Talk:Lung

An entire section needs to be added on diseases of the lung

An entire section needs to be added on diseases and traumas of the lung, especially in mammals, primates, and human beings. As of the present, this article hardly mentions lung diseases and other forms of lung damage. There is only minor mention of infection, and nome at all on black lung disease, lung cancer, emphysema, and the effects of poisons such as mustard gas and tobacco tar on the lungs of human beings and other mammals. All of these things are surely serious omissions.98.81.5.18 (talk) 18:53, 19 February 2010 (UTC)

Tidal volume, capacity, vandalism

What is the difference between capacity and tidal volume of the lung? The article claims they differ by a factor of 10. AxelBoldt 16:07, 14 Oct 2003 (UTC)

The space the lung uses for inhalation of air is just a fraction (is called the tidal volume) of the space that is availible in the lung (capacity of the lung). —The preceding unsigned comment was added by 213.93.136.84 (talk • contribs) 16:19, 15 November 2004 (UTC)

True for Mammalian lungs, but not for Avian lungs, as far as the article Bird tells me. Speaking of which, should we describe the lungs of other classes here? Amphibia, Aves, Reptilia? -Wikibob | Talk 13:23, 2005 Mar 29 (UTC)

They used to be described here, the avian ones at least, but seem to have vanished. I don't have the time right now to sleuth through the article history in detail to find out why, but I've added a link for the avian one now and the others should at least be mentioned too. Bryan 16:27, 29 Mar 2005 (UTC)

I've restored the missing Avian and Amphibian sections.

The loss occurred between

• 11:05, 2004 Oct 28 Solitude and
• 02:10, 2004 Nov 9

(vandalism was only partially repaired).

Subsequent minor vanadalism had been correctly repaired, and I found no more losses. The Reptilian section was originally empty, and I didn't look further back than July 2004.

After restoration as a check I took this bookmark of the difference between the restored version and Solitude's Revision as of 11:05, 2004 Oct 28.

I will soon move Bryan's Avian section to the restored section as a summary (if my laptop doesn't crash again).

Finally here are the sections I've restored -Wikibob | Talk 00:47, 2005 Mar 30 (UTC) :

Human lungs

See human lung.

Avian lungs

Birds have a significantly different structure to their lungs than mammals do. In addition to the lungs themselves, birds have posterior and anterior air sacs (typically nine) which control air flow through the lungs, but do not play a direct role in gas exchange. They have a flow through respiration system.

When a bird inhales, air flows in through the trachea to the posterior air sacs, while air currently within the lungs flows into the anterior air sacs. When the bird exhales, the fresh air now contained within the posterior air sacs is driven into the lungs, and the stale air now contained within the anterior air sacs is expelled through the trachea and into the atmosphere. Two complete cycles of inhalation and exhalation are, therefore, required for one breath of air to make its way through the avian respiratory system.

Avian lungs do not have alveoli, as mammalian lungs do, but instead contain millions of tiny passages known as parabronchi, connected at either ends by the dorsobronchi and ventrobronchi. Air flows through the honeycombed walls of the parabronchi and into air capillaries, where oxygen and carbon-dioxide are traded with cross-flowing blood capillaries by diffusion, a process of crosscurrent exchange.

The purpose of this complex system of air sacs is to ensure that the airflow through the avian lung is always traveling in the same direction - posterior to anterior. This is in contrast to the mammalian system, in which the direction of airflow in the lung is tidal, reversing between inhalation and exhalation. By utilizing a unidirectional flow of air, avian lungs are able to extract a greater concentration of oxygen from inhaled air. Birds are thus equipped to fly at altitudes at which mammals would succumb to hypoxia.

Reptilian lungs

Amphibian lungs

The lungs of most frogs and other amphibians are simple balloon-like structures, with gas exchange limited to the outer surface area of the lung. This is not a very efficient arrangement, but amphibians have low metabolic demands and also frequently supplement their oxygen supply by diffusion across the moist outer skin of their bodies.

Lights

Should a mention of Lungs used in food be mentioned in this article?--Wynler | Talk 20:02, 5 June 2006 (UTC)

Of course! Got a reference? Melchoir 04:50, 19 August 2006 (UTC)

Nonrespiratory functions

Another nonrespiratory function is to filter out gas microbubbles occuring in the blood stream during Scuba diving Decompression stop. I think it is worth adding.Michagal 16:09, 12 February 2007 (UTC)

Circular redirect

There is a reference and link to circulatory lungs in the Avian Lungs section, but it redirects to Lungs --Anidnmeno 22:01, 26 September 2007 (UTC)

Thanks for catching that! I've fixed it. But you can edit the page, too, you know, it's only locked from IP's and accounts less than four days old. delldot talk 22:34, 26 September 2007 (UTC)

History of the study of the lungs?

