What makes erythrocytes

It also has a characteristic red pigment, giving blood its red color. Red blood cells contain hemoglobin and are covered with a membrane composed of proteins and lipids. Hemoglobin—an iron-rich protein that gives blood its red color—enables red blood cells to transport oxygen and carbon dioxide.

Red blood cells do not have nuclei, allowing for more room for hemoglobin. The shape of red blood cells is a unique biconcave shape round with a flat, indented center.

Their lack of nuclei makes them so flexible that they can pass through extremely small blood vessels. The red blood cells of adult humans are produced in the bone marrow, which is the soft fatty tissue inside bones. In human embryos, they originate in the yolk sac and liver. From the bone marrow, blood circulates through the human body via the veins and arteries. In general, the production of red blood cells is controlled by erythropoietin, a hormone produced and released by the kidneys.

Erythropoietin stimulates the production of red blood cells in the bone marrow. The average adult human produces 2 to 3 million red blood cells every second, equating to about billion red blood cells every day. Sickle cells die much more quickly than normal blood cells—in about 10 to 20 days instead of days. This causes a shortage of red blood cells. Normocytic anemia.

With this type of anemia your red blood cells are a normal shape and size. But you don't have enough of them to meet your body's needs. Diseases that cause this type of anemia are often long-term conditions, such as kidney disease, cancer, or rheumatoid arthritis. Hemolytic anemia. This type of anemia happens when red blood cells are destroyed by an abnormal process in your body before their lifespan is over. As a result, your body doesn't have enough red blood cells to function.

And your bone marrow can't make enough to keep up with demand. Fanconi anemia. This is a rare inherited disorder in which your bone marrow isn't able to make enough of any of the components of blood, including red blood cells. Children born with this disorder often have serious birth defects because of the problems with their blood. They give rise to all of the formed elements in blood. If a stem cell commits to becoming a cell called a proerythroblast, it will develop into a new red blood cell.

The formation of a red blood cell takes about 2 days. The body makes about two million red blood cells every second! Oxygen levels are also directly monitored from free oxygen in the plasma typically following an arterial stick. When this method is applied, the amount of oxygen present is expressed in terms of partial pressure of oxygen or simply pO 2 and is typically recorded in units of millimeters of mercury, mm Hg.

In response to hypoxemia, less oxygen will exit the vessels supplying the kidney, resulting in hypoxia low oxygen concentration in the tissue fluid of the kidney where oxygen concentration is actually monitored. Interstitial fibroblasts within the kidney secrete EPO, thereby increasing erythrocyte production and restoring oxygen levels.

In a classic negative-feedback loop, as oxygen saturation rises, EPO secretion falls, and vice versa, thereby maintaining homeostasis. Populations dwelling at high elevations, with inherently lower levels of oxygen in the atmosphere, naturally maintain a hematocrit higher than people living at sea level.

Consequently, people traveling to high elevations may experience symptoms of hypoxemia, such as fatigue, headache, and shortness of breath, for a few days after their arrival. In response to the hypoxemia, the kidneys secrete EPO to step up the production of erythrocytes until homeostasis is achieved once again. To avoid the symptoms of hypoxemia, or altitude sickness, mountain climbers typically rest for several days to a week or more at a series of camps situated at increasing elevations to allow EPO levels and, consequently, erythrocyte counts to rise.

When climbing the tallest peaks, such as Mt. Everest and K2 in the Himalayas, many mountain climbers rely upon bottled oxygen as they near the summit. Production of erythrocytes in the marrow occurs at the staggering rate of more than 2 million cells per second.

For this production to occur, a number of raw materials must be present in adequate amounts. These include the same nutrients that are essential to the production and maintenance of any cell, such as glucose, lipids, and amino acids. However, erythrocyte production also requires several trace elements:. Erythrocytes live up to days in the circulation, after which the worn-out cells are removed by a type of myeloid phagocytic cell called a macrophage , located primarily within the bone marrow, liver, and spleen.

The breakdown pigments formed from the destruction of hemoglobin can be seen in a variety of situations. At the site of an injury, biliverdin from damaged RBCs produces some of the dramatic colors associated with bruising.

With a failing liver, bilirubin cannot be removed effectively from circulation and causes the body to assume a yellowish tinge associated with jaundice. Stercobilins within the feces produce the typical brown color associated with this waste.

And the yellow of urine is associated with the urobilins. Figure 4. Erythrocytes are produced in the bone marrow and sent into the circulation. At the end of their lifecycle, they are destroyed by macrophages, and their components are recycled. When the number of RBCs or hemoglobin is deficient, the general condition is called anemia.

There are more than types of anemia and more than 3. Anemia can be broken down into three major groups: those caused by blood loss, those caused by faulty or decreased RBC production, and those caused by excessive destruction of RBCs. Clinicians often use two groupings in diagnosis: The kinetic approach focuses on evaluating the production, destruction, and removal of RBCs, whereas the morphological approach examines the RBCs themselves, paying particular emphasis to their size.

A common test is the mean corpuscle volume MCV , which measures size. Normal-sized cells are referred to as normocytic, smaller-than-normal cells are referred to as microcytic, and larger-than-normal cells are referred to as macrocytic. Reticulocyte counts are also important and may reveal inadequate production of RBCs.