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From Developing Limbs, Insights That May Explain Much Else

For developmental biologists, the development of limbs captures all that is marvelous about embryos: how a few cells can give rise to complicated anatomy. In fact, biologists understand the development of the limb much better than any other part of the body.

They have been experimenting on developing limbs for almost a century, and today they are figuring out how limb-building genes are organized into a network that almost always manages to build the same structures with the same shape.

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 We Are Upright-Walking Cats: Human Limbs as Sensory Antennae During Locomotion

Humans and cats share many characteristics pertaining to the neural control of locomotion, which has enabled the comprehensive study of cutaneous feedback during locomotion. Feedback from discrete skin regions on both surfaces of the human foot has revealed that neuromechanical responses are highly topographically organized and contribute to “sensory guidance” of our limbs during locomotion.

Articles of Interest

Why You Should Never Ignore Swelling in Your Arms or Legs

From pregnancy to deep vein thrombosis to broken bones to medication side effects, there are many reasons you might notice swelling in your arms or legs. While you could be tempted to brush off swelling, you should know why you have swelling so you can take the appropriate steps to mitigate it.

71% of Americans Believe That by 2050, Artificial Limbs Will Perform Better Than Natural Ones

The year 2050 may well bring advances in medical science and in medical technology; the bigger question -- the one suggested by the telling phrase "the average person" -- is whether those advances will be distributed across the population.

Development and the evolvability of human limbs

The long legs and short arms of humans are distinctive for a primate, the result of selection acting in opposite directions on each limb at different points in our evolutionary history. This mosaic pattern challenges our understanding of the relationship of development and evolvability because limbs are serially homologous and genetic correlations should act as a significant constraint on their independent evolution.

Going out on a limb: regrowing human limbs is possible, although we can’t yet do it

Knowing it can be done and how to go about it is still a great step.

Humans Are One Crucial Step Closer to Regenerating Limbs

Deer can do it—and we could eventually have the ability, too.

In northern humans, evolution favored shorter bones — but with a painful trade-off

Humans in Europe and Asia evolved to have shorter bones and an increased risk of osteoarthritis, a trade-off that may have helped them in colder climates, Stanford researchers say.

Let’s Regrow Our Limbs, Salamander-Style

The DoD wants to take a page from the axolotl's book.

Life and Limb

Prosthetics research is being fueled by new thinking, new materials, and new demands from those who rely on them.

Long Legs vs. Short Legs. The Surprising Advantages.

Consider your legs for a moment. Are they long? Short? Does it matter? Surprisingly, the length of our legs – whether short or long – offers unique advantages and drawbacks. The good news is that no leg length is “better.”

Our Primate Heritage

Humans may learn to walk by crawling on hands and feet, but it would seem a bit odd if adult humans were walking around on their hands and feet. Unlike other primates, human hands are not used for walking. Because of this they are adapted to other tasks. Our wrists and thumbs are very mobile and are particularly well-suited to making tools. We rely on only our legs for walking and running. Therefore, our legs are relatively longer than our arms. Other primates rely on their arms for movement, like gibbons, and have much shorter legs than arms.

Persuading the Body to Regenerate Its Limbs

None of the developmental biologists I spoke with expressed any doubt that we would someday be able to regrow human limbs. They disagreed only about how long it would take us to get there, and about how, exactly, regrowth would work. Other projects explore growing body parts in labs for transplantation; 3-D-printing them whole, using tissue cells; flipping genetic switches (“master regulators”); or injecting stem cells into residual limbs. The solution may eventually involve a medley of techniques.

Researchers are getting better at regenerating lab animals' limbs. They might regrow human body parts in your lifetime.

Like humans, African clawed frogs can't regrow missing limbs — yet. Scientists have gotten frogs with amputated legs to grow new, leglike appendages in the laboratory, and may be able to help humans regrow limbs in your lifetime.

Study reveals why the brain can’t forget amputated limbs, even decades later

Amputees often report the phenomenon of “phantom limbs”, where they can still sense the presence of missing fingers, hands, arms, feet or legs, and even feel pain where the amputated parts once were. So far, science has had no explanation for this phenomenon.

The current state of bionic limbs from the surgeon’s viewpoint

Amputations and, consequently, prostheses as their most immediate solution, have a long history, starting with hooks and other prosthetic replacements of the Middle Ages, continuing to Ambroise Paré’s mechanical hand, to modern robotic, osteointegrated and bionic limbs.

The limbs

Our upper limbs are free, mobile, and adapted for prehension. Each articulates with the trunk at the sternoclavicular joint. Our lower limbs have to bear the weight of the body when walking, runnning, jumping, or standing. They are united behind to the vertebral column at the sacroiliac joints and in front to each other at the symphysis pubis

The silent “sixth” sense

Proprioception is the body’s mysterious ability to locate our limbs, even in darkness. We’re just beginning to understand it.

What Makes An Arm An Arm And A Leg A Leg?

"This is the first time that a gene has been shown to direct a transformation of forelimb (arm or wing) to hindlimb (leg) structures," said Logan, principal author of the study.

What’s Actually Happening When Part of Your Body Falls Asleep?

You wake up from a hard sleep and think everything is excellent—until you try to move your arm. Instead of responding to the commands of your central nervous system, your forelimb, which has been trapped under a pillow or pinned between couch cushions, stays limp. With growing alarm, you realize your arm is devoid of sensation.

Why Are Our Arms the Same Length?

What would you say if someone asked you, “Why do our limbs grow at the same time and to the same length?” Think about it. Our limbs, such as our arms and legs, grow basically at the same time and to the same length. Why and how do our limbs do this? It seems like a simple question, but if you are having trouble answering, you are not alone. Scientists are still unsure of how exactly human arms, legs, ears, or lungs grow in such a symmetrical way.