Detailed Histology of Erythrocytes (Red Blood Cell Formation)

The erythrocyte is formed from the hemocytoblast in the red bone marrow. The hemocytoblast forms the pro-erythroblast, The initial cell of this series has a deep blue (basophilic) staining cytoplasm and therefore is called a basophilic erythroblast. The chief change in the erythroblast is accumulation of hemoglobin in the cytoplasm. As the basophilic material decreases and the amount of hemoglobin increases, the cell is called a polychromatic erythroblast, which describes its mixture of staining properties. At the same time as the nucleus is decreasing in size, the basophilic material disappears, so that the cell is uniformly stain by eosin dye, hence the name orthochromatic erythroblast, or normoblast, Finally the normoblast completely loses its nucleus by a process of extrusion as it squeezes through the pores of the membrane into the capillary. As a result of losing its nucleus, the cell caves on both sides, giving the mature erythrocyte its characteristic appearance as a biconcave disc. During each of these stages the different cells continue to undergo mitosis so that increasingly greater numbers of cells are produced.

Normally some of the circulating erythrocytes, called reticulocytes, retain a small amount of basophilic reticulum. Ordinarily the total proportion of circulating reticulocytes (known as the reticulocyte count) is between 0.5% and 1.5%. A change in the number of reticulocytes is an indicator of increased red blood cell production or hyper-functioning of the bone marrow. The reticulocyte count is a simple laboratory test frequently used to indirectly analyze hemopoiesis.

Regulation of erythrocyte production
The usual life span of the mature erythrocyte is 120 days. Apparently as red blood cells grow old, their membranes become fragile and eventually mature. The contents of the cell fragment as they circulate through the blood vessels and are phagocytized by the reticuloendothelial cells in the spleen, liver, and bone marrow. The hemoglobin is broken down into the iron-containing pigment hemosiderin and the bile pigments biliverdin and bilirubin. Most of the iron is reused by the bone marrow for production of new red blood cells or stored in the liver and other tissues for future use. The bile pigments are excreted by the liver in bile.

Normally there is a homeostatic balance between the regulation of red blood cell production and destruction. This balance ensures adequate tissue oxygenation and a blood viscosity that allows the blood to flow freely through the vessels. The basic regulator of erythrocyte production is believed to be tissue oxygenation. In states of tissue hypoxia, erythropoietin (also called erythropoietic stimulating factor or hemopoietin) is released by the kidneys into the blood stream. As a result, the bone marrow is stimulated to produce new red blood cells. The major activity seems to be an increase in both the maturation rate and mitosis of all stages of erythrocyte production, but primarily at the stem cell level.

During this rapid increase of red blood cell production, the circulating erythrocytes may not be totally matured. Consequently, the number of reticulocytes may increase dramatically (as high as 30% or more of the total red blood cell count). Even normoblasts may appear in the blood. Failure to observe this rise in erythrocyte and reticulocyte count is an indicator of bone marrow failure.

Once tissue oxygenation is adequate, the production of erythropoietin ceases. Thus, tissue oxygen requirements control both the stimulation and termination of erythrocyte production. It is important to note that it is the function of red blood cells to transport oxygen to the tissues in response to their needs, not the circulating numbers of erythrocytes that is the basic regulatory mechanism. This explains why polycythemia (increase in the number of erythrocytes) occurs in conditions of prolonged tissue hypoxia, such as cyanotic heart defects. If the circulating numbers of erythrocytes controlled erythropoietin release, this feedback mechanism would control erythrocyte production at a constant level (4.5 to 5.5 million/mm3 of blood) regardless of exiting tissue hypoxia.

Detailed Histology of Erythrocytes (Red Blood Cell Formation)

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

Tube. Duration : 7.50 Mins.

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

Watch all my video & photo tutorials here: bit.ly Filmmaking DVD's etc are all here: www.tlapro.com In this tutorial I explain basic camera framing, angles and lens choice. I show that lens size really has nothing to do with framing.

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14

No URL Photography Tips: Composition & Camera Angles - Filmmaking Tutorial 14




Watch all my video & photo tutorials here: bit.ly Filmmaking DVD's etc are all here: www.tlapro.com In this tutorial I explain basic camera framing, angles and lens choice. I show that lens size really has nothing to do with framing.

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Basic Photography Techniques Pdf

Detailed Histology of Erythrocytes (Red Blood Cell Formation)

Detailed Histology of Erythrocytes (Red Blood Cell Formation)
Detailed Histology of Erythrocytes (Red Blood Cell Formation)

Basic Photography Techniques Pdf