The larynx is situated at the crossroads of the air and food passages. It must serve not only as a conduit for air and waste gases to and from lungs but also as a valve to prevent the passage of secretions, of food and of other foreign material into the upper respiratory tract. Larynx also serves as an organ of communication; therefore it is also referred as organ of voice.
Anatomy of adult larynx
- The larynx is situated in front of hypopharynx opposite to third to sixth cervical vertebrae and ends at the lower border of C6 vertebrae in adults.
- The skeletal support of larynx is provided by Six cartilages, 3 out of which are paired (so there are total 9 cartilages.
- Unpaired: - Thyroid, cricoid, epiglottis.
- Paired : Arytenoid, Corniculate, cuneiform
- Larynx is larger in males than females.
1. Important features of individual laryngeal cartilages
It is the largest of all laryngeal cartilages. It is 'V' shaped with right and left lamina. Both laminae (alae) meet anteriorly forming an angle of 900 in males and 1200 in females and forms laryngeal prominence. Vocal cords are attached to the middle of thyroid angle. Upper border of thyroid cartilage lies at C3-C4 junction (at upper border of C4). Thyroid cartilage itself lies at C4-C5level.
2. Cricoid (unpaired)
It is the only cartilage forming a complete ring, therefore is shaped like a ring. It articulates with arytenoid cartilage to form cricoarytenoid joint, a type of synovial joint. It lies at the level of C6 vertebra
3. Epiglottis (unpaired)
It is leaf-shaped elastic cartilage (in adults). It is omega shaped in children. It forms the anterior wall of laryngeal inlet. It lies above glottis.
4. Arytenoid cartilage (paired)
Each Arytenoid cartilage is pyramidal in shape. Base articulates with cricoid cartilage, and apex supports the corniculate cartilage. A vocal process directed anteriorly and gives attachment to vocal cord. A muscular process directed laterally and gives attachment to intrinsic laryngeal muscles.
5. Corniculate cartilage (of Santorini) : Paired
Articulates with apex of Arytenoid cartilage
6. Cuneiform cartilage (ofWrisberg) : Paired
Situated in aryepiglottic fold in front of corniculate cartilage.
7. Histology of laryngeal cartilages:
|Hyaline cartilages||Elastic cartilages (do not ossify)|
8. Muscles of larynx
- Larynx has two types of muscles.
- Intrinsic muscles: -Confined entirely to the larynx.
- Extrinsic muscles: -Pass between the larynx and other structure around the larynx.
These muscles connect the larynx to neighbouring structures. The muscles are: -
- Elevators: Primary elevators act directly as they are attached to the thyroid cartilage and include Stylopharyngeus, salpingopharyngeus, palatopharyngeus and thyrohyoid. Secondary elevators act indirectly as they are attached to the hyoid bone and include mylohyoid. Digastric, stylohyoid, geniohyoid.
- Depressors: They include sternohyoid, sternothyroid and omohyoid.
Ligaments/Membranes of larynx
Membranes Ligaments of larynx can be divided in to two groups:
- Extrinsic: - On outer surface of the larynx.
- Intrinsic: - Inside the larynx
These membranes/ligaments connect the laryngeal cartilages and epiglottis to neighbouring structure.
- Thyrohyoid membrane (Thyroid cartilage to hyoid bone)
- Lateral thyrohyoid ligament
- Median Thyrohyoid ligament
- Hyoepiglottic ligament (Epiglottis to body of hyoid).
- Cricotracheal membrane (Cricoid to the first ring of trachea).
Intrinsic ligament / membranes
These membranes/Ligaments connect the laryngeal cartilage and epiglottis with each other.
- Quadrangular membrane
- Aryepiglottic ligament (superior border of membrane)
- Vestibular ligament (Inferior border of membrane)
- Triangular membrane (Cricovocal membrane)
- Vocal ligament (Superior end of membrane)
- Cricothyroid ligament (anterior part of membrane)
- Median Cricothyroid ligament
- Lateral cricothyroid ligament
- Thyroepiglottic ligament
Interior of larynx (cavity of larynx)
- The cavity of larynx extends from the laryngeal inlet (where it communicates with pharynx) to lower border of cricoid cartilage where it is continuous with that of trachea.
- There are two pairs of mucosal folds ;n laryngeal cavity: -
- Vestibular folds
- Vocal fold (vocal cords)
- These two pairs of folds divide the laryngeal cavity into three parts: -
- Vestibule: - It is the part of larynx which is above the vestibular folds, i.e., it extends from laryngeal inlet to vestibular folds.
- Ventricle (sinus of larynx): - It is the part. of larynx between vestibular folds and vocal folds. Thesacculeis a diverticulum of mucous membrane which starts from the anterior part of ventricular cavity and extends upwards between vestibular fold and extends upward. When abnormally enlarged and distended, it may form a laryngocele, i.e., an air containing sac which may present in the neck.
- Subglottic space (infraglottic larynx): - It is the space of larynx below the vocal folds, i.e., it extends from vocal cords to the lower border of cricoid cartilage.
Inlet of larynx
It is an oblique opening bounded: -
- Anteriorly: - Free margins of epiglottis
- On the sides : - Aryepiglottic folds
- Posteriorly: - Interarytenoid folds
Vestibular folds (False vocal cords)
- Two folds of mucous membrane extending anteroposteriorly across the laryngeal cavity.
- It contains vestibular ligament, a few fibres of thyroarytenoides mus1ce and mucous glands.
Vocal folds (Vocal cords or true vocal cords)
- Two pearly-white sharp fibroelastic bands extending from the middle of thyroid angle to vocal process of arytenoids.
- They are formed by reflection of the mucosa over vocal ligaments.
- They have stratified squamous epithelium with no submucosa layer.
- Their blood supply is poor and are almost devoid oflymphatics, this gives vocal cord a pale appearance,
- Vocal cords along with the upper part of the vestibule are the only part of laryngeal mucous membrane which is lined by epithelium of stratified squamous type. Elsewhere in the larynx epithelium of the mucous membrane is ciliated columnar type.
Glottis (Rima glottidis)
- It is the opening between the true vocal cords (anteriorly).
- It is the narrowest part of larynx in adults.
- It is the space between two vestibular folds.
Anatomical sites of larynx
Conventionally, larynx is divided into: -
- Supraglottic larynx
- It is the part of larynx above the vocal cords (vocal folds or true vocal cords). So, it includes vestibule of larynx as well as ventricle (sinus of larynx).
- It consists of suprahyoid epiglottis (both lingual and laryngeal surface), infrahyoid epiglottis, aryepiglottic folds (only laryngeal aspect), false vocal cord (vestibular fold or ventricular band).
- It is the part at the level of vocal cords.
- Subglottic larynx
- It is the part of larynx below the vocal cords and is continuous with the trachea.
Nerve supply of larynx
- The main cranial nerve innervating the larynx is the vagus nerve via its branches; superior laryngeal nerve (SLN) and recurrent laryngeal nerve (RLN).
Sensory supply of larynx
- Above the level of vocal cords, larynx is supplied by internal laryngeal nerve, a branch of superior laryngeal nerve.
- Below the vocal cord, larynx is supplied by recurrent laryngeal nerve.
Motor supply of larynx
- All the intrinsic muscles of larynx are supplied by recurrent laryngeal nerve except for cricothyroid muscle.
- Cricothyroid is supplied by external laryngeal nerve, a branch of superior laryngeal nerve.