Chapter 17 is an in depth view of the blood within the human body.  Above is an image of what is called a Hematocrit.  A Hematocrit is the sepration of blood after it has gone through a centrifuge.  Above you can clearly see the 3 different layers of blood.

The first layer is the Plasma which is 55% of the blood volume.  Plasma is divided into to different parts.  90% of plasma is water.  The second part consists of 10% is a mixture of gases (specifically Oxygen and Carbon Dioxide).

The second part is the Buffy Coat.  It consists of Leukocytes and Platelets.  Leukocytes are white blood cells (WBC) that protect the body.  Platelets are fragments of blood cells that are used for blood clotting.

The third part is Erythrocytes which constitutes for roughly 45% of the hematocrit.  Erythrocytes are red blood cells (RBC).  They are small, biconcaved shaped, anucleated cells that are used to transport oxygen to cells and tissues throughout the body.

**Both the buffy coat and the erythrocytes make up the formed elements layer of the hematocrit.