Blood part two

Platelets

Cell fragments

• Break off from megakaryocytes

• Function in clotting of blood

Hematopoiesis

process by which blood cells are formed in red marrow

Red marrow

actively generates new blood cells

Contains immature erythrocytes

• In adults, red marrow is located

• Between trabeculae of spongy bone of axial

skeleton

• Girdles

• In proximal epiphyses of humerus and femur

Yellow marrow—dormant

Contains many fat cells

• Located in the long bones of adults

Tissue framework of bone marrow

Reticular connective tissue

Hemopoietic blood stem cell

original cell

Lymphoid stem cells

Give rise to lymphocytes

Myeloid stem cells

Give rise to all other blood cells

proerythroblasts

are Committed cells

Remain in the reticulocyte stage for 1–2 days in circulation

• Make up about 1–2% of all erythrocytes

myeloblasts

Committed cell type in each granulocyte line are

Monoblasts

enlarge and form monocytes

Megakaryoblasts

differentiate into megakaryocytes

• Break apart into platelets