Interesting!

Yes interesting! With horses the liver exists in lobes to aid function - so it is related to structure and therefore function like all good anatomy and physiology. As the horse does not have a gallbladder the liver provides a constant source of bile to digest fats in the diet - they evolved this way we think due to their diet being very low in fat and not needing that injection of bile we do when we eat a doughnut! So for horses lobes exist in the liver to provide more surface area for absorption and other cellular functions - we think!

Thanks Rose!

I am, however, not sure… I have heard that animal brains are often folded (manatee brain are smooth though) to fit in more cortex in a smaller volume (as the cortex represents the surface, if the brain is folded, the exterior surface area increase and so does the space occupied by the cortex). But it seems to me that the liver is a different matter. The liver have a very slow, low pressure blood flow (‘percolative blood flow’) to enhance the ‘filtering’ function. But this filter-function is not dependent on the exterior surface- it is dependent on the capillaries density inside the liver. So, folding (and ‘lobe-ing’) would increase the exterior surface area of the liver, it would not increase the surface area exposed to capillaries (and that is where the magic is happening!)

Isn't it just to do with embriology and how the tissue is developed? For example, liver has 'lobes' due to various ligaments and previous fetal vessels, but functionaly it is divided into segments (8 of them according to vascularization). Brain lobes are nothing but human anatomical descriptive terms since each brain is individual in its convolutions. For example, anatomists consider prostate to have lobes, etc. There are numerous examples and I think one can be swayed by using anatomical terminology in teleological search for biological design. Maybe sometimes it can coincide to be useful, but then being an exception. 

Hey Karlo, thanks for the answer!

I think the embryology answer 'how' the organs end up as lobes, but it does not answer 'why' they are in lobes. That is, mechanistically, the developmental biology explain 'lobe-ing', but I am more interested in the functional intension behind why organs as lobes (what benefit do you get from arrange organs in lobes versus large solid structures?)

I think it is an important point you make to keep in mind the possibility that organs ended up as lobes purely by coincidence (i.e. result from neutral selection/drift). But I must confect, I would consider it a spectacular coincidence! Why do so many animals all 'use' lobes? Why are lobes architecture obsurved with such consistency that we catalogue their appearance in anatomical text books? As you point out, there are measurable differences in brain architecture between individuals (apparently, in low frequency, differences in liver-lobe architectural also occur). However, there are also global morphological structures that are basically universal in all normal people. By analogy, eye colour differ, but the essentials for vision remains the same- similarly, minor differences in lobes may exist, but the functional intension (i.e. ‘goal’) behind ‘lobe-ing’ may still have an important implication.

My gut tells me that partitioning organ in lobes performed a vital function.

From cellular level to macroscopic, a universal pattern appears. Each cell is made of similar organells, each tissue of similar cells, and organs are made of tissue. 'Lobes' appear macroscopically and therefore provide a bias towards thinking they might be crucial in organ's function. It's just a spontaneous embriological and growth process for arrangement of that praticular tissue in the organism and space. Take for example varoius deformations that occur when different physical forces press onto to tissue.

The only justification for lobe-importance which seems palusible to me is by  following this polimerization of tissues (structures you call 'lobes'), into organs in case of losing a part of an organ (i.e. lobe); the total function isn't compromised qulaitatively, only quantitatively. If you'd have a single large organ (such is the brain or heart), by damaging a part of it it is substantially compromised, whereas the liver or lung can whitstand a larger functional injury. But that seems to be the consequence of the organization, not the cause of 'lobization'.

Very Interesting..

Interesting topic indeed

The lobes of the lung are bounded by impermeable fissures, which serve a 'containment' function in helping to keep a problem (for example, infection) localized to that region. This would seem likely to have been a strong survival advantage in the pre-antibiotic era. There might, therefore, be an evolutionary explanation of their development. By the way, why do we have two lungs?

Hi John

Your argument makes sense: modular design is a feature that renders biological systems more robust. I guess this line of reasoning works well for the lung, as the lung is not sterile and probably more prone to infections that most other organs. But, why then stop at only 2 (for left) and 3 (right) lobes? Why not say 7 lobes (like cats and dogs)? And also, why then not also ‘lobe-ing’ of other organs such as the kidneys? (Kidneys are probably not as often infected as the lung, but urinary tract infection can often also spread up).

About waving two lungs, I suspect that a partial answer might be because bilateral symmetry is an ancestral trait (i.e. we might be descendants of an animals that use a bilateral body plan for lungs and other organs). This however just shifts the question: why did our ancestor had two lungs.