Red Blood Cells Function In The Body – Erythrocytes, commonly called red blood cells (or RBCs), are the most commonly formed element: One drop of blood contains millions of erythrocytes and only thousands of leukocytes (Figure 18.3.1). Specifically, men have about 5.4 million erythrocytes per microliter (

L. In fact, erythrocytes are estimated to make up to 25 percent of the total cells in the body. They are small cells, with an average diameter of 7-8 micrometers (

Red Blood Cells Function In The Body

M). The primary function of erythrocytes is to take oxygen from the lungs and transport it to the tissues of the body, and to take carbon dioxide from the tissues and transport it to the lungs. Although leukocytes normally leave blood vessels to perform their defense functions, the movement of erythrocytes from blood vessels is abnormal.

Blood Structure And Its 3 Main Circulatory Functions In The Body

As an erythrocyte matures in the red bone marrow, it extrudes the nucleus and most of its other organelles. In the first day or two it is in circulation, an immature erythrocyte, known as a reticulocyte, still typically contains the remains of organelles. Reticulocytes should comprise about 1-2 percent of the total erythrocytes and provide a rough estimate of the rate of RBC production. A low or high level of reticulocytes indicates an abnormality in the production of these erythrocytes. The remains of these organelles are quickly shed, so that erythrocytes circulate several components of the internal cellular structure. They lack endoplasmic reticulum and do not synthesize proteins.

The function of erythrocytes to transport blood gases is complimented 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 delivered to tissues. Erythrocytes are biconcave discs; that is, they are plump in their periphery and very thin in the middle (picture 18.3.2). Because they lack most organelles, there is more interior space for the presence of hemoglobin molecules which, as you will see in a moment, transport gases. The biconcave shape also provides a larger surface area across which gas exchange can occur, relative to its volume; a ball with a similar diameter will have a lower surface area-to-volume ratio. In the capillaries, the oxygen transported by the erythrocytes can diffuse into the plasma and pass through the capillary wall to reach the cells, while some of the carbon dioxide produced by the cells as a waste product diffuses into the capillaries to be picked up by the capillaries. erythrocytes. The capillary bed is very narrow, slowing down the passage of erythrocytes and giving them a longer opportunity for gas exchange. However, the space in the capillary can be so small that, despite its small size, erythrocytes travel in single-file and sometimes fold in themselves through. Fortunately, their structural proteins like spectrin, are flexible, so they bend and then spring back when they enter a wide container.

Figure 18.3.2 – Shape of Red Blood Cells: Erythrocytes are biconcave discs with a very shallow center. This shape optimizes the ratio of surface area to volume, facilitating gas exchange. It also allows them to bend as they pass through narrow blood vessels.

Hemoglobin is a large molecule composed of protein and iron. It consists of four folded chains of 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 iron ions (Fe

The Molecular Structure Of Human Red Blood Cell Membranes From Highly Oriented, Solid Supported Multi Lamellar Membranes

Figure 18.3.3 – Hemoglobin: (a) The hemoglobin molecule contains four globin proteins, each of which is bound to one molecule of the pigment heme that contains iron. (b) A single erythrocyte can contain 300 million hemoglobin molecules, thus more than 1 billion oxygen molecules.

Each iron ion in heme can bind one oxygen molecule, so each hemoglobin molecule can carry four oxygen molecules. An individual erythrocyte can contain approximately 300 million hemoglobin molecules, and can bind and transport up to 1.2 billion oxygen molecules.

