Final answer:
Hematopoiesis after the age of 25 predominantly occurs in the red marrow located within the pelvic bones, vertebrae, sternum, and proximal epiphyses of long bones. The liver and spleen also have the potential to produce blood cells if bone marrow fails.
Step-by-step explanation:
After the age of 25, hematopoiesis in the human body primarily takes place in the red marrow, which is the connective tissue within the spaces of spongy (cancellous) bone. Adults have hematopoiesis largely occurring within the pelvic bones, the vertebrae, the sternum, and the proximal epiphyses of the femur and humerus. In cases where bone marrow fails due to disease, extramedullary hematopoiesis can occur, which engages the liver and spleen as additional sites for creating blood cells.
The hematopoietic process is driven by hematopoietic stem cells located in the bone marrow, where they differentiate into various blood cells after being exposed to hemopoietic growth factors. These essential cells can self-renew and also generate a variety of differentiated blood cells, thereby ensuring the continual replenishment of the blood. Red bone marrow is responsible for generating billions of red blood cells, white blood cells, and platelets daily to maintain healthy bodily functions.