Pharynx & larynx

Question 1

What is the pharynx?

Answer 1

Half-cylindrical fibromuscular tube extending from the base of the skull (superior) to the lower border of the cricoid cartilage (inferior) at level C6

Question 2

What is the function of the pharynx?

Answer 2

Links together oral cavity, nasal cavity and larynx, acting as common passage for food and air.

Question 3

What are the divisions of the pharynx and their associations?

Answer 3

• Nasopharynx – Nasal cavity (via choanae)
• Oropharynx – Oral cavity (via oropharyngeal isthmus)
• Laryngopharynx – Larynx (via laryngeal inlet)

Question 4

What is the innervation of the pharyngeal muscles?

Answer 4

• All muscles of the pharynx are innervated by the pharyngeal branch of the vagus nerve [X].
• Fibres of inferior constrictor receive additional branches from external and recurrent laryngeal branches of vagus nerve.

Question 5

What is the sensory innervation of the pharynx?

Answer 5

• Nasopharynx: Maxillary branch of trigeminal nerve
• Oropharynx: Glossopharyngeal nerve
• Laryngopharynx: Vagus nerve

Question 6

What are the components of Waldeyer’s ring?

Answer 6

• Pharyngeal tonsil: Posterior to nasal cavity in roof of nasopharynx
• Tubal tonsils: Medial end of Eustacian tube
• Palatine tonsils: Between palatoglossal and palatopharyngeal arches
• Lingual tonsil: Posterior surface of tongue

Question 7

What is the process of swallowing?

Answer 7

1. After the food has undergone mastication in the oral cavity, it is pushed against the palate the tongue.
2. Contraction of tensor palatini and levator palatini causes closure of the nasopharynx by the soft palate (with contributions from the longitudinal muscles of the pharynx).
3. Pharynx is pulled in a antero-superior direction by the longitudinal muscles of the pharynx (stylopharyngeus, salpingopharyngeus and palatopharyngeus).
4. Action of levator palatini, tensor palatine and salpingopharyngeus opens Eustachian tube.
5. Oropharynx is closed by palatoglossus, styloglossus and intrinsic muscles of the tongue behind the bolus.
6. The rima glottidis is closed by adduction of the vocal folds by lateral cricoarytenoids and interarytenoids.
7. The laryngeal inlet is closed by the epiglottis (passively by weight of bolus and actively through contraction of aryepiglotticus).
8. The bolus is moved down the pharynx towards the oesophageal opening by the sequential constriction of pharyngeal constrictor muscles from superior to inferior.

Question 8

What is the composition of the larynx?

Answer 8

• Cartilage
• Ligaments
• Muscles
• Mucosal lining

Question 9

What are the functions of the larynx?

Answer 9

1. Airway protection
2. Effort closure (e.g. coughing, sneezing…)
3. Phonation (speech)

Question 10

What are the cartilages of the larynx?

Answer 10

• Epiglottis
• Arytenoid cartilages
• Cricoid cartilage
• Thyroid cartilage
• Corniculate cartilage
• Cuneiform cartilage

Question 11

What is the sructure of the epiglottis?

Answer 11

• Leaf-shaped cartilage.
• Stem is located below the hyoid and is attached to the thyroid cartilage by thyro-epiglottic ligament.
• Tip is located ~1 cm abover the hyoid.
• Mucosa from the anterior surface of the epiglottis reflects onto the tongue to form median and lateral glosso-epiglottic folds, with depression between called the valleculae.
• Space below the vallecular is a recess either side of the laryngeal oriface called the piriform fossa.

Question 12

What is the structure of the arytenoid cartilage?

Answer 12

• Pyramidal-shaped with apex pointing superiorly and base sitting on cricoid cartilage.
• It has several processes:
  1. Anterior aspects of these cartilages form the vocal processes, which are the attachments for the vocal ligaments.
  2. Lateral aspects of these cartilages form the muscular processes, which are the attachments for the cricoarytenoid muscles.

Question 13

What is the structure of the cricoarytenoid joint?

Answer 13

• Articulation between base of the arytenoid cartilage and sloping articular facet on superolateral surface of cricoid lamina.
• Synovial joint allowing rotation and gliding.

Question 14

What is the structure of the cricoid cartilage?

Answer 14

• Only complete cartilaginous ring in respiratory tract.
• Divided into 2 parts: Anterior arch and posterior lamina.
• Facets superiorly articulate with base of arytenoid cartilages.
• Facets laterally articulate with inferior horns of thyroid cartilages.
• Posterior surface of lamina consists of 2 depression separated by ridge. Ridge is attachment of oesophagus and depressions are attachments for posterior cricoarytenoids.

Question 15

What is the structure of the thyroid cartilage?

Answer 15

• Consists of 2 pentagonal plates (lamina) fused anteriorly at the laryngeal prominence.
• Posterior borders of plates consist of upward projection (superior horn) and downward projection (inferior horn).
• Superior horn connected to greater horn of hyoid bone by lateral thyrohyoid ligament.
• Inferior horn articulates with lateral facets of cricoid cartilage.
• Superior border connected to hyoid via thyrohyoid ligament.

Question 16

What are the differences between thyroid cartilage in males compared to females?

Answer 16

• Thyroid angle in males is 90^o compared to 120^o in females.
• Laryngeal prominence is more prominent in males.

