Which of the following determines the direction of gas movement?

partial pressure gradient

When the inspiratory muscles contract, _________________.

the size of the thoracic cavity increases in both length and diameter

The nutrient blood supply of the lungs is provided by ______________.

the bronchial arteries

Oxygen and carbon dioxide are exchanged in the lungs and through all cell membranes by ________________.

diffusion

Which of the following would not normally be treated by 100% oxygen therapy? (Choose all that apply.)

respiratory crisis in an emphysema patient and

eupnea

Most oxygen carried in the blood is _____________.

chemically combined with the heme in red blood cells

Which of the following has the greatest stimulating effect on the respiratory centers in the brain?

carbon dioxide

In mouth-to-mouth artificial respiration, the rescuer blows air from his or her own respiratory system into that of the victim. Which of the following statements are correct?

Expansion of the victim's lungs is brought about by blowing air in at higher than atmospheric pressure (positive-pressure breathing).

During inflation of the lungs, the intrapleural pressure increases.

and Expiration during this procedure depends on the elasticity of the alveolar and thoracic walls.

A baby holding its breath will _____________.

automatically start to breathe again when the carbon dioxide levels in the blood reach a high enough value

Under ordinary circumstances, which of the following blood components is of no physiological significance?

nitrogen

Damage to which of the following would most likely result in cessation of breathing?

the ventral respiratory group of the medulla

The bulk of carbon dioxide is carried ___________________.

as the ion HCO3− in the plasma after first entering the red blood cell

Trace the route of air from the nares to an alveolus. Name subdivisions of organs where applicable, and differentiate between conducting and respiratory zone structures.

The route of air from the external nares to an alveolus and the organs involved are as follows: conducting zone structures—external nares, nasal cavity, pharynx (nasopharynx, oropharynx, laryngopharynx), larynx, trachea, and right and left primary bronchi, secondary bronchi, tertiary bronchi and successive bronchi orders, bronchioles, and terminal bronchioles; respiratory zone structures—respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. (pp. 805–816)

1. Why is it important that the trachea is reinforced with cartilage rings?
2. Why is it advantageous that the rings are incomplete posteriorly?

1.The trachea is reinforced with cartilage rings to prevent the trachea from collapsing and to keep the airway patent despite the pressure changes that occur during breathing.

2. The advantage of the rings not being complete posteriorly is that the esophagus is allowed to expand anteriorly during swallowing.

Briefly explain the reasons that men have deeper voices than boys or women.

The adult male larynx as a whole is larger and the vocal cords are longer than those of women or boys. These changes occur at puberty under the influence of rising levels of testosterone. (p. 808)

The lungs are mostly passageways and elastic tissue.

1. What is the role of the elastic tissue?
2. Of the passageways?

1. The elastic tissue is essential both for normal inspiration and expiration; expiration is almost totally dependent on elastic recoil of the lungs when the inspiratory muscles relax. (p. 819)

2. The passageways are air conduits used to warm, moisten, and transport air into the alveoli, the site of gas exchange. (p. 803)

Describe the functional relationships between volume changes and gas flow into and out of the lungs.

The volume of gas flow to and from the alveoli is directly proportional to the difference in pressure between the external atmosphere and the alveoli. Very small differences in pressure are sufficient to produce large volumes of gas flow. As thoracic volume increases, intrapulmonary pressure decreases, resulting in air flow into the lungs. When the lungs recoil, thoracic volume decreases, causing intrapulmonary pressure to increase, and gases flow out of the lungs. (p. 820)

Discuss how airway resistance, lung compliance, and alveolar surface tension influence pulmonary ventilation.

Pulmonary ventilation, or gas flow into and out of the lungs, relies on the pressure gra-dient between the atmosphere and alveoli, and airway diameter. Given that gas flow in a system is equal to the pressure gradient divided by the resistance, when resistance increases, gas flow decreases, and vice versa. Changes in resistance are related to airway diameter, which is greatest in medium-sized bronchi. Lung compliance is based on two factors: distensibility and alveolar surface tension. Distensibility is the degree of stretch possible in the lung tissue, while alveolar surface tension is related to the collapsing force of water vapor within the alveoli. Surfactant is secreted in the alveoli to optimize surface tension. In terms of lung compliance, the greater the volume increase for a given rise in pressure, the greater the compliance. (pp. 820–821)

1. Differentiate clearly between minute ventilation and alveolar ventilation rate.
2. Which provides a more accurate measure of ventilatory efficiency, and why?

