Phases and Regulations of Hematopoiesis

Summary:

Hematopoiesis, the process of blood cell formation, is a complex and fascinating phenomenon that plays a crucial role in maintaining the body’s immune system and oxygen-carrying capacity. It involves the production of various types of blood cells, including red blood cells (RBCs), white blood cells (WBCs), granulocytes, monocytes, and lymphocytes.

The process of hematopoiesis occurs in three distinct phases. The first phase, the mesoblastic phase, occurs during the early stages of fetal development, specifically from 0 to 2 months in the yolk sac. During this phase, primitive blood cells are formed and begin to differentiate.

The second phase, the hepatic phase, occurs from 2 to 7 months of fetal development, primarily in the liver and spleen. During this period, the liver and spleen are major hematopoietic organs, producing blood cells to support the growing fetus.

The final phase, the myeloid phase, starts around 7 months of fetal development and continues throughout life. In this phase, the bone marrow becomes the primary site of hematopoiesis. In infants, all bone marrow sites are involved in blood cell production. However, as individuals transition into adulthood, specific bone marrow sites, such as the pelvic bones, femur, vertebrae, sternum, and ribs, take over the responsibility of blood cell formation.

The regulation of hematopoiesis is a tightly controlled process orchestrated by various hematopoietic growth factors. Different cell types, including fibroblasts, endothelial cells, macrophages, fat cells, and T lymphocytes, produce these growth factors. They play a crucial role in stimulating blood cell proliferation, differentiation, and maturation.

Excerpt:

Phases and Regulations of Hematopoiesis

Hematopoiesis
Definition
The phases of hematopoiesis
Regulations of hematopoiesis ( growth factors)

Definition
Hematopoiesis
The formation of blood cells. Examples of RBCs, WBCs, granulocytes, monocytes and lymphocytes.

Phases Of Hematopoiesis
Three phases mesoblastic, hepatic and myeloid phase
Mesoblastic: In fetus 0-2 months in York sac.
Hepatic: 2-7 months in the liver and spleen.
Myeloid phase: 7- 9 months bone marrow
In infants: all bone marrow
In adults: specific bone marrow, such as pelvic bones, the femur, vertebrae, sternum, the ribs.