A good addition to this article would be a section on the history of the study of lungs. LinaMishima (talk) 20:02, 28 January 2008 (UTC)

Invertibrate lungs???

The first sentence of this article implies that only vertibrates have lungs. Snail says that some kinds of snails have lungs. This needs to be clarified and/or corrected. -- RoySmith (talk) 22:13, 5 April 2008 (UTC)

Quite correct, Roy. There are a group of air breathing snails called the pulmonata who have lungs. So who's going to change the article? 122.105.84.37

Shouldn't diseases and other problems/defects be mentioned in this article?

(talk) 00:12, 7 April 2008 (UTC)

Vandalism

Just to let you know someone put something like nhhhhhhjksud so I deleted it —Preceding unsigned comment added by 86.129.40.99 (talk) 16:36, 16 October 2008 (UTC)

Pleura and Pleural Cavity

I think this article should mention the pleura (membrane covering the lungs) and the pleural cavity in which the lungs are contained. I would have to do some research on this if I were to do it myself, which I'm willing to do. I thought I would mention it here first in case somebody else more knowledgable than myself could do this more quickly. --Lance E Sloan (talk) 23:06, 25 November 2008 (UTC)

Inaccuracies

Do you think that the comment about their being three branches of the trachea might be inaccurate. I am not sure how the third branch travels through the abdomen, does anyone know?

Page Improvement

I think the page could be better improved. Couldn't there be some more color pictures in the articles? —Preceding unsigned comment added by 68.76.123.166 (talk) 17:07, 13 March 2010 (UTC)

At the top of the article it says "The lung is the essential respiration organ in all air-breathing animals". However, insects, for example, do not have lungs so perhaps it should be reworded to not say "all". You may argue that "breathing" implies only the animals that have lungs, but then the whole sentence becomes redundant, and a semantic tautology. I propose something more succinct and clear along the lines of.. "The lung is an organ used for respiration in many large animals". 188.220.85.6 (talk) 22:29, 12 November 2010 (UTC)

Fixed. Let me know if you see anything else - many anatomical articles are very human/chordate biased, and I fix what I can when I'm not busy. Mokele (talk) 22:53, 12 November 2010 (UTC)

Avian lung airflow

The third paragraph on the section on the Avian Lung states that it is a misunderstanding that it takes two breathing cycles for air to flow through the whole system, and goes on to say that air is not stored in the air sacs. The source it cites actually says: "During expiration the major part of inspired air streams from the reservoirs (caudal air sacs, thick open arrows) through the parabronchi/air capillaries into major distal airways, where it mixes with the deoxygenated respiratory gas stored in cranial air sacs during the inspiratory phase." which seems to contradict the article's mention of the air sacs not storing air. While I think this is more of a technicality (air isn't stored there forever, of course), I can find no justification on the sourced site for saying that it does not take two cycles. In fact, since it states that air moves from the reservoir of the caudal air sacs, through the parabronchi, into the cranial sacs upon expiration. This suggests that it takes more than one respiratory cycle for a single "packet" of air to circulate completely. Is there a credible source that describes this differently or is more up-to-date on avian respiration? Faunablues (talk) 23:23, 15 May 2010 (UTC)

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I think Faunablues’ criticism is right, and the version commented on should be changed. On page 62 of:

Bretz, W. L. and K. Schmidt-Nielsen. 1972. The movement of gas in the respiratory system of the duck. The Journal of Experimental Biology 56: 57–65. 
http://jeb.biologists.org/cgi/reprint/56/1/57 a table shows the number of cycles required to wash out half the gas inhaled on a particular cycle, from four different airsacs. In all cases, between 2 and 3.5 cycles are required. Unless the volumes retained in the uncompressible lung and airvessels are reasonably comparable to the airsacs, that washout table shows there is substantial gas held in most/all airsacs at the end of the exhalation phase.

