File:Human lung stages 01.jpg

From Embryology

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Overview of lung development

blue Black Red
Lung development is subdivided into 5 morphologically defined stages

Embryonic - Pseudoglandular - Canalicular - Saccular - Alveolar

Stages correlated to development of airways

Initial airways are all of the conducting system

Stages correlated to development of blood vessels
Ventilatory unit is a tree of alveolar ducts served by a most distal respiratory bronchiole.

Acinus is defined as a small tree of airways served by a most distal purely conducting airway (terminal bronchiole).

On average a human airway ends after 23 generations (range 18–30) in an alveolar saccule. A capillary plexus surrounding the growing lung buds give rise to the pre-acinar arteries by the mechanism of vasculogenesis. The intra-acinar arteries are formed by angiogenesis.

In mouse and rat the acini and the ventilatory units are the same entity because they do not possess any respiratory bronchioles.

(above text modified from figure information)

Respiratory Links: respiratory | Science Lecture | Lecture Movie | Med Lecture | Stage 13 | Stage 22 | upper respiratory tract | diaphragm | Histology | Postnatal | respiratory abnormalities | Respiratory Quiz | Respiratory terms | Category:Respiratory
Historic Embryology - Respiratory 
1902 The Nasal Cavities and Olfactory Structures | 1906 Lung | 1912 Upper Respiratory Tract | 1912 Respiratory | 1913 Prenatal and Neonatal Lung | 1914 Phrenic Nerve | 1918 Respiratory images | 1921 Respiratory | 1922 Chick Pulmonary Vessels | 1934 Right Fetal Lung | 1936 Early Human Lung | 1937 Terminal Air Passages | 1938 Human Histology


Schittny JC. (2018). How high resolution 3-dimensional imaging changes our understanding of postnatal lung development. Histochem. Cell Biol. , 150, 677-691. PMID: 30390117 DOI.

Based on Hislop (2005) and adapted from Schittny (2014).


© The Author(s) 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.


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current13:01, 22 February 2019Thumbnail for version as of 13:01, 22 February 2019787 × 534 (138 KB)Z8600021 (talk | contribs)==Overview of lung development== Development of the airways and blood vessels in humans. Lung development is subdivided into morphologically defined stages (blue). These stages are correlated to the development of the airways (black) and blood vessels...

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