Upper Respiratory Tract: Anatomy, Structure, and Function

The upper respiratory tract is the first portion of the respiratory system encountered by inspired air. It includes the nose, nasal cavity, oral cavity, pharynx, and larynx, all of which help conduct air toward the lower respiratory tract.

These structures do much more than provide a passageway. They filter inhaled material, warm and humidify inspired gas, support speech and smell, and help protect the lungs from aspiration and foreign material.

Understanding upper-airway anatomy and function is important for recognizing obstruction, infection, airway compromise, and problems that may affect ventilation.

What Is the Upper Respiratory Tract?

The upper respiratory tract is the portion of the respiratory system extending from the nose and mouth through the pharynx and larynx. Its primary role is to provide a pathway for air as it moves toward the trachea and lungs.

Although it does not directly perform pulmonary gas exchange, the upper respiratory tract plays an essential role in preparing inspired air before it reaches the lower airways. Air entering the body may be cold, dry, and contaminated with particles or microorganisms. The upper airway helps modify these conditions by filtering, warming, and humidifying the gas.

The upper respiratory tract also contains structures involved in swallowing, speech, smell, taste, and immune defense. Because the airway and digestive tract share portions of the pharynx, protective mechanisms are required to prevent food, fluids, and secretions from entering the lower respiratory tract.

The major structures of the upper respiratory tract include:

• Nose
• Nasal cavity
• Paranasal sinuses
• Oral cavity
• Pharynx
• Larynx

Note: These regions form a complex and highly specialized pathway for airflow and airway protection.

Functions of the Upper Respiratory Tract

The upper respiratory tract performs several important functions before inspired gas reaches the trachea and lower airways.

These functions include:

• Conducting air
• Filtering inhaled particles
• Warming inspired gas
• Humidifying inspired gas
• Supporting smell and taste
• Participating in speech
• Providing immune defense
• Protecting the lower respiratory tract from aspiration
• Initiating protective reflexes such as sneezing and coughing

Note: The effectiveness of these functions depends heavily on the anatomy of the nasal passages, mucosal surfaces, airway reflexes, and muscular activity of the pharynx and larynx.

Nose and Nasal Cavity

The nose is the primary entrance for air during normal quiet breathing. Air enters through the external nares, or nostrils, and passes into the nasal vestibules before traveling deeper into the nasal cavity.

The external nose contains both bone and cartilage. Inside, the nasal septum separates the nasal cavity into right and left chambers.

The anterior nasal vestibules contain coarse hairs known as vibrissae. These hairs provide an initial filtration mechanism by trapping larger airborne particles before they move deeper into the respiratory tract.

As air continues through the nasal cavity, it encounters a highly vascular, moist mucosal surface that helps warm and humidify the inspired gas.

Nasal Turbinates

Three shelf-like structures project from the lateral walls of each nasal cavity. These structures are known as the:

• Superior turbinate
• Middle turbinate
• Inferior turbinate

They are also called nasal conchae. The turbinates increase the internal surface area of the nasal cavity and create a more complex route for airflow. Rather than allowing inspired air to move directly through the nose in a straight path, the turbinates cause it to contact the mucosal surfaces more extensively.

This increased contact improves the ability of the nose to filter, warm, and humidify inspired gas.

The nasal mucosa has an extensive blood supply. Heat from the circulating blood is transferred to incoming air, helping warm it before it reaches the lower respiratory tract. The mucus covering the nasal surfaces also adds moisture to inspired gas.

Filtration in the Nasal Cavity

The nose serves as an important filtering system. Larger particles may be trapped by the vibrissae in the vestibules. Smaller particles can become trapped in mucus deeper within the nasal cavity.

The shape of the nasal passages also promotes deposition of inhaled particles. When moving air changes direction around the turbinates, particles with enough momentum may be unable to follow the airflow and instead strike the mucosal surfaces.

This process helps prevent some inhaled particles from reaching the lower respiratory tract. Particles that become trapped in mucus can later be transported toward the pharynx by ciliary action.

Warming Inspired Air

Inspired air is often cooler than body temperature, particularly in cold environments. The nasal cavity contains a rich network of blood vessels immediately beneath the mucosal surface. As inspired gas passes over these tissues, heat transfers from the blood to the incoming air.

This process helps bring inspired gas closer to body temperature before it reaches the lungs.

Warming is important because exposure of the lower respiratory tract to cold, dry gas can interfere with normal airway function and contribute to mucosal drying.

Humidification of Inspired Gas

The respiratory tract requires adequate moisture for normal function. The mucosal lining of the nose provides water vapor that humidifies inspired gas. As air passes through the nasal cavity, moisture evaporates from the mucosal surface and enters the inspired gas.

By the time air reaches the lower respiratory tract, it has normally been warmed and humidified substantially.

The nose is more effective at this process than the mouth because the nasal passages provide more surface area and greater contact with moist mucosa.