Although Bretz & SchmidtNielsen ‘72 is not more recent than the source site originally referenced, it doesn’t matter as Bretz & SchmidtNielsen ‘72 has perfectly adequate authority, the originally sourced site did not endorse the original version, and I believe it’s hard to find one that does. Strangetruther (talk) 18:25, 29 August 2010 (UTC)

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Also, the Ritchson reference "BIO 554/754 - Ornithology: Avian respiration" (reference #15 when I saw it) talks about moveable valves, for which it references: Bernhard, W., P. L. Haslam, and J. Floros. 2004. From birds to humans: new concepts on airways relative to alveolar surfactant. American Journal of Respiratory Cell and Molecular Biology 30: 6-11. Ritchson uses a diagram it gets from Bernhard et al, but the latter simply imply moveable valves and of course give no evidence for them (they are now thought not to exist). Too much of this original Wikipedia page and its references are problematic, and I'm going to give this section, and the Respiratory System section of the bird anatomy page a good spring cleaning soon. Strangetruther (talk) 21:14, 3 January 2011 (UTC)

Please do, this page could definitely do with some expert attention on the topic. Mokele (talk) 00:18, 10 January 2011 (UTC)

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The third paragraph does contain an error but the error is this, "air moves continuously from the posterior to anterior air sacs throughout respiration".

There is no significant flow of air from one set of air sacs to the other. The entire thoracoabdominal cavity expands and contracts during inhalation and exhalation. This means that the caudal and cranial air sacs are always expanding and contracting at the same time. When the caudal sacs are being compressed and are expelling air, the cranial sacs are also expelling air.

This paper is behind a pay wall but the abstract gives a clear and concise picture of the air flow through the avian respiratory system. (pay particular attention to points 2.2 and 3.3 in the abstract) J.H Brackenbury, Airflow and respired gases within the lung-air-sac system of birds, Comparative Biochemistry and Physiology Part A: Physiology, Volume 68, Issue 1, 1981, Pages 1-8, ISSN 0300-9629, DOI: 10.1016/0300-9629(81)90309-1. (http://www.sciencedirect.com/science/article/pii/0300962981903091)

The author of the third paragraph is correct to state that it is a misunderstanding that it takes two breathing cycles for air to flow through the whole system.

The expression, "flow through the whole system" is likely to cause confusion. It doesn't explicitly state that every air molecule flows through every major feature of the entire system - it is possible to see that air splits and takes different paths - but it conditions the unwary to think that all the air follows one path. When novices try to account for where the air goes they tend to imagine a puff of air entering the bird, they try to picture the route it would take as it flows through the entire system and eventually exits the bird.

Let's list the major points of interest:

• outside (outside of the bird)
• trachea (I'm also lumping the extrapulmonary primary bronchi and the mesobronchi into this one unit for brevity)
• caudal air sacs
• lungs
• cranial air sacs

How would a single lump of air move through that system?

The obvious answer is: outside -> trachea -> caudal -> lungs -> cranial -> trachea -> outside. But you can't make that work with one inhale/exhale cycle. Two is the smallest number of cycles where that could work.

The two cycle idea requires somewhere to store significant quantities of air between one cycle and the next. The lungs are essentially fixed in volume, are relatively small compared to the air sacs, and there are no, physical, valves in the system. The lack of hard valves means that the lungs can't be pressurized. Since they are small and can't be pressurized, they can't store enough air to make a significant contribution. The caudal air sacs can hold large amounts of air but they can't transfer that air to the cranial air sacs because both sets of sacs are emptying at the same time.

So how do birds breathe?

The short answer is that they breathe in and out, in one cycle, just like mammals.

The long answer is that air travels: outside -> trachea and then SPLITS! There are 2 destinations.

1. trachea -> lungs -> cranial air sacs
2. trachea -> caudal air sacs

When the bird exhales there are two sources of air and they join in the trachea. (Technically they join in the ventrobronchi then pass into the trachea)

1. cranial -> trachea -> outside
2. caudal -> lungs -> trachea -> outside

Go here, do a text search in the page for: " During inhalation, air moves into the posterior air sacs " (don't include the quotes) and you will see some diagrams that show the airflow through the system. Note the airflow splits at the end of the mesobronchus during inhalation, and note the air flows joining at the other end during exhalation. You can also see that both sets of air sacs empty and fill at essentially the same times. Scarabaeidae (talk) 00:38, 16 June 2011 (UTC)

Thanks for the description. Your path description especially, along with the description and diagram in the bird anatomy article have enabled me to understand the airflow. If I may compress it slightly:

Inhalation:

outside -> trachea -> lungs -> cranial air sacs

outside -> trachea -> caudal air sacs

Exhalation:

cranial air sacs -> trachea -> outside

caudal air sacs -> lungs -> trachea -> outside

I'll try to draw this up in Powerpoint or something similar.--Wikimedes (talk) 19:42, 21 October 2011 (UTC)

---

The diagrams Scarabaeidae directs us to are rather nice. They do show the front (cranial) and rear (caudal) sacs expanding and contracting together. I think there are three things we need to sort out now.

First, one reason all the air does not go through every part of the whole system is because air leaving the lungs on the expiration phase pretty well bypasses the front sacs and goes straight out. We might want to change anything that seems to contradict this.

