21. If the thoracic wall is punctured, air leaking in will cause the lung to collapse. Thus in
the normal, intact thoracic cavity,
a. lung expansion is passive.
b. air pressure is the same as it is on the outside.
c. a slight suction keeps lungs inflated.
d. breathing movements keep lungs inflated.
e. Both a and b
22. Which part of the blood is most efficient at carrying oxygen?
23. Which of the following would increase the amount of oxygen diffusing from the
lungs into the blood?
24. Each molecule of hemoglobin, when fully saturated, carries how many molecules of