Explain the origin of blood cells

Thrombopoietin

-TPO. -a hormone produced by the liver that stimulates the formation of platelets (thrombocytes) from megakaryocytes.

precursor cells

-the next generation. -also known as blasts. -Precursor cells have recognizable microscopic appearances. -Over several cell divisions they develop into the actual formed elements of blood. (For example, monoblasts develop into monocytes, eosinophilic myeloblasts develop into eosinophils, and so on.)

two important families of cytokines that stimulate white blood cell formation:

1. colony-stimulating factor. 2. interleukins

hemopoiesis

Blood cell production, which occurs in red bone marrow after birth. Also called hematopoiesis.

From which connective tissue cells do pluripotent stem cells develop?

Pluripotent stem cells develop from mesenchyme.

Erythropoietin

-EPO. -A hormone released by the juxtaglomerular cells of the kidneys that stimulates red blood cell production.

colony‐forming units

-Following the CFU designation is an abbreviation that indicates the mature elements in blood that they will produce: -CFU-E ultimately produces erythrocytes (red blood cells). -CFU-Meg produces megakaryocytes, the source of platelets. -CFU-GM ultimately produces granulocytes (specifically, neutrophils) and monocytes.

pluripotent stem cells aka hemocytoblasts

-Immature stem cell in red bone marrow that gives rise to precursors of all the different mature blood cells. -These cells have the capacity to develop into many different types of cells

hemopoietic growth factors

-regulate the differentiation and proliferation of particular progenitor cells.

Cytokines

-small glycoproteins. -typically produced by cells such as red bone marrow cells, leukocytes, macrophages, fibroblasts, and endothelial cells. -act as local hormones. -stimulate proliferation of progenitor cells in red bone marrow and regulate the activities of cells involved in nonspecific defenses (such as phagocytes) and immune responses (such as B cells and T cells).

formation of blood cells

-some lymphocytes have a lifetime measured in years. -most formed elements of the blood last only hours, days, or weeks, and must be replaced continually.

Red bone marrow and blood formation:

-the primary site of hemopoiesis in the last 3 months before birth, and continues as the source of blood cells after birth and throughout life. -highly vascularized connective tissue located in the microscopic spaces between trabeculae of spongy bone tissue. -present in bones of the axial skeleton, pectoral and pelvic girdles, and the proximal epiphyses of the humerus and femur. -About 0.05-0.1% of red bone marrow cells are derived from mesenchyme and are called pluripotent stem cells

How is the formation of blood cells regulated?

-via Negative feedback systems. -regulate the total number of RBCs and platelets in circulation, and their numbers normally remain steady.

Why do WBCs vary?

The abundance of the different types of WBCs, however, varies in response to challenges by invading pathogens and other foreign antigens.

progenitor cells

During hemopoiesis, some of the myeloid stem cells differentiate into progenitor cells. -no longer capable of reproducing themselves and are committed to giving rise to more specific elements of blood. -Progenitor cells, like stem cells, resemble lymphocytes and cannot be distinguished by their microscopic appearance alone -Some are known as colony‐forming units (CFUs).

Colony‐stimulating factor

One of a group of molecules that stimulates development of white blood cells. Examples are macrophage CSF and granulocyte CSF.