Mechanics of Breathing

Question 1

Four main functions of the respiratory system

Answer 1

1. Exchange of gasses between the atmosphere and blood
2. Homeostatic regulation of blood pH
3. Protection from inhaled pathogens and irritating substances
4. Speech/vocalization

Question 2

Pressure gradient

Answer 2

Fluid flows from regions of high pressure to low pressure

Question 3

Upper respiratory system

Answer 3

Nasal cavity, pharynx, down to top of trachea

Question 4

Lower respiratory system

Answer 4

Trachea down through diaphragm

Question 5

What does it mean to condition air in the upper respiratory system?

Answer 5

Warm, humidify, filter using nose hairs

Question 6

Resistance to air flow is caused by?

Answer 6

Inappropriate bronchoconstriction and presents as wheezing. Smooth muscle surrounds the bronchioles to allow for changes in air resistance.

Question 7

Thoracic cavity

Answer 7

Region of the chest housing the lungs. Lungs are sealed within the TC. The TC helps maintain appropriate pressure gradients. Each lung exists within its own membrane - pleural sac.

Question 8

Bronchioles branch several times until they terminate in a cluster of?

Answer 8

Alveoli

Question 9

Factors that affect airway resistance

Answer 9

• length of the system (which is constant)
• viscosity of air (changes slightly with humidity and altitude)
• diameter of upper airways (physical obstructions, mediated by mucus)
• diameter of bronchioles

Question 10

What mediates bronchoconstriction?

Answer 10

parasympathetic neurons, histamine, leukotrienes

Question 11

What mediates bronchodilation?

Answer 11

Carbon dioxide, epi

Question 12

What surrounds a cluster of alveoli?

Answer 12

Elastic fibers and a network of capillaries

Question 13

Two types of alveolar cells

Answer 13

Type I - gas exchange

Type II - secretes surfactant

Question 14

Alveolar macrophage

Answer 14

Ingests foreign material

Question 15

Pathway of oxygen from alveolar air space to RBC

Answer 15

1. Alveolar air space
2. Alveolar epithelium (covered in surfactant)
3. “Fused basement membranes” tiniest space between basement membranes
4. Capillary endothelium
5. Plasma
6. RBC

Question 16

Upper airway mucus

Answer 16

Ciliated epithelium lines the upper airway/trachea secreting mucus from submucosal glands

Mucus traps inhaled particles and sits atop a watery saline layer that allows cilia to push mucus toward the pharynx (upwards)

Submucosal glands are made up of goblet cells which secretariat mucous

Cilia have a beating motion to clear pathogens. CF patients have thicker mucus which prevents this beating action.

Question 17

What solution thins the mucous of the airway and how is it formed?

Answer 17

A saline layer sits atop the layer of respiratory epithelial cells. I

Chloride ions move into the epithelial cell from the ECF via secondary active transport. They then travel down their concentration gradient out of the epithelial cell to the lumen of airway via anion channels (CFTR).

Sodium ions follow through junctions between cells. Movement of ions into the lumen draws water through junctions between cells to form the saline layer.

Question 18

Why does air move into the lungs when the thoracic cavity expands?

Answer 18

Volume increases so intrapleural pressure decreases forming a pressure gradient/negative pressure in the thoracic cavity so air flows down the pressure gradient into the lungs

Question 19

How does altitude affect the partial pressure of oxygen?

Answer 19

Decreases

The % of oxygen in the air remains the same, but the amount we’re able to breathe decreases.

Question 20

During inspiration, the diaphragm ________.

Answer 20

Contracts and flattens increasing the volume of the thoracic cavity

Question 21

During expiration, the diaphragm ________.

Answer 21

Relaxes, decreasing the volume of the thoracic cavity

Question 22

Pleural fluid

Answer 22

Fluid that keeps the lung adhered to the chest wall

Question 23

What happens to the lungs during a pneumothorax?

Answer 23

Air flows into the pleural cavity, lung is no longer stuck to the chest wall, lung collapses

Question 24

Surfactant

Answer 24

A fatty substance that reduces the surface tension of a liquid. Without surfactant, water-water interactions would make it harder to expand the alveolus.

Secreted by type II alveolar cells

Surrounds alveoli and aids in alveoli expansion especially when lung volume is low

Question 25

Stale air in the respiratory system

Answer 25

After exhalation, 150 mL of stale air is left in the airway. This stale air is pushed down with the next inhalation in addition to fresh air. Fresh (Po2 = 150 mm Hg) and stale (Po2 = 100 mm Hg) mix. This leads to the Po2 of the alveoli being much lower than that of air.

Question 26

Maximum alveolar partial pressure of oxygen

Answer 26

100 mm hg

Question 27

How do changes in alveolar ventilation (volume/min) affect alveolar partial pressure of oxygen?

Answer 27

Decreasing ventilation decreases alveolar partial pressure of oxygen and vice versa to a maximum of 100 mm Hg

Question 28

How does minute ventilation (L/min) change with exercise?

Answer 28

Exercise —> higher minute ventilation

Question 29

How does arterial oxygen change with with exercise?

Answer 29

Stays the same - 100 mm Hg, max

Question 30

How does arterial CO2 change with exercise?

Answer 30

Decreases with exercise

Question 31

How does arterial pH change with oxygen consumption/exercise?

Answer 31

PH decreases (becomes more acidic) with more exercise

Question 32

Breathing rate is governed by which gas in the body?

Answer 32

CO2

Very big changes in oxygen change breathing rate

Patients with lung disease for a long time will eventually switch over to using oxygen as a breathing rate signal because they’ve been in an oxygen-deprived state for a while