In the lungs, hemoglobin takes oxygen, which binds to iron ions, forming oxyhemoglobin. Bright red hemoglobin, oxygen travels to the capillaries of body tissues, where it releases some oxygen molecules, becoming dark red deoxyhemoglobin. The release of oxygen depends on the need for oxygen in the surrounding tissue, so hemoglobin rarely leaves all of its oxygen behind. At that time, carbon dioxide (CO

Is the bicarbonate ion. About 23-24 percent of it binds to amino acids in hemoglobin, forming a molecule known as carbaminohemoglobin. From the capillaries, hemoglobin carries CO

Red Blood Cells Red Blood Cells Structure: Large Surface Area

Changes in RBC levels can have a significant effect on the body’s ability to effectively deliver oxygen to tissues. Overproduction of RBCs results in a condition called polycythemia. The main weakness with polycythemia is not the failure to deliver enough oxygen to the tissues, but more viscosity of the blood, which makes it harder for the heart to circulate the blood. ineffective hematopoiesis leads to an insufficient number of RBCs and leads to one of several forms of anemia. In patients with insufficient hemoglobin, the tissue may not receive enough oxygen, resulting in another form of anemia.

In determining tissue oxygenation, the value of greatest interest in health is percent 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 “sitting percent”. Percent saturation is usually monitored using a device known as a pulse oximeter, which is applied to a thin part of the body, usually the patient’s fingertips. The device works by sending two different wavelengths of light (one red, one infrared) through the finger and measuring the light with a photodetector as it exits. Hemoglobin absorbs light differently depending on its saturation with oxygen. The machine calibrates the amount of light received by the photodetector against the amount absorbed by partially oxygenated hemoglobin and displays the data as percent saturation. A normal pulse oximeter reading ranges from 95-100 percent. A lower percentage represents hypoxemia, or low blood oxygen. The term hypoxia is more general and refers only to low oxygen levels. The oxygen level is also directly monitored from the free oxygen in the plasma usually following an arterial stick. If this method is applied, the amount of oxygen present is expressed in terms of partial pressure of oxygen or simply pO

Receptors for oxygen saturation are located in the kidneys, which are an ideal site for monitoring saturation, as the kidneys filter about 180 liters (~380 pints) of blood in the average adult each day. In response to hypoxemia, less oxygen is diffused into the kidneys, resulting in kidney cell hypoxia where the oxygen concentration is actually monitored. Interstitial fibroblasts in the kidney secrete erythropoietin (EPO), leading to increased production of erythrocytes and ultimately restoring oxygen levels. In a negative feedback loop, when oxygen saturation increases, EPO secretion decreases, and vice versa, thereby maintaining homeostasis. Populations living at high altitudes, with lower oxygen levels in the atmosphere, naturally maintain a higher hematocrit than people living at sea level. Consequently, 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 release EPO to increase erythrocyte production until homeostasis is achieved once again. To avoid symptoms of hypoxemia, or altitude sickness, mountaineers usually rest for a few days to a week or more in a series of camps at increasing elevations to allow EPO levels and, consequently, erythrocyte counts to rise. When climbing the highest peaks, such as Mount Everest and K2 in the Himalayas, many mountaineers rely on bottled oxygen when nearing the summit.

The production of erythrocytes in the marrow occurs at a staggering rate of more than 2 million cells per second. For this production to take place, some raw materials must be present in sufficient quantities. These include the same nutrients that are essential for the production and maintenance of any cell, such as glucose, lipids, and amino acids. However, the production of erythrocytes also requires some trace elements:

Microfluidic Study Of Retention And Elimination Of Abnormal Red Blood Cells By Human Spleen With Implications For Sickle Cell Disease

Erythrocytes live up to 120 days in the circulation, after which the worn-out cells are removed by a type of myeloid phagocyte called macrophages, located mainly in the bone marrow, liver, and spleen. The degraded erythrocyte hemoglobin component is further processed as follows:

The breakdown pigment formed from the breakdown of hemoglobin can be seen in several situations. At the site of injury, green biliverdin from damaged RBCs produces some dramatic colors associated with bruising. With liver failure, bilirubin cannot be effectively removed from the circulation and causes the body to turn a yellow color associated with jaundice. Stercobilins in feces produce the characteristic brown color associated with this waste. And the yellow of the urine associated with urobilins.

Figure 18.3.4 – Life Cycle of Erythrocytes: Erythrocytes are

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