Final answer:
Blood contains formed elements such as red blood cells, which transport oxygen and carbon dioxide; white blood cells, which defend against infections; and platelets, which are involved in blood clotting and tissue repair.
Step-by-step explanation:
The Formed Elements of Blood and Their Functions
The formed elements of blood include red blood cells (RBCs or erythrocytes), white blood cells (WBCs or leukocytes), and platelets (thrombocytes). These elements play critical roles in the body's functions and are suspended in the plasma, the extracellular matrix of the blood.
Functions of Red Blood Cells
Red blood cells are biconcave cells that carry hemoglobin, a molecule essential for transporting oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. They lack a nucleus and mitochondria, which allows for more space to carry hemoglobin. Erythrocytes have a lifespan of about 120 days and are produced in the bone marrow.
Functions of White Blood Cells
White blood cells are key to the body's immune response. They fight infections and foreign bodies through processes like diapedesis, where they pass out of blood vessels into tissues. Leukocytes include granular types such as neutrophils, eosinophils, and basophils, and agranular types such as monocytes, NK cells, B cells, and T cells.
Functions of Platelets
Platelets are small cell fragments that originate from megakaryocytes in the bone marrow. They play a significant role in hemostasis, the process of blood clotting, by forming a temporary plug at a site of injury to the blood vessels. Platelets also release growth factors to repair and heal tissues.
Together, these elements ensure proper oxygenation of tissues, defense against pathogens, and prevention of excessive bleeding.