This daily doodle represents the development of the Red Blood Cell in the bone marrow. This process is called Erythropoiesis and it is stimulated by decreased oxygen in the circulation, which is detected in your Kidneys. In response to low oxygen, your kidneys make erythropoietin, a hormone that stimulates proliferation and differentiation of the red blood cell precursors in the bone marrow.

Erythropoiesis starts with a proerythroblast, which is on the top left hand corner. The proerythroblast differentiates into a basophilic erythroblast which further turns into a polychromatophilic erythroblast (greyish). The next stage is called a normoblast, which is pink and at day 5-7 of erythropoiesis, the nucleus is ejected out of the cell to make more room for haemoglobin. After the nucleus is gone, this reticulocyte cell still has some lingering RNA and ribosomes which will eventually degrade. Once the cell enters circulation, it is called a Red Blood Cell and it lives for about 120 days.

What causes the colour change? Proerythroblasts are filled with RNA and ribosomes. As the cell matures, it starts to make haemoglobin, which is red. It cells continue to make haemoglobin and once the nucleus is ejected, it stops making RNA. Red Blood Cells are bright red because they are essentially bags of haemoglobin with a little bit of enzymes.

Something else to note: the nucleus condenses (gets smaller and smaller)

Today’s Lectures: 1. Life of the Red Blood Cell 2. Inherited Disorders of the Erythrocyte