MedCourseFinder

System

Respiratory system

Not medically reviewed · Content last updated · 1 min read ·

This is the date the draft was written, not a medical review date.

The respiratory system conducts air between the atmosphere and the lungs and provides the surface for gas exchange. It supplies oxygen, removes carbon dioxide and contributes to acid-base balance and phonation.

Terminologia Anatomica (Latin): Systema respiratorium

Components

The upper tract comprises the nose, nasal cavity, paranasal sinuses and pharynx; the lower tract comprises the larynx, trachea, bronchial tree and lungs, ending in alveoli. The diaphragm, intercostal muscles and thoracic cage form the ventilatory pump, and each lung is enclosed in a pleural sac.

Function

Ventilation moves air by pressure gradients generated by the respiratory muscles, and gas exchange occurs by diffusion across the alveolar-capillary membrane. Ventilation is controlled by brainstem centres responding mainly to arterial PCO2, pH and PO2.

Clinical correlations

Asthma, chronic obstructive pulmonary disease, pneumonia, tuberculosis, pulmonary embolism, lung cancer and pleural disease are major respiratory conditions. Auscultation, spirometry, imaging and arterial blood gases are standard assessments; interpretation follows local laboratory and guideline practice.

Common exam points

  • Conducting versus respiratory zones of the airway, and the generations of bronchial division.
  • Right lung has three lobes and two fissures; left lung has two lobes, one fissure and a lingula.
  • Right main bronchus is shorter, wider and more vertical, hence the usual site of aspirated foreign bodies.
  • Phrenic nerve (C3 to C5) innervates the diaphragm.
  • Type I pneumocytes are the gas-exchange cells; type II secrete surfactant.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology. Elsevier, 14th edition (2020) — Tier 3 (textbook)
  4. Murray and Nadel's Textbook of Respiratory Medicine. Elsevier, 7th edition (2021) — Tier 3 (textbook)

References are listed only where the article cites them. See the sources page for the full policy. How sources are chosen and credited

Back to the index