Moreover, endocrine glands scattered throughout the body release their products, called hormones, into the bloodstream, which carries them to distant target cells. Oxygen from the air you breathe diffuses into the blood, which moves from the lungs to the heart, which then pumps it out to the rest of the body. Most of these travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. Nutrients from the foods you eat are absorbed in the digestive tract. The specific functions of blood also include defense, distribution of heat, and maintenance of homeostasis. The primary function of blood is to deliver oxygen and nutrients to and remove wastes from body cells, but that is only the beginning of the story. This fluid, which is mostly water, perpetually suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system. The extracellular matrix, calledÂ plasma, makes blood unique among connective tissues because it is fluid.

The cellular elementsâreferred to as theÂ formed elementsâincludeÂ red blood cells (RBCs),Â white blood cells (WBCs), and cell fragments calledÂ platelets. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. Recall thatÂ bloodÂ is a connective tissue.

Identify the composition of blood plasma, including its most important solutes and plasma proteins.

Discuss the unique physical characteristics of blood.

Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample.

Identify the primary functions of blood in transportation, defense, and maintenance of homeostasis.

An Overview of Bloodīy the end of this section, you will be able to: This chapter focuses on the medium of transport: blood. Together, these three componentsâblood, heart, and vesselsâmakes up the cardiovascular system. The heart pumps blood throughout the body in a network of blood vessels. Our large, complex bodies need blood to deliver nutrients to and remove wastes from our trillions of cells. They obtain nutrients directly from and excrete wastes directly into their environment. Single-celled organisms do not need blood.

Explain the significance of AB and Rh blood groups in blood transfusions.

Describe the structure of platelets and explain the process of hemostasis.Classify and characterize white blood cells.Discuss the structure and function of red blood cells and hemoglobin.Describe the formation of the formed element components of blood.Identify the most important proteins and other solutes present in blood plasma.Identify the primary functions of blood, its fluid and cellular components, and its physical characteristics.One of each type is shown here, isolated from a scanning electron micrograph.Īfter studying this chapter, you will be able to: FigureÂ 18.1Â Blood CellsÂ A single drop of blood contains millions of red blood cells, white blood cells, and platelets.

Platelets are cell fragments.