Larynx Anatomy and Function

Overview of the Larynx

• Found in the anterior neck, in front of the cervical esophagus.
• Connects the pharynx and trachea.
• Solely allows air passage.
• Situated at the C3-C6 vertebral level; may be higher in females/children.

Functions of the Larynx

• Protects airways from large, swallowed materials.
• Involved in sound production (phonation).

General Anatomy of Larynx

• Laryngeal inlet serves as the entrance from the pharynx.

Three Main Spaces of the Larynx

Vestibule

• Most superior space in the larynx.
• Extends from the laryngeal inlet to the vestibular folds.

Ventricle

• Middle and smallest laryngeal space.
• Located between the vestibular and vocal folds.

Infraglottic Cavity

• Most inferior space in the larynx.
• Spans from the inferior vocal fold aspect to the first tracheal ring.

Rima Glottidis

• Opening located between the vocal and arytenoid cartilages.

Cartilages of the Larynx

• Unpaired cartilages: epiglottis, thyroid, and cricoid.
• Paired cartilages: arytenoid, corniculate, and cuneiform.

Epiglottis

• Leaf-shaped elastic cartilage.
• Sits behind the hyoid bone and in front of the laryngeal inlet.
• Primary function: seals off the laryngeal inlet during swallowing to prevent food entry.
• Two parts: free superior edge and attached inferior stem-like part.
• Free superior part: broad, rounded, may have a midline notch.
• Attached inferior stem-like part: connects to the thyroid cartilage's posterior via the thyroepiglottic ligament.

Thyroid Cartilage

• Largest laryngeal cartilage.
• Formed by 2 hyaline cartilage laminae that merge in the midline.
• Laryngeal prominence is located in the inferior two-thirds, also known as the Adam's apple; the epiglottis cartilage attaches to its posterior aspect.
• Superior thyroid notch sits above the prominence and is V-shaped.
• Superior and inferior horns are posterolateral extensions, also known as superior and inferior cornua.

Cricoid Cartilage

• Complete hyaline cartilage ring.
• Lies between the thyroid cartilage and trachea.
• Has two parts: an anterior curved arch and a flattened posterior lamina.

Arytenoid Cartilages

• Located on the cricoid cartilage.
• Composed of hyaline cartilage.
• Pyramidal in shape, tapering to an apex that articulates with the corniculate cartilage.
• Two key projections for attachments: vocal and muscular processes.
• Vocal process is an elongated, sharp anterior projection, whilst the Muscular process is rounded and projects posterolaterally.

Corniculate Cartilages

• Sit on top of the arytenoid cartilages.
• Conical in shape and considered minor cartilages.

Intrinsic Structures of the Larynx

Quadrangular Membrane

• A submucosal layer of broad, thin connective tissue.
• Extends from the epiglottis' lateral edges to the arytenoid cartilages.
• Covered in mucosa.
• The superior free border forms the aryepiglottic fold, and forms the lateral border of the laryngeal inlet.
• The cuneiform tubercle contains the cuneiform cartilages at the inferior end of each aryepiglottic fold.

Vestibular Fold

• Inferior free edge of the quadrangular membrane.
• Commonly called the false vocal cord.

Conus Elasticus

• Connective tissue located between the superior cricoid rim and the thyroid cartilage.
• Its superior free edge forms the vocal ligament.

Vocal Ligaments

• Superior free edges of the conus elasticus.
• They extend from the arytenoid cartilages to the inner thyroid cartilage surface.
• Covered by a mucous membrane.
• The combination of the ligament and mucous membrane are called the vocal folds.
• Crucial for sound production, commonly known as the vocal cords.

Pharynx Anatomy

• Muscular column behind the oral cavity, nasal cavity, and larynx.
• Lined with mucosa and muscle fibers running circularly and longitudinally.
• Important for voice production and as a passageway for food and air.

Nasopharynx

• Uppermost pharynx portion.
• Located behind the nasal cavity's posterior part, behind the conchae.
• Communicates with the nasal cavity through the nasal conchae.
• Torus tubarius are folds elevating the auditory (Eustachian) tube.
• Torus levatorius: just below the torus tubarius.
• Levator Veli Palatini muscle elevates the soft palate during swallowing, preventing food from entering the nasopharynx.
• Pharyngeal recesses are located behind the Eustachian tube.
• Salpingopharyngeal folds are ridges formed by the salpingopharyngeus muscle.
• Soft palate is located behind the hard palate, and is comprised of the tensor veli palatini muscle.
• Palatine uvula is a conical projection from the soft palate's posterior free edge and hangs into the oropharynx.
• Pharyngeal tonsil also called adenoids, contains lymphatic tissue in the nasopharyngeal area.

