33.1 The Circulatory System

The circulatory system transports oxygen, nutrients, and other substances throughout the body, and removes wastes from tissues.

Powerful contractions of the myocardium pump blood through the circulatory system.

As blood flows through the circulatory system, it moves through three types of blood vessels—arteries, capillaries, and veins.

• myocardium (949)

• systemic circulation (950)

• atrium (949)

• pacemaker (951)

• ventricle (949)

• artery (952)

• valve (950)

• capillary (952)

• pulmonary circulation (952)

• vein (950)

33.2 Blood and the Lymphatic System

Plasma is about 90 percent water and 10 percent dissolved gases, salts, nutrients, enzymes, hormones, waste products, plasma proteins, cholesterol, and other important compounds.

The main function of red blood cells is to transport oxygen.

White blood cells guard against infection, fight parasites, and attack bacteria.

Blood clotting is made possible by plasma proteins and cell fragments called platelets.

The lymphatic system is a network of vessels, nodes, and organs that collects the lymph that leaves capillaries, “screens” it for microorganisms, and returns it to the circulatory system.

Three common and serious diseases of the circulatory system are heart disease, stroke, and high blood pressure.

Research indicates that high cholesterol levels, along with other risk factors, lead to atherosclerosis and higher risk of heart attack.

• plasma (954)

• platelet (955)

• red blood cell (954)

• lymph (956)

• hemoglobin (954)

• atherosclerosis (958)

• white blood cell (955)

33.3 The Respiratory System

The human respiratory system picks up oxygen from the air we inhale and releases carbon dioxide into the air we exhale.

Oxygen and carbon dioxide are exchanged across the walls of alveoli and capillaries. Chemical properties of blood and red blood cells allow for efficient transport of gases throughout the body.

Movements of the diaphragm and rib cage change air pressure in the chest cavity during inhalation and exhalation.

Chemicals in tobacco smoke damage structures throughout the respiratory system and have other negative health effects, too.

• pharynx (964)

• bronchus (964)

• trachea (964)

• alveolus (964)

• larynx (964)

• diaphragm (967)

Think Visually Make a two-column table. Title the first column Structure and the second column Function. Fill in the table with the structures described in this chapter—from both circulatory and respiratory systems—and their functions.