Hematopoiesis is the process by which the formed elements of blood are produced. The process is regulated through a series of steps beginning with the hematopoietic stem cell. Stem cells are capable of producing red cells, all classes of granulocytes, monocytes, platelets, and the cells of the immune system. The precise molecular mechanism—either intrinsic to the stem cell itself or through the action of extrinsic factors—by which the stem cell becomes committed to a given lineage is not fully defined.
Following lineage commitment, hematopoietic progenitor and precursor cells come increasingly under the regulatory influence of growth factors and hormones.
For red cell production, erythropoietin EPO is the primary regulatory hormone. EPO is required for the maintenance of committed erythroid progenitor cells that, in the absence of the hormone, undergo programmed cell death apoptosis. The regulated process of red cell production is erythropoiesis , and its key elements are illustrated in Fig. The physiologic regulation of red cell production by tissue oxygen tension. Hb, hemoglobin. In the bone marrow, the first morphologically recognizable erythroid precursor is the pronormoblast.
This cell can undergo four to five cell divisions, which result in the production of 16—32 mature red cells. With increased EPO production, or the administration of EPO as a drug, early progenitor cell numbers are amplified and, in turn, give rise to increased numbers of erythrocytes.
The regulation of EPO production itself is linked to tissue oxygenation. In mammals, O 2 is transported to tissues bound to the hemoglobin contained within circulating red cells. Normal red cell production results in the daily replacement of 0. The organ responsible for red cell production is called the erythron. The erythron is a dynamic organ made up of a rapidly proliferating pool of marrow erythroid precursor cells and a large mass of mature circulating red blood cells.
The size of the red cell mass reflects the balance of red cell production and destruction. The physiologic basis of red cell production and destruction provides an understanding of the mechanisms that can lead to anemia.
The physiologic regulator of red cell production, the glycoprotein hormone EPO, is produced and released by peritubular capillary lining cells within the kidney.
Disclaimer » Advertising. Erica Hyman Kates, Jacqueline S. Kates; Anemia and Polycythemia in the Newborn. Pediatr Rev January ; 28 1 : 33— Physiologic Anemia of Infancy. Glader B. Am Fam Physician. Pediatr Clin North Am. Garcia-Prats JA. Available at: www. Red blood cell RBC mass in the newborn is highly variable.
As an infant makes the transition from the intrauterine to the extrauterine environment, a change occurs in both the mass and the composition of RBCs. The range of normal, while clearly defined, is wide because of the many fluctuating variables involved in the physiology of the peripartum period.
Advertising Disclaimer ». Sign In or Create an Account. Search Close. Create Account. Advanced Search. Doctors may then recommend myelosuppressive drugs to help control blood cell counts.
These drugs include hydroxyurea Hydrea , which suppresses the bone marrow to keep it from producing as many blood cells. In cases where a person does not respond well to other medications, doctors may recommend drugs that inhibit the JAK2 enzyme, which the JAK2 gene is responsible for producing. These include ruxolitinib Jakafi. Doctors will also often recommend other drugs to help control symptoms.
These include aspirin and antihistamines. Taking low dose aspirin helps reduce the risk of clotting in many people with PV, and it may also alleviate troubling symptoms, such as headaches. Doctors may recommend antihistamine drugs to help relieve itchiness. Determining the underlying type of polycythemia helps doctors know how best to treat or manage the issue.
If treatment is possible, the person should make a full recovery. In cases of PV, treatment will focus on managing the condition and symptoms, as there is currently no cure. In most cases, the person will have a normal or nearly normal quality of life, and doctors can effectively manage the condition for a very long time. In addition to managing symptoms, new treatments will look to help slow the progression of the disease.
Polycythemia is an increase in the number of red blood cells in the body. Doctors may discover it as part of a routine blood check, or they might diagnose it once the person starts experiencing symptoms. PV is a chronic condition with no known cure. However, effective treatment can help sufficiently manage the disease and its symptoms.
Anyone who has symptoms or a family history of polycythemia vera should see a doctor for a diagnosis. People with polycythemia vera have a shorter-than-average life expectancy, but timely treatment can improve a person's outlook and prevent…. Polycythemia vera can cause the skin to look flushed and blotchy. The blotches often occur on the face, but they can appear nearly anywhere on the….
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