Final answer:
Extramedullary hematopoiesis occurs when blood cell production happens outside of the bone marrow, such as in the liver.
Step-by-step explanation:
In an adult, when hematopoiesis occurs in the liver, it is referred to as extramedullary hematopoiesis. This means that the production of blood cells is happening outside of the bone marrow. The liver is one of the organs involved in generating the formed elements of the blood.
When hematopoiesis occurs in the liver in an adult, it is called extramedullary hematopoiesis. This process refers to blood cell formation outside the medullary cavity of adult bones. Under normal conditions, hematopoiesis takes place in the red bone marrow; however, when a disease such as bone cancer damages the bone marrow and inhibits hematopoiesis, the body can initiate hematopoiesis in the liver or spleen.
Physiologic EMH occurs during embryonic and fetal development; during this time the main site of fetal hematopoiesis are liver and the spleen.
Pathologic EMH can occur during adulthood when physiologic hematopoiesis can't work properly in the bone marrow and the hematopoietic stem cells (HSC) have to migrate to other tissues in order to continue with the formation of blood cellular components. Pathologic EMH can be caused by myelofibrosis, thalassemias or disorders caused in the hematopoietic system.