Blood has been called the river of life, transporting various substances that must be
carried to one part of the body or another.
On screen is a cross section of an artery with cells -- mostly red,
but a few purple and white ones -- flowing through it toward the audience.
Red blood cells are an important element of blood.
Their job is to transport oxygen to the body's tissues in exchange for carbon dioxide,
which they carry to the lungs to be expelled.
The screen image changes to a skeletal view of the pelvis
with the upper thighbones and lower spine.
Red blood cells are formed in the red bone marrow of bones.
A cutout of a small section of the upper thighbone enlarges.
Inside it is a large round purple stem cell.
Stem cells in the red bone marrow are called hemocytoblasts.
They give rise to all of the formed elements in blood.
The stem cell gets smaller and more compact.
Its deep purple tightens and then erupts from the cell.
If a stem cell commits to becoming a cell called a proerythroblast,
it will develop into a new red blood cell.
The light purple cell turns red and deflates in the middle.
The formation of a red blood cell takes about 2 days.
Two more purple cells form next to the blood cell, then transform into red blood cells.
The body makes about two million red blood cells every second!
The screen image changes to a white glass container on a blue background.
Blood is made up of both cellular and liquid components.
If a sample of blood is spun in a centrifuge, the formed elements
and fluid matrix of blood can be separated from each other.
A layer of red blood forms in the bottom of the container.
Blood consists of 45% red blood cells,
A thin, light blue layer of white blood cells forms on top the red layer.
That's followed by a thicker yellow layer on top.
less than 1% white blood cells and platelets, and 55% plasma.