Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 222 The stabilization of body temperature: Heat generated by active skeletal muscles is absorbed by the blood and redistributed to other tissues. If the case of high body temperature, that heat will escape across the surface of the skin. If the body’s temperature is too low, the warm blood is directed to the temperature-sensitive organs, such as the brain and vital organs of the core. 18.3 Blood Composition Blood has a unique composition. It is a fluid connective tissue with a matrix called plasma . Plasma proteins are in solution rather than forming insoluble fibers like those in other connective tissues, such as loose connective tissue or cartilage. Because these proteins are in solution, plasma is slightly of 368 Chapter 18: Blood 18.1 Blood In adults, circulating blood provides the roughly 75 trillion cells of the body a source of nutrients, oxygen, waste removal, and transportation of other necessities. The blood also transports specialized cells that defend tissues from infection and disease. These services are essential—so much so that cells in a body region deprived of circulation may die in a matter of minutes. 18.2 Characteristics of Blood Blood has many unique physical characteristics and important functions. The functions of blood include: • The Transportation of dissolved gases, hormones, nutrients, and metabolic wastes: Blood carries oxygen from the lungs to peripheral tissues and carbon dioxide from those tissues to the lungs. Blood delivers nutrients absorbed from the digestive tract and released from storage in adipose tissue or liver. It absorbs and carries the wastes produced by tissue cells to the kidneys for excretion, and blood carries hormones from endocrine glands toward their target cells. • The regulation of the pH and ion composition of interstitial fluids: Diffusion between interstitial fluids and blood eliminates local deficiencies or excesses of ions, such as calcium or potassium. Blood also absorbs and neutralizes acids generated by active tissues, such as lactic acid produced by skeletal muscles. • The restriction of fluid losses at injury sites: Blood contains enzymes and other substances. Blood responds to breaks in vessel walls by initiating the process of repair with enzymes, platelets, and other substances. A temporary blood clot acts as a patch that prevents further blood loss until a permanent one forms over time. • Defense against toxins and pathogens: Blood transports leukocytes, which are specialized cells that combat infections or take away debris. Blood also transports antibodies, which are proteins that mount a specific attack depending on the invading organisms or foreign compounds. •