The larynx

الدكتور سعد يونس سليمان

Objectives
To discuss the basic anatomy of the larynx To enumerate the main functions of the larynx

Location: C4-C6

Laryngeal Cartilages
Paired Arytenoid cartilage Corniculate cartilage Cuneiform cartilage
Unpaired: Thyroid cartilage Cricoid cartilage Epiglottis

Thyroid Cartilage

Hyaline cartilage Largest Encloses the larynx anteriorly and laterally Two alae Ossification: 20-30 years

Cricoid Cartilage

Hyaline cartilage Directly below the thyroid cartilage It is the only cartilage forming a complete ring. Its posterior part is expanded to form a lamina while anteriorly it is narrow forming an arch. Ossifies after the thyroid cartilage, first part to be calcified being the superior portion (which can be mistaken for a foreign body)


Epiglottis
Fibroelastic cartilage Leaf-shaped structure It never ossifies

Arytenoid Cartilage

Paired. Smaller in size Responsible for opening and closing of the larynx

Arytenoid Cartilage

Shape: pyramidal Base---articulate with cricoids cartilage. Muscular process---laterally giving attachment to intrinsic muscle. Vocal process--- anteriorly, giving attachment to vocal cord. Apex---support the corniculate cartilage.

Corniculate Cartilages

Fibroelastic Small cartilages that lie over the arytenoids.

Cuneiform Cartilages

Fibroelastic cartilages Elongated pieces of small yellow elastic cartilage in the aryepiglottic folds
Cuneiform Cartilage

Laryngeal Joints

Cricothyroid Joint Cricoarytenoid Joint Both are synovial joints. Both have two movements: Rotation Gliding


Laryngeal Muscles
1- Extrinsic Muscles Depressor group Elevator group 2- Intrinsic muscles: All are paired except Interarytenoid muscle. They open and close the glottis; and they are of three groups: Abductors: posterior cricoarytenoid muscle. It opens the glottis and it is the most important muscle of the body. Adductors: Lateral cricoarytenoid, interarytenoid, thyroarytenoid (external part) Tensors: cricothyroid and vocalis (internal part of thyroarytenoid )

The glottis: composed of the vocal cords The subglottis: from the lower border of the glottis to the inferior border of the cricoid. The supraglottis: extend from the upper border of the glottis inferiorly to the hyoid bone superiorly.
Laryngeal compartments


Histology Lining epithelium: squamous over the vocal cords Mucous glands and lymphatics: rich in supraglottis, nil in glottis and very few in subglottis. The mucosa of the glottis and supraglottis is firmly bound down to the underlying tissue, but not so in the subglottic region. Here, the laxity of tissue allows a dangerous degree of oedema, especially in children, where the diameter of the area is relatively smaller than in adult.

Nerve Supply

Supplied by Vagus nerve:Superior laryngeal n.Internal branch (sensory) – areas above the glottisExternal branch (motor and sensory) Motor – Cricothyroid muscle only.Recurrent laryngeal n.Motor – all intrinsic laryngeal musclesSensory – areas below the glottis

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

Blood Supply External carotid artery Subclavian artery Venous Drainage Internal jugular vein Innominate vein Lymphatic drainage Main: Deep Cervical group L.N. The glottic area has NO lymphatic network.

Paediatric larynx It is positioned high in the neck opposite C3 or C4 (level of vocal cord) at rest and reaches C1 or C2 during swallowing. The laryngeal cartilage are soft and collapse easily. The thyroid cartilage in an infant is flat and the cricothyroid and thyrohyoid spaces are narrow. It is small and conical in shape ( while it is cylindrical in adult). Submucosal tissues of infant's larynx are loose and easily undergo oedematous changes with trauma or inflammation leading to obstruction.

Function of the larynx

1- Protection a. sphincteric closure b. cough reflex 2- Respiration 3- Phonation 4- Fixation of chest When the larynx is closed, chest wall gets fixed and various thoracic and abdominal muscles can then act best--> a-powerful voluntary muscular use of the arms. b-fixes the diaphragm to assist in the act of straining.


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