Larynx Anatomy: Spaces and Cartilages

Overview of the Larynx

• Located in the anterior neck
• Anterior to the cervical part of the esophagus
• Links the pharynx and the trachea
• Only air passes through
• Sits between the third and sixth cervical vertebrae
• In females and children, it tends to sit slightly higher

Functions of the Larynx

• Protects airways from large, swallowed matter
• Involved in the production of sound (phonation)

General Anatomy of Larynx

• The laryngeal inlet is the entrance from the pharynx

Three Main Spaces of the Larynx

• Vestibule is the most superior space, from the laryngeal inlet to the vestibular folds
• Ventricle is the middle and smallest space, between the vestibular and vocal folds
• Infraglottic cavity is the most inferior space, extending from the vocal folds to the first tracheal ring

Rima Glottidis

• The rima glottidis is the opening between the vocal folds and arytenoid cartilages

Cartilages of the Larynx

• The unpaired cartilages are the epiglottis, thyroid, and cricoid cartilages.
• The paired cartilages are the arytenoid, corniculate, and cuneiform cartilages.

Epiglottis

• Leaf-shaped piece of elastic cartilage
• Posterior to the hyoid bone and anterior to the laryngeal inlet
• Closes off the laryngeal inlet during swallowing
• Prevents food from entering the airways
• Has a free edge and an attached part
• The free superior part is broad and rounded, sometimes with a notch
• The attached inferior stem-like part connects to the thyroid cartilage via the thyroepiglottic ligament

Thyroid Cartilage

• Largest cartilage of the larynx, composed of two hyaline cartilage laminae fused in the midline
• The laryngeal prominence is the inferior two-thirds, i.e., Adam's apple
• Epiglottis cartilage attaches to the posterior aspect of the laryngeal prominence
• Superior thyroid notch is above the prominence and V-shaped
• Superior and inferior horns have posterolateral extensions, also called superior and inferior cornua

Cricoid Cartilage

• A complete ring of hyaline cartilage
• Located between the thyroid cartilage and trachea
• Consists of two parts: an anterior arch (curved) and a posterior lamina (flattened)

Arytenoid Cartilages

• Sit on the cricoid cartilage
• Made of hyaline cartilage
• Pyramidal in shape and taper into an apex
• Articulate with the corniculate cartilage above
• Have two important projections for muscle attachment: vocal process and muscular process
• The Muscle process is rounded and projects posterolaterally
• The vocal process is an elongated sharp projection of the anterior surface

Corniculate Cartilages

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

Quadrangular Membrane

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

Vestibular Fold

• The vestibular fold is the inferior free edge of the quadrangular membrane
• Commonly known as the false vocal cord

Conus Elasticus

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

Vocal Ligaments

• Superior free edges of the conus elasticus
• Extend from the arytenoid cartilages to the inner surface of the thyroid cartilage
• Covered in mucous membrane
• Ligament and mucous membrane combined forms the vocal folds
• Commonly known as vocal cords and are essential for producing sound

Pharynx

• Muscular column posterior to the oral cavity, nasal cavity, and larynx
• Lined by mucosa and muscle fibers arranged circularly and longitudinally
• Important for voice production and serves as a passageway for food and air

Nasopharynx

• Uppermost portion of pharynx
• Posterior to nasal cavity, behind the conchae
• Communicates with nasal cavity via the nasal conchae
• Contains the torus tubarius a fold that are elevations of the auditory tube or Eustachian tube
• Contains Torus levatorius is an elevation just below, produced by the levator veli palatini muscle
• Levator veli palatini elevates the soft palate during swallowing, preventing food from entering the nasopharynx
• Posterior to Eustachian tube sits Pharyngeal, or Eustachian, recesses
• Salpingopharyngeal folds are ridges formed by the salpingopharyngeus muscle
• The soft palate is posterior to hard palate, comprised of the tensor veli palatini muscle
• Palatine uvula is a conical projection hanging down into the oropharynx from the posterior free edge of the soft palate
• Pharyngeal tonsil- also known as the adenoids- is in the nasopharyngeal portion of the pharynx and is lymphatic tissue