During expiration, some heat and moisture can also be recovered. Warm, humid exhaled gas cools as it passes through the nasal passages, allowing some water to condense on the nasal mucosa. This helps conserve both heat and water.

Nasal Epithelium

Different portions of the nasal cavity contain different types of epithelial tissue. The anterior region is more exposed to physical stress and contains stratified squamous epithelium.

Deeper portions contain pseudostratified ciliated columnar epithelium with mucus-producing cells.

The cilia move mucus toward the nasopharynx. Material trapped in the mucus can then be swallowed or expelled. This system contributes to the mucociliary defense mechanism that helps protect the respiratory system from inhaled contaminants.

Sneezing

The sneeze reflex is an important protective mechanism of the upper respiratory tract. Particles, chemicals, or other irritants can stimulate sensory nerve endings in the nasal mucosa. This triggers a reflex response that produces a sudden, forceful expulsion of air.

Sneezing helps remove irritants and accumulated material from the nasal passages.

Although the reflex is simple in appearance, it involves coordinated activity of respiratory muscles and upper-airway structures.

Sense of Smell

The nasal cavity also contains receptors responsible for olfaction, or smell. These receptors are concentrated in the upper portions of the nasal cavity near the superior nasal structures.

Airborne molecules dissolve in the mucus covering these receptors and stimulate sensory cells. The sense of smell contributes not only to the perception of odors but also to the perception of flavor during eating.

Paranasal Sinuses

The paranasal sinuses are air-filled cavities located within bones of the skull.

They include the:

• Frontal sinuses
• Maxillary sinuses
• Ethmoid sinuses
• Sphenoid sinuses

These cavities communicate with the nasal passages and are lined with respiratory mucosa. The sinuses produce mucus that drains into the nasal cavity. They also contribute to the resonance of the voice and reduce the overall weight of the skull.

Inflammation or obstruction of sinus drainage can result in accumulation of mucus and pressure within the sinus cavities.

Oral Cavity

The oral cavity provides an alternative route for breathing. During quiet breathing, the nose is usually the preferred pathway. However, mouth breathing becomes more important during exercise, respiratory distress, or nasal obstruction.

The oral cavity generally offers less resistance to airflow than the nasal passages. This can be helpful when ventilatory demand increases. However, the mouth is less effective at filtering, warming, and humidifying inspired gas. As a result, prolonged mouth breathing may contribute to drying of airway surfaces.

Tongue and Airway Patency

The tongue occupies a large portion of the oral cavity and is clinically important in airway management. When a person is awake, muscle tone helps maintain the position of the tongue and other upper-airway structures.

During unconsciousness, sedation, or anesthesia, muscle tone may decrease. The tongue can then fall backward toward the pharynx and contribute to airway obstruction.

This is one reason airway-positioning maneuvers are important in unconscious patients. In some individuals, a relatively large tongue can also contribute to difficult airway management and obstructive sleep apnea.

Hard and Soft Palate

The roof of the mouth is formed by the hard and soft palates.

The hard palate is supported by bone and forms the anterior portion of the roof of the oral cavity. The soft palate is located posteriorly and is made primarily of flexible tissue.

During swallowing, the soft palate moves upward and backward to help close the opening between the nasopharynx and oropharynx. This helps prevent swallowed material from entering the nasal passages.

Tonsils and Immune Defense

Several collections of lymphatic tissue are located within the upper respiratory tract.

These include the:

• Pharyngeal tonsils
• Palatine tonsils
• Lingual tonsils

The pharyngeal tonsils, also called adenoids, are located in the nasopharynx. The palatine tonsils are located in the oropharynx. The lingual tonsils are located near the base of the tongue.

These structures help recognize and respond to microorganisms entering through the nose or mouth. Because they are positioned along major entry routes into the body, they provide an early component of immune defense.

Pharynx

The pharynx is a muscular passageway extending from the nasal cavity toward the larynx and esophagus. It serves both respiratory and digestive functions.

The pharynx is divided into three major regions:

• Nasopharynx
• Oropharynx
• Laryngopharynx

Note: Each region has distinct anatomical features and functions.

Nasopharynx

The nasopharynx is located behind the nasal cavity and above the soft palate. Inspired gas normally passes from the nasal cavity into the nasopharynx before continuing downward.

The nasopharynx contains the pharyngeal tonsils and the openings of the pharyngotympanic tubes. These tubes connect the nasopharynx with the middle ears and help equalize pressure across the tympanic membranes.

The nasopharynx is lined primarily with ciliated respiratory epithelium, which contributes to mucus transport.

Oropharynx

The oropharynx lies behind the oral cavity. It begins near the soft palate and extends downward toward the base of the tongue.

Because both air and swallowed material pass through this region, the oropharynx participates in both respiration and digestion. The palatine and lingual tonsils are located in this area.

The oropharynx is lined with stratified squamous epithelium, which provides greater resistance to abrasion than ciliated respiratory epithelium.

