H&N Viscera

Viscera of the Neck

  • Deeper Viscera of the Head

    • Includes the following structures:

    • Pharynx

    • Larynx

    • Trachea

    • Cervical Esophagus (discussed as part of the gastrointestinal system)

Larynx

  • Definition: The larynx is described as a complex organ responsible for voice production.

  • Anatomy:

    • Composed of nine cartilages that are connected by membranes and ligaments and encompass the vocal folds.

    • Position: Located in the anterior neck at the levels of vertebrae C3 to C6.

    • Function:

    • Primary function is phonation (voice production).

    • Most crucial role is serving as a sphincter valve for the lower respiratory tract, maintaining a patent airway.

  • MRI Video by Tylee Ross:

    • Shows the larynx during singing.

    • Illustrates anatomy such as the lips, tongue, and the velum (soft palate).

    • The velum controls airflow and sound to the nasal cavity and operates unconsciously while speaking and singing.

Cartilages of the Larynx

  • Laryngeal Skeleton: Composed of nine cartilages:

    • Thyroid Cartilage

    • Largest cartilage, superior border sits opposite to vertebra C4.

    • The anterior fusion of the lamina forms the laryngeal prominence (Adam's apple), more prominent in men than women.

    • Notches:

      • Superior thyroid notch (V-shaped) above the prominence.

      • Inferior thyroid notch below.

    • Cricoid Cartilage:

    • Articulates with inferior horn lateral surface at the cricothyroid joints.

    • This joint allows rotation and gliding of the thyroid cartilage, affecting vocal fold length.

    • Epiglottic Cartilage:

    • Provides flexibility to the epiglottis, located posterior to the root of the tongue and anterior to the laryngeal inlet.

    • Paired Cartilages:

    • Arytenoid Cartilages: Each has an apex (superior), vocal process (anterior), and muscular process (lateral) from the base.

    • Corniculate and Cuneiform Cartilages: Support the arytenoids and the laryngeal structure.

  • Vocal Folds:

    • Movement of cricoarytenoid joints permits vocal cord tension adjustments, allowing for phonation and singing.

    • Rima Glottidis: The opening between the vocal folds.

    • Elastic Vocal Ligaments:

    • Extend from the thyroid cartilage to the arytenoid cartilage and comprise the submucosal skeleton of the vocal folds.

Laryngeal Muscles

  • Extrinsic Laryngeal Muscles:

    • Move the entire larynx.

    • Include:

    • Infrahyoid Muscles: Depress rather than elevate the hyoid and larynx.

    • Suprahyoid Muscles: Elevate the hyoid and larynx.

  • Intrinsic Laryngeal Muscles:

    • Modify the tension of the vocal folds and alter the shape and size of the rima glottidis.

    • All except cricothyroid innervated by the recurrent laryngeal nerve.

    • Cricothyroid Muscles: Innervated by the external laryngeal nerve (branch of the superior laryngeal nerve).

Laryngeal Arteries and Veins

  • Arterial Supply:

    • Supplied by branches from the superior and inferior thyroid arteries.

    • Superior Laryngeal Artery: Accompanies the internal laryngeal nerve.

    • Cricothyroid Artery: Supplies the cricothyroid muscle.

    • Inferior Laryngeal Artery: Branch of inferior thyroid artery, accompanies the inferior laryngeal nerve.

  • Venous Drainage:

    • Superior Laryngeal Vein: Drains into the superior thyroid vein, then internal jugular vein.

    • Inferior Laryngeal Vein: Drains into the inferior thyroid vein or venous plexus before connecting to the left brachiocephalic vein.

  • Lymphatic Drainage:

    • Superior Deep Cervical Lymph Nodes: Drain lymph from areas superior to vocal folds.

    • Inferior Deep Cervical Lymph Nodes: Drain lymph inferior to vocal folds.

Nerves of the Larynx

  • Superior Laryngeal Nerve:

    • Branch of the inferior vagal ganglion, dividing into:

    • Internal Laryngeal Nerve: Sensory and autonomic functions.

    • External Laryngeal Nerve: Motor functions.

  • Inferior Laryngeal Nerve: Continuation of the recurrent laryngeal nerve, enters the larynx through the inferior border of the inferior pharyngeal constrictor muscle.

    • Function:

    • Supplies various muscles including lateral cricoarytenoid, thyroarytenoid, vocalis, and more.

Pharynx

  • Definition: The pharynx is the superior expanded portion of the digestive system, positioned posteriorly to the nasal and oral cavities.

  • Anatomy:

    • Extends from the cranial base to the inferior border of the cricoid cartilage and narrows at its inferior end, connecting to the esophagus.

    • Three divisions:

    • Nasopharynx:

      • Located posterior to the nose, superior to the soft palate, and has respiratory functions. Opens into the nasal cavities through the Choanae.

    • Oropharynx:

      • Posterior to the oral cavity, extending from the uvula/soft palate to the epiglottis; acts in digestion.

    • Laryngopharynx:

      • Lying posterior to the larynx, between the superior border of the epiglottis to the cricoid cartilage.

    • Lateral Pharyngeal Structures: The Waldayer's Tonsillar Ring includes lymphoid structures such as pharyngeal, tubal, palatine, and lingual tonsils.

Muscles of the Pharynx

  • External Circular Layer:

    • Composed of three pharyngeal constrictors:

    • Superior Pharyngeal Constrictor

    • Middle Pharyngeal Constrictor

    • Inferior Pharyngeal Constrictor

  • Internal Longitudinal Muscles:

    • Include the palatopharyngeus, stylopharyngeus, and salpingopharyngeus.

    • Function to elevate the larynx and shorten the pharynx during swallowing and speaking.

  • Innervation:

    • All except stylopharyngeus innervated by the pharyngeal branch of the vagus nerve.

    • Stylopharyngeus supplied by the glossopharyngeal nerve (Cranial Nerve IX).

Tonsillar Artery and Veins

  • Tonsillar Artery:

    • Branch of the facial artery, passes through superior pharyngeal constrictor muscle to enter the palatine tonsils.

    • Receives supply from additional arteries:

    • Ascending palatine

    • Lingual

    • Descending palatine

    • Ascending pharyngeal arteries.

  • Venous Drainage:

    • External palatine vein approaches the tonsil, drains into the pharyngeal venous plexus.

  • Lymphatic Drainage of Tonsils:

    • Lymphatic vessels drain into the jugulodigastric node (tonsillar node), which often enlarges during tonsillitis.

Conclusion

  • Nerve Supply of the Pharynx:

    • Derived from the pharyngeal plexus of nerves. Motor innervation through the vagus nerve except for stylopharyngeus (supplied by cranial nerve IX).

    • Mucous membrane of the anterior and superior nasopharynx innervated by the maxillary nerve (trigeminal nerve division).

  • Final Notes:

    • After the lecture, additional questions and clarifications are welcomed. Students are encouraged to engage and utilize laboratory resources.