Upper Airway and Nose Anatomy

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@SeasonedYeti

Study Notes

The upper airway consists of the nose, oral cavity, pharynx, and larynx
Its functions include conducting air, humidifying and cooling air, preventing foreign materials from entering the respiratory system, and assisting with speech and smell.

Consists of lateral nasal cartilage, greater alar cartilage, lesser alar cartilage, septal cartilage, and fibrous fatty tissue.

The nasal septum divides the nasal cavity into two equal parts.
- Posteriorly, the septum is formed by the perpendicular plate of the ethmoid bone and the vomer.
- Anteriorly, it's formed by the septal cartilage.
The roof of the nasal cavity is formed by the nasal bones, the frontal process of the maxilla, and the cribriform plate of the ethmoid bone.
The floor of the nasal cavity is formed by the palatine process of the maxilla and the palatine bones.
- The posterior section of the nasal cavity floor is formed by the superior portion of the soft palate of the oral cavity.
Air enters through the nares (nostrils), which are formed by the septal cartilage and the alae nasi.

Composed of a vestibule (outer portion) between the teeth and gums and lips.
A larger section behind the teeth and gums extends to the oropharynx.
The tongue is located on the floor of the oral cavity and is composed of skeletal muscles and fibers.
- Intrinsic skeletal muscle fibers change the shape of the tongue, aiding in speech and swallowing.
- Extrinsic skeletal muscle fibers allow for changes in tongue position, like protruding outward and inward, and moving side to side.
The lingual frenulum secures the tongue to the floor of the mouth.
Papillae on the tongue contain taste buds.
The roof of the mouth is formed by the hard and soft palate.
- The hard palate is formed by the palatine process of the maxilla and palatine bones.
- The soft palate is a flexible, fleshy structure composed of densely packed collagen fibers.
  - It closes off the opening between the nasal and oropharynx.
  - The levator veli palatini muscle elevates the soft palate.
  - The palatopharyngeal muscles draw the soft palate forward and down.
The oral cavity is lined with stratified squamous epithelium.

The palatopharyngeal arch and the palatoglossal arch form the two arches in the oral cavity.
The palatine tonsil is located on each side of the oral cavity, situated between the palatine arches.

Inhaled air passes from the nasal cavity to the pharynx.
The pharynx is divided into three parts:
- Nasopharynx: Posterior to the nasal cavity, superior to the soft palate. It contains the adenoid (pharyngeal tonsil) posterior to the nasopharynx.
- Oropharynx: Between the soft palate, superior to the base of the tongue, and inferiorly to the level of the hyoid bone. It contains the palatine tonsils and the vallecula epiglottica, which is located between the glossoepiglottic folds.
- Laryngopharynx (hypo): Between the base of the tongue, inferiorly to the level of the hyoid bone. It contains the aryepiglottic folds (mucous membrane folds).

The voice box is located between the base of the tongue and the trachea.
It acts as a passageway for air from the pharynx to the trachea, provides protection, and generates sound.
The larynx contains nine cartilages:
- Single: Thyroid, Cricoid, Epiglottis
- Paired: Arytenoid, Corniculate, Cuneiform
These cartilages are held together by ligaments and intrinsic and extrinsic muscles.
The epiglottis is a spoon-shaped structure that covers the entrance of the larynx.
- It prevents food aspiration and is connected to the base of the tongue via the vallecula.
The cricoid cartilage is narrow in adults, creating a point of pressure.
The arytenoid, corniculate, and cuneiform cartilages help with the movement of the vocal cords.
The epiglottis prevents aspiration.

The thyrohyoid membrane forms the roof of the larynx.
- This is the narrowest part of the larynx.
The cricothyroid membrane forms the floor of the larynx.