Final answer:
Reticulocytes mature into mature red blood cells in the bloodstream, a process that is part of hematopoiesis and typically completes within 1 to 2 days.
Step-by-step explanation:
Reticulocytes complete their development into mature red blood cells in the circulation. Reticulocytes are immature red blood cells that are released into the bloodstream from the bone marrow. They mature into erythrocytes, or mature red blood cells, as they circulate, a process that takes about 1 to 2 days. These erythrocytes then circulate in the blood for an average of 120 days. During their maturation, reticulocytes expel their nucleus and lose most other organelles before becoming fully mature red blood cells. This process is a part of hematopoiesis, more specifically erythropoiesis, which is the production of red blood cells.
The presence of reticulocytes in the blood is often used as an indicator of the bone marrow's ability to produce red blood cells and can be monitored in conditions such as anemia or during recovery from certain treatments.