Upper respiratory tract
Conducting passages.

The upper respiratory tract refers to the following parts of the respiratory system:

• nose and paranasal sinuses
• oral cavity (also part of the digestive system)
• throat
  • pharynx
    • nasopharynx
    • oropharynx
    • laryngopharynx
  • larynx (The larynx can be considered part of the upper respiratory tract or the lower respiratory tract depending on the source. Some specify that the glottis (vocal cords) is the defining line between the upper and lower respiratory tracts; others make the line at the cricoid cartilage.)

Upper respiratory tract infections are amongst the most common infections in the world.

Contents 1 Role in Respiration 1.1 The Upper Airway during Sleep 2 See also 3 External links

[edit] Role in Respiration

Unlike the trachea and bronchi, the upper airway is a collapsible, compliant tube. As such, it has to be able to withstand suction pressures generated by the rhythmic contraction of the diaphragm that sucks air into the lungs. This is accomplished by the rhythmic contraction of upper airway muscles, such as the genioglossus (tongue) and the hyoid muscles. In addition to rhythmic innervation from the respiratory center in the medulla oblongata, the motoneurons controlling the muscles also receive tonic innervation that sets a baseline level of stiffness and size.

[edit] The Upper Airway during Sleep

During non-REM sleep, the tonic drive to most respiratory muscles of the upper airway is inhibited. This has two consequences:

1. The upper airway becomes more floppy.
2. The rhythmic innervation results in weaker muscle contractions because the intracellular calcium levels are lowered, as the removal of tonic innervation hyperpolarizes motoneurons, and consequently, muscle cells.

However, because the diaphragm is largely driven by the autonomous system, it is relatively spared of non-REM inhibition. As such, the suction pressures it generates stay the same. This narrows the upper airway during sleep, increasing resistance and making airflow through the upper airway turbulent and noisy. For example, one way to determine whether a person is sleeping it to listen to their breathing - once the person falls asleep, their breathing becomes noticeably louder. Not surprisingly, the increased tendency of the upper airway to collapse during breathing in sleep can lead to snoring, a vibration of the tissues in the upper airway. This problem is exacerbated in overweight people when sleeping on the back, as extra fat tissue may weigh down on the airway, closing it. This can lead to sleep apnea.

[edit] See also

• Lower respiratory tract

[edit] External links

• Image at rsdrx.com

v • d • e Head and neck, upper RT: Nose (TA A06.1, GA 10.992) External nose Ala of nose nasal cartilages (of the septum, Greater alar, Lesser alar, Lateral nasal, Accessory nasal, Vomeronasal) Nasal cavity Openings Nasal vestibule · Nostril · Posterior nasal apertures Lateral wall Nasal concha/meati: Superior nasal concha · Middle nasal concha · Inferior nasal concha · Superior nasal meatus · Middle nasal meatus · Inferior nasal meatus Sphenoethmoidal recess · Ethmoid bulla · Agger nasi · Ethmoidal infundibulum · Semilunar hiatus · Maxillary hiatus Medial wall Nasal septum · Vomeronasal organ Mucous membrane Olfactory mucosa Paranasal sinuses Maxillary sinus · Sphenoidal sinuses · Frontal sinus · Ethmoid sinus Naso-pharynx Pharyngeal opening of auditory tube (Salpingopharyngeal fold, Salpingopalatine fold, Torus tubarius) · Pharyngeal tonsil · Pharyngeal recess respiratory system navs: anat nose,larynx/lower+thoracic cavity/physio/dev, noncongen/congen/tumors, symptoms+signs/eponymous, proc

v • d • e Head and neck anatomy, Upper RT: Larynx (TA A06.2, GA 11.1072) Cartilages major/unpaired: Epiglottis (Vallecula) · Thyroid (Laryngeal prominence, Oblique line, Superior thyroid notch, Superior horn, Inferior horn) · Cricoid minor/paired: Arytenoid (Vocal process, Muscular process) · Corniculate · Cuneiform Ligaments/folds extrinsic ligaments: Hyoepiglottic ligament · Thyrohyoid membrane (Lateral ligament, Median ligament) · Thyroepiglottic ligament · Cricotracheal ligament intrinsic ligaments · upper: Quadrangular membrane (Aryepiglottic, Vestibular ligament/Vestibular fold) intrinsic ligaments · lower: Cricothyroid ligament (Median, Lateral/Conus elasticus, Vocal ligament/Vocal folds) Laryngeal cavity Laryngeal inlet · Vestibule · Rima vestibuli · Ventricle · Rima glottidis/Glottis · Infraglottic cavity Other Muscles of larynx · Cricothyroid articulation · Cricoarytenoid articulation respiratory system navs: anat nose,larynx/lower+thoracic cavity/physio/dev, noncongen/congen/tumors, symptoms+signs/eponymous, proc

v • d • e Anatomy: lower respiratory system (TA A06.3-5, GA 11.1084) Lower RT Trachea Tracheal rings · Annular ligaments of trachea · Carina Lungs Surface right/left · apex/base/root/hilum · cardiac impression/cardiac notch/lingula borders (anterior, posterior, inferior) surfaces (costal, mediastinal, diaphragmatic) fissures (oblique, horizontal) Airway Conducting zone bronchi · main bronchus (right, left) · lobar/secondary bronchi (eparterial bronchus) · segmental/tertiary bronchi (bronchopulmonary segment) · bronchiole · terminal bronchiole Respiratory zone respiratory bronchiole · alveolar duct · alveolus · alveolar-capillary barrier respiratory system navs: anat nose,larynx/lower+thoracic cavity/physio/dev, noncongen/congen/tumors, symptoms+signs/eponymous, proc

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