Squirrels have relatively typical rodent anatomy as they have long tails, four limbs and large incisors. Aside from their large front teeth, adult squirrels have 20 other teeth that allow them to chew food. The teeth of squirrels grow constantly, and the squirrels' constant gnawing activities help to keep the teeth from growing too large. Squirrels have four toes on each front foot, while their back feet have five toes.
Squirrels are covered in thick fur, which helps to prevent injuries and insulate them from the cold. Additionally, because the fur is usually brown, gray or black, it helps them to hide from predators. Some squirrels have furry tufts on their ears, although the function or purpose of the tufts is not understood. Squirrels have long, bushy tails, which help them to maintain their balance while climbing through trees. Additionally, squirrels use their tails for communication.
Internally, squirrels have anatomy that is similar to most other vertebrates. Their mouth leads to their esophagus and windpipe, which connect to the stomach and lungs, respectively. The stomach connects to the small intestine, which in turn connects to the large intestine. Additionally, squirrels possess a brain, a liver, kidneys, a pancreas, a spleen, a gall bladder and reproductive organs.