Vallecula

The vallecula is a depression located between the base of the tongue and the epiglottis. It is an important anatomical landmark during airway management.

During direct laryngoscopy, the tip of certain laryngoscope blades may be positioned in the vallecula to indirectly elevate the epiglottis and improve visualization of the glottic opening.

Because of this role, understanding the location of the vallecula is particularly important for clinicians who perform endotracheal intubation.

Laryngopharynx

The laryngopharynx, also called the hypopharynx, is the lowest portion of the pharynx. It extends from the region around the base of the tongue toward the openings of the larynx and esophagus. At this point, the respiratory and digestive pathways separate.

Air moves anteriorly toward the larynx, while swallowed material moves posteriorly toward the esophagus. Coordination of muscles and protective reflexes is required to prevent food or fluid from entering the respiratory tract.

Swallowing and Aspiration Prevention

Swallowing requires coordinated activity involving the tongue, pharynx, soft palate, epiglottis, larynx, and esophagus.

During normal swallowing, upper-airway structures help protect the respiratory tract. The larynx moves, the vocal cords close, and the epiglottis helps direct material away from the airway.

Protective reflexes, including the gag and cough reflexes, provide additional defense. When these mechanisms are impaired, aspiration can occur.

Risk factors for aspiration include:

• Reduced consciousness
• Sedation
• Anesthesia
• Neurological impairment
• Swallowing dysfunction
• Weak cough
• Impaired airway reflexes

Note: Aspiration may result in airway obstruction, chemical lung injury, or infection.

Larynx

The larynx is located between the pharynx and the trachea. It is commonly referred to as the voice box, but its functions extend beyond speech.

The larynx serves three major roles:

• Conducting air
• Protecting the lower respiratory tract
• Producing sound

Note: It is composed of cartilages, muscles, ligaments, and membranes that work together to regulate airflow and protect the airway.

Laryngeal Cartilages

The larynx contains nine major cartilages.

Three are unpaired:

• Thyroid cartilage
• Cricoid cartilage
• Epiglottis

Three occur as pairs:

• Arytenoid cartilages
• Corniculate cartilages
• Cuneiform cartilages

Note: These structures provide support and allow controlled movement of the vocal folds.

Thyroid Cartilage

The thyroid cartilage is the largest cartilage of the larynx. It forms much of the anterior and lateral walls of the laryngeal framework. Its anterior projection is commonly known as the Adam’s apple.

The thyroid cartilage helps protect the vocal cords and other internal structures of the larynx.

Cricoid Cartilage

The cricoid cartilage lies below the thyroid cartilage. It is unique because it forms a complete ring around the airway. This feature distinguishes it from the C-shaped cartilage rings of the trachea.

The cricoid region is clinically important because swelling in this area can significantly narrow the airway, particularly in children.

Epiglottis

The epiglottis is a broad, flexible structure located near the entrance to the larynx. During swallowing, it helps protect the airway by contributing to closure of the laryngeal opening.

Although it does not function alone, it is an important component of the coordinated swallowing mechanism. Severe inflammation of the epiglottis can produce upper-airway obstruction.

Vocal Folds and Glottis

The larynx contains two pairs of folds. The upper pair are the false vocal folds. The lower pair are the true vocal folds, commonly called the vocal cords. The opening between the true vocal cords is called the glottis.

During quiet inspiration, the vocal cords move apart to widen the glottic opening. During speech, they move closer together and vibrate as air passes between them. The vocal folds can also close tightly to protect the airway.

Phonation

Speech requires controlled airflow through the larynx. Air moving from the lungs passes through the vocal cords and causes them to vibrate.

Changes in vocal cord tension and position alter the pitch and character of the sound. The pharynx, mouth, tongue, lips, and nasal cavity then modify the sound into recognizable speech. The upper respiratory tract therefore contributes substantially to phonation.

Coughing and Airway Protection

The larynx plays an important role in producing an effective cough. Before a forceful cough, the vocal cords close while expiratory muscles generate increased pressure within the thorax.

The glottis then opens suddenly, producing a high-velocity flow of air. This rapid airflow helps remove mucus, foreign material, and other substances from the respiratory tract.

Note: If laryngeal function is impaired, cough effectiveness may decrease.

Upper-Airway Obstruction

Upper-airway obstruction can occur anywhere from the nose to the upper trachea. Because airflow must pass through these structures before reaching the lungs, severe obstruction can rapidly interfere with ventilation.

Possible causes include:

• Tongue obstruction
• Foreign bodies
• Airway edema
• Croup
• Epiglottitis
• Tumors
• Trauma
• Allergic reactions
• Secretions
• Enlarged tonsils
• Structural abnormalities

Note: The clinical presentation depends on the location and severity of the obstruction.

Stridor

Stridor is one of the most important signs of upper-airway narrowing. It is a high-pitched or coarse respiratory sound produced when gas moves rapidly through a narrowed airway.

