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Pulmonary Anatomy & Physiology: What Do You Need to Know?

By: Suzan Miller-Hoover DNP, RN, CCNS, CCRN-K

Pulmonary Anatomy

The pulmonary system consists of upper and lower pulmonary structures, bronchial/systemic circulation, and gas exchange at the level of the lungs and tissue cells. These anatomical structures work together to achieve two main goals: delivery of oxygen and removal of carbon dioxide (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).

The upper structures include the nose and the pharynx. The pharynx includes the nasopharynx, oropharynx, and laryngopharynx. These structures act to filter, humidify, warm the outside air, and equalize ear pressure (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).

The lower structures include the larynx, trachea, carina, bronchi, bronchioles, and alveoli. The primary purpose of these structures is to move oxygen to and carbon dioxide from the alveoli where gas exchange takes place. Would you be surprised to learn that there are approximately 300 million alveoli in the lungs; which, if opened and laid out flat would cover 900 square feet, that’s the size of an apartment!

The lungs encompass the entire thoracic cavity except for the area around the mediastinal space. The heart, major blood vessels, bronchi, esophagus, among other organs occupy the mediastinal space. (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).

The lungs perform two main functions: ventilation and diffusion.
  •   Ventilation: exchange of air between the atmosphere and the alveoli
  •   Diffusion: exchange of oxygen and carbon dioxide across the respiratory membrane, from a higher       concentration to a lower concentration
  (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014)

The right lung is divided into three lobes and responsible for about 55% of lung activity.
The left lung is divided into two lobes and responsible for about 45% of lung activity (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).)

The pulmonary circulation is unique in that oxygenated blood is carried by veins, as opposed to arteries. The lungs receive deoxygenated blood from the heart via the pulmonary artery and return oxygenated blood via the pulmonary vein (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).)

Every wonder why the oxygen saturation is not 100% in the left atrium and left ventricle? The answer lies in the bronchial circulation where deoxygenated blood from the bronchial circulation is removed by both the bronchial veins and the pulmonary veins. This mixing of oxygenated and unoxygenated blood in the pulmonary vein is why the oxygen saturation of blood on the left side of the heart is never 100% (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).)

The inhalation phase of respiration occurs when the diaphragm contracts and moves downward forcing air into the lungs. This movement is responsible for 70% of tidal volume. The other 30% of tidal volume is facilitated by the movement of the external and internal intercostal muscles, abdominals, and accessory muscles in the neck (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).)

Did you know that the act of breathing helps maintain the body’s acid-base balance by regulating the amount of carbon dioxide within the pulmonary system? This is done by increasing and decreasing the respiratory rate (Nurseslabs.com, 2017 & Tortora & Derrickson, 2014).)

Did this short article peak your interest in learning more about how the pulmonary system works and how it maintains pH balance? If so, please review RN.com’s course: Interpreting ABGs: The Basics and Pulmonary Anatomy and Physiology.



References
Tortora, G., & Derrickson, B. (2014). Principles of anatomy and physiology (14th ed.). Hoboken, NJ: John Wiley & Sons.

Nurseslabs.com. (2017). Respiratory system anatomy and physiology. Retrieved from: Respiratory system anatomy and physiology

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