Module 7: Blood and Blood Vessels
Learning Objectives:
By the end of this module, students will be able to:
- Describe the components of blood.
- Compare and contrast the formed elements of blood and their functions.
- Explain blood types, blood donor compatibility, and the Rh factor.
- Describe the three layers that make up blood vessels.
- Compare and contrast the structure of the walls of the different types of arteries, veins, and capillaries.
- Explain how blood returns to the heart despite low blood pressure in veins.
- Explain the importance of collateral circulation.
Terms to Know
|
Blood
|
Vessels
|
Fluid Connective Tissue
Blood and lymph are fluid connective tissues. Cells circulate in a liquid extracellular matrix. The formed elements circulating in the blood are derived from hematopoietic stem cells located in the bone marrow and include red blood cells (RBCs), white blood cells (WBCs), and cell fragments called platelets. Erythrocytes, red blood cells, transport oxygen, and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues. The extracellular matrix, called plasma, makes blood unique among connective tissues because it is fluid. This fluid, which is mostly water, perpetually suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body. Blood constitutes approximately 8 percent of adult body weight. Adult males typically average about 5-6 liters of blood. Females average 4–5 liters.
Functions of Blood
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. The specific functions of blood also include defense and regulation.
Transportation
- Oxygen and carbon dioxide from the air you breathe and cellular metabolism.
- Nutrients from the foods you eat are absorbed in the digestive tract. 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.
- Hormones are released by endocrine glands into the bloodstream.
- Enzymes and waste products are transported from cells in the bloodstream.
Defense
Many types of WBCs protect the body from external threats, such as disease-causing bacteria that have entered the bloodstream in a wound. Other WBCs seek out and destroy internal threats, such as cells with mutated DNA that could multiply to become cancerous or body cells infected with viruses.
When damage to the vessels results in bleeding, blood platelets and certain proteins dissolved in the plasma, the fluid portion of the blood, interact to block the