Solutions to Review Problems

  1. If erythrocytes were aerobic, they would use some of the O2 that they carry for their own energy requirements, thus decreasing the amount of O2 transported to the rest of the body. Because they are anaerobic, they do not have any O2 requirements of their own and can deliver all the O2 they carry to other cells.
  2. B
    The main function of the lymphatic system is to collect excess interstitial fluid and return it to the circulatory system, maintaining the balance of body fluids. However, this is not one of the answer choices. A second function of the lymphatic system is to absorb chylomicrons from the small intestine and deliver them to cardiovascular circulation; this is choice (B). The remaining answer choices describe the circulatory system but not the lymphatic system.
  3. See Figure 17.5.
  4. In a blood transfusion, the donor blood must be carefully matched with the blood of the recipient. If the erythrocytes in the donor blood have a different class of surface proteins (antigens) than the recipient’s erythrocytes, the recipient’s immune system might “attack” the surface protein of the donor, thus rejecting the donor blood. For example, if the donor blood is type A and the recipient blood is type B, the recipient’s anti-A antibodies would attack the donor’s erythrocytes, because type A blood has type A antigens.
  5. D
    Discussed in gas exchange section of this chapter.
  6. The muscles involved in ventilation are the diaphragm, which separates the thoracic cavity from the abdominal cavity, and the intercostal muscles of the rib cage. During inhalation, the diaphragm contracts and flattens while the external intercostals contract, pushing the rib cage up and out. These actions cause an overall increase in the size of the thoracic cavity. During exhalation, both the diaphragm and the external intercostals relax, causing a decrease in the size of the thoracic cavity. In forced expiration, the internal intercostals contract, pulling the rib cage down.
  7. D
    Discussed in vertebrate respiratory system section of this chapter.
  8. A
    Exhalation is generally a passive process involving elastic recoil of the lungs and relaxation of both the diaphragm and the external intercostal muscles. (However, during vigorous exercise, active muscular contraction assists in expiration.) Gas exchange and diffusion are also passive processes and involve molecules moving down their partial pressure gradients. Inhalation is an active process requiring contraction of the diaphragm and the external intercostals.