Respiration 2

Question 1

A single layer of flattened Type I alveolar cells

Answer 1

forms the alveolar walls.

Question 2

Type II alveolar cells

Answer 2

• embedded within the alveolar wall

- secrete pulmonary surfactant.

Question 3

Wandering alveolar macrophages are found

Answer 3

within the alveolar lumen.

Question 4

The diameter of an alveolus is actually about

Answer 4

300 μm

Question 5

the size of the intervening space between air and blood .

Answer 5

0.5 μm

Question 6

Each alveolus is encircled with

Answer 6

a dense network of pulmonary capillaries.

Question 7

each alveolus is surrounded by

Answer 7

an almost continuous sheet of blood.

Question 8

Diaphragm

Answer 8

• Dome-shaped sheet of skeletal muscle
• Separates thoracic cavity from the abdominal
  cavity

Question 9

Pleural sac

Answer 9

• Double-walled, closed sac that separates
  each lung from the thoracic wall
• Pleural cavity – interior of plural sac
• secretes:
  > Intrapleural fluid

Question 10

Intrapleural fluid

Answer 10

• Secreted by surfaces of the pleura

- Lubricates pleural surfaces

Question 11

Interrelationships among ________________ the lungs are important in ventilation

Answer 11

pressures inside and outside

Question 12

3 different pressure considerations important in ventilation

Answer 12

• Atmospheric (barometric) pressure
• Intra-alveolar pressure
  (intrapulmonary pressure)
• Intrapleural pressure
  (intrathoracic pressure)

Question 13

why is the atmospheric pressure at sea level 760 mm Hg?

Answer 13

The pressure exerted on objects by the atmospheric air above Earth’s surface at sea level can push a column of mercury to a height of 760 mm.

Question 14

Atmospheric pressure depends on ____________

Answer 14

altitude and weather conditions

Question 15

LEARN

Question 16

2 additional forces in the chest:
2 recoil forces in opposing directions

(not Intrapleural fluid cohesiveness
Transmural pressure gradient )

Answer 16

• Elastic recoil of the chest wall tries to pull chest wall outwards
• Elastic recoil of lung creates inward pull

=Transmural pressure gradient.

Question 17

Transmural pressure gradient.

Answer 17

• Across the lung wall, the intra-alveolar
  pressure of 760 mm Hg pushes outward
• while the intrapleural pressure of 756 mm Hg pushes inward.
• This 4 mm Hg difference in pressure constitutes a transmural pressure gradient that pushes out on the lungs, stretching them to fill the larger thoracic cavity.
• Across the thoracic wall, the atmospheric pressure of 760 mm Hg pushes inward, while the intrapleural pressure of 756 mm Hg pushes outward.
• This 4 mm Hg difference in pressure constitutes a transmural pressure gradient that pushes inward and compresses the thoracic wall.

Question 18

Changes in lung volume and intra-alveolar pressure during inspiration and expiration

Answer 18

1. Before inspiration, at the end of the
   preceding expiration, intra-alveolar
   pressure is equilibrated with atmospheric
   pressure, and no air is flowing.
2. As the lungs increase in volume during
   inspiration, the intra-alveolar pressure
   decreases, establishing a pressure gradient
   that favours the flow of air into the alveoli from
   the atmosphere; that is, an inspiration occurs. 3. As the lungs recoil to their preinspiratory size
   on relaxation of the inspiratory muscles, the
   intra-alveolar pressure increases, establishing
   a pressure gradient that favors the flow of air
   out of the alveoli into the atmosphere; that is,
   an expiration occurs.

Question 19

Intra-alveolar and intrapleural pressure changes throughout the respiratory cycle.

Answer 19

Question 20

Pneumothorax:

Answer 20

[sub-atmospheric pressure going atmospheric]
1. In traumatic pneumothorax, a puncture in the
chest wall permits air from the atmosphere to flow down its pressure gradient and enter the pleural cavity, abolishing the transmural pressure gradient.
2. When the transmural pressure gradient is abolished, the lung collapses to its unstretched size, and the chest wall springs outward.
3. In spontaneous pneumothorax, a hole in the lung wall permits air to move down its pressure gradient and enter the pleural cavity from the lungs, abolishing the transmural pressure gradient. As with traumatic pneumothorax, the lung collapses to its unstretched size.

Question 21

Primary determinant of resistance to airflow is

Answer 21

the radius of the conducting airway

Question 22

controls contraction of smooth muscle in walls of bronchioles (changes the radii)

Answer 22

Autonomic nervous system

Question 23

abnormally increases airway resistance

Answer 23

Chronic obstructive pulmonary disease (COPD)

- Expiration is more difficult than inspiration