Erythrocytic refers to red blood cells, also known as erythrocytes. These microscopic cells are fundamental for sustaining human life. Their proper function ensures continuous oxygen delivery throughout the body, a process without which cellular activities cannot occur.
The Role of Red Blood Cells
Red blood cells primarily transport gases throughout the circulatory system, carrying oxygen from the lungs to every tissue and organ. This is accomplished by hemoglobin, a specialized protein inside them, which contains iron and gives blood its characteristic red color. Oxygen binds to the iron in hemoglobin within the lungs, forming oxyhemoglobin, which then circulates.
Once oxygenated red blood cells reach tissues, oxygen is released from hemoglobin and diffuses into surrounding cells for metabolic energy production. Red blood cells have a biconcave disc shape, which increases their surface area for efficient gas exchange and allows them to squeeze through narrow capillaries. After oxygen delivery, these cells also pick up carbon dioxide, a waste product, and transport it back to the lungs for exhalation.
How Red Blood Cells Are Made and Replaced
The body continuously produces new red blood cells through a process called erythropoiesis. This process primarily occurs within the red bone marrow in adults, the soft, spongy tissue inside bones. The kidneys play a significant role in this regulation by producing a hormone known as erythropoietin (EPO).
When oxygen levels in the body decrease, the kidneys detect this change and secrete more EPO. This hormone then travels to the bone marrow, stimulating it to increase red blood cell production. Each red blood cell typically circulates for about 120 days before becoming old or damaged. Aged cells are then removed from circulation, primarily by specialized cells in the spleen and liver.
Common Conditions Involving Red Blood Cells
Disruptions in red blood cell count or function can lead to various health conditions. Anemia occurs when there is a deficiency in healthy red blood cells or hemoglobin, leading to reduced oxygen transport to the body’s tissues. Causes include insufficient iron, necessary for hemoglobin production, or a lack of vitamin B12. Chronic diseases and significant blood loss, such as from heavy menstrual bleeding or internal ulcers, can also contribute to anemia. Symptoms include tiredness, weakness, shortness of breath, pale or yellowish skin, and sometimes an irregular heartbeat or dizziness.
Conversely, polycythemia is characterized by an excess number of red blood cells. This overproduction causes the blood to become thicker and flow more sluggishly through the blood vessels. The increased blood thickness raises the risk of blood clots, which can lead to serious complications such as a heart attack or stroke. Individuals with polycythemia may experience symptoms like headaches, dizziness, fatigue, high blood pressure, blurred vision, or ringing in their ears. An enlarged spleen can also develop as it works harder to filter the increased number of cells, and some people report generalized itchiness, especially after a warm bath or shower.