Inspiratory stridor commonly suggests obstruction within an extrathoracic airway, such as the larynx or upper trachea.

As obstruction becomes more severe, stridor may become louder or occur during both inspiration and expiration. However, a sudden decrease in stridor in a deteriorating patient is not always reassuring. Extremely limited airflow may produce less audible sound even as obstruction becomes more severe.

Stertor

Stertor is a low-pitched, snoring-like sound produced by obstruction in the upper airway. It is typically associated with narrowing or vibration of tissues in the nasopharynx, oropharynx, or hypopharynx.

Stertor differs from stridor in both sound quality and typical location. Recognizing this distinction can help identify the approximate level of airway obstruction.

Croup

Croup is an upper-airway disorder most commonly seen in children. It causes inflammation and narrowing in the laryngeal and subglottic regions.

Typical findings may include:

• Barking cough
• Hoarseness
• Inspiratory stridor
• Respiratory distress

Note: On an anteroposterior neck radiograph, narrowing below the larynx may produce the characteristic steeple sign. Because pediatric airways are small, relatively minor swelling can cause substantial airflow obstruction.

Epiglottitis

Epiglottitis is inflammation and swelling of the epiglottis and surrounding structures. It can produce rapid and severe upper-airway compromise.

A lateral neck radiograph may reveal an enlarged epiglottis resembling a thumb, known as the thumb sign.

Because manipulation of a severely inflamed upper airway can worsen obstruction, airway assessment and management require caution.

Foreign-Body Obstruction

Foreign objects can obstruct the upper respiratory tract, particularly in children. The severity depends on the size, location, and completeness of the obstruction.

A partial obstruction may allow some airflow and produce coughing, stridor, or abnormal respiratory sounds. A complete obstruction can prevent effective airflow entirely and quickly lead to hypoxemia.

Foreign-body aspiration should be considered when respiratory symptoms begin suddenly, particularly during eating or play.

Upper-Airway Assessment

Assessment of the upper respiratory tract begins with inspection.

The nose can be examined for:

• Deformity
• Swelling
• Bleeding
• Septal deviation
• Nasal polyps
• Edema
• Lesions
• Obstruction

Nasal patency can be assessed by occluding one nostril at a time and observing airflow through the other. The mouth and pharynx should also be inspected when appropriate.

Important findings include dental appliances, tongue size, secretions, swelling, visible obstruction, and structural abnormalities.

Neck Assessment

The neck provides important information about airway accessibility.

Clinicians may evaluate:

• Neck length
• Neck circumference
• Range of motion
• Swelling
• Masses
• Tracheal position

Note: A short, thick neck may make airway management more difficult. Limited neck flexion or extension can complicate bag-mask ventilation and endotracheal intubation. Neck circumference may also be relevant when assessing risk for obstructive sleep apnea.

Mallampati Classification

The Mallampati classification is used to estimate the visibility of structures within the mouth and pharynx. The patient opens the mouth and protrudes the tongue while the examiner observes structures such as the soft palate, uvula, and tonsillar pillars.

Greater visibility generally suggests easier access to the airway. When only limited structures are visible, endotracheal intubation may be more difficult.

Note: The Mallampati classification should not be used alone, but it can contribute to an overall airway assessment.

Upper Airway and Sleep

Upper-airway anatomy is important during sleep. Muscle tone normally decreases during sleep. In susceptible individuals, this can allow pharyngeal tissues to narrow or collapse.

Repeated upper-airway collapse can lead to obstructive sleep apnea.

Factors that can contribute include:

• Enlarged tonsils
• Large tongue
• Increased neck circumference
• Narrow pharyngeal anatomy
• Reduced upper-airway muscle tone

Note: Obstructive events can repeatedly interrupt airflow despite continued respiratory effort.

Pediatric Upper Respiratory Tract

The pediatric upper airway differs significantly from the adult airway. These differences are especially important in neonates and infants because small changes in airway diameter can produce major changes in airflow resistance.

Important pediatric characteristics include:

• Proportionally larger tongue
• Higher laryngeal position
• Long, floppy epiglottis
• Small airway diameter
• Narrow subglottic region
• Softer airway cartilage
• Greater dependence on nasal breathing

Note: These characteristics make children more vulnerable to airway obstruction.

Infant Nasal Breathing

Young infants depend heavily on nasal breathing, particularly during the first several months of life. This is partly related to their airway anatomy and immature coordination between breathing and oral motor activity.

The tongue is relatively large, and the oral cavity is small. As a result, nasal obstruction can significantly impair ventilation in a young infant.

Secretions, swelling, or congenital obstruction of the nasal passages can therefore produce marked respiratory distress.

Pediatric Larynx

The infant larynx is positioned higher in the neck than the adult larynx. The epiglottis is relatively long, floppy, and angled differently from that of an adult. These features can make visualization of the larynx more challenging during intubation.

