What Is The Main Function Of Red Blood Cells – The erythrocyte, commonly known as a red blood cell (or RBC), is by far the most common element formed: One drop of blood contains millions of erythrocytes and only thousands of leukocytes (Figure 18.3.1). Specifically, men have approximately 5.4 million erythrocytes per microliter (
L. In fact, it is estimated that erythrocytes make up about 25 percent of the total number of cells in the body. They are small cells with an average diameter of 7–8 micrometers (
What Is The Main Function Of Red Blood Cells
M). The primary function of erythrocytes is to capture oxygen from the lungs and transport it to the tissues of the body and to capture carbon dioxide in the tissues and transport it to the lungs. Although leukocytes normally leave the blood vessels to perform their defensive functions, the movement of erythrocytes out of the blood vessels is abnormal.
Blood: Function, What It Is & Why We Need It
As an erythrocyte matures in the red bone marrow, it expels its nucleus and most other organelles. During the first day or two that it is in circulation, an immature erythrocyte, known as a reticulocyte, will still typically contain remnant organelles. Reticulocytes should make up about 1–2 percent of the erythrocyte count and should provide a rough estimate of the rate of red blood cell production. Abnormally low or high levels of reticulocytes indicate abnormalities in the production of these erythrocytes. These organelle remnants are rapidly shed, so that circulating erythrocytes have few internal cellular structural components. They lack endoplasmic reticulum and do not synthesize proteins.
The function of erythrocytes in the transport of blood gases is complemented by their structure, such as the lack of organelles, especially mitochondria, their biconcave shape and the presence of a flexible cytoskeletal protein element called spectrin. Because erythrocytes lack mitochondria and must rely on anaerobic metabolism, they do not use any of the oxygen they transport when delivering it to tissues. Erythrocytes are biconcave discs; that is, they are plump at the edge and very thin in the center (Figure 18.3.2). Because they lack most organelles, there is more internal space for the presence of hemoglobin molecules, which, as you will soon see, transport gases. The biconcave shape also provides a larger surface area over which gas exchange can occur, relative to its volume; a sphere of similar diameter would have a lower surface area to volume ratio. In the capillaries, the oxygen carried by the erythrocytes can diffuse into the plasma and then through the capillary walls to reach the cells, while some of the carbon dioxide produced by the cells as a waste product diffuses into the capillaries where it is taken up by the cells. erythrocytes. Capillary beds are extremely narrow, slowing the passage of erythrocytes and providing an extended opportunity for gas exchange. However, the space in the capillaries can be so small that, despite their small size, erythrocytes move in a single file and sometimes fold to pass. Fortunately, their structural proteins, such as spectrin, are flexible, allowing them to fold up and then pop up again when they enter a wider vessel.
Figure 18.3.2 – Shape of red blood cells: Erythrocytes are biconcave discs with very shallow centers. This shape optimizes the ratio of surface area to volume, thus facilitating gas exchange. It also allows them to fold as they move through narrow blood vessels.
Hemoglobin is a large molecule composed of protein and iron. It consists of four folded chains of the protein globin, designated alpha 1 and 2 and beta 1 and 2 (Figure 18.3.3a). Each of these globin molecules is bound to a red pigment molecule called heme, which contains an iron ion (Fe
Metaphor Function Of Red Blood Cell To Transport Oxygen 3072845 Vector Art At Vecteezy
Figure 18.3.3 – Hemoglobin: (a) The hemoglobin molecule contains four globin proteins, each bound to one molecule of the iron-containing pigment heme. (b) One erythrocyte can contain 300 million molecules of hemoglobin and therefore more than 1 billion molecules of oxygen.
Each iron ion in heme can bind to one molecule of oxygen, therefore each molecule of hemoglobin can transport four molecules of oxygen. A single erythrocyte can contain about 300 million hemoglobin molecules and can bind and transport up to 1.2 billion oxygen molecules.
