Composition of Blood
Blood is composed of various cellular components and plasma. Plasma is the liquid component of blood that carries the cellular elements and dissolved materials. It makes up about 55% of total blood volume. The remaining 45% contains the cellular elements - red blood cells (RBCs), white blood cells (WBCs) and platelets.
Red Blood Cells
Red blood cells, also called erythrocytes, make up about 45% of total Blood and Blood Components volume. Their main function is to transport oxygen from the lungs to tissues and return carbon dioxide from tissues back to the lungs. RBCs are biconcave disks without nuclei and contain hemoglobin, an iron-rich protein that binds oxygen. The normal RBC count for adult men is 4.7-6.1 million cells/microliter and for adult women is 4.2-5.4 million cells/microliter. Reduced RBC counts can cause anemia.
White Blood Cells
White blood cells, or leukocytes, help fight against infections and foreign invaders in the body. They make up about 1% of total blood volume. There are different types of WBCs - neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Neutrophils are the most abundant type, making up about 40-75% of the total WBC count. They are the primary defenders against bacterial infections. Lymphocytes help the immune system identify and attack viruses, bacteria, foreign substances, and cancer cells. Monocytes defend against infections and also help remove dead or dying cells. Eosinophils and basophils are less common and help defend against parasites and allergies.
Platelets
Platelets, or thrombocytes, help control bleeding by forming blood clots. They make up about 1% of total blood volume. When a blood vessel is damaged, platelets detect the injury and quickly aggregate at the site. They secrete chemicals that activate the clotting mechanism, causing a mesh-like clot to form and plug the hole in the blood vessel. Normal platelet counts range from 150,000 to 450,000 per microliter of blood. Low platelet counts can cause excessive bleeding.
Blood Types
There are four main blood groups - A, B, AB, and O. The blood type is determined by the presence or absence of antigens (proteins) on the surface of red blood cells. Antigens A and B are glycoproteins that characterize the four different blood groups. Group O has neither antigen, group A has only the A antigen, group B has only the B antigen, and group AB has both antigens. The ABO blood group is an important factor in blood transfusions. A person can only receive blood of their own type or type O.
Blood Transport Functions
In addition to transporting oxygen, carbon dioxide, nutrients and wastes, blood performs several critical functions in the body. It helps regulate body temperature and pH levels. It also transports hormones and enzymes to different tissues and organs. The coagulation factors in blood help control bleeding from injuries by forming clots. As an integral part of the lymphatic and immune systems, blood also carries white blood cells to fight infection and disease. Flowing through an extensive system of arteries and veins, blood efficiently circulates nutrients, gases, hormones and cellular products to nourish body tissues and remove metabolic wastes.
Blood cells are continuously produced and broken down in the body through hematopoiesis - the process of blood cell formation. In adults, about 1 million new RBCs are produced every second in the bone marrow to replace old or damaged cells. Platelets have a lifespan of only 7-10 days before being replaced. WBCs live for only a few hours to a few months depending on the type. Strict regulation is needed to maintain appropriate blood cell counts and volumes through continuous production and recycling.
Testing of Blood and Clinical Significance
Blood tests are routinely performed in clinical pathology laboratories to obtain important health information. Complete blood counts (CBCs) measure red blood cell, white blood cell and platelet levels. This screening test can help detect anemia, infection, clotting problems and some cancers. Additional blood tests analyze specific components like hemoglobin, hematocrit, clotting factors, blood type, metabolic components and markers for certain diseases. Abnormal test results may indicate underlying health conditions affecting the blood or bone marrow like leukemia, lymphoma, infections and nutritional deficiencies. Monitoring blood test trends over time also helps manage chronic conditions and monitor treatment progress. Overall, analysis of blood components provides invaluable insights into a person's medical status.
In blood is a complex bodily fluid with critical transport functions. Its precise composition of plasma, cells and factors helps sustain life through oxygen delivery, waste removal, immune defense and clotting control. Understanding blood and its components aids diagnosis and management of many medical conditions. Proper blood formation and circulation throughout the circulatory system is essential for overall health and well-being.
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Alice Mutum is a seasoned senior content editor at Coherent Market Insights, leveraging extensive expertise gained from her previous role as a content writer. With seven years in content development, Alice masterfully employs SEO best practices and cutting-edge digital marketing strategies to craft high-ranking, impactful content. As an editor, she meticulously ensures flawless grammar and punctuation, precise data accuracy, and perfect alignment with audience needs in every research report. Alice's dedication to excellence and her strategic approach to content make her an invaluable asset in the world of market insights.
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