German Contact Help Login Register

The Lung

Contents

Macroscopic anatomy

The lung is a pair of organs, consisting of the right and left lung (Pulmo dexter, Pulmo sinister). The right lung has three lobes, the left two. The lobes are further divided into segments (10 on the right, 9 on the left). Because of the heart the left lung is slightly smaller than the right one. The basis of both lungs rest on the diaphragm. The lung is covered by the visceral pleura which is a layer of simple squamous epithelium. The visceral pleura changes to the parietal pleura at the inner surface of the chest wall. Both the visceral pleura and parietal pleura play a key role in the respiration. One needs to understand their structures in order to diagnose and treat respiratory diseases (e.g. pneumothorax). The windpipe (trachea) provides ventilation of the lung by bifurcating into a right and left primary bronchus. The lung volume is about 5 to 6 liters. The alveoli mark the end of the bronchial tree. They are surrounded by a filigree network of blood capillaries. These capillaries are tightly close to the alveoli wall and together they form the blood-air barrier. This allows the gas exchange.

Microscopic anatomy

The primary bronchi in both lungs branch further and terminate in alveoli. Histologically, there are different types of epithelium cells within the bronchial tree: The inner surface of the trachea and both primary bronchi are lined by pseudostratified columnar epithelium. As the branching continues through the bronchial tree the epithelium flattens more and more. Finally the alveoli are lined by a single layer of pneumocytes. The thin wall between the alveoli (type I pneumocytes) and capillary endothelium cells of the surrounding blood vessels allows the passage of gases (e.g. oxygen, carbon dioxide).

Functions

The function of the lung is to supply the organism with oxygen and remove carbonic acid by breathing out carbon dioxide. Therefore the lung as an eliminating organ plays an important role in the acid-base homeostasis (as well as the kidney). The primary task of the lung is the gas exchange in the alveoli. Carbon dioxide produced by cell metabolism is transported in the blood as bicarbonate and released in the alveoli as carbon dioxide. On the other hand oxygen is transferred to the alveoli by inspiration where it diffuses into blood due to the concentration gradient.

Get me the rest of this article for free
Create your account and you’ll be able to see the rest of this article, plus videos and a quiz to help you memorize the information, all for free. You’ll also get access to articles, videos, and quizzes about dozens of other anatomy systems.
Create your free account ➞
Show references

References:

  • H.Fritsch/ W.Kühnel: Taschenatlas der Anatomie, 7. Auflage, Thieme Verlag
  • Benninghoff/Drenckhahn: Anatomie, Band 2, 16. Auflage (2004), S. 533-584
  • Herold: Innere Medizin, Auflage 2010, S. 313-356
  • Schiebler: Anatomie, 9. Auflage, Springer Verlag (2005), S. 478-489

Author & Layout:

  • Christopher A. Becker
  • Achudhan Karunaharamoorthy

Illustrators:

  • Lungs - Yousun Koh 
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.
Create your free account.
Start learning anatomy in less than 60 seconds.