Introduction to the Upper Respiratory System

Core Concepts

The nose and nasal cavity: conditioning the air

Air enters through the nostrils into the nasal cavity, divided by the nasal septum and lined by a highly vascular mucous membrane. Three features make the nose an excellent air conditioner:

• Warming — a dense network of blood vessels (including the turbinates, bony shelves covered in vascular tissue) transfers heat to incoming air.
• Humidifying — mucus-producing glands keep the air moist so it does not dry out the lower airways.
• Filtering — coarse hairs at the entrance trap large particles, while the mucus blanket traps smaller ones; cilia (tiny hair-like projections on epithelial cells) sweep the mucus toward the pharynx, where it is swallowed — the mucociliary escalator.

This is also where olfaction (smell) happens: odor molecules dissolve in mucus and reach receptor cells high in the nasal cavity. When the lining swells — from infection, allergy, or irritants — the passages narrow and the person feels congested. That congestion is exactly what decongestants target (Chapter 24): they shrink the swollen blood vessels so the passages open again.

The pharynx: a shared passageway

The pharynx is the muscular tube behind the nasal cavity and mouth that carries both air and food. It has three regions: the nasopharynx (behind the nose, where the eustachian tubes open to equalize ear pressure), the oropharynx (behind the mouth, the common path for air and food), and the laryngopharynx (the lowest portion, leading to both the esophagus and the larynx). Because the pharynx is shared, it is a frequent site of infection — pharyngitis (sore throat) — and of lymphatic tissue: the tonsils and adenoids are immune clusters that sample inhaled and ingested material and help mount an immune response. Swollen, tender lymph tissue in the throat is a common finding the nurse assesses during the exam.

The larynx: voice, protection, and the gateway to the lungs

The larynx is the cartilaginous structure at the top of the trachea — the voice box — with three critical functions:

• Phonation — the vocal cords (true vocal folds) vibrate as air passes between them to produce sound; pitch changes as the cords tighten or loosen.
• Airway protection — during swallowing, the epiglottis tips down over the laryngeal opening and the vocal cords close, so food and liquid go into the esophagus instead of the trachea.
• Coughing and airway clearance — when irritants reach the larynx, the cords close and then open explosively, producing a cough that expels material; antitussives (cough suppressants) intentionally quiet this reflex when coughing is dry and exhausting.

Because the larynx is the narrowest point of the airway in children, swelling here — as in croup — can rapidly become dangerous, and stridor (a high-pitched sound on inspiration) signals a partially blocked upper airway that requires urgent attention.

Upper respiratory defense and the immune response

The upper airway's defense is layered: mechanical (hairs, mucus, cilia, coughing, sneezing), chemical (enzymes and antibodies in mucus and saliva), and cellular (immune tissue such as the tonsils and adenoids, plus immune cells patrolling the mucosa). When a virus like the common cold infects the nasal mucosa, the immune response causes the classic symptoms: swelling (congestion), increased mucus production (runny nose), sneezing, and sometimes fever. Most upper respiratory drug classes work by dampening these symptoms — antihistamines block histamine, the chemical released during allergic responses; decongestants shrink swollen vessels; expectorants and mucolytics thin mucus so it can be cleared. The point to carry forward: most "cold medicine" is symptom management while the immune system clears the infection — which is why antibiotics (which treat bacteria, not viruses) are not appropriate for typical viral colds.

The nurse's assessment of the upper airway

Assessment is quick, non-invasive, and highly informative. The nurse inspects the nose for discharge and swelling, looks in the mouth and oropharynx for redness, swelling, or exudate, palpates the neck for tender lymph nodes, and listens to the voice and cough. Key questions: is the discharge clear or colored (color alone does not distinguish viral from bacterial), is there difficulty swallowing, is breathing noisy, and can the person speak normally? Red-flag findings requiring urgent escalation include stridor, drooling with inability to swallow, severe difficulty breathing, or a muffled voice — any of which may signal airway obstruction. Scope note: examination and assessment are core nursing work; diagnosis, testing decisions (such as strep tests or imaging), and prescribing are provider responsibilities and vary by setting and scope of practice.

Common Confusions