Erythrocyte physiology

Erythrocyte physiology . The erythrocytes, like the rest of the blood cells , come from an undifferentiated cell ( stem or primitive pluripotential cell ).

Summary

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  • 1 Erythropoiesis
  • 2 Erythrocyte metabolism
  • 3 Erythrocatheresis
  • 4 Source

Erythropoiesis

The most primitive erythroid parent that has been cultivated is the so-called early erythroid colony forming unit (CFU). After it, a more mature one is produced, the erythroid colony forming unit (CFU). Both are sensitive to erythropoietin and other growth factors.

They then differentiate into proerythroblasts, normoblasts, reticulocytes (after removing the nucleus), and erythrocytes. This process occurs in the adult in the bone marrow. In the fetus it occurs in the liver, spleen and bone marrow from the fourth month. Incorporation of hemoglobin. To fulfill their oxygen transport function, red blood cells need to incorporate hemoglobin into their cytoplasm. To do this, they accumulate globin chains progressively from the proerythroblast state. They also need to synthesize the heme group, where iron is incorporated (each hemoglobin has 4 heme groups and four globin chains).

In normal adult red blood cells, hemoglobin A (alpha2-beta2) constitutes 97%, almost 3% hemoglobin A2 (alpha2-delta2), and less than 1% fetal hemoglobin or F (alpha2-gamma2).

Erythrocyte metabolism

Glucose is practically the only fuel used by the red blood cell. This is used for: Glycolytic or Embden-Meyerhof routes . Glucose is metabolized to lactate, producing two moles of ATP for each mole of glucose. About 80-90% glucose is metabolized in this way.

Hexose monophosphate pathway. Retaining reduced glutathione to protect sulfhydryl groups in hemoglobin and the cell membrane from oxidation. 10% of glucose is metabolized in this way.

The red blood cell has quite modest metabolic requirements aimed at making Na + / K + ATPase work, maintaining and repairing the membrane, as well as its flexibility, and keeping iron atoms in a reduced form to avoid the formation of methemoglobin.

Erythrocatheresis

Red blood cells have a half-life of approximately 120 days. It is possible that their physiological death is due to an alteration of the membrane, specifically its flexibility, which prevents them from crossing the narrow channels of the spleen’s microcirculation. The spleen, in addition to eliminating defective erythrocytes, has other functions, including the sequestration of part of normal red blood cells and platelets, the possibility of extramedullary hematopoiesis, the elimination of microorganisms and the regulation of portal circulation.

Hemoglobin catabolism. After removal of the red blood cell, the hemoglobin they contain is rapidly phagocytosed by macrophages (mainly from the liver, spleen, and bone marrow) that catabolize it. Amino acids are released by proteolytic digestion, the heme group is catabolized by a microsomal oxidizing system, and the porphyrin ring is converted into bile pigments that are almost entirely excreted by the liver. Iron is incorporated into ferritin (a deposit protein found mainly in the liver and bone marrow ), and from there it can be transported to the marrow by transferrin according to the body’s needs.

 

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