The pediatric airway also contains a relatively narrow cricoid or subglottic region. Because this area cannot expand substantially, even minor mucosal swelling can significantly reduce its diameter.

Why Small Airways Matter in Children

Airway resistance increases dramatically as airway radius decreases. Because pediatric airways are already narrow, a small amount of swelling or mucus can cause a proportionally large reduction in internal diameter.

This explains why upper-airway infections that are relatively mild in adults can become much more serious in children. Respiratory distress may progress quickly, especially because children have relatively high oxygen demands and smaller oxygen reserves.

Signs of Pediatric Upper-Airway Distress

Clinical signs may include:

• Tachypnea
• Nasal flaring
• Retractions
• Stridor
• Stertor
• Cyanosis
• Agitation
• Decreased air movement
• Altered mental status

Note: As respiratory distress worsens, a child may initially become anxious or restless. Progressive hypoxemia and hypercarbia can lead to lethargy and eventually loss of consciousness. A reduction in respiratory effort after prolonged severe distress may indicate fatigue rather than recovery.

Upper Airway and Artificial Airways

Endotracheal intubation bypasses much of the normal upper respiratory tract.

Once an endotracheal tube is inserted, inspired gas no longer receives the same degree of filtration, warming, and humidification from the nose and upper airway. For this reason, artificial humidification becomes important during invasive mechanical ventilation.

An artificial airway also bypasses some normal protective mechanisms and can interfere with swallowing, cough, mucociliary clearance, and secretion management.

Loss of Upper-Airway Conditioning

The upper respiratory tract normally conditions inspired gas before it reaches the lower airways. When the upper airway is bypassed by an endotracheal or tracheostomy tube, cold and dry gas can reach the trachea directly unless humidification is provided.

Insufficient humidification can contribute to:

• Dry airway mucosa
• Thick secretions
• Impaired ciliary function
• Mucus plugging
• Increased airway resistance
• Artificial-airway obstruction

Note: This demonstrates the importance of the upper airway’s normal heat and moisture exchange functions.

Upper Respiratory Tract and Aerosol Deposition

The upper respiratory tract also affects inhaled medication delivery. Large aerosol particles are more likely to deposit in the nose, mouth, and pharynx rather than reaching the lower lungs.

Particles larger than approximately 10 to 15 µm are commonly filtered in the upper respiratory tract. Particles approximately 5 to 10 µm may deposit in the upper airway and larger central airways.

Smaller particles are generally more likely to penetrate farther into the lungs. Airway anatomy, breathing pattern, inspiratory flow, age, and disease can all affect deposition.

Importance of the Upper Respiratory Tract

The upper respiratory tract is much more than an entrance to the lungs. It provides a protected and conditioned route for inspired gas, supports speech and smell, participates in swallowing, and acts as an important defensive barrier.

Disruption at any level can impair respiratory function.

Nasal obstruction can interfere with airflow and humidification. Pharyngeal collapse can obstruct ventilation. Laryngeal swelling can produce stridor and potentially severe airway compromise. Impaired swallowing can lead to aspiration. For this reason, upper-airway assessment is an important part of respiratory evaluation.

Upper Respiratory Tract Practice Questions

1. What structures are included in the upper respiratory tract?
The upper respiratory tract includes the nose, nasal cavity, oral cavity, pharynx, and larynx.

2. What are the primary functions of the upper respiratory tract?
The upper respiratory tract conducts airflow, filters inhaled material, warms and humidifies inspired gas, contributes to smell and speech, supports immune defense, and helps protect the lower respiratory tract from aspiration.

3. What is the primary route for airflow during normal quiet breathing?
During normal quiet breathing, most inspired air enters through the nose and nasal passages.

4. Why does mouth breathing become more important during exercise?
Mouth breathing becomes more important during exercise because it provides a lower-resistance pathway for the increased airflow required during higher levels of ventilation.

5. What are the external nares?
The external nares are the nostrils through which air normally enters the nasal cavity.

6. What is the function of the vibrissae in the nasal vestibule?
The vibrissae are coarse nasal hairs that trap larger inhaled particles and provide an initial form of respiratory filtration.

7. What structure divides the nasal cavity into right and left chambers?
The nasal septum divides the nasal cavity into right and left chambers.

8. What are the three nasal turbinates?
The three nasal turbinates are the superior, middle, and inferior turbinates, which are also called nasal conchae.

9. How do the nasal turbinates improve the conditioning of inspired air?
The turbinates increase nasal surface area and create a more complex airflow pathway, increasing contact between inspired gas and the warm, moist nasal mucosa.

10. How does the nasal cavity warm inspired gas?
A rich vascular network beneath the nasal mucosa transfers heat from circulating blood to inspired gas as it passes through the nasal passages.

11. How does the nasal cavity humidify inspired gas?
Moisture from the nasal mucosa evaporates into inspired air, increasing its water-vapor content before it reaches the lower respiratory tract.

