Curious youngsters: Do all animals have stomach buttons?

Do reside lizards have navels and reside reptiles have umbilical cords? – Gaelle, 12, Bristol, UK What an attention-grabbing query.

The navel or stomach button is technically often called navel or navel.

People have navels as a result of they had been related to their moms by the umbilical wire earlier than they had been born. That is the tube that delivers vitamins to a fetus, referred to as the fetus, and removes waste. It runs from the placenta (the maternal organ that gives a supply of meals and oxygen) to the stomach of the embryo.

As soon as the child is born, she or he can soak up milk and different vitamins by the mouth, and the umbilical wire is now not wanted. The umbilical wire will shrink and fall off after a number of weeks. So the navel is mainly a scar from the place the umbilical wire was connected to the child’s tummy.

People are a part of a gaggle of animals referred to as mammals, and infants of different mammals equally develop inside their moms and get their nourishment from the placenta by the umbilical wire.

The human navel is kind of massive, so it’s fairly noticeable. They’re additionally present in massive mammals reminiscent of dolphins, orangutans, and whales. Scars don’t kind massive holes and are sometimes lined with hair or fur, though they’re additionally present in small mammals reminiscent of cats, canine, and mice.

Nonetheless, different animal infants develop in numerous methods. Animals are literally divided into three teams in response to how the embryo develops.

The primary kind is the sort now we have already talked about. That is when the embryo develops contained in the mom and will get the meals and oxygen it wants from the placenta.

The second kind is egg-laying animals. These animals, together with reptiles, birds, amphibians and a few mammals, would not have a placenta to supply meals for his or her infants.

animal that lays eggs

Animals that develop in eggs somewhat than within the womb nonetheless want meals. However as an alternative of getting this from the mom, the meals resides within the egg in a particular space often called the yolk sac. please don’t worry. There aren’t any infants within the eggs you eat. It’s an unfertilized egg. In different phrases, it by no means grows right into a child.

A fertilized egg embryo can not drink the extremely nutritious egg yolk by mouth, simply as a human embryo can not drink till it’s born.

As an alternative, the embryo contained in the egg is connected to the yolk sac by a small feeding tube referred to as the yolk stalk that goes into the embryo’s tummy.

The yolk stem resembles the umbilical wire and dries out as it’s now not wanted as soon as the child hatches. So, sure, animals born from eggs have stomach button scars, however they’re normally so small that they’re troublesome to see.

However what about reptiles reminiscent of lizards and snakes? They do not have a placenta like mammals, however they typically do not lay eggs. They belong to his third group of animals.


In these animals, the embryo develops contained in the egg, which stays within the mom’s physique. These animals are referred to as ovoviviparous animals. A mom could lay an egg simply earlier than her child is born. That is what the Australian mammal, the platypus, does. In lots of circumstances, the eggs hatch contained in the mom’s physique, leading to reside infants. That is how some sharks and rays are born.

Reptiles reminiscent of snakes and lizards are sometimes ovoviviparous. They’re born alive however aren’t connected to their moms through the umbilical wire. As an alternative, they acquired their diet by the yolk sac, through the yolk stalk.

Sure, all animals have navels. Even dinosaurs had navels! Lately, a fossil of an in depth relative of Triceratops was discovered with a umbilical scar similar to that discovered on fashionable crocodiles.

Nonetheless, animals connected to the mom through the umbilical wire usually have a lot bigger navels than animals connected to the yolk through the stem of the egg.

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