In the lungs, hemoglobin captures oxygen, which binds to iron ions and forms oxyhemoglobin. The bright red, oxygenated hemoglobin travels to the capillaries of the body’s tissues, where it releases some oxygen molecules and becomes the darker red deoxyhemoglobin. The release of oxygen depends on the oxygen demand of the surrounding tissues, so hemoglobin rarely gives up all its oxygen. At that time, carbon dioxide (CO
Is the bicarbonate ion. About 23 to 24 percent binds to amino acids in hemoglobin to form a molecule known as carbaminohemoglobin. Hemoglobin transports CO from the capillaries
Blood Function And Composition
Changes in red blood cell levels can have a significant impact on the body’s ability to effectively deliver oxygen to tissues. Overproduction of red blood cells causes a condition called polycythemia. The primary disadvantage of polycythemia is not the failure to deliver enough oxygen to the tissues, but rather the increased viscosity of the blood, which makes it difficult for the heart to circulate blood. Inefficient hematopoiesis results in an insufficient number of red blood cells and leads to one of several forms of anemia. In patients with insufficient hemoglobin, tissues may not receive enough oxygen, leading to another form of anemia.
When determining tissue oxygenation, the most interesting value in health care is the percentage of saturation; that is, the percentage of hemoglobin sites occupied by oxygen in the patient’s blood. Clinically, this value is commonly referred to simply as “percent sat”. The percentage of saturation is commonly monitored using a device known as a pulse oximeter, which is applied to a thin part of the body, usually the tip of the patient’s finger. The device works by sending two different wavelengths of light (one red, the other infrared) through the finger and measuring the light output with a photodetector. Hemoglobin absorbs light differently depending on its oxygen saturation. The instrument calibrates the amount of light received by the photodetector against the amount absorbed by the partially oxygenated hemoglobin and presents the data as a percentage of saturation. Normal pulse oximeter readings range from 95 to 100 percent. Lower percentages reflect hypoxemia, or low oxygen levels in the blood. The term hypoxia is more general and simply refers to low oxygen levels. Oxygen levels are also directly monitored from free oxygen in the plasma typically after the arterial rod. When this method is used, the amount of oxygen present is expressed as the partial pressure of oxygen, or simply pO
Oxygen saturation receptors are located in the kidneys, which is an ideal place to monitor saturation because the kidneys filter about 180 liters (~380 pints) of blood per day in the average adult. In response to hypoxemia, less oxygen diffuses into the kidney, resulting in renal cell hypoxia, where oxygen concentration is actually monitored. Interstitial fibroblasts in the kidney secrete erythropoietin (EPO), which leads to increased production of erythrocytes and possibly restoration of oxygen levels. In a negative feedback loop, as oxygen saturation increases, EPO secretion decreases and vice versa, thus maintaining homeostasis. Populations living at high altitudes with naturally lower atmospheric oxygen levels naturally maintain a higher hematocrit than people living at sea level. As a result, people traveling to high altitudes may experience symptoms of hypoxemia, such as fatigue, headache, and shortness of breath, for several days after arrival. In response to hypoxemia, the kidneys secrete EPO to increase erythrocyte production until homeostasis is again achieved. To avoid symptoms of hypoxemia or altitude sickness, climbers typically rest for several days to a week or more in a series of camps located at increasing altitudes to allow EPO levels and, consequently, erythrocyte counts to increase. When climbing the highest peaks such as Mt. Everest and K2 in the Himalayas, many climbers rely on bottled oxygen as they approach the summit.
The production of erythrocytes in the bone marrow occurs at an astonishing rate of more than 2 million cells per second. For this production to occur, a number of raw materials must be present in adequate quantities. These include the same nutrients that are essential for the formation and maintenance of any cell, such as glucose, lipids and amino acids. However, the production of erythrocytes also requires several trace elements:
Functions Of Blood: Transport Around The Body
Erythrocytes live in the circulation for up to 120 days, after which the worn-out cells are removed by a type of myeloid phagocytic cell called a macrophage, which is found primarily in the bone marrow, liver, and spleen. The hemoglobin components of degraded erythrocytes are further processed as follows:
Decomposition pigments formed by the destruction of hemoglobin can be observed in various situations. At the site of injury, green biliverdin from damaged red blood cells creates some of the dramatic colors associated with bruises. In a failing liver, bilirubin cannot be effectively removed from the circulation and causes the body to take on the yellowish tinge associated with jaundice. Stercobilins in feces produce the typical brown color associated with this waste. And the yellow color of urine is associated with urobilins.
Figure 18.3.4 – Life cycle of erythrocytes: Erythrocytes are
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