The integumentary system is the physical system that forms the barrier between the external environment and the internal systems of the body. In humans, this system consists of skin, hair, nails, and ...

The endocrine system is the name for the glands that produce hormones in a person’s body. These glands include the thyroid gland, pituitary gland, and adrenal gland. The endocrine system produces ...

Bones are a key part of your skeletal system. They’re lightweight structures that are incredibly strong. A normal adult has around 206 bones in their body. Your bones join together to make your ...

When a person is at rest, meditating or reading a book, the parasympathetic nervous system is at work. Also known as the "rest and digest" system, the parasympathetic nervous system is responsible for ...

An organ is a group of tissues that work together to perform a specific task in the body, such as digesting nutrients or producing chemical messengers that enable brain cells to communicate. Although ...

Although most known for its effect on the lungs, cystic fibrosis is a far-reaching condition that affects most of the body’s systems. Cystic fibrosis is a chronic condition that’s primarily associated ...

The subcutaneous layer is the deepest skin layer. It protects a person’s body and keeps it warm. This layer also provides insulation and protection for vital tissues such as muscles, bones, and organs ...

Most of the laws of physics are the same whether you run the clock forwards or backwards. A planet that revolves around a star appears to obey the same rules as it would if you recorded it and played ...