Hematopoiesis Flashcards
Where does hematopoiesis occur in the fetus?
The yolk sac is the site of erythropoiesis during the first 2-8 weeks of fetal life. The liver and spleen are the predominant sites from the 2nd-5th month. In the 4th month of gestation, the bone marrow begins to function and after the 5th month is the predominant site.
Where does hematopoiesis occur in the child?
In the bone marrow, including the marrow of the long bones.
Where does hematopoiesis occur in the adult?
In the bone marrow of the sternum, ribs, pelvis, vertebrae, and skull (collectively referred to as the flat bones). The red marrow of the long bones is replaced with fat. The liver, spleen, and marrow of the long bones can become active again, if increased hematopoiesis is needed. Extramedullary hematopoiesis refers to hematopoiesis outside of the bone marrow, ie. in the spleen, liver, and lymph nodes.
Which hormones regulates the rate of erythropoiesis?
Erythropoietin, produced primarily in the kidneys.
What is recombinant human erythropoietin?
A hormone that stimulates RBC production. It is used to reduce transfusions in patients with end-stage renal disease.
Which cells are derived from a common multipotential stem cell in the bone marrow?
Erythrocytes, granulocytes, monocytes, and thrombocytes (platelets).
What is the precursor of the platelet?
The megakaryocyte. Platelets are fragments of megakaryocyte cytoplasm.
Where are lymphocytes produced?
In the thymus and bone marrow (primary lymphoid tissue), and in the spleen, lymph nodes, intestine-associated lymphoid tissue, and tonsils (second lymphoid tissue).
What is the normal life span of an erythrocyte?
120 days. The phagocytic cells of the reticuloendothelial (RE) system remove the aged RBCs from the circulation. The iron and globin chains are recycled and the heme is degraded and excreted as bilirubin.
In a normal individual, what percentage of RBCs is replaced daily?
Approximately 1%. Reticulocytes are released from the bone marrow into the circulation to replace the aged cells removed by the RE system.
What happens to the nuclear:cytoplasmic (N:C) ratio as most cells mature?
The N:C ratio decreases as the volume of the nucleus decreases.
What is the best indicator of the age of a cell?
The amount of chromatin clumping in the nucleus.
What is the color of the cytoplasm in blasts?
Royal blue due to the presence of RNA.
What is the significance of nucleoli in a cell nucleus?
Nucleoi are sites of ribosomal RNA synthesis. They are seen in the nuclei of immature cells and reactive lymphocytes.
