Answer
The average lifespan of a red blood cell (RBC), also known as an erythrocyte, is approximately 120 days. During this time, RBCs perform their essential role of transporting oxygen from the lungs to the body's tissues and carrying carbon dioxide from the tissues back to the lungs for exhalation. However, as RBCs age, they become less flexible and more susceptible to damage.
**Disposal of Old RBCs:**
When RBCs reach the end of their lifespan, they are removed from circulation and broken down in a process known as hemolysis. The main organs involved in the disposal of old RBCs are the liver and the spleen.
1. **Macrophage Phagocytosis:** Macrophages are specialized immune cells found in various tissues, including the liver and spleen. They play a crucial role in the disposal of old RBCs. As RBCs age, they become less flexible and more rigid due to changes in their membrane proteins. This rigidity makes it more difficult for them to pass through narrow capillaries. Macrophages recognize and phagocytize these aged and damaged RBCs as they flow through the blood.
2. **Hemoglobin Breakdown:** Once RBCs are phagocytized by macrophages, the cell membranes are broken down, and the contents are processed. Hemoglobin, the protein responsible for oxygen transport, is a major component of RBCs. It is broken down into its constituent parts:
- **Heme:** The iron-containing heme portion of hemoglobin is converted into biliverdin and then bilirubin.
- **Globin:** The protein globin is broken down into amino acids, which can be reused by the body.
3. **Bilirubin Processing:** Bilirubin is released into the bloodstream and travels to the liver. In the liver, bilirubin is conjugated (chemically modified) to make it water-soluble, allowing it to be excreted in bile.
4. **Excretion:** Conjugated bilirubin is excreted into the small intestine as part of bile. It eventually reaches the large intestine, where it is further modified by bacteria and converted into urobilinogen. Some urobilinogen is reabsorbed into the bloodstream, while the rest is excreted in feces, giving stool its characteristic color.
In summary, the average lifespan of a red blood cell is approximately 120 days. As RBCs age, they become less flexible and are removed from circulation by macrophages in the liver and spleen. The breakdown products of hemoglobin, such as bilirubin, are processed and excreted by the liver and eventually eliminated from the body. This continuous cycle of RBC production and disposal helps to maintain the body's oxygen-carrying capacity and overall health.
Work Step by Step
The average lifespan of a red blood cell (RBC), also known as an erythrocyte, is approximately 120 days. During this time, RBCs perform their essential role of transporting oxygen from the lungs to the body's tissues and carrying carbon dioxide from the tissues back to the lungs for exhalation. However, as RBCs age, they become less flexible and more susceptible to damage.
**Disposal of Old RBCs:**
When RBCs reach the end of their lifespan, they are removed from circulation and broken down in a process known as hemolysis. The main organs involved in the disposal of old RBCs are the liver and the spleen.
1. **Macrophage Phagocytosis:** Macrophages are specialized immune cells found in various tissues, including the liver and spleen. They play a crucial role in the disposal of old RBCs. As RBCs age, they become less flexible and more rigid due to changes in their membrane proteins. This rigidity makes it more difficult for them to pass through narrow capillaries. Macrophages recognize and phagocytize these aged and damaged RBCs as they flow through the blood.
2. **Hemoglobin Breakdown:** Once RBCs are phagocytized by macrophages, the cell membranes are broken down, and the contents are processed. Hemoglobin, the protein responsible for oxygen transport, is a major component of RBCs. It is broken down into its constituent parts:
- **Heme:** The iron-containing heme portion of hemoglobin is converted into biliverdin and then bilirubin.
- **Globin:** The protein globin is broken down into amino acids, which can be reused by the body.
3. **Bilirubin Processing:** Bilirubin is released into the bloodstream and travels to the liver. In the liver, bilirubin is conjugated (chemically modified) to make it water-soluble, allowing it to be excreted in bile.
4. **Excretion:** Conjugated bilirubin is excreted into the small intestine as part of bile. It eventually reaches the large intestine, where it is further modified by bacteria and converted into urobilinogen. Some urobilinogen is reabsorbed into the bloodstream, while the rest is excreted in feces, giving stool its characteristic color.
In summary, the average lifespan of a red blood cell is approximately 120 days. As RBCs age, they become less flexible and are removed from circulation by macrophages in the liver and spleen. The breakdown products of hemoglobin, such as bilirubin, are processed and excreted by the liver and eventually eliminated from the body. This continuous cycle of RBC production and disposal helps to maintain the body's oxygen-carrying capacity and overall health.
