Chap 23

Question 1

What is Tidal Volume (TV)?

Answer 1

The amount of air inhaled or exhaled during a normal breath (~500 mL in adults)

Tidal Volume is a key measurement in assessing respiratory function.

Question 2

What is Total Lung Capacity (TLC)?

Answer 2

The maximum amount of air the lungs can hold. TLC = Vital Capacity (VC) + Residual Volume (RV). Typical value: ~6,000 mL

TLC varies with age, sex, and body size.

Question 3

What is Vital Capacity (VC)?

Answer 3

The total amount of air that can be exhaled after a maximal inhalation. VC = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV). Typical value: ~4,800 mL

VC is an important measure for lung health.

Question 4

What muscles are primarily involved in normal inhalation?

Answer 4

Diaphragm and external intercostals

The diaphragm is the most important muscle for breathing.

Question 5

What happens during normal exhalation?

Answer 5

It is a passive process due to elastic recoil of lungs and relaxation of diaphragm and intercostals

No active muscle contraction is involved in normal exhalation.

Question 6

What accessory muscles assist in forced inhalation?

Answer 6

Scalenes, sternocleidomastoid, and pectoralis minor

These muscles help expand the thorax during forceful breathing.

Question 7

What muscles are involved in forced exhalation?

Answer 7

Internal intercostals and abdominal muscles (e.g., rectus abdominis, obliques)

These muscles actively push air out during forceful exhalation.

Question 8

Define inhalation.

Answer 8

Active process where thoracic cavity volume increases, causing pressure to decrease, and air flows into the lungs

This process is explained by Boyle’s Law: Volume = (Pressure).

Question 9

Define exhalation.

Answer 9

Normally passive, driven by elastic recoil of the lungs, which decreases thoracic cavity volume, increasing pressure and pushing air out

Exhalation typically requires no muscle contraction.

Question 10

What is the role of surfactant in the lungs?

Answer 10

Reduces surface tension, preventing alveolar collapse during exhalation

Surfactant is produced by Type II alveolar cells.

Question 11

What factors affect ventilation?

Answer 11

Surface tension of alveolar fluid, airway resistance, lung compliance

Each factor plays a crucial role in efficient breathing.

Question 12

How does airway resistance affect ventilation?

Answer 12

Resistance increases with smaller airways (e.g., due to mucus or bronchoconstriction)

High airway resistance can impede airflow and reduce ventilation efficiency.

Question 13

What does lung compliance refer to?

Answer 13

The lung’s ability to expand

Damaged elastic fibers (e.g., in emphysema) decrease compliance and increase the work of breathing.

Question 14

What percentage of oxygen is bound to hemoglobin as oxyhemoglobin (HbOz)?

Answer 14

~98%

This indicates that the majority of oxygen transport in the blood relies on hemoglobin.

Question 15

What is the primary form of carbon dioxide transport in the blood?

Answer 15

~70% as bicarbonate ions (HCO3~)

This is formed by the reaction of CO2 with water, catalyzed by carbonic anhydrase.

Question 16

What is carbaminohemoglobin?

Answer 16

Hemoglobin bound to carbon dioxide

It is formed when CO2 binds to the globin portion of hemoglobin.

Question 17

Define ventilation-perfusion coupling.

Answer 17

The matching of airflow (ventilation) and blood flow (perfusion) in the lungs

This process ensures that well-ventilated areas of the lung receive adequate blood flow.

Question 18

What happens to hemoglobin’s affinity for oxygen in metabolically active tissues?

Answer 18

Decreased affinity

This occurs due to lower pH from increased CO2 production, facilitating oxygen delivery.

Question 19

What effect does increased pH have on hemoglobin’s affinity for oxygen in the lungs?

Answer 19

Increased affinity

This occurs because CO2 is exhaled, leading to a lower concentration of H+ ions.

Question 20

Where is the dorsal respiratory group (DRG) located?

Answer 20

In the medulla oblongata

It is part of the brainstem and plays a role in controlling breathing.

Question 21

What is the primary function of the dorsal respiratory group (DRG)?

Answer 21

Sends rhythmic impulses to the diaphragm and external intercostal muscles

This initiates inhalation and primarily controls quiet breathing.

Question 22

What is one effect of aging on lung compliance?

Answer 22

Decreased lung compliance

Aging reduces the elasticity of lung tissues, making breathing more difficult.

Question 23

How does aging affect oxygen levels in the lungs?

Answer 23

Decreased oxygen levels

This is due to a decline in alveolar surface area and capillary density.

Question 24

What happens to vital capacity as a person ages?

Answer 24

Decreased vital capacity

This is the maximum amount of air that can be exhaled after deep inhalation, reduced by aging-related factors.

Question 25

What is the impact of aging on alveolar macrophage activity?

Answer 25

Decreased alveolar macrophage activity

This leads to an increased risk of infections and reduced ability to clear debris.