Larynx & Trachea

Head & Neck Unit – Lecture 14األعسم. جليل حيدر د

LarynxLarynx is an organ that is responsible for voice production. It is situated below the tongue and hyoid bone and between great blood vessels of the neck and lies at the level of 4th, 5th & 6th cervical vertebrae. It opens above into laryngeal part of pharynx, and below is continuous with trachea. Larynx is covered in front by infrahyoid muscles and laterally by thyroid gland. Framework of larynx is formed of cartilages that are held together by ligaments & membranes, moved by muscles & lined by mucous membrane.

Cartilages of the Larynx1. Thyroid cartilage: is largest cartilage of larynx and consists of 2 laminae of hyaline cartilage that meet in midline in the prominent V angle (Adam's apple). Its posterior border extends upward into Superior Cornu &downward into Inferior Cornu.Lamina outer surface has Oblique Line for muscles attachment.2. Cricoid cartilage: is formed of hyaline cartilage like signet ring with broad Lamina behind & shallow arch in front. Its lamina has a facet for articulation with inferior cornu of thyroid cartilage & another facet for articulation with arytenoid cartilage on upper border of cricoid lamina, posteriorly.3. Arytenoid cartilages: are 2 small pyramidal shaped cartilages located at back of larynx. Each hasApex: above, articulates with corniculate cartilageBase: below, articulates with cricoid laminaVocal process: projects forward for vocal ligamentMuscular process: projects laterally for attachment of posterior & lateral cricoarytenoid muscles.

Cartilages of the Larynx4. Corniculate cartilages: are 2 small conical-shaped cartilages that articulate with Arytenoid Cartilages and give attachment to Aryepiglottic Folds. 5. Cuneiform cartilages: are 2 small rod-shaped cartilages in the Aryepiglottic folds to strengthen them. 6. Epiglottis: is leaf-shaped lamina of elastic cartilage lies behind root of tongue. Its stalk is attached to back of thyroid cartilage and its sides are attached to arytenoid cartilages by Aryepiglottic folds. Its upper edge is free and its mucous membrane covering passes forward onto posterior surface of tongue as median glossoepiglottic fold; while the depression on each side of this fold is called vallecula. Laterally the mucous membrane passes onto the wall of the pharynx as Lateral glossoepiglottic fold.

Membranes and Ligaments of LarynxThyrohyoid membrane: connects upper margin of thyroid cartilage to hyoid bone. In the midline it is thickened to form median thyrohyoid ligament. It is pierced on each side by superior laryngeal vessels and internal laryngeal nerve. Cricotracheal ligament: connects cricoid cartilage to first ring of trachea. Quadrangular membrane: extends between epiglottis and arytenoid cartilages. Its thickened inferior margin forms vestibular ligaments. Cricothyroid ligament: is attached to upper border of cricoid cartilage (inferiorly) & ascends on medial surface of thyroid cartilage. Its upper free border is composed entirely of elastic tissue and forms the important vocal ligament on each side. Vocal ligaments form interior of vocal folds (vocal cords). Vocal ligaments are attached to thyroid cartilage anteriorly, and to vocal process of arytenoid cartilage posteriorly.

Inlet of the LarynxThe inlet of the larynx looks backward and upward into laryngeal part of pharynx. It is wider anteriorly than posteriorly and is bounded: Anteriorly by epiglottisLaterally by aryepiglottic foldPosteriorly by arytenoid cartilages with corniculate cartilages. Cuneiform cartilage lies within and strengthens aryepiglottic fold and produces a small elevation on its upper border.

Piriform Fossa:It is a recess on either side of aryepiglottic fold and laryngeal inlet. It is bounded Medially: by aryepiglottic fold and Laterally: by thyroid cartilage and thyrohyoid membrane.

Laryngeal FoldsVestibular Fold: is a fixed fold on each side of larynx and is formed by mucous membrane covering vestibular ligament and is vascular and pink in color. Vocal Fold (Vocal Cord): is a mobile fold on each side of larynx and is concerned with voice production. It is formed by mucous membrane covering vocal ligament and is avascular and white in color. The gap between vocal folds is called rima glottidis or glottis. Glottis is the narrowest part of larynx in adults and is bounded in front by vocal folds and behind by medial surface of arytenoid cartilages. In children lower part of larynx within cricoid cartilage is the narrowest part.

Cavity of the LarynxIt extends from inlet to lower border of cricoid cartilage. It is divided into 3 regions: Vestibule: is situated between inlet and vestibular folds.Middle region: is situated between vestibular folds above and vocal folds below.Lower region: is situated between vocal folds above and lower border of cricoid cartilage below. Sinus of the Larynx: (Laryngeal Ventricle)It is a small recess on each side of larynx between vestibular & vocal folds and is lined by mucous membrane. Saccule of the Larynx:It is a diverticulum of mucous membrane that ascends from the sinus. Mucous secretion lubricates vocal cords

Muscles of the LarynxExtrinsic Muscles: move larynx up and down during swallowing and because many of them are attached to hyoid bone, which is attached to thyroid cartilage by thyrohyoid membrane. Elevation: digastric, stylohyoid, mylohyoid, geniohyoid, stylopharyngeus, salpingopharyngeus, and palatepharyngeus muscles.Depression: sternothyroid, sternohyoid & omohyoid.

