CCMA · Anatomy and Physiology · 7 min read
Respiratory Structures, Breathing and Lung Disease
- Identify the structural components of the upper and lower respiratory tracts and explain the physiological mechanisms of pulmonary ventilation and gas exchange.
- Describe common respiratory disorders encountered in ambulatory care, including asthma, chronic obstructive pulmonary disease, and pneumonia, along with their characteristic signs and symptoms.
- Explain the clinical medical assistant's responsibilities during respiratory vital sign assessment, diagnostic procedures, medication and vaccine administration, and urgent clinical situations under provider supervision.
Anatomical Organization of the Respiratory Tract
The respiratory system is divided anatomically into the upper respiratory tract and the lower respiratory tract. The upper respiratory tract includes the nose, nasal cavity, pharynx, and larynx. An essential protective structure in this area is the epiglottis; during swallowing, the epiglottis folds over the laryngeal opening, helping prevent food and liquids from entering the airway. Ciliated epithelial cells in the conducting airways move mucus and trapped particles toward the pharynx; alveoli do not have a mucociliary lining.
The lower respiratory tract begins below the larynx and includes the trachea, bronchi, bronchioles, and alveoli. As the trachea descends through the thoracic cavity, it bifurcates into the right and left primary bronchi at an anatomical ridge called the carina. The right primary bronchus is wider, shorter, and more vertical than the left primary bronchus. This architectural difference is accompanied by lung asymmetry: the right lung has three lobes, whereas the left lung has two lobes.
The lungs are enveloped by a double-layered serous membrane called the pleura. The visceral pleura covers the outer surface of the lungs, while the parietal pleura lines the thoracic cavity wall. Between the visceral and parietal pleura is a thin film of pleural fluid that reduces friction during breathing. At the terminal ends of the respiratory tree are the alveoli, which serve as the microscopic functional units of the lung where external gas exchange occurs. Within these structures, specialized type II alveolar cells produce surfactant, a lipoprotein substance that lowers surface tension to prevent alveolar collapse.
Common mistakes
- Averaging the three attempts during peak flow testing instead of recording only the single highest value obtained.
- Alerting the patient that respirations are being counted, which causes the patient to become self-conscious and alter their natural breathing rate.
- Collecting saliva instead of deep bronchial secretions, or failing to follow the ordered sputum collection instructions; early-morning collection before food or drink is preferred when feasible, but a later specimen may still be collected as directed.
- Failing to recognize stridor as an emergency sign of upper airway obstruction, confusing it with lower airway wheezing, and delaying immediate provider notification.
Key points
- The upper respiratory tract includes the nose, nasal cavity, pharynx, and larynx; the epiglottis helps protect the airway during swallowing, and cilia help clear mucus from conducting airways. The lower tract includes the trachea, bronchi, bronchioles, and alveoli, whose lining contains both gas-exchanging type I cells and surfactant-producing type II cells.
- The trachea bifurcates at the carina into the right primary bronchus (shorter, wider, and more vertical) and the left primary bronchus, leading to a three-lobed right lung and a two-lobed left lung surrounded by visceral and parietal pleura with friction-reducing pleural fluid.
- Inhalation is an active process led by diaphragm contraction and external intercostal activity, quiet exhalation is passive elastic recoil, and breathing rhythm is controlled in the brainstem by the medulla oblongata and pons, triggered primarily by elevated arterial carbon dioxide and decreased pH.
- External respiration exchanges gases between alveoli and pulmonary capillaries, internal respiration occurs between systemic capillaries and tissues, with oxygen transported primarily as oxyhemoglobin and carbon dioxide mainly as bicarbonate ions or carbaminohemoglobin.
- Clinical assessment includes unobtrusive counting of resting respirations (normal: 12-20 breaths per minute), pulse oximetry (typically 95 percent or higher in a healthy adult), performing provider-delegated peak flow testing (recording the best of three trials), and collecting deep bronchial secretions for a sputum specimen, preferably in the morning.
- Respiratory disorders include asthma (airway inflammation and variable airflow obstruction), COPD (persistent airflow limitation commonly associated with smoking, with chronic bronchitis and emphysema as common features), and pneumonia (lung infection that may cause consolidation, fever, cough, and crackles).
- Under provider supervision, the medical assistant administers nebulizer treatments, reinforces inhaler and spacer instructions, administers prescribed influenza and pneumococcal vaccines per state law and policy, and immediately alerts the provider if stridor, cyanosis, gasping, or intercostal retractions occur.
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