12. Why is nasal breathing more effective than mouth breathing at conserving heat and moisture?
The nasal passages provide greater contact with warm, moist mucosal surfaces and can recover some heat and water from expired gas as it passes through the nose.

13. What type of epithelium is found in deeper portions of the nasal cavity?
Deeper portions of the nasal cavity contain pseudostratified ciliated columnar epithelium with mucus-producing cells.

14. What is the purpose of mucus within the nasal cavity?
Nasal mucus traps inhaled particles and microorganisms, moisturizes inspired gas, and supports the clearance of contaminants from the upper airway.

15. What is the function of cilia within the nasal passages?
Cilia move mucus and trapped material toward the nasopharynx, where it can be swallowed or otherwise removed.

16. What can trigger the sneeze reflex?
Dust, pollen, chemicals, and other irritants can stimulate sensory nerve endings in the nasal mucosa and trigger sneezing.

17. What is the purpose of the sneeze reflex?
The sneeze reflex produces a forceful expulsion of air that helps remove irritants and foreign material from the nasal passages.

18. What are the four groups of paranasal sinuses?
The four groups are the frontal, maxillary, ethmoid, and sphenoid sinuses.

19. What functions do the paranasal sinuses perform?
The paranasal sinuses produce mucus, communicate with the nasal cavity, contribute to vocal resonance, and help reduce the weight of the skull.

20. Why is the oral cavity considered an accessory respiratory passageway?
The oral cavity provides an alternative route for airflow when nasal breathing is inadequate or when ventilation increases, such as during exercise or respiratory distress.

21. Why is the oral cavity less effective than the nasal cavity at conditioning inspired air?
The mouth provides less filtration, warming, humidification, and heat-and-moisture recovery than the nasal passages.

22. Why can the tongue contribute to upper-airway obstruction in an unconscious patient?
Loss of muscle tone can allow the tongue to fall backward into the pharynx and partially or completely obstruct airflow.

23. What are the two major portions of the palate?
The palate consists of the hard palate anteriorly and the soft palate posteriorly.

24. What happens to the soft palate during swallowing?
The soft palate moves upward and backward to help close the connection between the nasopharynx and oropharynx, limiting entry of swallowed material into the nasal passages.

25. What are the three major divisions of the pharynx?
The pharynx is divided into the nasopharynx, oropharynx, and laryngopharynx, which is also called the hypopharynx.

26. Where is the nasopharynx located?
The nasopharynx is located behind the nasal cavity and above the soft palate.

27. What lymphatic tissue is located in the nasopharynx?
The pharyngeal tonsils, also called adenoids, are located in the nasopharynx.

28. What is the function of the pharyngotympanic tubes?
The pharyngotympanic tubes connect the middle ears to the nasopharynx and help equalize pressure across the tympanic membranes.

29. Where is the oropharynx located?
The oropharynx lies behind the oral cavity and extends from the soft palate toward the base of the tongue.

30. Which tonsils are located in the oropharynx?
The palatine tonsils and lingual tonsils are located in the oropharynx.

31. What is the vallecula?
The vallecula is a depression located between the base of the tongue and the epiglottis.

32. Why is the vallecula clinically important?
The vallecula serves as an important anatomical landmark during direct laryngoscopy and endotracheal intubation.

33. Where is the laryngopharynx located?
The laryngopharynx, or hypopharynx, extends from the base of the tongue toward the entrances of the larynx and esophagus.

34. What happens to the respiratory and digestive pathways in the laryngopharynx?
They separate, with air moving toward the larynx and swallowed material moving toward the esophagus.

35. What mechanisms help protect the airway during swallowing?
The soft palate, epiglottis, vocal cords, laryngeal movement, gag reflex, and cough reflex work together to reduce the risk of aspiration.

36. What is aspiration?
Aspiration is the entry of food, liquid, saliva, or other material into the respiratory tract.

37. What conditions can increase the risk of aspiration?
Reduced consciousness, sedation, anesthesia, neurological impairment, swallowing dysfunction, weak cough, and impaired airway reflexes can increase aspiration risk.

38. What are the three major functions of the larynx?
The larynx provides a passageway for air, protects the lower respiratory tract from aspiration, and produces sound for speech.

39. What are the three unpaired cartilages of the larynx?
The unpaired laryngeal cartilages are the thyroid cartilage, cricoid cartilage, and epiglottis.

40. What are the three paired cartilages of the larynx?
The paired laryngeal cartilages are the arytenoid, corniculate, and cuneiform cartilages.

41. What is the largest cartilage of the larynx?
The thyroid cartilage is the largest laryngeal cartilage.

42. What is unique about the cricoid cartilage?
The cricoid cartilage forms a complete ring around the airway.

43. What is the function of the epiglottis?
The epiglottis helps protect the respiratory tract by contributing to closure of the laryngeal opening during swallowing.

44. What are the false vocal folds?
The false vocal folds are the upper pair of folds within the larynx that lie above the true vocal cords.

