Circulation and Gas Exchange

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In a closed circulatory system, the blood is confined to vessels and is distinct from the interstitial fluid.

Closed systems are more efficient at transporting circulatory fluids to tissues and cells.

Slide 10

Open and closed circulatory systems

Heart

Hemolymph in

sinuses

surrounding organs

Heart

Interstitial

fluid

Small branch vessels

In each organ

Blood

Dorsal vessel

(main heart)

Auxiliary hearts

Ventral vessels

(b) A closed circulatory system

(a) An open circulatory system

Tubular heart

Pores

Slide 11

Organization of Vertebrate Closed Circulatory Systems

Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system.

The three main types of blood vessels are:

arteries - away from the heart.

veins - toward the heart.

capillaries - exchange with body cells.

Slide 12

Arteries branch into arterioles and carry blood to capillaries.

Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid.

Venules converge into veins and return blood from capillaries to the heart.

Slide 13

Vertebrate hearts contain two or more chambers.

Blood enters through an atrium and is pumped out through a ventricle.

Atria - receive blood

Ventricles - pump blood

Slide 14

Single Circulation

Bony fishes, rays, and sharks have single circulation with a two-chambered heart.

In single circulation, blood leaving the heart passes through two capillary beds before returning.

Slide 15

Single circulation in fishes

Artery

Ventricle

Atrium

Heart

Vein

Systemic capillaries

Systemic

circulation

Gill

circulation

Gill capillaries

Slide 16

Double Circulation

Amphibian, reptiles, and mammals have double circulation.

Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart.

Slide 17

Double circulation in vertebrates

Amphibians

Lung and skin capillaries

Pulmocutaneous

circuit

Atrium (A)

Ventricle (V)

Atrium (A)

Systemic

circuit

Right

Left