1. Minute ventilation is the total amount of gas that flows into and out of the respiratory tract in one minute. Alveolar ventilation rate takes into account the amount of air wasted in dead space areas and provides a measurement of the concentration of fresh gases in the alveoli at a particular time.

2. Alveolar ventilation rate provides a more accurate measure of ventilatory efficiency because it considers only the volume of air actually participating in gas exchange.

State Dalton’s law of partial pressures and Henry’s law.

Dalton’s law of partial pressures states that the total pressure exerted by a mixture of gases is the sum of the pressure exerted independently by each gas in the mixture. Henry’s law states that when a mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to its partial pressure and its solubility in the liquid. (p. 824)

1. Define hyperventilation.

2.If you hyperventilate, do you retain or expel more carbon dioxide?

3.What effect does hyperventilation have on blood pH?

1. Hyperventilation is rapid or deep breathing.
2. Hyperventilation causes and increases the release of carbon dioxide from the blood.
3. Hyperventilation increases blood pH, due to the increased loss of H+ associated with CO2 in the blood.

Describe age-related changes in respiratory function.

Age-related changes include a loss of elasticity in the lungs and a more rigid chest wall. These factors result in a slowly decreasing ability to ventilate the lungs. Accompanying these changes is a decrease in blood oxygen levels and a reduced sensitivity to the stimulating effects of carbon dioxide. (p. 842)

Critical Thinking

After a week of scuba diving in the Bahamas, Mary Ann boards an airplane. During her flight home, she develops aching joints, nausea, and dyspnea which resolve during landing. During the flight, the cabin pressure was equivalent to an altitude of 8000 feet. Explain her problem.

Mary Ann is suffering from decompression sickness, brought on by the rapid ascent in the plane. During the week of diving, she accumulated nitrogen gas in her tissues that at normal altitudes leaves her tissues slowly and unnoticed. However, on the flight, cabin pressure decreased quickly enough to allow residual nitrogen gas to leave more rapidly, causing her symptoms. The return to a lower altitude with a higher atmospheric pressure upon landing alleviates her symptoms. (p. 825)

At the ClinicClinical Case Study: Respiratory System

Barbara Joley was in the bus that was hit broadside. When she was freed from the wreckage, she was deeply cyanotic and her respiration had stopped. Her heart was still beating, but her pulse was fast and thready. The emergency medical technician reported that when Barbara was found, her head was cocked at a peculiar angle and it looked like she had a fracture at the level of the C₂ vertebra. The following questions refer to these observations.

How might the “peculiar” head position explain Barbara’s cessation of breathing?

Spinal cord injury from a fracture at the level of the C₂ vertebra would interrupt the normal transmission of signals from the brain stem down the phrenic nerve to the diaphragm, and Barbara would be unable to breathe due to paralysis of the diaphragm.

What procedures (do you think) the emergency personnel should have initiated immediately?

Barbara’s head, neck, and torso should have been immobilized to prevent further damage to the spinal cord. In addition, she required assistance to breathe, so her airway was probably intubated to permit ventilation of her lungs.

Why is Barbara cyanotic? Explain cyanosis.

Cyanosis is a decrease in the degree of oxygen saturation of hemoglobin. As Barbara’s respiratory efforts cease, her alveolar P_{O 2} will fall, so there is less oxygen to load onto hemoglobin. In her peripheral tissues, what little oxygen hemoglobin carries will be consumed, leaving these tissues with a bluish tinge.

Assuming that Barbara survives, how will her accident affect her lifestyle in the future?

Injury to the spinal cord at the level of the C₂ vertebra will cause quadriplegia (paralysis of all four limbs).

Barbara survived transport to the hospital and notes recorded at admission included the following observations.

• Right thorax compressed; ribs 7 to 9 fractured
• Right lung atelectasis

Relative to these notes:

1. What is atelectasis and why is only the right lung affected?

Atelectasis is the collapse of a lung. Because it is the right thorax that is compressed, only her right lung is affected. Because the lungs are in separate pleural cavities, only the right lung collapsed.

How do the recorded injuries relate to the atelectasis?

Barbara’s fractured ribs probably punctured her lung tissue and allowed air within the lung to enter the pleural cavity.

What treatment will be done to reverse the atelectasis? What is the rationale for this treatment?

The atelectasis will be reversed by inserting a chest tube and removing the air from the pleural cavity. This will allow her lung to heal and reinflate.