Oropharynx

• Between the nasopharynx and the laryngopharynx
• Just behind the oral cavity
• Extends from the soft palate to the hyoid bone
• Contains Vallecula epiglottica, a fossa is located between glossoepiglottic folds and the epiglottis
• Palatopharyngeal arches are two folds of mucous membrane overlying the palatopharyngeal muscle
• The palatopharyngeal muscle depresses the palate
• Root of the tongue anchors the tongue to the mandible and hyoid bone
• The structures on the root of the tongue are the Vallate papillae, which contain taste buds and also Lingual tonsils
• Palatine tonsils, which are comprised of lymphoid tissue and also known as MALT - Mucosa-associated lymphoid tissue

Laryngopharynx

• Located behind the larynx
• Extends from the oropharynx to the esophagus
• Piriform recess is located on both sides of the laryngopharynx
• The Epiglottis closes during swallowing to close off the larynx from the food bolus
• When not swallowing it is otherwise open during you're breathing
• Laryngeal inlet opens from the pharynx to the larynx
• Connection between the pharynx and the larynx
• Is closed by the epiglottis to prevent food and liquid from entering the respiratory tract
• Aryepiglottic folds are Mucosal folds overlying the aryepiglottic muscle located at the opening of the larynx and aid in phonation
• Interarytenoid notch is a depression or indentation is found between the 2 apices of the arytenoid cartilages and is covered by mucosa
• Cuneiform tubercles are Mucosa-covered prominence formed by the underlying cuneiform cartilage located on the posterior part of the aryepiglottic folds
• Corniculate tubercles Eminences formed by the underlying corniculate cartilage and are covered by mucosa
• Piriform fossa/piriform recess: Located between the aryepiglottic folds and the thyroid cartilage on either side of the laryngeal inlet and the Mucosa houses a branch of the superior laryngeal nerve

External Nasal Anatomy

• External nose is a pyramidal structure that the root is located superiorly and apex sitting inferiorly
• The part between the root and the apex is called the dorsum of the nose
• Inferior to the apex are the two nares (nostrils)
• These are the openings to the nasal cavity
• The nares are separated by the nasal septum and are laterally bounded by the ala nasi (wings of the nostrils)
• Bones shape the nose root and bony nasal root is formed by the nasal, maxillae and frontal bones
• Cartilaginous part made up of alar, lateral nasal, and septal cartilages
• Alar cartilages: Major forms the apex of the nose and the Minor supports the ala nasi
• Lateral nasal cartilage forms the dorsum of the nose
• Septal cartilage bounds the nares medially

Nasal Cavity Anatomy

• Two nasal cavities sit within the external nose and the adjacent skull
• 12 cranial bones contribute to its structure.
• Anterior openings are the Nares
• Posterior openings are the Choanae: communicate with nasopharynx
• The Roof is the Ethmoid bone
• The Lateral walls contain the Nasal conchae which are split into Inferior, Middle, and Superior
• The Conchae are three bony shelves that are attached to the lateral walls and project into the nasal cavities
• They divide the nasal cavities into four air channels

Air channels of the nasal cavities split into four segments

• Inferior nasal meatus: Between the floor and inferior concha
• Middle nasal meatus: Between the inferior and middle concha
• Superior nasal meatus: Between the middle and superior concha
• Sphenoethmoidal recess: Between the superior concha and the nasal cavity roof
• Common nasal meatus: Between the conchae and nasal septum

Regions of the Nasal Cavity

• Vestibule: Located just inside the anterior external opening of the nose that contains hair follicles
• Olfactory region: A small area 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 is lined with respiratory epithelium

Paranasal Sinuses

• Four bony recesses communicate with the nasal cavities
• Named according to the bones in which they are located
• Covered by respiratory mucosa and innervated by the trigeminal nerve (Cranial Nerve V)
• Sphenoidal sinus
• Maxillary sinus
• Frontal sinus
• Ethmoidal cells

Blood supply to the nasal cavity

• Blood supply to the vestibule and respiratory portion occurs in the external nose and the apex and dorsum

External carotid artery are branches

• Sphenopalatine artery
• Greater palatine artery
• Superior labial artery
• Lateral nasal artery

Blood supply to the olfactory region and surrounding external nose

• Internal artery branches; Anterior and posterior ethmoidal arteries

Nerve supply of the nasal cavity

• Innervated by three cranial nerves

Olfactory nerve (CN I)

• Provides olfactory function

Trigeminal nerve (CN V)

• General sensation

CN VII (Facial Nerve)

• Parasympathetic fibers
• Innervate serous glands in the nasal mucosa

Sympathetic innervation

• T1 level of spinal cord
• Regulates blood flow through nasal mucosa