Second, no sac empties on exhalation. The Bretz and Schmidt-Nielson papers I cite in Bird Anatomy/Respiratory System wiki article and Talk, show there’s really rather a lot left behind after full exhalation, at least in the duck, and when anaesthetised.

Third is the question of exactly how much air goes straight into the lungs on inhalation, bypassing the rear sacs. The impression I’ve got is that less than half a lungful goes straight into the lungs, and very little if any of that reaches the front sacs by the end of the inhalation which took it in. I also suspect that a lungful is a bit less than half an average inhalation. Complicating this is the way air is inhaled into (both of) the rear sacs from the primary bronchus, while at the same time, air, mostly different air, goes from (both of) the rear sacs into the lung. This seems unlikely but then much of bird breathing has always seemed unlikely. Have a look at those Bretz and S-N flow figures (the other wiki article has the online link to them) and see if they can be explained in any other way. For this bizarre trick to be achieved, birds must be using the neopulmo:

primary bronchus -> rear airsacs (using some parabronchi of the neopulmo as well as direct via prim. bronchus);

simultaneous with:

rear airsacs -> dorsomedial secondary bronchi, via other parabronchi of the neopulmo.

Without the neopulmo it really does seem to be completely impossible to get air out of the rear sacs and into the lungs while they’re being inflated from the primary bronchus. This means that the scheme of half an intake directly into the lungs and half into the rear sacs does indeed apply to penguins and other types without the neopulmo.

That third question really needs experimental evidence showing that the mass of air going straight into the lungs bypassing the rear sacs, is comparable to that going straight into the rear sacs; without a reference showing that, I suggest we must rely on the Bretz and S-N scheme, as regards birds with a neopulmo.

Actually, we’re short of a diagram or two on both this Lungs/Birds page and the Bird Anatomy/Respiratory System page. We need a diagram of the secondary bronchi; I’ve provided one clickable one, mentioned in the Bird Anatomy/Respiratory System page, just after “dorsobronchi and ventrobronchi.”, but I haven’t got it loaded up to Wikipedia yet. However, the finest scale diagram, usually depicted by the classic Duncker diagram found by searching for “(From: Duncker 1971” in http://people.eku.edu/ritchisong/birdrespiration.html (or click the blue: “Go here” in the Scarabaeidae text just above this) is presumably owned by Duncker, and he presumably hasn’t released the copyright. I commissioned an image drawn by an artist after that diagram, and have it in my “Secret Dinobird Story”, and would be willing for it to be used. I think the complication of that diagram is the reason others haven’t drawn up their own. Strangetruther (talk) 18:42, 26 July 2012 (UTC)

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Oh dear. Got be explicit here: I'm afraid the 'in and out on one cycle' system proposed above by Scarabaeidae and adjusted by Wikimedes isn't right.

[It couldn't work exactly like that, because for one thing the air inhaled directly into the lungs would need to displace into the front sacs air already in the lungs, which must have come from the rear sacs. This would mean that at least that air would be retained for two complete cycles and would visit both rear and front sacs. This would then be the system in birds lacking a neopulmo.Strangetruther (talk) 17:54, 27 July 2012 (UTC)]

It should be:

Inhalation 1: trachea -> primary bronchus -> rear sacs (almost all of it; a little straight to lungs)

Exhalation 1a: rear sacs -> lung (a little continues beyond to front sacs)

Exhalation 1b: stays in rear sacs

Inhalation 2a: The Exh1a air goes: lung -> front sacs

Inhalation 2b: The Exh1b air goes: rear sacs -> lungs

Exhalation 2a: front sacs -> primary bronchus -> trachea and out

Exhalation 2b: lungs -> primary bronchus -> trachea and out

Diagram here: http://sciencepolice2010.files.wordpress.com/2012/07/fig71.gif

Strangetruther (talk) 19:10, 26 July 2012 (UTC)

So in terms of the diagram used in the article to illustrate airflow, this means that the arrow showing air flowing directly from the trachea to the lung and continuing on to the front sacs is (mostly) wrong? (I.e. most of the air that flows through the lung goes from the rear to front sacs.)--Wikimedes (talk) 22:47, 24 January 2013 (UTC)

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The article does not establish why it should take 2 cycles for one breath to make its way through the system. When the bird inhales BOTH sets of airsacs fill. When it exhales BOTH sets of airsacs empty. It is true that there is always some air left in the system but that is also true of the mammalian respiratory system - yet we don't say that it takes multiple cycles for air to flow through the mammalian system.

Here are some true statements...

It is a true statement to say that some air is transferred between the posterior and anterior sacs between cycles.

