LARYNX

The larynx is a cartilaginous segment of the respiratory tract found in the anterior aspect of the neck.
Primary Functions:
- Protects the lower respiratory tract from aspirating food into the trachea during breathing.
- Contains vocal cords and functions as a voice box for producing sounds, known as phonation.
Phylogenetic Overview:
- The larynx has achieved high evolutionary development in humans, enabling speech articulation, a feature absent in invertebrates and fishes.

Dimensions: The larynx measures approximately 4 to 5 cm in length and width, with a slightly shorter anterior-posterior diameter. The size varies between genders and ages:
- Smaller in women than men.
- Larger in adults than children due to growth during puberty.
- A larger larynx is associated with a deeper voice.
Location: Positioned at the level of cervical vertebrae C3 to C7, stabilized by muscles and ligaments:
- The superior region is the epiglottis, attached to the hyoid bone linked to the pharynx.
- The inferior aspect connects to the trachea.

The larynx consists of:
- A cartilaginous skeleton
- Ligaments and muscles for movement and stabilization
- A mucous membrane
Laryngeal Skeleton: Composed of nine cartilages:
- Unpaired Cartilages:
- Thyroid cartilage
- Cricoid cartilage
- Epiglottis
- Paired Cartilages:
- Arytenoid cartilage
- Corniculate cartilage
- Cuneiform cartilage
Thyroid Cartilage:
- Largest cartilage, shield-like structure protecting the larynx.
- Resembles a half-opened book, forming the laryngeal prominence (Adam's apple).

Cricoid Cartilage:
- Known as the cricoid ring or signet ring.
- Positioned at the inferior part of the larynx at C6.
- Comprises an anterior arch and a wider posterior lamina.
Epiglottis:
- An elastic, leaf-shaped cartilage that covers the laryngeal opening and allows air passage while swallowing to prevent aspiration.

Arytenoid Cartilages:
- Pyramid-shaped, flexible, and sit above the cricoid cartilage.
- Each has:
- Vocal process (anterior angle)
- Muscular process (lateral angle)
Corniculate Cartilages:
- Small, cone-shaped cartilages articulating with the arytenoid cartilages.
Cuneiform Cartilages:
- Two elongated fibrous pieces of yellow cartilage providing support to the vocal cords and epiglottis.

Types of Ligaments:
- Extrinsic Ligaments: Connecting the larynx to other structures (e.g., hyoid).
- Intrinsic Ligaments: Connecting laryngeal cartilages to each other.
Extrinsic Ligaments Include:
- Thyrohyoid ligament
- Hyoepiglottic ligament
- Cricotracheal ligament
Intrinsic Ligaments Include:
- Cricothyroid ligament (membrane) - pyramid-shaped.
- Cricocorniculate ligaments - link cricoid to Santorini cartilage.
- Thyroepiglottic ligament - connects thyroid cartilage to the epiglottis.
- Thyroarytenoid ligaments - connect arytenoid to thyroid cartilage, divided into superior and inferior ligaments.
- Arytenoidepiglottic ligaments - connect arytenoids to the epiglottis.

Structure:
- Internally, the larynx extends from the laryngeal inlet to the lower border of the cricoid cartilage, featuring a pyramid shape with three main sections:
- Posterior
- Superior (thyroid region)
- Inferior (cricoid region)
Dimensions and Sections:
- The laryngeal cavity narrows in the middle to form the glottis, dividing the space into:
- Supraglottic
- Glottis
- Infraglottic
Vocal Folds:
- Comprise true and false vocal cords:
- True vocal folds (inferior, muscular, capable of vibration and sound production)
- False vocal folds (superior, do not produce sound)

Blood Supply: Derived from:
- Superior laryngeal artery (from the superior thyroid artery), supplying the epiglottis and supraglottic region.
- Inferior laryngeal artery (also a branch of the superior thyroid artery), supplying the subglottic region.
Venous Drainage:
- Accompanies arteries, named similarly (superior and inferior laryngeal veins) draining into the superior and inferior thyroid veins.
**Lymphatic Drainage: ** Subdivided into:
- Supraglottic: Dense nodes draining into deep cervical lymphatics.
- Subglottic: Less dense, draining into lower deep cervical nodes.
- The glottic region lacks lymphatics.

Innervation: from:
- Superior laryngeal nerve (branch of vagus nerve), supplying mucous membranes.
- Recurrent laryngeal nerve, responsible for intrinsic muscle innervation (except cricothyroid).
**Recurrent Nerve Paths: **
- Left recurrent nerve loops around the aortic arch.
- Right recurrent nerve loops around the subclavian artery.
- Both enter the larynx beneath the inferior constrictor muscle.
Galen Anastomosis: Connection between internal and inferior laryngeal nerves.

Intrinsic Muscles:
- Primarily involved in voice production.
- Include:
- Cricothyroid Muscle: Increases pitch by elongating vocal folds.
- Posterior Cricoarytenoid Muscle: Abducts (opens) vocal cords.
- Lateral Cricoarytenoid Muscle: Adducts (closes) vocal folds.
- Thyroarytenoid Muscle: Relaxes and approximates vocal folds.
- Aryepiglottic Muscle: Adducts aryepiglottic folds.
- Transverse Arytenoid Muscle: Adducts vocal folds, only impaired intrinsic muscle.
Extrinsic Muscles:
- Move the larynx and include:
- Thyrohyoid Muscle: Depresses the hyoid, elevating the larynx.
- Sternothyroid Muscle: Depresses the larynx.
- Inferior Pharyngeal Constrictor Muscle: Narrows pharynx during swallowing.
- Stylopharyngeus Muscle: Elevates both larynx and pharynx.
- Palatopharyngeus Muscle: Elevates larynx and pharynx, part of soft palate.
- Other muscles not strictly laryngeal, such as geniohyoid and mylohyoid assist in elevating the larynx.

Laryngitis:
- Inflammation of the larynx, symptoms include hoarseness, pain, coughing; may accompany fever.
- Chronic laryngitis lasts over 3 weeks, while acute is less than 3 weeks.
Vocal Fold Paralysis (VFP):
- Result of recurrent laryngeal nerve paralysis.
- Comes from various diseases or disorders affecting the nerve.
Laryngeal Cancer:
- Commonly manifests as squamous cell carcinoma originating in the glottis, symptoms include hoarseness, lumps in neck, cough, stridor, or swallowing difficulty.