Chapter 17 concept questions

Question 1

What is the difference between cellular respiration and external respiration?

Answer 1

Cellular respiration is intracellular and uses O2 and organic substrates to produce ATP. External respiration is the exchange and transport of gases between the atmosphere and cells.

Question 2

Name the components of the upper respiratory tract and those of the lower respiratory tract.

Answer 2

The upper respiratory tract includes the mouth, nasal cavity, pharynx, and larynx.
The lower respiratory tract includes the trachea, bronchi, bronchioles, and exchange surface of lungs.

Question 3

Name the components (including muscles) of the thoracic cage. List the contents of the thorax.

Answer 3

The thoracic cage consists of the rib cage with intercostal muscles, spinal (vertebral) column, and diaphragm.

The thorax contains two lungs in pleural sacs, the heart and pericardial sac, esophagus, and major blood vessels.

Question 4

Which air passages of the respiratory system are collapsible?

Answer 4

The bronchioles are collapsible.

Question 5

Cigarette smoking paralyzes cilia in the airways and increases mucus production. Why would these effects cause smokers to develop a cough?

Answer 5

If cilia cannot move mucus, the mucus collecting in the airways triggers a cough reflex to clear out the mucus.

Question 6

Is blood flow through the pulmonary trunk greater than, less than, or equal to blood flow through the aorta?

Answer 6

Blood flow is approximately equal in the pulmonary trunk and aorta. (Normally, some venous blood leaving the bronchi, pleura, and part of the heart bypasses the pulmonary circulation and drains directly into the left side of the heart. This is called an anatomic shunt.)

Question 7

A person has left ventricular failure but normal right ventricular function. As a result, blood pools in the pulmonary circulation, doubling pulmonary capillary hydrostatic pressure. What happens to net fluid flow across the walls of the pulmonary capillaries?

Answer 7

Increased hydrostatic pressure causes greater net filtration out of capillaries and may result in pulmonary edema.

Question 8

Calculate the mean pressure in a person whose pulmonary arterial pressure is 25/8 mm Hg.

Answer 8

Mean pressure = 8 mm Hg + 1/3 (25-8) mm Hg = 13.7 mm Hg

Question 9

If nitrogen is 78% of atmospheric air, what is the partial pressure of nitrogen (PN2) in a sample of dry air with an atmospheric pressure of 720 mm Hg?

Answer 9

720 mm Hg x 0.78 = 562mm Hg

Question 10

The partial pressure of water vapor in inspired air is 47 mm Hg when inhaled air is fully humidified. If atmospheric pressure is 700 mm Hg and oxygen is 21% of the atmosphere at 0% humidity, what is the PO2 of fully humidified air?

Answer 10

700 mm Hg - 47 mm Hg = 653 mm Hg x 21% = 137.1 mm Hg PO2

Question 11

How are lung volumes related to lung capacities?

Answer 11

Lung capacities are the sum of two or more lung volumes.

Question 12

Which lung volume cannot be measured directly?

Answer 12

Residual volume cannot be measured directly.

Question 13

If vital capacity decreases with age but total lung capacity does not change, which lung volume must be changing? In which direction?

Answer 13

If aging individuals have reduced vital capacity while total lung capacity does not change, then residual volume must increase.

Question 14

As inhaled air becomes humidified passing down the airways, what happens to the PO2 of the air?

Answer 14

As the air becomes humidified, the PO2 decreases.

Question 15

Compare the direction of air movement during one respiratory cycle with the direction of blood flow during one cardiac cycle.

Answer 15

Air flow reverses direction during a respiratory cycle, but blood flows in a loop and never reverses direction.

Question 16

Explain the relationship between the lungs, the pleural membranes, the pleural fluid, and the thoracic cage.

Answer 16

See Figs. 17.2c and 17.3. The lungs are enclosed in a pleural sac. One pleural membrane attaches to the lung, and the other lines the thoracic cage. Pleural fluid fills the pleural sac.

Question 17

Scarlett O’Hara is trying to squeeze herself into a corset with an 18-inch waist. Will she be more successful by taking a deep breath and holding it or by blowing all the air out of her lungs? Why?

Answer 17

Scarlett will be more successful if she exhales deeply, as this will decrease her thoracic volume and will pull her lower rib cage inward.

Question 18

Why would loss of the ability to cough increase the risk of respiratory infections? (Hint: What does coughing do to mucus in the airways?)

Answer 18

Inability to cough decreases the ability to expel the potentially harmful material trapped in airway mucus.

Question 19

A person has periodic spastic contractions of the diaphragm, otherwise known as hiccups. What happens to intrapleural and alveolar pressures when a person hiccups?

Answer 19

A hiccup causes a rapid decrease in both intrapleural pressure and alveolar pressure.

Question 20

A stabbing victim is brought to the emergency room with a knife wound between the ribs on the left side of his chest. What has probably happened to his left lung? To his right lung? Why does the left side of his rib cage seem larger than the right side?

Answer 20

The knife wound would collapse the left lung if the knife punctured the pleural membrane. Loss of adhesion between the lung and chest wall would release the inward pressure exerted on the chest wall, and the rib cage would expand outward. The right side would be unaffected as the right lung is contained in its own pleural sac.

Question 21

In a normal person, which contributes more to the work of breathing: airway resistance or lung and chest wall elastance?

Answer 21

Normally, lung and chest wall elastance contribute more.

Question 22

Coal miners who spend years inhaling fine coal dust have much of their alveolar surface area covered with scarlike tissue. What happens to their lung compliance as a result?

Answer 22

Compliance decreases.

Question 23

How does the work required for breathing change when surfactant is not present in the lungs?

Answer 23

The work of breathing increases.

Question 24

A cancerous lung tumor has grown into the walls of a group of bronchioles, narrowing their lumens. What has happened to the resistance to air flow in these bronchioles?

Answer 24

Resistance increases.

Question 25

Name the neurotransmitter and receptor for parasympathetic bronchoconstriction

Answer 25

acetylcholine on muscarinic receptor.

Question 26

If a lung tumor decreases blood flow in one small section of the lung to a minimum, what happens to
PO2 in the alveoli in that section and in the surrounding interstitial fluid? What happens to PO2 in that section? What is the compensatory response of the bronchioles in the affected section? Will the compensation bring ventilation in the affected section of the lung back to normal? Explain.

Answer 26

PO2 in alveoli in the affected section will increase because O2 is not leaving the alveoli. PCO2 will decrease because new CO2 is not entering the alveoli from the blood. Bronchioles constrict when PCO2 decreases (see Fig. 17.14), shunting air to areas of the lung with better blood flow. This compensation cannot restore normal ventilation in this section of the lung, and local control is insufficient to maintain homeostasis.

Question 27

Restrictive lung diseases decrease lung compliance. How will inspiratory reserve volume change in patients with a restrictive lung disease?

Answer 27

IRV decreases

Question 28

Chronic obstructive lung disease causes patients to lose the ability to exhale fully. How does residual volume change in these patients?

Answer 28

Residual volume increases.