It is also a true statement to say that some air is transferred from the anterior sacs to the posterior sacs between cycles. (See EXPLANATION below)

Both of the statements above are true. But neither of those true statements are helpful in describing how bird respiration works or what it is for. They are true but unhelpful.

Don't get hung up on washout experiments. The same experiments performed on a mammal would show that it takes multiple cycles for a tracer gas to be completely washed out of a mammal's lungs. There is nothing surprising or SIGNIFICANT about this.

Here is an analogy: when a human inhales, about half of the air enters the right lung. When the human exhales most of that air leaves the body but a small amount remains in the trachea at the end of the first exhalation. Some of this air could be drawn back into the left lung during the 'second' inhalation.

So we can make a true statement about mammalian breathing, "Mammalian breathing is a multi-cycle process under which air is exchanged between the two lungs".

The above statement isn't wrong; it isn't inaccurate. It just isn't helpful. It doesn't help us understand how human breathing works and what human breathing is for (what it accomplishes).

It is a mistake to try to account for every molecule of air that entered the system during an inhalation. There will always be some molecules that never left during the first exhalation. It is also a mistake to think that every molecule was gone by the end of a second exhalation. Given that air passes from posterior to anterior between cycles and given that air passes from anterior to posterior between cycles - we can see that some hapless molecules could be stuck in a loop for many cycles. It can happen but it isn't important for understanding how bird respiration works.

(EXPLANATION) - how does air transfer from the anterior to posterior air sacs between cycles? It does it by the same mechanism that air is transferred from posterior to anterior. That mechanism is via unexpired air that was left in the system between cycles. It's the same mechanism that transfers air between the two mammalian lungs.

It is the unexpired air in the lungs and (some of the) secondary bronchi that transfers a little air from posterior to anterior sacs. It is unexpired air in the primary bronchus and trachea that transfer a little air from anterior to posterior between cycles. Both these things happen but they are not important to the task of understanding how birds breathe.

If you believe that it is important to account for all air that entered the system then you can't stop at two cycles. There will still be some molecules of air present from the first inhale after the second exhale. The only inaccurate thing about the two cycle idea is that it stops at two. :-)

I think that our task here is to explain avian respiration and how it works. Any explanation given has to be accurate but it also has to be helpful. The two cycle idea is not helpful and just confuses a fairly simple process. So the two cycle idea fails the helpful test and if the purpose of it is to account for all air inhaled then it fails the accuracy test as well.

Please reconsider your edits. Frustratingnamesearch (talk) 19:50, 28 September 2013 (UTC)

As far as I can see, the article does not claim that it takes two cycles for one breath to make its way through the system. In fact, the final paragraph of the section on avian lungs explicitly refutes this. Am I missing something?--Wikimedes (talk) 22:43, 28 September 2013 (UTC)

My bad, I had several web pages open and confused one page with another. Or I'm just going mad (it's probably the latter). Frustratingnamesearch (talk) 23:43, 28 September 2013 (UTC)

No worries.--Wikimedes (talk) 13:55, 29 September 2013 (UTC)

Lungs of Lung?

There is some confusion in the English language about "the lung" and "the lungs". As far as I understand, physicians talk about the lung, whereas laypeople talk about the lungs. Is there a right lung and a left lung, so that a mammal has two lungs? or five lungs? In the article, "lungs" and "lung" are used apparently randomly. Some consistency would be desirable, as well as an explanation of the use of the singular/plural in the lead paragraph.  Andreas  ^(T) 21:53, 23 April 2011 (UTC)

File:Right lung.jpg Nominated for Deletion

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Can you remove the picture of pig lungs at the front?

It is as from a butcher's shop. I don't think this should be the first picture you see on this article.

--Emil K2 (talk) 16:24, 16 March 2013 (UTC)

Is such a graphic image right at the start of the article necessary to demonstrate what a lung is?

Would a simple diagram not do? --Editor510 ^{drop us a line, mate} 22:36, 2 April 2013 (UTC)

typo

Section on bird lungs reads "higher mean total morphometnc pulmonary" should read "higher mean total morphometric pulmonary" morphometnc is not a thing. --Aidanomatic (talk) 15:07, 5 May 2013 (UTC)

Good eyes. Fixed it. Thanks.--Wikimedes (talk) 03:28, 22 May 2013 (UTC)

Unidirectional airflow in birds also appears in other archosaurs

I don't know enough about the subject to confidently edit this in, but this article suggests that unidirectional airflow in the lungs is not an adaptation unique to birds, but is shared with all descendents of an ancestral diapsid and had developed 100 million years before the origin of birds. 82.139.86.180 (talk) 12:03, 12 December 2013 (UTC)