Tag Archives: skin

Dolphin Magic or Dolphin Muscle?

Because of the film Bee Movie, many people at one point were intrigued by the idea that bumblebees should not physically be able to fly due to their large bodies and tiny wings. But, they fly anyway. Technology is advanced enough to study bee wing movement and determine that they produce enough lift to allow them to fly, disproving the previous notion. Similarly, Gray’s Paradox for a long time inferred that dolphins should not be able to swim nearly as fast as they do. But, they still consistently swim at speeds over twenty miles per hour. It was not until recent history that advancements allowed researchers to determine why they are able to reach such high speeds.

Gray’s Paradox

All the way back in 1936, Sir James Gray observed the high speeds dolphins could reach in the ocean. He calculated an approximation of the amount of power the dolphins would need to produce to sustain these speeds, based on the drag force on the dolphin as it travels through the water. Gray compared this to the amount of power he expected the dolphin to be able to produce. In order to compute this, Gray used muscle power data from oarsmen. When he compared the muscle mass of these oarsmen compared to dolphins, he determined that the power dolphins could produce was only about one seventh what was needed to travel at the high speeds of which they are capable.

Force Diagram, showing that the same forces that the swimming mammal applies to water are applied back on it. Allows observation of max speed to determine these forces.
This diagram shows that the drag force, D, thrust force, T, and net axial force, Fx, must be equal for the swimmer and the fluid. The lateral velocity, u, can be used to determine the resulting drag force, allowing researchers to estimate how much thrust is needed. Credit: [2]

And now we have arrived at Gray’s Paradox. What allows dolphins to move so quickly? To Gray and other researchers for most of a century, this was a mystery. If the assumptions they had made were correct, that would mean dolphins have some way of travelling through water more efficiently than was thought to be possible. This sparked a large amount of speculation into how dolphin skin could reduce the drag force of the water, which was originally believed to be the way Gray’s Paradox would be resolved.

Answering Questions while Creating More

Finally in 2008, Timothy Wei’s research team was able to definitively disprove Gray’s Paradox. He set up an experiment that would allow the force that dolphins exert to be measured. This mainly consisted of having dolphins swim through a curtain of bubbles in a tank. By recording at high resolution the movement of these bubbles as the dolphins swam by, the researchers determined the speed of the water around the dolphin as it traveled. With this information, Wei’s team showed that dolphins are able to produce over 300 pounds of force at one moment, and over longer periods of time 200 pounds of force. This is approximately ten times more force than Gray estimated.

Wei’s findings resolve Gray’s paradox by showing that dolphins have the ability to produce sufficient power from their tail movement to overcome the strong drag force of the water as they move at high speeds. However, this does not explain how dolphins produce so much power with their amount of muscle mass, which is still being examined. One idea is that this is caused by anaerobic muscle fibers that behave in different ways than in humans, and allow more power to be generated than Gray expected.

Future Plans: Investigating Force Generation

Timothy Wei plans to continue examining force generation in the swimming of other marine animals. This has the potential to provide more understanding of how marine animals evolved in their swimming aptitude. On the level of microbiology, this research could improve understanding of how dolphin and other animal muscles can perform such high levels of power generation over sustained periods of time.

Additional Reading and Sources

Why your scar tissue isn’t an issue

What do knee scrapes, adolescent acne, and paper cuts have in common? They all have the potential to leave a nasty scar. For people who have undergone trauma that results in serious wounds, especially on the face, scar aging is a serious concern. What are scars, and why does scar tissue tend to look different than regular skin as aging occurs?

In 1861, Karl Langer began observing the nature of the skin’s tensile properties. He cut small, circular holes into cadavers, and looked to see where on these holes the skin pulled the most. From these experiments, he developed “Langer’s Lines,” which he asserted were lines of tension all around the human skin. Later, Borges noticed that Langer’s lines only applied to cadavers, and began to perform similar experiments on live people to see if he saw different results. He pinched the skin of live people, and then saw how the direction of pinching impacted the length of the wrinkle formed. From these experiments, he identified RSTL, or relaxed skin tension lines. More and more researchers after Langer and Borges investigated the “tension line” phenomena, and they all noticed the same thing: wounds cut across these lines always led to nastier, uglier scars than wounds parallel to the tension lines. Why would that happen?

Figure 1 outlines the differences of Langer's lines, Kraissl's lines, and Borges's RSTL on the human face.
Image courtesy of MedMedia

To answer this question, let’s first identify the cellular mechanisms at work during healing. According to David Leffell of the Yale School of Medicine, there are three key stages of scar formation. The first stage of scar formation is inflammation. This happens right after the wound is incurred. Blood flows to the site, and tissue called granulation tissue begins to form at the base of the wound. Next is proliferation, when that granulation tissue helps the surrounding fibroblast cells to duplicate as quickly as possible. Fibroblasts are very important; they are the cells that produce collagen, a key protein in tissue formation. During proliferation, more and more fibroblasts fill the site, and they begin rebuilding the collagen networks for new skin. The final stage of scar formation is maturation/remodeling, when fibroblast levels decrease slowly as fresh tissue is rebuilt.