Question 17

What is the structure of the corniculate and cuneiform cartilages?

Answer 17

• Corniculate cartilages are small conical cartilages whose bases articulate with the apex of the arytenoids.
• Cuneiform cartilages are small wedge-shaped cartilages embedded within the quadrangular membrane.

Question 18

What are the membranes of the larynx?

Answer 18

• Thyrohyoid membrane
• Quadrangular memrbane
• Cricothyroid membrane

Question 19

What is the structure of the thyrohyoid membrane?

Answer 19

• Runs between the superior margins of the thyroid cartilage and superior margins of the inferior surface of hyoid.
• Consists of the median thyrohyoid ligament on anterior aspects at midline and lateral thyrohyoid ligaments posteriorly.

Question 20

What structures pierce the thyrohyoid membrane?

Answer 20

• Superior laryngeal vessels
• Internal laryngeal branch of superior laryngeal nerve

Question 21

What is the structure of the quadrangular membrane?

Answer 21

• Runs between the lateral margins of the epiglottis and anterolateral surface of arytenoid cartilages.
• Has a free upper margin which is covered by mucosa to form the ary-epiglottic folds.
• Has free lower margin that forms the vestibular ligaments which are covered by mucosa to form the vestibular folds (false vocal cords).

Question 22

What is te structure of the cricothyroid membrane?

Answer 22

• Runs between the superior border of the cricoid cartilage and 2 superior points of attachments:
  1. Internal surface of thyroid cartilage
  2. Vocal process of arytenoid
• Thickening of free upper margin forms the vocal ligaments.
• Thickening of anterior surface forms the median cricothyroid ligament.

Question 23

What are the boundaries of the laryngeal inlet?

Answer 23

• Anterior: Epiglottis
• Posteror: Arytenoid cartilages
• Lateral: Ary-epiglottic folds

Question 24

What are the divisions of the laryngeal cavity?

Answer 24

The laryngeal cavity is divided by the vocal cords into the supraglottic space and infraglottic space.

Question 25

What is the structure of the supraglottic space?

Answer 25

• The supraglottic space is made up of 3 parts:
  1. Vestibule: Between laryngeal opening and vestibular folds
  2. Laryngeal ventricles: Between false and true vocal cords
  3. Laryngeal saccules: Anterior extensions of the laryngeal ventricles projecting superiorly (contains mucous glands that lubricate vocal cords)

Question 26

What is the structure of the infraglottic space?

Answer 26

Extends from the vocal cords superiorly to the opening of the trachea inferiorly at level of C6 vertebrae

Question 27

What types of epithelia are associated with the larynx?

Answer 27

• Vocal cords + epiglottis: Non-keratinised stratified squamous epithelium
• Other parts: Respiratory epithelium (pseudostratified ciliated columnar)

Question 28

What are the intrinsic muscles of the larynx?

Answer 28

Opening/closing laryngeal inlet:

• Aryepiglotticus: Close
• Thyroepiglotticus: Open

Abduction/adduction of vocal cords:

• Posterior cricoarytenoids: Abduct
• Lateral cricoarytenoids: Adduct
• Interarytenoids (oblique, transverse): Adduct

Changing tension in vocal cords:

• Cricothyroid: Lengthen
• Thyroarytenoid: Shorten
• Vocalis: Fine-tuning

Question 29

What are the extrinsic muscles of the larynx?

Answer 29

• Elevators (via hyoid):
  1. Mylohyoid
  2. Stylohyoid
  3. Geniohyoid
  4. Digastric
• Elevators (direct):
  1. Stylopharyngeus
  2. Palatopharyngeus
  3. Salpingopharyngeus
• Depressors (via hyoid):
  1. Sternohyoid
  2. Omohyoid
  3. Thyrohyoid
• Depressors (direct):
  1. Sternothyroid

Question 30

What is the blood supply of the larynx?

Answer 30

• Supraglottic space:

Arterial: Superior laryngeal branch of superior thyroid artery (ECA)

Venous: Superior laryngeal vein → Superior thyroid vein → IJV

• Infraglottic space:

Arterial: Inferior laryngeal branch of inferior thyroid artery (thyrocervical trunk of subclavian artery)

Venous: Inferior laryngeal vein → Inferior thyroid vein → Brachiocephalic vein

Question 31

What is the sensory innervation of the larynx?

Answer 31

• Supraglottic space + vocal cords: Superior laryngeal nerve (internal branch) - Vagus nerve
• Infraglottic space: Recurrent laryngeal nerve - Vagus nerve

Question 32

What is the lymphatic drainage of the larynx?

Answer 32

• Supraglottic space: Anterosuperior group of deep cervical nodes
• Infraglottic spac: Posteroinferior group of deep cervical nodes

Question 33

What is the sympathetic innervation of the larynx?

Answer 33

• Supraglottic space: Superior cervical ganglion (via superior thyroid artery)
• Infraglottic space: Middle cervical ganglion (via inferior thyroid artery)

Question 34

What is the muscular innervation of the larynx?

Answer 34

All intrinsic muscles of the larynx are innervated by the recurrent laryngeal nerve except the cricothyroid which is innervated by the external branch of superior laryngeal nerve.

Question 35

What is the cricopharyngeus?

Answer 35

Upper oesophageal sphincter