Chapter 33 Circulatory System 33 1 The Circulatory

Chapter 33 Circulatory System

33. 1 The Circulatory System Functions of the Circulatory System • The circulatory system transports oxygen, nutrients, and other substances throughout the body, and removes wastes from tissues.

The Heart • The muscle layer of the heart is the myocardium. Its powerful contractions pump blood through the circulatory system. The human heart has four chambers. A wall called the septum separates the right side of the heart from the left side. On each side of the septum are an upper and lower chamber.

• Each upper chamber, or atrium (plural: atria), receives blood from the body; each lower chamber, or ventricle, pumps blood out of the heart. • Flaps of connective tissue called valves are located between the atria and the ventricles and between the ventricles and blood vessels leaving the heart. • The valves open and close to keep blood moving in one direction.

• The heart pumps blood through two pathways: • Pulmonary circulation pumps blood from the heart to the lungs and back to the heart again. Blood picks up oxygen and releases carbon dioxide in the lungs. • Systemic circulation pumps blood from the heart to the rest of the body. Cells absorb much of the oxygen and load the blood with carbon dioxide. • Video

Blood Vessels Blood flows through the circulatory system in blood vessels: • Arteries are large vessels that carry blood away from the heart to the tissues of the body. Except for the pulmonary arteries, all arteries carry oxygen-rich blood. • Capillaries are the smallest vessels. Their thin walls allow oxygen and nutrients to pass from blood into tissues and wastes to move from tissues into blood. • Veins return blood to the heart. Many have valves that prevent backflow.

Blood Pressure • The contractions of the heart produce a wave of fluid pressure in the arteries, known as blood pressure. • Without that pressure, blood would stop flowing through the body. • The body regulates blood pressure through actions of the brain and the kidneys. Read Page 953

33. 2 Blood and Lymphatic system Blood has four main components: – Plasma is a straw-colored fluid. It is about 90 percent water and 10 percent dissolved gases, salts, nutrients, enzymes, hormones, waste products, plasma proteins, cholesterol, and other important compounds. Parts of plasma help control body temperature, transport substances, and fight infection. Plasma proteins are involved in blood clotting. – Red blood cells transport oxygen. Blood gets its red color from the iron in hemoglobin, a protein that binds oxygen in the lungs and releases it in the capillaries. – White blood cells guard against infection, fight parasites, and attack bacteria. – Platelets are cell fragments involved in blood clotting.

Lymphatic system • The lymphatic system is a network of vessels, nodes, and organs that collects the fluid that leaves the capillaries, “screens” it for microorganisms, and returns it to the circulatory system. Fig 33 -10 • Lymph is fluid that consists of blood components that have moved through the walls of capillaries. • Lymph vessels transport materials and lymph nodes act as filters, trapping microorganisms, stray cancer cells, and debris.

Circulatory System Diseases Three common and serious diseases of the circulatory system are: 1. Heart disease: A leading cause of heart disease is atherosclerosis, a condition in which fatty deposits called plaque build up in artery walls and eventually cause the arteries to stiffen. A heart attack occurs as heart muscle cells become damaged. Read Page 958 Video

Circulatory System Diseases 2. Stroke: A clot that blocks a blood vessel in the brain may cause a stroke, which is the sudden death of brain cells when their blood supply is interrupted. A stroke can also occur if a weak vessel breaks and causes bleeding in the brain. Page 958 Video

Circulatory System Diseases 3. High blood pressure, or hypertension, is usually defined as blood pressure higher than 140/90. Uncontrolled high blood pressure can damage the heart and blood vessels. It can also lead to heart attack, stroke, and kidney damage. Page 959 Video

Understanding Circulatory Disease Cholesterol is a lipid that is part of animal cell membranes. • It is transported in the blood primarily by two types of lipoproteins: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). • The liver manufactures cholesterol, but it also comes from animal product foods. • High cholesterol levels, along with other risk factors, lead to atherosclerosis and higher risk of heart attack. Page 959 Video