45. What are the true vocal folds?
The true vocal folds, or vocal cords, are the lower pair of folds in the larynx that vibrate during phonation.

46. What is the glottis?
The glottis is the opening between the true vocal cords.

47. What happens to the vocal cords during quiet inspiration?
The vocal cords move apart, widening the glottis and allowing air to pass more freely.

48. How does the larynx contribute to an effective cough?
The vocal cords close while pressure builds in the chest, then open suddenly to create high-velocity expiratory airflow that helps clear material from the airway.

49. What is stridor?
Stridor is a high-pitched or coarse respiratory sound caused by airflow through a narrowed upper or central airway.

50. What does inspiratory stridor usually suggest?
Inspiratory stridor usually suggests an extrathoracic upper-airway obstruction involving structures such as the larynx or upper trachea.

51. What is stertor?
Stertor is a low-pitched, snoring-like sound caused by obstruction in the nasopharynx, oropharynx, or hypopharynx.

52. How does stertor differ from stridor?
Stertor is typically low-pitched and associated with pharyngeal obstruction, while stridor is usually higher-pitched and associated with narrowing of the larynx or upper trachea.

53. What are common causes of upper-airway obstruction?
Common causes include the tongue, foreign bodies, edema, croup, epiglottitis, tumors, trauma, allergic reactions, secretions, enlarged tonsils, and structural abnormalities.

54. What type of cough is commonly associated with croup?
A barking cough is commonly associated with croup.

55. What radiographic finding is associated with croup?
Croup may produce the steeple sign, which reflects narrowing of the subglottic airway.

56. What radiographic finding is associated with epiglottitis?
Epiglottitis may produce the thumb sign, which represents a swollen epiglottis on a lateral neck radiograph.

57. Why can severe epiglottic swelling be dangerous?
Swelling of the epiglottis and surrounding tissues can rapidly narrow the upper airway and interfere with ventilation.

58. Why should foreign-body obstruction be suspected when respiratory symptoms begin suddenly?
A sudden onset of coughing, stridor, or respiratory distress during eating or play may indicate that an object has entered and obstructed the airway.

59. What findings may occur with a partial upper-airway obstruction?
A partial obstruction may cause coughing, stridor, noisy breathing, and reduced airflow while still permitting some movement of gas.

60. What happens during complete upper-airway obstruction?
A complete obstruction prevents effective airflow and can quickly cause severe hypoxemia.

61. How can nasal patency be assessed?
Nasal patency can be assessed by occluding one nostril at a time and observing airflow through the opposite side.

62. What nasal abnormalities should be assessed during an upper-airway examination?
The nose should be assessed for deformity, swelling, bleeding, septal deviation, polyps, edema, lesions, and obstruction.

63. Why are dentures and dental appliances important during airway assessment?
They can interfere with airway procedures and may become dislodged, creating an aspiration or obstruction risk.

64. Why is tongue size important when evaluating the upper airway?
A large tongue can contribute to airway obstruction and can make visualization of the pharynx and larynx more difficult during intubation.

65. What is the Mallampati classification used for?
The Mallampati classification helps estimate airway difficulty by evaluating how much of the soft palate, uvula, and other pharyngeal structures are visible.

66. What Mallampati finding suggests a potentially more difficult airway?
Limited visualization of the soft palate and pharyngeal structures suggests that endotracheal intubation may be more difficult.

67. Why is neck range of motion important during airway assessment?
Limited neck flexion or extension can make positioning for bag-mask ventilation and endotracheal intubation more difficult.

68. Why can a short, thick neck complicate airway management?
A short, thick neck can make airway positioning, visualization of the larynx, endotracheal intubation, and tracheostomy placement more difficult.

69. How is neck circumference related to obstructive sleep apnea?
A larger neck circumference can be associated with increased upper-airway narrowing and a greater risk of obstructive sleep apnea.

70. What happens to the upper airway during obstructive sleep apnea?
Pharyngeal tissues repeatedly narrow or collapse during sleep, obstructing airflow despite continued respiratory effort.

71. Why does reduced muscle tone during sleep contribute to upper-airway obstruction?
Reduced muscle tone allows pharyngeal soft tissues to become more collapsible and more likely to narrow the airway.

72. Why are infants particularly vulnerable to upper-airway obstruction?
Infants have smaller airways, a proportionally larger tongue, a higher larynx, softer airway cartilage, and a greater dependence on nasal breathing.

73. How does the infant epiglottis differ from the adult epiglottis?
The infant epiglottis is relatively long, floppy, and positioned at a different angle, which can make airway visualization more difficult.

74. Why can minor swelling cause severe upper-airway obstruction in children?
Because pediatric airways are already narrow, a small amount of edema can cause a large proportional reduction in airway diameter and a major increase in resistance.

75. Why is maintaining nasal patency especially important in young infants?
Young infants depend heavily on nasal breathing, so nasal obstruction can significantly interfere with ventilation.