This figure shows each stage of wound healing, as is outlined by the supporting paragraph.
Image courtesy of biodermis.com

Because scars are formed differently than regular skin, they also tend to age differently. Normal consequences of skin aging can be seen around us in older people every day. As you may notice in your parents and grandparents, older skin tends to be dry, rough, wrinkly, and sometimes discolored. While these changes can also occur within scar tissue, the biggest factor in scar tissue aging is the difference in the rate of skin cell renewal. Skin cell renewal occurs when new skin cells travel from the basal layer of the skin up to the epidermis. Scar tissue’s renewal rate is different than normal skin’s renewal rate. This is why adults recover from wounds more slowly than young people – there is a greater difference between their cell renewal rates. The age at which the scar was formed, and the quality of the care provided, are critical in evaluating how well the scar will age.

If you’re interested in learning more about how that cut on your hand might heal and age, watch this video from TED-Ed, or for more detailed reading, check out this article.

Can we 3D print our own skin?

Can you imagine a world where amputees receive replacement limbs which are able to detect temperature and pressure like an actual limb? How about a world where when you get a cut, you can 3D print some of your own skin to patch the wound?

To the average citizen, this might seem like something out of a science fiction movie. To researchers at the Graz University of Technology, the Wake Forest School of Medicine, and the Universidad Carlos III de Madrid, this is a reality that they are helping bring ever closer. Both of these scenarios are discussed in a recent article by Mark Crawford, who investigated the recent breakthroughs in 3D printing human skin and creating sense-sensitive artificial skin.

photograph of an arm reaching into the sky to feel the rain in the palm of their hand
photo by Alex Wong on Unsplash

At the Graz University of Technology, researchers are working on creating an artificial skin that can sense temperature, humidity, and pressure. Currently, artificial skins can measure one sense at best, but with the use of the nanoscale sensors that these researchers are developing, sensing all three at once could be possible. This is achieved through the materials that the nanosensors are created out of: a smart polymer core and a piezoelectric shell. The smart polymer core can detect humidity and temperature through expansion, and the piezoelectric shell detects pressure through an electric signal that is created when pressure is applied. With this technology, prosthetics could be made which could allow the wearer to retain some of their lost senses.

At the Wake Forest School of Medicine, researchers have created a handheld 3D printer which produces human skin. This device could be used to replace skin grafts, as it can apply layers of skin directly onto the wound. Through the use of bioink, this handheld printer can create different types of skin cells. After scanning the wound to see what layers of tissue have been disrupted, it can print the appropriate skin needed to correct the injury.

Photograph of the 3D skin printer created at the Universidad Carlos III de Madrid, which is still in its prototype phase.
modified from Crawford, ASME January 2019

At the Universidad Carlos III de Madrid, researchers are also 3D printing human skin using bioink. They are creating both allogenic and autologous skin to create the optimal skin, which is a combination of the patient’s own cells and cells created from a stock. Although they have managed to print functioning skin in its natural layered state, it is tricky to create the cells in such a way that they do not deteriorate.

It is also tricky to correctly deposit the product. To illustrate, more research needs to be done on the mechanical properties of artificial skin before it could be used on humans. The artificial skin must be able to stretch and react to tension in a similar manner to the real skin it will be connected to. Additionally, researchers must figure out how to safely send the signals the artificial skin is detecting to the brain.

Overall, both advancing artificial skins and 3D printing human skins could largely impact humanity. Even though we have yet to use these skins on people, they are already being used in industries, such as L’Oreal, to limit testing on humans and animals. Already, these skins are being used on robots, as seen in this video, to help prepare the skin for human transplant:


Interested in seeing more? Check out some more articles on the advancement of artificial skin from Caltech and Time.

Cause and Management of Stretch Marks

Stretch marks. How are they caused? Can they even be treated?

Stretch marks can happen to anyone, of any age, so these questions are important to many. In short, our skin is made up of both collagen and elastin, two elements that support and shape our skin through their natural elasticity. This elasticity, however, does have its limits. And when that breaking point is reached, the collagen and elastin rupture, leaving behind scars many know well – a stretch mark.

