Diaphysis facts for kids

Quick facts for kids Diaphysis
A long bone, with the diaphysis labeled at right.

The diaphysis (say it: dy-AF-iss-iss) is the main, middle part of a long bone. Think of it as the long shaft of a bone, like the middle part of your thigh bone (femur) or arm bone (humerus). It's super important for making your bones strong and helping you move!

This part of the bone is mostly made of a tough, dense material called cortical bone. Inside the diaphysis, there's a hollow space called the marrow cavity. This cavity usually holds bone marrow, which can be red or yellow. Red marrow helps make blood cells, while yellow marrow stores fat.

What is the Diaphysis?

The diaphysis is the long, central part of a long bone. It's like the main body of the bone. This strong, tube-shaped section gives the bone its length and helps it support your body's weight. It's built to be very strong and a bit flexible.

What's Inside the Diaphysis?

The outer layer of the diaphysis is made of compact bone. This bone is very dense and hard, like the outer shell of a tree trunk. It gives the bone its strength and protects the inside.

Inside this strong outer layer is a space called the marrow cavity. This cavity is filled with two types of marrow:

• Red marrow: This is where your body makes new blood cells, including red blood cells, white blood cells, and platelets.
• Yellow marrow: This type of marrow is mostly fat. It acts as an energy reserve for your body.

How Bones Grow: Ossification

The diaphysis is also where a big part of bone growth happens. This process is called ossification. It's how cartilage (a soft, flexible tissue) slowly turns into hard bone. This is especially important when you are growing up, as your bones get longer and stronger.

Additional images

• 
• 

  Long bone

See also

• Epiphysis
• Metaphysis