Art of Acinus

This collage reflects the range of the respiratory system from the macroscopic and anatomic to the microscopic – a continuum of structure. Image 2 is a post-mortem specimen taken from the front and slightly above. It shows the trachea and bronchi supplying the two lungs above, with the aortic arch and cardiac structures in the middle and below. Note how pink the lungs are in this specimen from an unfortunate baby with congenital heart disease. Image 3, the chest X-ray, shows the lucent lungs within the thoracic cavity while image 4 is a diagram of the trilobed right lung and the bilobed left lung. Two respiratory units of the lung are shown in the next image each called a pulmonary lobule (5). The lobule consists of a central bronchiole (light blue) and pulmonary arteriole (dark blue), surrounded by the air filled acinus (teal) with its peripheral venules. (red) The acinus is magnified in the next image (6), showing first the tubular terminal bronchiole branching into the respiratory bronchioles, alveolar sacs, and finally the grape like alveoli. The organization of the connective tissues of the lung is shown in image 7. Finally we get down to the grapes or alveoli of the lung with surrounding vessels (8), and a single alveolus is seen in 9. It seems a long way for the air to travel but the system can deliver the air to and from the outside in a single breath, and exchange the gases at the capillary level even more rapidly. It is a remarkable system.
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The Terminal Bronchiole and Acini
This artistic rendition of the small parts of the lung shows the beginning of the peripheral system just before it enters the acinus. This duct is called the terminal duct and it is the last part of the ductal system that has no ability for  gas exchange. After its first division, the bronchioles become the respiratory bronchioles, and they are the first in the system to have an ability to both transport the gases as well as enable gas exchange.
Ashley Davidoff TheCommonVein.net
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The Structure of the Acinus is reminiscent of the morphology of a bunch of grapes.
Ashley Davidoff MD TheCommonVein.net lungs-0059
Alveolus as a Part of the Acinus
Ashley Davidoff MD TheCommonvein.net lungs-0056
The Terminal Bronchiole Acini
This artistic rendition of the small parts of the lung shows the beginning of the peripheral system just before it enters the acinus. This duct is called the terminal duct and it is the last part of the ductal system that has no ability for  gas exchange. After its first division, the bronchioles become the respiratory bronchioles, and they are the first in the system to have an ability to both transport the gases as well as enable gas exchange.
Ashley Davidoff
TheCommonVein.net
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Ashley Davidoff TheCommonVein.net

Acinus.
The acinus with its arborizations is shaped more like a bunch of grapes.
Courtesy of: Ashley Davidoff, M.D 42650
TheCommonVein.net
The Acinus
The acinus is defined as a unit of lung consisting of a single first order respiratory bronchiole that subtending a cluster of alveoli reminiscent of a bunch of grapes or berries (acinus in Latin means berry) .  The lobular bronchiole (lb) branches into the terminal bronchiole (tb), which then branches into the first order respiratory bronchiole (rb).  Subsequent branching  after the respiratory bronchiole,  includes in order, the  alveolar duct (ad), alveolar sac (as), and then finally the berry like alveoli.
Courtesy Ashley Davidoff 2019
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Alveoli in an Acinus of a Secondary Lobule
Ashley Davidoff MD TheCommonVein.net lungs-0008
Emphysema
A drawing showing the normal acinus in teal and the abnormal emphysematous acinus in green characterised by destruction of the septal walls, enlargement of the alveoli, and loss of elasticity. The absence of involvement of the respiratory bronchiole makes the pathological diagnosis of centrilobular emphysema. Ashley Davidoff MD
TheCommonVein.net  32645

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