Difference between normal skin tissue and stretch mark tissue
From Ud-Din, McGeorge, and Bayat, Journal of the European Academy of Dermatology and Venereology 2015

Stretch marks are caused when skin expands or shrinks at a more rapid pace than the collagen and elastin can accommodate, resulting typically in raised scars that can appear rather inflamed at first. Over time, however, these stretch marks may fade, nearly matching one’s natural skin tone, and usually fall below the surface of the skin. This results in the feeling of a slight indentation when touching older stretch marks.

Like all scars, stretch marks are permanent. But this does not mean that they cannot be treated. There are many treatments available to diminish the visual effect of a stretch mark; not all of them are effective, and some seem not to work at all.

Collagen’s elasticity is controlled by the body’s  cortisone levels, which are commonly associated with episodes of high stress. Basically, heightened cortisone production may decrease the skin elasticity, suggesting that reducing one’s stress may be the most cost-effective and cheap treatment for stretch marks.

Researchers S. Ud-Din, D. McGeorge, and A. Bayat put these post-stretch mark treatments to the test in their paper, focusing on three topical treatment categories – marketed skin creams and oils, over-the-counter home remedies, and prescription medicines and dermatologist procedures.

These topical treatment methods are mainly marketed at increasing collagen production with both hydrating and anti-inflammatory traits. Ultimately, testing yielded mixed results about the efficacy of these treatments. Since participants both massaged their scars and used a topical treatment, the observed improvements to stretch mark appearance could be tied to either of these. Ultimately, however, the researchers did conclude that the age of the scar plays a role in treatment effectiveness, as younger, newer scars were more responsive to treatments.

Beyond these topical treatment methods tested, there are many other dermatological procedures designed to reduce the appearance of stretch marks, including chemical peels, laser therapy, and microdermabrasion. Chemical peels and microdermabrasion focus on removing layers of skin to expose new, non-scarred tissue underneath the stretch mark. And laser therapies are divided into two categories: those that stimulate collagen production and those that promote melanin production (so that the scar tissue matches the natural skin). While these dermatologist procedures can be more effective than the topically applied treatments, they are often expensive and are not guaranteed to be effective. Additionally, dermatologists often combine several procedures, eliminating this treatment for those with cost constraints.

All in all, there are no sure-fire ways to prevent stretch marks, but certain practices do demonstrate that one can prevent stretch marks or at least lessen their appearance fairly cheaply and effectively without any of the products and procedures detailed above. By maintaining a healthy weight, one may avoid the rapid weight loss or gain commonly associated with stretch marks.

For more information, check out these articles on Healthline and AAD.

Scleroderma and Raynaud’s Phenomenon: Cold Weather’s Influence on Skin

Anyone who is familiar with winters that are mainly at temperatures in single digit range knows how crucial gloves are to surviving the tough, frigid weather. If one was to go outside without them, their hands become extremely pale (or sometimes almost blue) and, once back inside, take a bit of time to get back to normal. It’s a tough life, I know, but people with a scleroderma have an even harder time surviving the winter. What is scleroderma, you ask? Scleroderma is an autoimmune disease that causes skin and internal organs to thicken, and if that wasn’t tough enough, a good chunk of people with it also experience secondary Raynaud’s phenomenon, which is an exaggerated vasoconstriction of arterioles in response to cold weather and causes a drop in blood flow. The main, visible outcome from this disease is how the skin whitens and swells. Problems must ensue from the combination of thick skin and lack of blood flow to the extremities, right?

Raynaud's Phenomenon in ring finger
Thomas Galvin [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Modified from Balbir-Gurman, Denton, Nichols, Knight, Nahir, Martin, and Black, Annals of Rheumatic Diseases 2002

With the thickening of skin, certain properties of skin will noticeably alter when a person has scleroderma. In a recent study, researchers from multiple backgrounds used a new suction device to compare mechanical properties of skin of patients with scleroderma and healthy patients. In the experiment, the researchers used a modified Rodnan skin score to observe skin involvement. This way of testing focuses on how easy it is to pinch skin and witness how it folds. The skin was tested on 3 parts of the body including back, forearm, and shoulder in order to see how the skin not only differs between patients, but to see how different areas have different properties due to activity and use of those parts of the body. To test the skin of the patients, the new suction device used, the BTC-2000, also proved beneficial due to its non-invasive nature that could be used more frequently to produce data. The biomechanical properties of skin depend greatly on the dermis, or skin thickness, due to the properties being derived from witnessing skin response to pressure and stress. The study that these researchers performed supported the idea that mechanical properties of skin are altered negatively when a patient has scleroderma. The major properties that were observed were less extensibility, stretchiness, and a larger resistance to stress.

So the struggle to go outside in the winter is even bigger for people with scleroderma. But in their case, the damage brought on by cold weather is greater and typically more permanent. Similarly, if this is how the disease influences the mechanical properties of the outer skin, the potential impact on internal organs is intriguing.