The Larynx

Question 1

What are the functions of the larynx

Answer 1

The most important function of the larynx is in ventilation and airway protection (preventing food and liquid that we swallow from entering the airway). The larynx also allows us to cough, an important protective mechanism to expel rapidly certain substances. The final function of the larynx is in the production of sound (phonation), which is modified by the actions of the pharynx, oral cavity, lips, teeth and tongue.

Question 2

What makes up the structural framework of the larynx

Answer 2

The structural framework of the larynx is formed by the epiglottis, thyroid, cricoid and arytenoid cartilages. The thyroid cartilage is attached superiorly to the hyoid bone by the thyrohyoid membrane, and inferiorly to the cricoid cartilage by the cricothyroid membrane. This can be palpated anteriorly and, in acute laryngeal obstruction can be punctured to enable the patient to breathe.

Question 3

What must you consider when treating travelling families?

Answer 3

Travelling families – less vaccines so more likely to go abnormal infections such as epiglottitis from haemophilus influenza.

Question 4

Where does the epiglottis attach and what cell type lines its different surfaces?

Answer 4

The leaf-shaped epiglottis (elastic cartilage) is attached superiorly to the body of the hyoid and inferiorly to the back of the thyroid cartilage. The sides of the epiglottis are connected to the arytenoids by aryepiglottic folds that run backwards to form the margins of the laryngeal entrance, or aditus, of the larynx. It has two surfaces – the lingual surface made form stratified squamous epithelium, underneath is pseudostratified epithelium.

Question 5

What s the vallecula?

Answer 5

The vallecula is a depression between the base of the tongue and the epiglottis.

Question 6

How is the thyroid cartilage formed?

Answer 6

The thyroid cartilage is shield-like, being made up of two lateral plates meeting in the midline as a prominent V also known as an Adam’s apple or the laryngeal prominence.

Question 7

Describe the crioid cartilage and why is it special?

Answer 7

The cricoid cartilage is signet-ring shaped and the only complete ring of cartilage throughout the respiratory tract. Inferiorly, it is attached to the trachea by the cricotracheal membrane.

Cricoid pressure – compressing the cricoid cartilage to compress the oesophagus to prevent aspiration of food from the stomach.

Question 8

What are the arytenoids?

Answer 8

The arytenoids sit on top of the cricoid cartilage posteriorly, one on each side.

Question 9

Describe what makes up the two cords and what the holes inbetween are called. What forms the folds?

Answer 9

Just below the epiglottic attachment there are two folds of mucosa lining the interior of the larynx. The upper is the vestibular fold, forming on each side, the false vocal cord. The lower fold, the true vocal cord (or fold) contains the vocal ligament. The space in the middle, between the vocal cords is the rima glottidis. The true vocal cords are formed from the cricothyroid membrane are covered by stratified squamous epithelium and the false vocal cords are formed from the quadrangular membrane and are covered pseudostratified epithelium

Question 10

What is the quadrangular membrane?

Answer 10

The quadrangular membrane or aryepiglottic membrane connects the arytenoids to the epiglottis.

Question 11

What is the function of the arytenoids?

Answer 11

Arytenoids pivot on the cricoid cartilages when pulled by intrinsic laryngeal muscles to move the cords.

Question 12

How is the larynx divided into three zones?

Answer 12

The larynx consists of three zones: the supraglottis from the epiglottis to the vestibular folds, glottis from the cords and 1cm below and subglottis is the lower border of the glottis to the cricoid cartilage.

Question 13

Describe the important muscles involved in phonation

Answer 13

Intrinsic muscles are within the thyroid cartilage except cricothyroid which increases the vocal pitch. Posterior cricoarytenoid is the only muscle to abduct the vocal cords. Cricoarytenoid, arytenoid, vocalis and thyroarytenoid muscles all adduct. The infrahyoid and suprahyoid muscles, which depress and elevate the hyoid and larynx support the larynx in its function.

Question 14

What do the vocal cords do during, respiration, phonation and swallowing

Answer 14

During respiration, the vocal cords are abducted, in phonation they are partially abducted and when swallowing they are fully adducted.

Question 15

What muscles move the epiglottis?

Answer 15

Aryepiglottics and thyroepiglottics both function to move the epiglottis and cover the laryngeal inlet during swallowing.

Question 16

Describe neural and vascular innervation to the larynx

Answer 16

Vagus innervates all laryngeal muscles. Superior laryngeal is split into the internal and external branches. Internal innervates sensory to the supraglottic region and external gives motor to the cricothyroid. The recurrent laryngeal nerves give sensory to subglottic regions and motor to the intrinsic muscles of the larynx.

Superior and recurrent laryngeal nerves are accompanied by the arterial branches from the superior and inferior thyroid arteries.

Question 17

What happen when there is damage to the superior laryngeal nerve

Answer 17

Damage to the superior laryngeal nerve (or its external branch) may only cause some weakness of phonation (particularly higher pitch) due to loss of the tightening effect of the cricothyroid muscle on the vocal cord.

Question 18

What happens in damage to both recurrent laryngeal nerves?

Answer 18

If both recurrent laryngeal nerves are completely damaged, both vocal cords assume this paramedian position, with the rima glottidis becoming extremely narrow (note: not completely closed). While this will affect the patient’s ability to speak, this position of the vocal cords will also obstruct movement of air into and out of the trachea. As such patients will present with difficulties in breathing, and may even develop stridor. Whilst unilateral will only impair their ability to speak

Question 19

What can cause recurrent laryngeal nerve injury?

Answer 19

Idiopathic, laryngeal cancer, thyroid disease (benign or malignant), trauma and surgery, cervical lymphadenopathy, oesophageal cancer, apical lung cancer, aortic aneurysm and neuropathic such as diabetes.

Question 20

What are the most common cancers of the larynx

Answer 20

Most squamous cell carcinomas that is very common, especially in men. laryngeal cancer is small and involves the glottis, prognosis is favorable if it is caught early as this area of the larynx (glottis) has very minimal lymphatic drainage (so less likely to spread). Unfortunately, the supra- and infraglottic regions drain to neck nodes and paratracheal nodes respectively and so have a poorer prognosis.

Question 21

What is the cervical plexus?

Answer 21

The cervical plexus is formed by the anterior primary rami of the first four cervical nerves. It lies on the surface of scalenus medius and levator scapulae muscles, deep to the internal jugular vein and emerges from the posterior border of sternocleidomastoid, to lie within the posterior triangle.

Question 22

What is the function of the cervical plexus?

Answer 22

It has a number of sensory (cutaneous) and motor branches. The sensory branches supply the skin of the neck, part of the scalp and ear, and the superior part of the thorax. A number of the muscular branches form a loop known as the ansa cervicalis, which gives rise to nerves supplying most of the four paired infrahyoid muscles.

One of the important motor branches of the cervical plexus is the phrenic nerve, which carries nerve roots from C3 and 4, as well as roots from the ventral ramus of C5.