Why don’t cats and dogs have bellybuttons?

Introduction: The Curious Case of Belly Buttons in Cats and Dogs

When we think of belly buttons, we often associate them with mammals, including humans, cows, horses, and even whales. However, you may have noticed that your furry friends, cats and dogs, don’t have belly buttons like we do. This raises the question, why don’t cats and dogs have belly buttons? The answer lies in their evolutionary history, developmental biology, and unique reproductive physiology.

Evolutionary History: Absence of Placental Attachment

Cats and dogs belong to the group of mammals known as placental mammals, which means their young develop inside the mother’s uterus and receive nutrients and oxygen through the placenta. However, unlike humans and other placental mammals, cats and dogs have a different type of placental attachment. In cats and dogs, the placenta does not penetrate deeply into the uterine wall and instead creates a small area of contact, known as a diffuse attachment. As a result, the placenta is not separated from the uterus during the birthing process, and the young are born with a functional respiratory system, eliminating the need for a belly button.

Developmental Biology: Different Formation of the Umbilicus

The formation of the umbilicus, also known as the navel, in cats and dogs differs from that in humans. In humans, the umbilicus is created when the umbilical cord, which connects the fetus to the placenta, is cut after birth. The remaining stump of the cord then dries and falls off, leaving the belly button. In cats and dogs, however, the umbilical cord does not detach from the young after birth, and the stump eventually shrinks and disappears, leaving no visible navel. This is because the umbilical cord in cats and dogs is not needed to transport nutrients and oxygen during fetal development, as the placenta provides these functions.

Stay tuned for the next headings to learn more about the unique reproductive physiology of cats and dogs, the role of the umbilical cord in fetal development, and the differences in umbilical cord attachment between canines and felines.