Blood Cell Production and Hematopoiesis - Anatomy and Physiology
- Which organ is the main site of blood cell production during mid-gestation in the fetus?
- The liver. Production shifts to the bone marrow late in fetal development.
- Which hormone stimulates red blood cell production, and where is it mainly made?
- Erythropoietin, made mainly by the kidneys in response to low tissue oxygen.
- What is a reticulocyte?
- An immature red blood cell that has lost its nucleus but still holds residual ribosomal RNA. It normally makes up about 1 percent of circulating red cells.
- Which hormone, made mainly by the liver, stimulates platelet production?
- Thrombopoietin, which drives megakaryocyte development.
- What is the typical life span of a circulating red blood cell?
- About 120 days. Old red cells are removed mainly by macrophages in the spleen and liver.
- A person moves to high altitude. How does red blood cell production respond?
- Erythropoietin secretion rises in response to hypoxia, increasing red cell production and hematocrit over weeks.
- What is the main site of hematopoiesis in adults?
- Red bone marrow, found mainly in flat bones (sternum, pelvis, skull, vertebrae) and the proximal ends of the femur and humerus.
- From which bone marrow cell are platelets derived?
- The megakaryocyte. Platelets are cytoplasmic fragments pinched off from it.
- Which class of cytokines stimulates the bone marrow to produce specific white blood cell lines?
- Colony-stimulating factors (such as G-CSF for neutrophils), with help from interleukins.
- Deficiency of which two B vitamins impairs DNA synthesis and causes large (macrocytic) red cells?
- Vitamin B12 and folate (folic acid).
- Which progenitor line gives rise to B cells, T cells, and natural killer cells?
- The lymphoid stem cell line. All other formed elements come from the myeloid line.
- Which cell gives rise to all formed elements of the blood?
- The hematopoietic stem cell (hemocytoblast), which is self-renewing and multipotent.