Pulmonary Anatomy, Physiology, and Breathing

Question 1

Respiratory system

Answer 1

(1) Facilitates the uptake of oxygen from the atmosphere, and (2) release of carbon dioxide into the atmosphere

Question 2

Nose

Answer 2

Turbinates: highly vascularized passages that heat and moisten air

Nasal passages: cilia trap particles and pathogens

Question 3

Throat

Answer 3

Epiglottis (or “cartilaginous horn”): small, movable flap just above the larynx that prevents food and drink from entering the trachea

Laryngeal cartilage and muscle: phonation and ventilation

Question 4

Trachea and bronchus

Answer 4

Main respiratory airway made up of cartilaginous rings that help provide a rigid structure

“Dead space” (Lots of ventilation, no perfusion)

Carina: divides left from right lungs

Cells:

1. Ciliated epithelial cells
2. Mucous-producing cells
3. Club cells: secretory cells that produce various proteins and enzymes that help protect the airway lining and detoxify substances

Question 5

Bronchioles

Answer 5

Last airway division that contains cartilage; lined with club cells

Question 6

Alveoli

Answer 6

Types of alveolar cells:
1. Type I: simplified squamous epithelial (permit gas exchange); DO NOT replicate

2. Alveolar macrophages: protection; clean-up
3. Type II: produce surfactant (a mixture of lipids and proteins) that lubricates the interior surface of alveoli to allow expansion and reduce surface tension; CAN replicate into Type I; last cells to develop in neonates

Question 7

Pleura of the lungs

Answer 7

Parietal pleura: adheres to internal thoracic wall (ribs)

Visceral pleura: adheres to the lungs

Parietal space: space between parietal and visceral pleura; fluid-filled (reduces friction and tension between pleura)

Question 8

Ventilation

Answer 8

Mechanical movement of air from the environment into the lungs to alveoli

Inhalation/Exhalation

Question 9

Diffusion

Answer 9

Gas exchange of oxygen into blood and carbon dioxide into lungs

Oxygen diffuses across the alveoli into the bloodstream and binds to Hgb in RBCs; carbon dioxide diffuses into alveoli

Factors:

1. Temperature
2. pH
3. Alveolar surface area
4. Partial pressure of gases within the system
5. Capillary perfusion

Question 10

Muscles of ventilation

Answer 10

Diaphragm: primary muscle; drops to create a negative pressure vacuum that forces air into the lung (~756 mmHg; compared to atmosphere 760 mmHg)

Intercostal muscles: control rib cage expansion during inspiration

Accessory muscles (neck, abdominal, back): recruited to help breathe when diaphragm and intercostals are not enough

Question 11

Involuntary neural control

Answer 11

Involuntary mechanism of breathing is controlled by the respiratory center in the brainstem; pons and medulla control rate of breathing

Types of receptors:
1. Peripheral chemoreceptors: in the carotid and aorta monitor O2 and CO2/pH (increased CO2 increases rate of breathing)

2. Central chemoreceptors: monitor CO2/pH (in the medulla)
3. Stretch receptors: regulate depth of breathing in the lungs and chest wall
4. Airway nerve cells: sense chemical irritants and stimulate cough/sneeze mechanism

Question 12

Diffusion of oxygen in blood

Answer 12

Requires:
1. Functioning alveoli: (1) one-cell thick; (2) moist environment; and (3) surfactant

2. Adequate partial pressure gradient
3. Adequate capillary perfusion

Question 13

V/Q Ratio

Answer 13

Ratio of air that reaches the alveoli to the amount of capillary perfusion = 0.8

High V/Q mismatch: Reduced perfusion in the lungs; PE

Low V/Q mismatch: Reduced ventilation; COPD

Question 14

Pulmonary circulation

Answer 14

Pulmonary circulation is a low-pressure system (20-30 mmHg) compared to the systemic circulation (80-120 mmHg) because the pulmonary arteries are not as muscularized as their systemic counterparts

Question 15

Partial pressure

Answer 15

Portion of the total pressure exerted by a particular gas within a gaseous mixture

The partial pressure of oxygen determines how easily oxygen leaves the alveoli and binds to Hgb (O2 goes to where there is less PaO2)

Gradient:
1. PaO2 > PaCO2 in the lungs (alveoli)

2. PaO2 < PaCO2 in the pulmonary artery side of capillaries
3. PaO2 > PaCO2 in the pulmonary vein side of capillaries

Question 16

Oxygen and Hgb

Answer 16

PaO2 in alveoli (100 mmHg) > PaO2 in Hgb; therefore, oxygen diffuses from alveoli into Hgb in RBCs

PaO2 in tissue (40 mmHg) < PaO2 in Hgb (~75-100 mmHg); therefore, oxygen diffuses from RBCs into tissue

Question 17

Atmospheric pressure changes

Answer 17

Altitude sickness results when atmospheric pressure is <760 mmHg (there is also decreased atmospheric PaO2)

As a result, PaO2 in alveoli will be <100 mmHg (thus, Hgb has decreased oxygen affinity)

S/S: Dizziness, lightheadedness, fatigue, HA, N/V/, tachycardia, SOBOE

Increased capillary hydrostatic pressure (in attempt to supply tissue with oxygen) leads to:

1. HAPE: High Altitude Pulmonary Edema
2. HACE: High Altitude Cerebral Edema

Question 18

Left-shift: Oxygen dissociation curve

Answer 18

Increased Hgb affinity for oxygen; at the lungs

Factors:

1. Low temperature
2. Alkalosis (decreased H+)

Question 19

Right-shift: Oxygen dissociation curve

Answer 19

Decreased Hgb affinity for oxygen

Factors:

1. Increased temperature
2. Acidosis (increased H+)
3. Increased 2,3-DPG

Question 20

Hypoxemia

Answer 20

Low concentration of oxygen in blood

Caused by:

1. Hypoventilation
2. Diffusion impairment
3. V/Q Mismatch
4. Shunt (mixing of de-/oxygenated blood)