Hematopoiesis:

               Hematopoiesis is blood cell production. Your body continually makes new blood cells to replace old blood cells to have a steady blood supply. Hematopoiesis starts before birth and continues as a cycle throughout life.

Hematopoiesis is derived from two Greek words

Haima: Blood.

Poiesis: To make something.

Hematopoiesis is also called as

                 •Hemopoiesis.

                 •Hemogenesis.

                 •Hematogenesis

Blood cells made during hematopoiesis:

    Hematopoiesis includes the production of all blood cell types, including:

1. Erythrocytes:

Red blood cells, or erythrocytes, carry oxygen from your lungs to organs throughout your body. They also carry carbon dioxide to your lungs so you can get rid of it by exhaling it. The production of red blood cells is called erythropoiesis.

2. Leukocytes:

White blood cells, or leukocytes, fight infection and protect your body from harmful invaders, or germs and destroy abnormal cells. The production of white blood cells is called leukopoiesis.

Types Of White Blood Cells:

                 •Neutrophils.

                 •Basophils.

                 •Eosinophils.

                 •Monocytes.

                 •Lymphocytes.

3. Thrombocytes:

Platelets, or thrombocytes, are sticky cell fragments that clump together to form a clot if you’re injured. They create a seal in damaged tissue that prevents you from losing too much blood. The production of platelets is called thrombopoiesis.

Where does hematopoiesis occur?

          Hematopoiesis occur in the spongy tissue inside the bones called bone marrow. Hematopoiesis that occurs in your bone marrow is called medullary hematopoiesis. 

Hematopoiesis also takes place in other parts of your body parts, like your liver and spleen. Hematopoiesis that occurs outside of your bone marrow is called extramedullary hematopoiesis.

Hematopoiesis takes place in different places before birth and after birth.

Before birth

Blood cell production starts when you’re still in the uterus. It begins in the yolk sac. Toward the end of pregnancy, most blood cell production happens in your bone marrow.

 Hemtopoiesis during pregnancy:

            •Week 3: A type of red blood cell slightly less developed than the red blood cells that get made during adulthood is made in the yolk sac.

             •Months 2 & 3: Red blood cells and platelets produced in liver and spleen. White blood cells produced in liver, spleen and thymus.

              •Month 5: Blood cell production happens in your bone marrow. The thymus, spleen and other lymph tissue also make some types of white blood cells.

 After Birth:

Most blood cell production happens in your bone marrow from infancy and into adulthood. Certain types of  lymphocytes are developed in your thymus.

Disease creates the exception. If a person have a condition that prevents  bone marrow from making enough blood cells, hematopoiesis shift the blood cell production sites before birth. Blood cell production  shift to your liver, spleen or lymph nodes.

What happens during hematopoiesis?

Hematopoiesis begins with an originator cell common to all blood cell types. It’s called a hematopoietic stem cell (HSC). An HSC develops into a precursor cell, or “blast” cell. A precursor cell is on track to become a specific type of blood cell, but it’s still in the early stages. A precursor cell goes through several cell divisions and changes before it becomes a fully mature blood cell.

The specific types of hematopoiesis include:

               •Erythropoiesis: Red blood cell production.

               •Leukopoiesis: White blood cell production.

               •Thrombopoiesis: Platelet production.