Which ion is essential for blood clotting to occur?

In adults, the ______________ is the only site of red blood cell production, and the primary site of white blood cell formation. 

The green structure indicated here is called the __________.

The green structure indicated here is called the __________.

This image depicts evidence of  __________.

The indicated indentation is called the __________.

The indicated structure is known as the __________.  

The outer layer covering this organ is known as the __________.

The indicated indentation is called the __________.

The outer layer covering this organ is known as the __________.