Oropharynx

• Middle portion of the pharynx between the nasopharynx and laryngopharynx.
• Just behind the oral cavity.
• Extends from the soft palate to the hyoid bone.
• Vallecula epiglottica is a fossa between the lateral/median glossoepiglottic folds and the epiglottis.
• Palatopharyngeal arches are 2 mucous membrane folds overlying the palatopharyngeal muscle, which depresses the palate.
• Root of the tongue is the posterior part anchored to the mandible and hyoid bone.
• Structures present - Contains vallate papillae (taste buds) as well as lingual tonsils.
• Palatine tonsils are comprised of lymphoid tissue, ( Mucosa-associated lymphoid tissue / MALT ).

Laryngopharynx

• Positioned behind the larynx.
• Stretches from the oropharynx down to the esophagus.
• Piriform recess: located on the sides of the laryngopharynx.
• The epiglottis is covered by mucous membrane, made of elastic cartilage, closes to seal off the larynx during swallowing and remains open during breathing.
• Laryngeal inlet: entrance from the pharynx, closed by the epiglottis to prevent food/liquid entry.

Aryepiglottic Folds

• Located at the larynx opening with mucosal folds overlying the aryepiglottic muscle.
• Aids in phonation.
• Interarytenoid notch: depression between the arytenoid cartilages covered by mucosa.
• Cuneiform tubercles: mucosa-covered prominence, formed by underlying cuneiform cartilage, located on the posterior aryepiglottic folds.
• Corniculate tubercles: eminences formed by corniculate cartilage, covered by mucosa.
• Piriform fossa/piriform recess: located between aryepiglottic folds and thyroid cartilage; houses a superior laryngeal nerve branch.

External Nasal Anatomy

• General Structure is a pyramidal structure with a superior root and an inferior apex.
• The root is continuous with the face's anterior surface.
• Dorsum of the nose is located between the root and apex.
• Nares (nostrils) are inferior to the apex; separated by the nasal septum, and laterally bounded by the ala nasi (nostrils wings).
• Bony part of the external nose are shaped by the nasal, maxillae, and frontal bones.
• Cartilaginous part is made of several cartilages; alar, lateral nasal and septal.
• Alar Cartilages have major alar cartilage forming the apex of the nose, and minor alar cartilages supporting the ala nasi.
• Lateral Nasal Cartilage forms the dorsum of the nose.
• Septal Cartilage medially bounds the nares.

Nasal Cavity Anatomy

• Two nasal cavities are situated within the external nose and adjacent skull, with 12 cranial bones contributing.
• Anterior Openings are the external Nares
• Posterior Openings connects the Choanae with the nasopharynx.
• Ethmoid bone forming the Roof.
• Lateral Walls & Nasal Conchae:
• Three bony shelves are attached to the lateral walls and project into four air channels
• Inferior nasal meatus is between the floor and inferior concha.
• Middle nasal meatus is between the inferior and middle concha.
• Superior nasal meatus is between the middle and superior concha.
• Sphenoethmoidal recess is between the superior concha and the nasal cavity roof.
• Common nasal meatus is between the conchae and nasal septum.

Three Regions of the Nasal Cavity

Vestibule

• Located just inside the anterior external opening of the nose and contains hair follicles.

Olfactory Region

• Small area that is located inside at the superior apex of the cavity, and is lined by olfactory epithelium.

Respiratory Region

• Remainder of the nasal cavity that is the largest region and lined with respiratory epithelium.

Paranasal Sinuses

• Four bony recesses communicate with the nasal cavities.
• Named after the bones they reside in.
• Lined with respiratory mucosa.
• Innervated by the trigeminal nerve (Cranial Nerve V).
• Includes: sphenoidal, maxillary, frontal and ethmoidal.
• Blood Supply includes supply to the vestibule and respiratory portion; external nose – apex and dorsum, branches come from both the external carotid artery and the internal artery.

Blood Supply and Innervation

• External Carotid Artery Branches: sphenopalatine, greater palatine, superior labial, and lateral nasal arteries.
• Internal Artery Branches: anterior and posterior ethmoidal arteries.
• Olfactory nerve (CN I) allows for olfactory function.
• Trigeminal nerve (CN V) is for general sensation.
• CN VII - parasympathetic fibers innervate serous glands in the nasal mucosa.
• Sympathetic innervation is at the T1 level of the spinal cord, it regulates blood flow through nasal mucosa.