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19.2: Upper Respiratory Tract

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    Upper Respiratory Tract

    When you breathe in air flows through the nostrils and enters the nasal cavity which is lined by goblet cells that release mucus. That mucus is salty sticky and has lysozyme, enzymes that help kill bacteria. Nose hairs at the entrance of the nasal cavity get coated with that mucus and are able to trap large particles of dust and pollen as well as bacteria forming tiny clumps in the nose. The nasal cavity is connected to four sinuses, which are air-filled spaces inside the bones that surround the nose called the paranasal sinuses. Maxillary sinus helps the inspired air to circulate for a bit so it has time to get warm and moist. They also act like tiny echo chambers that help amplify the sound of your voice, this is why you sound so different when you plug your nose.

    Paranasal sinuses including frontal sinuses ethmoid sinuses sphenoid sinuses maxillary s inuses

    Above: Paranasal sinuses.

    That relatively clean warm and moist air goes from the nasal cavity into the pharynx, composed of three regions (listed from superior to inferior): nasopharynx (posterior to the nasal cavity), oropharynx (posterior to the oral cavity), and laryngopharynx (at the pharynx-larynx transition). The soft palate which is the softer portion of the roof of your mouth behind the hard palate which is the part you can feel with your tongue and the pendulum-like uvula hanging at its end move together to form a flap or valve that closes the nasal pharynx off when you eat to prevent food from going up into the nasal pharynx. Finally there's the laryngopharynx the part of the pharynx that's continuous with the larynx or the voice box up to this point.

    Upper respiratory tract. Sphenoid sinus Internal nares Entrance to auditory tube Nasopharynx Uvula Oropharynx Laryngopharynx Trachea Nasal meatuses (superior, middle, and infetior) Epiglottis Glottis Vocal fold Frontal sinus asal ncha Superior Middle Inferior Nasal cavity Nasal vestibule External nares Hard palate Soft palate Oral cavity

    Above: Structures of the upper respiratory tract, lateral view.

    Food and air share a common path but at the top of the larynx, a spoon shaped flap of cartilage called the epiglottis acts like a lid that seals off the airway when you are eating so that food can only go one way down the esophagus and towards the stomach. If anything other than air gets into the larynx then you have a cough reflex that kicks it right back out.

    Cadaver images of upper respiratory anatomy. Superior concha Superior meatus Middle concha Middle Inferior concha Inferior Oral cavity Nasal cavity Epiglott's Opening of eustachian tube Nasopharynx Oropharynx Laryngo- pharynx cartilage Tongue Body" hyoid Vocal Laryngeal Thyroid cartilage True vocal cord

    Above: Cadaver images of upper respiratory structures (left) lateral view from the left side of the nasal and oral cavities and(right) lateral view from the right side of the larynx.

    Larynx anatomy. Thyrohyoid membrane, median thyrohyoid, ligament laryngeal incisure, laryngeal prominence, thyroid median cricothyroid, ligament conus elasticus, cricoid cartilage, trachea, hyoid bone, lateral thyrohyoid ligament, superior cornu of thyroid cartilage, superior laryngeal nerve and artery, oblique line, cricothyroid muscle, inferior cornu of thyroid cartilage, cricothyroid joint, tracheal cattilages

    Above: External structure of the larynx, anterolateral view of the left anterior of the larynx and superior trachea.

    Cadaver images of the larynx.

    Above: Images of larynx from a cadaver (left) anterior view, (middle) posterior view, and (right) superior view.

    Upper Respiratory Tract Structure

    Location

    Function

    epiglottis

    an elastic cartilage flap capable of moving to covering the boundary between the laryngopharynx and the larynx when swallowing

    when swallowing, the hyoid bone lifts causing the epiglottis to lower to protect the airways and prevent food and liquid from entering the larynx

    external nares

    the nostrils

    primary route for entering air; hair in the vestibule removes airborne particles

    vestibular folds (false vocal cords)

    a pair of folds in the mucous membranes of the glottis (within the larynx); each fold contains one of a pair of vestibular ligaments

    prevents food and liquid from entering the airways; prevents vocal hoarseness

    glottis

    part of the larynx that contains the vocal folds

    producing vocal sounds

    laryngopharynx

    inferior to the oropharynx and superior to the larynx and esophagus

    passageway for food, water, and air; lined with stratified squamous epithelium

    larynx

    structure surrounded in cartilage located anterior to the esophagus between the laryngopharynx and the trachea; has nine different types of cartilage: 1 thyroid cartilage (Adam's apple), 1 cricoid cartilage, 1 epiglottis, 2 arytenoid cartilages, 2 corniculate cartilages, 2 cuneiform cartilages

    voice box; conducts air to the lower respiratory tract

    nasal conchae (superior, middle, and inferior)

    medial-projecting bony protrusions in the nasal cavity; between the conchae are passageways called nasal meatuses

    cause the air to swirl in the nasal cavity and come in contact with mucous membranes that catch dust and debris in the incoming air; heat and humidify the air for respiration to allow diffusion of gases in the lungs

    nasal septum

    between the right and left nostril and nasal cavities; the body portion is composed of the perpendicular plate of the ethmoid bone and the vomer bone; bone and cartilage together form the septum

    divides the nasal cavity into right and left

    nasopharynx

    passageway posterior to the nasal cavity and superior to the oropharynx

    passageway for airflow from nasal cavity; has pseudostratified ciliated columnar epithelium, pharyngeal tonsils, and Eustachian tubes equalizing pressure with the middle ear

    oropharynx

    passageway posterior to the oral cavity, inferior to the nasopharynx, and superior to the laryngopharynx

    common passageway for food, water, and air; lined with stratified squamous epithelium; contains palatine and lingual tonsils

    paranasal sinuses (frontal, ethmoid, sphenoid, and maxillary sinuses)

    air-filled cavities within bones of the skull; connect to the nasal cavity

    make the head lighter; heat and humidify the air for respiration to allow diffusion of gases in the lungs

    vocal folds (true vocal cords)

    folds of tissue in the glottis of the larynx; each fold is attached to one of a pair of vocal ligaments

    responsible for sound production; only produces sound when air is exhaled over them; sound change when cords are stretched or relaxed

    Cadaver image of the glottis, vocal folds, and epiglottis.

    Above: Superior view of the glottis. The bottom of the photo is posterior and the top of the photo is anterior.

    This page titled 19.2: Upper Respiratory Tract is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna Hartline.

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