33.1 The Circulatory System Lesson Overview 33.1 The Circulatory System

Functions of the Circulatory System What are the functions of the circulatory system?

Functions of the Circulatory System What are the functions of the circulatory system? The circulatory system transports oxygen, nutrients, and other substances throughout the body, and removes wastes from tissues.

2 TYPES OF SYSTEMS OPEN SYSTEM: The open circulatory system is a system in which a fluid in a cavity called the hemocoel bathes the organs directly with oxygen and nutrients and there is no distinction between blood and interstitial fluid. CLOSED SYSTEM: Closed circulatory systems have the blood closed at all times within vessels of different size and wall thickness.

Functions of the Circulatory System The human body contains millions of cells that are not in direct contact with the external environment. Because of this, humans need a circulatory system. The circulatory system transports oxygen, nutrients, and other substances throughout the body, and removes wastes from tissues.

The Heart How does the heart pump blood through the body?

Heart Structure

Heart Structure On each side of the septum are an upper and lower chamber. Each upper chamber, or atrium, receives blood from the body. Each lower chamber, or ventricle, pumps blood out of the heart.

Blood Flow Through the Heart Blood from the body enters the heart through the right atrium; blood from the lungs enters through the left atrium. When the atria contract, blood flows into the ventricles.

Blood Flow Through the Heart Flaps of connective tissue called valves are located between the atria and the ventricles. When blood moves from the atria into the ventricles, the valves open. When the ventricles contract, the valves close, preventing blood from flowing back into the atria.

Blood Flow Through the Heart Valves are also located at the exits of each ventricle. This system of valves keeps blood moving through the heart in one direction.

Circulation The heart functions as two pumps. One pump pushes blood to the lungs, while the other pump pushes blood to the rest of the body. The two pathways of blood through the body are called pulmonary circulation and systemic circulation.

Pulmonary Circulation The right side of the heart pumps oxygen-poor blood from the heart to the lungs through pulmonary circulation. In the lungs, carbon dioxide diffuses from the blood, and oxygen is absorbed by the blood. Oxygen-rich blood then flows to the left side of the heart.

Systemic Circulation The left side of the heart pumps oxygen-rich blood to the rest of the body through systemic circulation. Cells absorb much of the oxygen and load the blood with carbon dioxide. This now oxygen-poor blood returns to the right side of the heart for another trip to the lungs to pick up oxygen.

Blood Vessels Oxygen-rich blood leaving the left ventricle passes into the aorta. The aorta is the first of a series of vessels that carries blood through the systemic circulation and back to the heart. Blood flows through three types of vessels—arteries, capillaries, and veins.

Arteries Arteries are large vessels that carry blood from the heart to the tissues of the body. Except for the pulmonary arteries, all arteries carry oxygen-rich blood. Arteries have thick elastic walls that help them withstand the powerful pressure produced when the heart contracts and pumps blood through them.

Capillaries The smallest blood vessels are the capillaries. Most capillaries are so narrow that blood cells pass through them in single file. Their extremely thin walls allow oxygen and nutrients to diffuse from blood into tissues, and carbon dioxide and other waste products to move from tissues into blood.

Veins After blood passes through the capillaries, it returns to the heart through veins.

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HUMAN HEART Human heart and circulatory system.

VERTEBRATE CIRCULATORY SYSTEMS: FISH What does the red and blue coloration represent? Why does the circulatory system include the gills?

VERTEBRATE CIRCULATORY SYSTEMS: FROG How is a frog heart different from a fish or human heart? Why? What parts are found in all hearts?

REPTILE CIRCULATION The reptile heart has a divided atrium, which receives blood from the lungs and body; the heart's ventricle, which pumps blood out of the heart, is partially divided in most reptiles. Crocodiles and alligators, however, have two separate, complete ventricles and thus have four-chambered hearts as do birds and mammals.

VERTEBRATE CIRCULATORY SYSTEMS: TURTLE Why would a turtle’s heart be different from another reptile like a crocodile? Compare a turtle heart to fish and frog hearts.

BIRD RESPIRATION The body temperature of a bird is higher than that of most other animals. A human being's normal temperature is 98.6o F (37o C). The swift has a temperature of 111.2o F (44o C); a duck, 109.1oF (42.8o C); a heron, 105.8oF (41o C); some thrushes, 113oF (45o C); and sparrows, 107oF (41.6o C). A bird's heart beats faster than a human heart, and birds breathe more rapidly than humans. The human heart beats, on average, 72 times a minute. The hummingbird's heart beats, on average, 615 times a minute. Because of their high rates of metabolism, birds burn up calories very quickly. Small birds must eat almost constantly during the daylight hours.

VERTEBRATE CIRCULATORY SYSTEMS: BIRD Why would a bird heart be a four-chambered heart like mammalian hearts?