40. Circulatory System

Which of the following is not a true statement about open and closed circulatory systems? a. Both systems have some sort of a heart that pumps a circulatory fluid through the body. b. A frog has an open circulatory system; other vertebrates have closed circulatory systems. c. The blood and interstitial fluid are separate in a closed system but are indistinguishable in an open system. d. Some of the circulation of blood in both systems results from body movements.

Trace the path of blood starting in a pulmonary vein, through the heart, and around the body, returning to the pulmonary vein. Name, in order, the heart chambers and types of vessels through which the blood passes.

Predict how Antarctic icefish can transport enough oxygen in their blood to meet their needs even though they lack hemoglobin.

If blood were supplied to all of the body's capillaries at one time, a. blood pressure would fall dramatically. b. resistance to blood flow would increase. c. blood would move too rapidly through the capillaries. d. the amount of blood returning to the heart would increase.

Why did separate systemic and pulmonary circulations evolve in species that have the high-pressure circulatory system required for rapid movement of blood?

Trace the path of an oxygen molecule in its journey from the air to a muscle cell in your arm, naming all the structures involved along the way.

If a blood clot forms inside a vein in the leg, it may travel through the circulatory system. What is the first capillary bed the clot would reach, where it might block blood flow?

Explain how the structure of capillaries relates to their function of exchanging substances with the surrounding interstitial fluid. Describe how that exchange occurs.

Here is a blood sample that has been spun in a centrifuge. List, as completely as you can, the components you would find in the straw-colored fluid at the top of this tube and in the dense red portion at the bottom.

Physiologists speculate about cardiovascular adaptations in dinosaurs—some of which had necks almost 10 m (33 feet) long. Such animals would have required a systolic pressure of nearly 760 mm Hg to pump blood to the brain when the head was fully raised. Some analyses suggest that dinosaurs' hearts were not powerful enough to generate such pressures, leading to the speculation that long-necked dinosaurs fed close to the ground rather than raising their heads to feed on high foliage. Scientists also debate whether dinosaurs had a 'reptile-like' or 'bird-like' heart. Most modern reptiles have a three-chambered heart with just one ventricle. Birds, which evolved from a lineage of dinosaurs, have a four-chambered heart. Some scientists believe that the circulatory needs of these long-necked dinosaurs provide evidence that dinosaurs must have had a four-chambered heart. Why might they conclude this?