76. At approximately what cervical vertebral level is the infant larynx located?
The infant larynx is positioned relatively high in the neck, approximately at the C3 to C4 level.

77. At approximately what cervical vertebral level is the adult larynx located?
The adult larynx is generally located lower in the neck, approximately at the C4 to C5 level.

78. Why can the base of the tongue make direct laryngoscopy more difficult in infants?
Because the infant larynx is positioned higher and the tongue is proportionally larger, the base of the tongue can obscure visualization of the laryngeal opening.

79. What is laryngomalacia?
Laryngomalacia is excessive collapsibility of the laryngeal structures due to relatively soft and poorly supported airway tissues.

80. What is tracheomalacia?
Tracheomalacia is excessive collapsibility of the trachea caused by unusually soft or weak cartilaginous support.

81. Why is pediatric airway cartilage more prone to collapse?
Airway cartilage in infants is softer and more compressible than in adults, making the airway more susceptible to dynamic narrowing.

82. What is the clinical significance of the pediatric cricoid region?
The cricoid region is narrow and nonexpandable, so even minor edema can markedly reduce airway diameter.

83. Why might an endotracheal tube pass through the vocal cords but not advance easily in a child?
The tube may encounter resistance at the narrower subglottic or cricoid region.

84. What early signs may indicate pediatric upper-airway distress?
Early signs can include tachypnea, nasal flaring, agitation, and mild retractions.

85. What do deep retractions generally indicate in a child?
Deep retractions generally indicate increased work of breathing and more severe respiratory distress.

86. Why can decreasing retractions be a concerning sign in a severely ill child?
A fatigued child may lose the strength to maintain vigorous respiratory effort, so decreasing retractions can reflect worsening exhaustion rather than improvement.

87. How can mental status change as hypoxemia worsens in a child?
A child may progress from fearfulness or agitation to lethargy and eventually unconsciousness as hypoxemia and hypercarbia worsen.

88. Why can children desaturate rapidly during severe upper-airway obstruction?
Children have smaller oxygen reserves, higher metabolic demands, and relatively small functional residual capacity.

89. What is the significance of listening over both the trachea and chest during airway assessment?
Comparing upper- and lower-airway sounds can help identify the location and severity of an obstruction.

90. What does a loud upper-airway sound with relatively clear lung fields suggest?
It suggests that the primary abnormality may be located in the upper or central airway rather than in the peripheral lungs.

91. Why can severe upper-airway obstruction become quieter as it worsens?
If airflow becomes extremely limited, there may not be enough moving gas to generate a loud stridor or other airway sound.

92. How does endotracheal intubation affect normal upper-airway filtration?
The tube bypasses the nose and much of the upper airway, so normal filtration of inspired gas is greatly reduced.

93. How does endotracheal intubation affect normal upper-airway humidification?
It bypasses the natural heat- and moisture-exchange surfaces of the upper airway, making artificial humidification necessary.

94. What problems can result from inadequate humidification after the upper airway is bypassed?
Inadequate humidification can cause dry mucosa, thick secretions, impaired ciliary function, mucus plugging, increased resistance, and artificial-airway obstruction.

95. Why is inspired gas conditioning important after tracheostomy?
A tracheostomy bypasses the nose and pharynx, so inspired gas no longer receives normal warming and humidification before entering the lower airway.

96. Why do large aerosol particles tend to deposit in the upper respiratory tract?
Their greater size and momentum make them more likely to impact on airway surfaces when airflow changes direction through the nose, mouth, and pharynx.

97. Where do aerosol particles larger than approximately 10 to 15 µm usually deposit?
They usually deposit in the nose, mouth, and other upper-airway structures.

98. What factors besides particle size affect aerosol deposition in the upper airway?
Inspiratory flow, breathing pattern, age, airway anatomy, nasal versus oral breathing, and disease can all affect deposition.

99. Why can nasal breathing reduce delivery of inhaled medication to the lower lungs?
The nasal passages act as an efficient filter and can remove a significant portion of larger aerosol particles before they reach the lower respiratory tract.

100. Why is the upper respiratory tract clinically important in respiratory care?
It regulates airflow, conditions inspired gas, protects against aspiration and contamination, contributes to speech and smell, and can become a critical site of airway obstruction.

Final Thoughts

The upper respiratory tract includes the nose, nasal cavity, oral cavity, pharynx, and larynx, each of which contributes to normal breathing and airway protection. These structures filter, warm, and humidify inspired gas while supporting smell, speech, swallowing, and immune defense.

Mucus, cilia, airway reflexes, and coordinated muscular activity help prevent foreign material from reaching the lungs. Because obstruction can occur anywhere along this pathway, recognizing findings such as stridor, stertor, swelling, abnormal anatomy, and impaired airway reflexes is essential.

Understanding upper-airway structure and function provides a foundation for effective respiratory assessment and airway management.