Tiny parts live in your blood. 
Your blood has many tiny parts. 
Your blood is made of many tiny parts. 
First are red blood cells. They are called erythrocytes. These cells carry oxygen from your lungs to your body. They also pick up carbon dioxide to take away. They use a protein called hemoglobin to do this. Hemoglobin is what makes them look red. These cells are shaped like small disks. They are very small and can squeeze through narrow paths.
Next are white blood cells. These are called leukocytes. They are part of your immune system. They help defend your body from sickness.
Finally, there are platelets. These are called thrombocytes. They are very small cell fragments. They help your body make blood clots. Clots stop you from bleeding too much. 
Your blood is made of many tiny parts that work together. 
Red blood cells work like tiny delivery trucks. 
People have studied these cells for a long time.
There are many important numbers to know about blood. 
Understanding blood cells helps us understand our own health. 
Blood cells, also known as hemocytes or hematocytes, are specialized units produced through a process called hematopoiesis. These cells are found primarily within the blood to perform vital tasks. 
Red blood cells, or erythrocytes, are the most abundant cells in the blood. They account for approximately 40% to 45% of the total blood volume. These cells are circular, biconcave, and disk-shaped. This unique shape allows them to be deformable so they can squeeze through narrow capillaries.
White blood cells, or leukocytes, serve as the primary cells of the immune system. They are responsible for defending the body against infectious diseases and foreign materials. 
Platelets, also called thrombocytes, are very different from the other two types. They are not whole cells but are small, irregularly shaped clear cell fragments. Each platelet is only 2 to 3 micrometers in diameter. They are created through the fragmentation of much larger cells called megakaryocytes. Platelets play a critical role in hemostasis, which is the process of stopping bleeding. They release thread-like fibers to help form blood clots. Platelets also act as a source of many growth factors. These factors, such as platelet-derived growth factor (PDGF), help repair and regenerate connective tissues. This makes them essential for the body's natural healing processes.
History shows how our understanding of these cells has grown through careful observation. In 1658, the Dutch naturalist Jan Swammerdam became the first person to observe red blood cells under a microscope. In 1695, another Dutch microscopist, Antoni van Leeuwenhoek, drew illustrations of what he called "red corpuscles." It took much longer to find the other cells. French physician Alfred Donné discovered platelets in 1842. The following year, Gabriel Andral and William Addison both discovered leukocytes. They believed that changes in these cells were linked to disease. Finally, in 1879, Paul Ehrlich developed a technique for staining blood films. This allowed for much better methods of counting different cell types.
There are many specific numbers and measurements that define healthy blood. In adults, the body produces about 2.4 million red blood cells every single second. A normal red blood cell count is between 4.5 and 5 million per cubic millimeter. These cells live for about 100 to 120 days before the spleen removes them. 
Understanding these cell counts is vital because imbalances can indicate serious health issues. Having too few red blood cells is known as anemia, while having too many is called polycythemia. If white blood cell levels are too low, the condition is called leukopenia. An overabundance of white blood cells is called leukocytosis. Platelet disorders are also classified by specific terms. Thrombocytopenia describes a low number of platelets, while thrombocytosis describes a high number. A decrease in platelet function is called thrombasthenia. If platelets cause dangerous clots, it is known as thrombosis. These medical terms help doctors monitor the general health status of a patient.
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