Blood

Blood is a vital fluid in the human body that functions as a key transport medium for nutrients, oxygen, carbon dioxide, hormones, and cellular waste products. It is composed of several elements: plasma, which is the liquid component comprising about 55% of blood volume, and formed elements such as red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Plasma is mostly water, containing dissolved proteins, glucose, clotting factors, mineral ions, hormones, and carbon dioxide. Red blood cells contain the protein hemoglobin, which binds oxygen and delivers it to tissues throughout the body, while removing carbon dioxide as a waste product.

In the medical context, blood plays a critical role in homeostasis, immune response, and the body's defense mechanisms. Leukocytes are involved in the immune response, fighting infections and foreign invaders. Platelets and plasma proteins are essential for blood clotting, preventing excessive bleeding after injuries. The regulation of blood composition and volume is critical for maintaining physiological balance, with organs like the kidneys and liver playing significant roles in filtration and detoxification. Blood analysis and typing are crucial in the medical field for diagnosing diseases, managing blood transfusions, and understanding the general health of patients.