What are the major components of the human blood and their functions?
Human blood is composed of several key components, each serving vital functions:

Red Blood Cells (Erythrocytes): These cells carry oxygen from the lungs to the body's tissues and take carbon dioxide back to the lungs to be exhaled. They contain a protein called hemoglobin, which binds to oxygen.
White Blood Cells (Leukocytes): These cells are part of the immune system and help the body fight infection and other diseases. They come in several types, including lymphocytes, neutrophils, eosinophils, monocytes, and basophils.
Platelets (Thrombocytes): These small cell fragments are crucial for blood clotting. When bleeding occurs, platelets swell, clump together, and form a sticky plug that helps stop the bleeding.
Plasma: This is the liquid component of blood, a yellowish fluid that is mostly water but also contains proteins, glucose, hormones, electrolytes, and waste products. Plasma serves as a transport medium for cells and a variety of substances essential for the body's functions.