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The kidney of a cow has lobules, while the kidney of a human hasn't any.

I can't think of any reason why it would be good for a kidney to have lobules. It would be good if the kidney needed to have a large surface area, but I don't see a reason why it would have to, since there is no diffusion or another proces that needs larger area.

  • Is there any reason why it would be beneficial for a kidney to have lobules?
  • Is there a known reason why the kidney of a cow has lobules, while the kidney of a human hasn't any?
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  • $\begingroup$ Please edit your questions to provide links that reference the facts you are questioning. This will help future readers of your question that may not be aware of these facts to learn more, should they be interested. Thank you. $\endgroup$
    – AMR
    Dec 22, 2015 at 22:23
  • $\begingroup$ @AMR Thank you for your answer. But I am not sure what you meant by your comment. Do you want me to add a link to a picture of a human kidney and a cow's kidney? $\endgroup$
    – wythagoras
    Dec 26, 2015 at 7:29
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    $\begingroup$ I basically meant that you should add the sources of your research. How did you learn that bovine kidneys are lobular? If it was an article or a book you could say something like "The kidney of a cow has lobules, -X..." where X is the title of the article or a link to the source where you read it. I suggest it because it may not be common knowledge and someone may want to read more than your question and my answer on the subject. Also, general guidelines for asking questions on the site can be found here. $\endgroup$
    – AMR
    Dec 26, 2015 at 23:34

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It appears that the invagination of the renal kidney is vestigial from development and unlike human and other mammals, the bovine kidney does not form a smooth outer cortex.

The kidneys of the bovine do not lose their foetal lobulation.

-Renal Anatomy - Anatomy & Physiology en.wikivet.net

However this is not related to its function.

Despite what it’s externally lobulated appearance may suggest, the cortex of the bovine kidney is continuous and the kidney is of multipyramidal type.

-Renal Anatomy - Anatomy & Physiology en.wikivet.net

If you want further information on the subject, The bovine kidney as an experimental model in urology: external gross anatomy; Carvalho, et. al. Cells Tissues Organs. 2009;190(1):53-8. doi: 10.1159/000159370 made measurements of the bovine kidneys and compared then to human measurements. This article is unfortunately behind a pay wall, so you will need academic access to Medline to access.

One observation that they do make is that

There are few publications about bovine kidney anatomy. The available information is general, contains little detail and is limited to the classical texts [Bossi et al., 1909; Nickel et al., 1979; Sisson, 1981; Dyce et al., 2004].

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The question seems based on a partially incorrect premise (i.e., that human kidneys don't have lobules), but I could not discover any known reason for the variation in external appearance.

To start, all mammal kidneys contain renal lobules that form during fetal development and are necessary for the organ's function; so they are certainly beneficial.

In some mammals the kidney develops a smooth covering cortex that leads to the well-known "kidney bean" shape (as far as I can tell this is the case across all adult primates). Dogs, cats, sheep have the bean shape, and also have thicker kidneys than pigs, who have a more flattened shape. In some animals the left and right kidneys appear nearly "mirror image" in size and shape; in others (such as horses) the left and right are very different in shape. In the context of all this variation, cows are not that unusual among mammals, they do have a larger rumen that can force both kidneys to be on the right side, and the cortex that covers the lobules just doesn't develop to be as smooth as it does in humans. Since the lobules are universal across all the kidney shapes, and are often visible in a fetus with the cortex forming later, it is likely that is the original structure to evolve, whereas the smooth cortex was only selected later in evolution, and only in certain species where it was useful.

source: I have seen a lot of kidneys.

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