q
What are the extrinsic muscles of the larynx
A
- These are found between the Larynx and Neighbouring Structures and move the Larynx as a whole up and down the neck (carried out by the Suprahyoid and Infrahyoid Muscles Respectively)
- Lowering the Vocal Pitch can be achieved by depressing the Larynx via the Infrahyoid Muscles and Raising the Vocal Pitch can be achieved by elevating the Larynx via the Suprahyoid Muscles
- Suprahyoid = Digastric, Stylohyoid, Mylohyoid, Geniohyoid and Styloglossus
- Infrahyoid Muscles = Sternohyoid, Thyrohyoid, Omohyoid and Sternothyroid
11
Q
What is the innervation of the larynx
A
- This is provided by the Superior and Recurrent Laryngeal Nerves from CN X
Superior Laryngeal Nerve
- This arises from CN X high up in the neck and after descending posterior to the Common Carotids, it divides into Internal and External Branches
- The Internal Laryngeal Nerve pierces the Thyrohyoid Membrane to enter the Larynx and provides sensory innervation to the Mucous Membrane of the Larynx Superior to the Vocal Folds (Vestibule, Epiglottis & Inlet and Piriform Fossa, Aryepiglottic Fold and each Vallecula)
- The External Laryngeal Nerve innervates Cricothyroid
Recurrent Laryngeal Nerve
- This is a mixed nerve conveying Motor and Sensory Fibres
- This enters the Larynx posterior to the Cricothyroid Joint
- It supplies all of the Intrinsic Laryngeal Muscles except for Cricothyroid
- It also provides sensation of the Mucous Membrane of the Larynx inferior to the Vocal Folds (Laryngeal Atrium, Cricoid Cartilage etc.)
- Terminal Branches of the Recurrent Laryngeal Nerve may intermingle with those of the Superior Laryngeal Nerve
- The Cricopharyngeal Part of the Inferior Pharyngeal Constrictor is often supplied by branches of either the Recurrent or External Laryngeal Nerves
12
Q
Laryngeal nerve lesions
A
- Lesions of the Vagus Nerve superior to where the Laryngeal Nerves arises causes complete paralysis of the Larynx
- Internal Laryngeal Nerve Lesions causes loss of sensation of the Laryngeal Mucosa superior to the Vocal Folds
13
Q
What happens particularly in a recurrent laryngeal nerve lesion
A
- Injury to one Recurrent Laryngeal Nerve paralyses the Ipsilateral Vocal Fold as all Intrinsic Muscles except Cricothyroid are paralysed , causing it to remain Abducted or Adducted whilst causing loss of sensation below the affected vocal fold
- If the Vocal Fold remains adducted, this will lead to Dyspnoea on exertion due to reduced airflow into the Trachea
- If the Vocal Fold remains Abducted, the voice will become weaker and hoarseness but there will be little to no breathlessness
- Bilateral Paralysis of the Recurrent Laryngeal Nerves which results in Adducted Cords leads to both Dyspnoea and Hoarseness and loss of sensation bilaterally below the level of the Vocal Folds
14
Q
What happens specifically to an injury in the recurrent laryngeal nerve
A
- Injury to one Recurrent Laryngeal Nerve paralyses the Ipsilateral Vocal Fold as all Intrinsic Muscles except Cricothyroid are paralysed , causing it to remain Abducted or Adducted whilst causing loss of sensation below the affected vocal fold
- If the Vocal Fold remains adducted, this will lead to Dyspnoea on exertion due to reduced airflow into the Trachea
- If the Vocal Fold remains Abducted, the voice will become weaker and hoarseness but there will be little to no breathlessness
- Bilateral Paralysis of the Recurrent Laryngeal Nerves which results in Adducted Cords leads to both Dyspnoea and Hoarseness and loss of sensation bilaterally below the level of the Vocal Folds
15
Q
What happens specifically in in an injury in the external recurrent laryngeal nerve
A
- Damage to the External Laryngeal Nerve (E.g via Stroke) causes paralysis of the Cricothyroid
- This causes the Vocal Folds to become less taunt (Relaxed and ‘Rubber-Band’ Like), making the voice sound hoarse as the vocal cord will not adduct and close properly
- This lack of Adduction of the Paralysed Vocal Fold means that there is incomplete closure of the Vocal Folds, meaning foreign materials can enter the Trachea and Bronchi through the gap between the Normal and Paralysed Vocal Folds, increasing the risk of Lung Infections
- There is also difficulty in singing high notes and the voice tires quickly as the Vocal Cords cannot be kept tense
- Recovery often occurs as the Contralateral Vocal Cord and Musculature adapts to generate the Vocal Cord Tensions needed for normal phonation
