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Red blood cells (RBCs), referred to as erythrocytes (from Ancient Greek erythros ' red ' and kytos ' hollow vessel ', with -cyte translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, [1] erythroid cells, and rarely haematids, are the most common type of blood cell and the vertebrate's principal means of delivering oxygen (O 2) to the body tissues ...
A feedback loop involving erythropoietin helps regulate the process of erythropoiesis so that, in non-disease states, the production of red blood cells is equal to the destruction of red blood cells and the red blood cell number is sufficient to sustain adequate tissue oxygen levels but not so high as to cause sludging, thrombosis, or stroke ...
Hemoglobin is an iron-containing protein that gives red blood cells their color and facilitates transportation of oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs to be exhaled. [3] Red blood cells are the most abundant cell in the blood, accounting for about 40–45% of its volume.
Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of these red blood cells are nucleated. [1] In mammals, NRBCs occur in normal development as precursors to mature red blood cells in erythropoiesis , the process by which the body produces red blood cells.
At this stage, the hemoglobin is called free hemoglobin. [3] Free hemoglobin (also called naked hemoglobin ) is the un-bound hemoglobin that is not enclosed in the red blood cell. The naked hemoglobin is devoid of its anti-oxidant sentries that are normally available within the RBC. [ 5 ]
A peripheral blood mononuclear cell (PBMC) is any peripheral blood cell having a round nucleus. [1] These cells consist of lymphocytes (T cells, B cells, NK cells) and monocytes, whereas erythrocytes and platelets have no nuclei, and granulocytes (neutrophils, basophils, and eosinophils) have multi-lobed nuclei.
After centrifugation, one can distinguish a layer of clear fluid (the plasma), a layer of red fluid containing erythrocytes, and a thin layer in between.Composing less than 1% of the total volume of the blood sample, the buffy coat (so-called because it is usually buff in hue), contains most of the leukocytes and thrombocytes.
[4] [5] Pericytes help in the maintainenance of homeostatic and hemostatic functions in the brain, where one of the organs is characterized with a higher pericyte coverage, and also sustain the blood–brain barrier. [6] These cells are also a key component of the neurovascular unit, which includes endothelial cells, astrocytes, and neurons.