Physics and the Human Body: Fetal Brain Development

     I've wanted to go to medical school for the longest time, and I never truly understood why physics was a pre-requisite until actually taking a physics course in college. My studying for the MCAT this semester has further shown me that physics is extremely relevant to the human body and how it functions. Thus, I was not surprised to find that physics plays an important role in the development of our brains when searching for a news article. During development, the fetal brain is completely smooth and not at all like a more developed brain that has many folds. You may ask, well how does the brain develop into what we imagine when we hear the word "brain" then? The answer has been found to lie in the forces we have looked at so far in class.

    Tallinen et al. (2016) created a 3D printed model of a fetal brain in order to mimic how the brain folds during development. The authors describe how the folding of the brain is important to fit more tissue into a relatively small space but note that the way in which this happen was not well understood. The 3D printed brain was made of gel that expands in solution to mimic a growing fetal brain. As the gel expanded upon contact with solution, the "brain" compression of the gel occurred and formed folds similar to real life development. The compression of the tissue into the shape of a brain results from compression forces acting on the brain in response to increased volume of the tissue. The gel acting as white matter exerts compression forces as the gel mimicking the cortex expands. Therefore, the cortex must fold and reduce pressure while growing as a result of the forces applied by the surrounding tissues. This can be related to Newton's laws of forces because the growing tissue exerts a force on the surrounding tissue. The tissue the brain comes into contact with then exerts a force back on the brain during development leading to the creation of these folds. 

    Interestingly, the 3D printed brains developed very similarly to real life fetal brains at the same developmental stage. These results suggest that these forces are mainly responsible for the structure of the brain observed in vivo. The authors state that this finding can be important in better understanding the development of neurological disorders that impact the size of the brain. They also discuss how cortex thickness could impact the compression forces and brain development. Thus, an understanding of physics is essential to understanding many biological processes. 

References

Maldarelli, C. (2016, February 3). You Have Basic Physics To Thank For Your Brain’s Funky Folds. 

Popular Science. https://www.popsci.com/thank-physics-for-your-brains-funky-folds/

Tallinen, T., Chung, J. Y., Rousseau, F., Girard, N., Lefèvre, J., & Mahadevan, L. (2016). 

On the growth and form of cortical convolutions. Nature Physics, 12(6), 588–593. 

          https://doi.org/10.1038/nphys3632