The Circulatory System of the Cat: Red Blood Cells

A cat's heart beats 110 to 140 times per minute, sending blood rushing through the body in a mere 11 seconds. And though the circulatory system has many purposes, none is as important as sending oxygen throughout the body. And this is accomplished through the most numerous cell is the cat's body -- the red blood cell.

Red blood cells are so numerous in the cat that I'm not even going to bother typing out the numbers. I don't like seeing that many 0s in a row. But there are a lot and they only live for two to six weeks before they must be replaced. Thankfully, the cat's body is constantly making new red blood cells. This starts when tissue, anticipating a shortage of oxygen, sends out a hormone (erthropoietin) through the bloodstream and to the bone marrow in red blood cell construction sites.  The hormone signals primitive cells to begin to grow.

The primitive cells develop into rubriblasts, which are sort of like adolescent red blood cells. Each of these rubriblasts divides into two separate cells, both of which continue dividing. Eventually, these two red blood cells (abbreviated to RBCs) become 16. The RBCs are composed mainly of water and hemoglobin. Each hemoglobin molecule contains four iron atoms. This allows for the transportation of over 1 billion molecules of oxygen throughout the cat's body.

The cells continue to grow until hemoglobin accounts for 95% of the dry weight of the red blood cell. This takes about three days (out of a six-day RBC production process). At this point, the cell ejects its nucleus in an act of self-sterilization. This leaves the cell free of all distractions. The cell can now work, and work it does. In fact, RBCs work themselves to death as they carry oxygen to the various organs of the body.

Even the shape of the red blood cell is important. It looks a little like an unperofrated doughnut and it is very flexible. So flexible that an RBC can squeeze through the smallest capillaries to deliver fresh oxygen and take away toxic carbon dioxide.

Without the all-important red blood cell, the cat would not be able to function. It is not an exaggeration to say that the red blood cell is the single most important cell in the circulatory system of the cat.