The Larynx - Overview
The larynx is a framework of cartilages haninng form the hyoid bone intercconnected by membranes and ligaments, lined by mucous membranes with muscular attachments that collectively function to forms a protective sphinter for the beginning of the tracheobronchial tree and to allow us the ability to speak.
The largest 3 cartilages are hyaline (thyroid, cricoid, arytenoid).
The epiglottis, cunieform and corniculate are fibroelastic.
The opening of the larynx, the laryngeal aperture, is formed by the epiglottis and aryepiglottic folds posteriorly.
The recurrent laryngeal nerve supplies all the intrinsic muscles and mucosa beneath the vocal cords.
The external branch of the superior laryngeal nerve supplies the thyrocricoid muscle and internal does mucosa above the cords.
Extrinsic Depressors: sternohyoid, sternothyroid, thyrohyoid, omohyoid (strap [infrahyoid] muscles; C1–C3)**
Extrinsic Elevators: geniohyoid (C1), digastric (CN V3, VII), mylohyoid (CN V3), stylohyoid (suprahyoid muscles; CN VII)**
There are 8 different intrinsic muscles, only 1 of which is unpaired, and only 1 of which is not supplied by recurrant laryngeal nerve.
2 muscles span artenoid cartilages to adduct vocal cords.
2 different crico-artenoid muscles that cause arytenoid rotation: one causing external rotation meaning vocal cord abduction the other the opposite.
2 muscles that change the length of the vocal cords (and so are important in pitch)
2 muscles specifically close the laryngeal apeture.
Superior Largyneal Artery
Relations of the Larynx
Superior border of the thyroid cartilage:
the phrenic nerve forms.
the CCA bifurcates.
Accessory thyroid tissue may develop lateral to the thyroid cartilage (pyramidal lobe in 75% people (called Lalouette's Lobe).
The cricoid cartilage is
- at c6.
- one thumbs bread under cricoid cartilage is isthmus of thyroid gland
Vocal Ligament + Conus Elasticus, Ventricular Ligaments + Quadrangular Membrane
Vocal Ligament + Conus Elasticus
The Vocal ligament is the submucosal skeleton of the vocal fold.
They attach from the vocal process of the arytenoid cartilage to the anterior commisure.
The vocal folds are the thickened, free superior border of the conus elasticus (cricovocal) membrane
The Broyle tendon is the anterior attachment of the vocal ligament to the inner perichondrium of the thyroid. It consists of the vocal ligament, conus elasticus, thyroarytenoid ligament, and thyroid perichondrium. It is very tough barrier to tumor spread.
** Ventricular Ligaments + Quadrangular Membrane**
The Quadrangular Membrane runs from the arytenoid cartilage to the epiglottis.
Anteriorly, it attaches to the lower half of the epiglottis.
Posteriorly, it attaches to the length of the arytenoid cartilage above the vocal process.
Its lower border is free, the ventricular ligament, which is the submucosal support for the ventricular fold, or the false vocal cord, its superior border is also free, this is also draped into mucosa and is known as the aryepiglottic fold.
cords are composed of five layers: the epithelial layer, 3 layers of lamina propria and the muscular layer.
The true vocal
fold can be divided into three major layers: the mucosa, the vocal ligament, and the underlying muscle.
The gelatinous superficial layer of the lamina propria, together with the squamous epithelium, moves freely over the underlying vocal ligament and muscle to form the vibrations that produce sound.
The vocal fold mucosa and vocal ligament cover the vocalis muscle and extend from the anterior commissure to the vocal processes of the arytenoids.
Membranous vocal fold: from anterior commissure to vocal process of arytenoid (ant 2/3ds)
Cartilaginous vocal fold: arytenoid cartilages (post 1/3).
Just behind the thyroid is the pre-epiglottic space: bounded by the vallecula, thyroid cartilage, thyrohyoid mem-
brane, and epiglottis
Paraglottic space: between thyroid ala, conus elasticus, and quadrangular membrane
Pre-epiglottic space: bounded by the vallecula, thyroid cartilage, thyrohyoid mem-
brane, and epiglottis.