Since they lack most organelles, there is more interior space for the presence of the hemoglobin molecules that, as you will see shortly, transport gases. This includes the protein spectrin, a cytoskeletal protein element.Įrythrocytes are biconcave disks that is, they are plump at their periphery and very thin in the center ( Figure 18.6). Erythrocytes do, however, contain some structural proteins that help the blood cells maintain their unique structure and enable them to change their shape to squeeze through capillaries. They also lack endoplasmic reticula and do not synthesize proteins.
This means that they do not utilize any of the oxygen they are transporting, so they can deliver it all to the tissues. Lacking mitochondria, for example, they rely on anaerobic respiration. These remnants, primarily of networks (reticulum) of ribosomes, are quickly shed, however, and mature, circulating erythrocytes have few internal cellular structural components. Reticulocytes should comprise approximately 1–2 percent of the erythrocyte count and provide a rough estimate of the rate of RBC production, with abnormally low or high rates indicating deviations in the production of these cells. During the first day or two that it is in the circulation, an immature erythrocyte, known as a reticulocyte, will still typically contain remnants of organelles. Although leukocytes typically leave the blood vessels to perform their defensive functions, movement of erythrocytes from the blood vessels is abnormal.įigure 18.5 Summary of Formed Elements in Blood Shape and Structure of ErythrocytesĪs an erythrocyte matures in the red bone marrow, it extrudes its nucleus and most of its other organelles. Erythrocytes remain within the vascular network. The primary functions of erythrocytes are to pick up inhaled oxygen from the lungs and transport it to the body’s tissues, and to pick up some (about 24 percent) carbon dioxide waste at the tissues and transport it to the lungs for exhalation. As you can imagine, they are quite small cells, with a mean diameter of only about 7–8 micrometers ( µm) ( Figure 18.5).
In fact, erythrocytes are estimated to make up about 25 percent of the total cells in the body. Specifically, males have about 5.4 million erythrocytes per microliter ( µL) of blood, and females have approximately 4.8 million per µL. The erythrocyte, commonly known as a red blood cell (or RBC), is by far the most common formed element: A single drop of blood contains millions of erythrocytes and just thousands of leukocytes. Explain the composition and function of hemoglobin.Discuss the various steps in the lifecycle of an erythrocyte.By the end of this section, you will be able to:
0 kommentar(er)