Intrinsic Muscles: Two muscles modify laryngeal inlet: Narrowing inlet: oblique arytenoid muscle.Widening inlet: thyroepiglottic muscle.Five muscles move vocal folds (cords):Tensing vocal cords: Cricothyroid muscle.Relaxing vocal cords: Thyroarytenoid (vocalis) muscleAdducting vocal cords: Lateral cricoarytenoid muscleAbducting vocal cords: Posterior cricoarytenoid mApproximates arytenoid cartilages: Transverse arytenoid muscle.

Movements of the Vocal Folds (Cords)Movements of vocal folds depend on movements of arytenoid cartilages, which rotate and slide up and down on sloping shoulder of superior border of cricoid cartilage.

Rima glottidis is opened by contraction of posterior cricoarytenoid, which rotates arytenoid cartilage and abducts vocal process. Elastic tissue in the capsules of cricoarytenoid joints keeps arytenoid cartilages apart so that posterior part of glottis is open. Rima glottidis is closed by contraction of lateral cricoarytenoid, which rotates arytenoid cartilage and adducts vocal process. Posterior part of glottis is narrowed when arytenoid cartilages are drawn together by contraction of transverse arytenoid muscles. Vocal folds are stretched by contraction of cricothyroid muscle. Vocal folds are slackened by contraction of vocalis, a part of thyroarytenoid muscle.

Sphincteric Function of LarynxThere are two sphincters in the larynx: A. Sphincter at the inlet is used only during swallowing. (to close the inlet and prevent inhalation of food)B. Rrima glottidis serves as a sphincter during coughing or sneezing (narrowing of glottis). While in Valsalva maneuver, forced expiration takes place against a closed glottis. In abdominal straining associated with micturition and defecation, air is often held temporarily in respiratory tract by closing rima glottidis.

Nerve Supply of the LarynxSensory Nerves:Above vocal cords: Internal laryngeal branch of superior laryngeal branch of vagus. Below vocal cords: Recurrent laryngeal nerve. Motor Nerves: All intrinsic muscles of larynx except cricothyroid muscle are supplied by recurrent laryngeal nerve. Cricothyroid is supplied by external laryngeal branch of superior laryngeal branch of vagus.

Blood Supply of the Larynx A. Upper half of larynx: Superior laryngeal branch of superior thyroid artery.B. Lower half of larynx: Inferior laryngeal branch of inferior thyroid artery.

Lymph Drainage of the Larynx:Deep cervical lymph nodes.

The TracheaIt is a mobile cartilaginous & membranous tube. It begins at the level of 6th cervical vertebra & descends in midline of neck. Trachea is kept patent by presence of U-shaped cartilaginous bar (rings) of hyaline cartilage embedded in its wall. Posterior free ends of cartilages are connected by smooth muscle (trachealis muscle). Relations of Trachea in the Neck: Anteriorly: Skin, fascia, isthmus of thyroid gland (2nd, 3rd & 4th rings), inferior thyroid vein, jugular arch, thyroidea ima artery, and left brachiocephalic vein in children, overlapped by sternothyroid and sternohyoid.Posteriorly: Right and left recurrent laryngeal nerves and esophagus.Laterally: Lobes of thyroid gland and carotid sheath and contents.

Nerve Supply of Trachea: Sensory nerve supply is from vagus & recurrent laryngeal nerves. Blood Supply of Trachea: Upper 2/3 is supplied by inferior thyroid arteries and lower 1/3 is supplied by bronchial arteries. Lymph Drainage of Trachea: Pretracheal & Paratracheal lymph nodes and deep cervical nodes.

Vagus NerveIt is composed of motor and sensory fibers and leaves skull through jugular foramen. It descends through the neck alongside carotid arteries and internal jugular vein within carotid sheath. It passes through mediastinum of thorax, passing behind root of lung, and enters abdomen through esophageal opening in the diaphragm. Important Branches of the Vagus Nerve in the Neck:1.Meningeal and auricular branches.2.Pharyngeal branch: joins pharyngeal plexus & supplies all muscles of pharynx (except stylopharyngeus) and of soft palate (except tensor veli palatini). •Superior laryngeal nerve: divides into internal andexternal laryngeal nerves. External branch is closely related to superior thyroid artery.1.Recurrent laryngeal nerve: On Right side, it hooks around first part of subclavian artery. On the left side, it hooks around arch of aorta. It is closely related to inferior thyroid artery and it supplies all muscles of larynx (except cricothyroid), mucous membrane of larynx below vocal cords and mucous membrane of upper trachea. 5.Cardiac branches (two or three) arise in the neck, descend into thorax, and end in cardiac plexus.

End of the Lecture

GOOD LUCK