Part 1 - Filtration

Today, we purchased a new coffee maker. It gave me an idea about how to explain the kidney. The coffee maker works by separating the flavored minerals in the ground beans from the actual bean itself. It works by a method we are all familiar with – filtration. In the process of filtration, there is a membrane and energy. The energy drives products that are small enough, to cross the membrane. Others that are too large to slide through the membrane’s tiny pores are left behind. The coffee maker uses water as the fluid and gravity as the source of energy. In the body, we have around 2 million filters, 1 million in each kidney. When blood is pumped by the heart past these filters, minerals, and solids such as red blood cells and proteins, are separated.

The coffee we drink is really a filtrate of this process. In the body, the filtrate is recycled so that we do not lose all of the minerals. 

The body is like a machine. After all the parts have been assembled it performs its daily functions, but as the parts wear out they are replaced. Cells are constantly turning over warn out parts and replacing them. These worn-out parts are broken down and eliminated. 

Blood is pumped from the heart through blood vessels that become smaller and smaller. The vessel that enters the glomerulus or filter is known as the afferent arteriole. The arterioles transition to capillaries and are surrounded by a basement membrane. Attached to the other side of that membrane are epithelial cells with projections known as foot processes. These are the podocyte cells. The filtrate enters Bowman’s capsule and travels to the proximal tubule. After filtration, the blood leaves the glomerular capillaries through the efferent arteriole.