1What are the 4 main functions of the respiratory system?
Gas exchange, pH regulation, protection, vocalization.
2How does the respiratory system regulate blood pH?
By changing the rate of respiration, which adjusts CO₂ levels in the blood.
3Describe the direction of air flow in terms of pressure.
Air flows from areas of high pressure to low pressure.
4What creates pressure changes in the lungs?
Muscular pumps (diaphragm & intercostals) change thoracic volume.
5What happens to resistance when bronchioles dilate?
Resistance decreases and airflow increases.
6What are the 3 exchanges in external respiration?
Atmosphere ↔ lungs, lungs ↔ blood, blood ↔ cells.
7What is internal respiration?
Gas exchange between blood and tissues at the cellular level.
8What's the pathway of air from the nose to alveoli?
Nasal cavity → pharynx → glottis → vocal cords → trachea → bronchi → bronchioles → alveoli.
9Where does the upper respiratory system end?
At the trachea
10Why does the left lung have fewer lobes?
To make space for the heart (cardiac notch).
11What are the 3 main functions of the nasal cavity?
Filter air, warm and moisten air, detect odors.
12What helps trap large particles in the nose?
Nasal hairs and mucus.
13Why is air warmed and humidified before reaching the lungs?
To prevent alveoli from drying out and to maintain body temperature.
14What is the purpose of the pleural fluid?
Reduces friction, allows lungs to move smoothly, adheres lungs to chest wall.
15What are the two layers of the pleural sac?
Visceral pleura (on lung) and parietal pleura (on thoracic wall).
16What causes airways to resist collapsing under pressure?
Cartilage in the trachea and bronchi.
17What is the function of ciliated epithelium in the airway?
Moves mucus and trapped debris toward the pharynx.
18What happens to airway diameter and pressure as airways branch?
Diameter decreases, pressure drops, and cross-sectional area increases.
19What are bronchioles missing that bronchi have?
Cartilage and glands.
20What is the purpose of mucus in the respiratory tract?
Traps pathogens and particulates, humidifies air, protects surfaces.
21What does the NKCC transporter do in lung epithelium?
Brings Na⁺, K⁺, and Cl⁻ into the epithelial cell from the extracellular fluid.
22What is the role of CFTR in the lungs?
Releases Cl⁻ into the lumen to draw Na⁺ and water for mucus hydration.
23What happens if CFTR is dysfunctional, as in cystic fibrosis?
Mucus becomes thick, traps pathogens, and is hard to clear—leading to infection.
24How does water enter the mucus in the lungs?
Follows NaCl by osmosis after Cl⁻ and Na⁺ move into the lumen.
25What is the difference between ion handling in sweat glands vs. lungs?
Sweat glands conserve ions; lungs use ions to draw water into mucus.
26What produces surfactant in the alveoli?
Type II alveolar cells.
27What is the role of surfactant?
Reduces surface tension to keep alveoli open during breathing.
28Which cells perform gas exchange in alveoli?
Type I alveolar cells.
29What does Dalton’s Law state?
Total pressure = sum of partial pressures of individual gases.
30What is Boyle’s Law?
P₁V₁ = P₂V₂; pressure and volume are inversely related.
31What does residual volume mean?
Air that stays in lungs after maximal exhalation to prevent collapse.
32What is vital capacity?
Max air that can be exhaled after a full inhalation (TV + IRV + ERV).
33What role do alveolar macrophages play?
Ingest pathogens and debris to protect the lungs.
34What happens to partial pressure of oxygen as air becomes more humid?
It decreases.
35What happens to the diaphragm during inspiration?
It contracts and flattens, increasing thoracic volume.
36What muscles assist in forced expiration?
Internal intercostals and abdominal muscles.
37Why does air flow into the lungs during inspiration?
Because thoracic volume increases and pressure in the lungs decreases, creating a pressure gradient.
38What is the primary equation that governs airflow?
Flow ∝ ΔP / R
39Where is airway resistance the greatest?
In larger bronchi (>2 mm in diameter).
40How does lung volume affect airway resistance?
As lung volume increases, airway resistance decreases.
41What are the effects of bronchoconstriction and bronchodilation?
Bronchoconstriction narrows airways (increases resistance), bronchodilation widens airways (decreases resistance).
42What mediates bronchodilation?
Epinephrine (β₂-receptors) and carbon dioxide.
43What are the motions of the rib cage during breathing?
Pump-handle (anterior-posterior) and bucket-handle (lateral) movements.
44What anatomical structures pass through the diaphragm?
Aorta, esophagus, and inferior vena cava.
45What is tidal volume?
The amount of air that moves in and out of the lungs during normal quiet breathing (~500 mL).
46What volumes contribute to vital capacity?
Tidal volume + Inspiratory reserve volume + Expiratory reserve volume.
47What is residual volume and why is it important?
It’s the air remaining in the lungs after forced expiration (~1200 mL) and prevents alveolar collapse.
48What is total lung capacity?
The total volume of air the lungs can hold: VC + RV
49What does a spirometer measure?
Volumes like TV, IRV, and ERV—but not residual volume.
50What is functional residual capacity (FRC)?
ERV + RV; the air remaining after normal exhalation.
51What happens to intrapleural pressure during inspiration?
It becomes more negative, dropping to about -6 mmHg.
52What causes pneumothorax?
Air enters the pleural space, equalizing pressure and collapsing the lung.
53What percentage of VC is typically exhaled in the first second (FEV1)?
About 70-75%.
54What are the four primary lung volumes?
Tidal volume, Inspiratory reserve volume, Expiratory reserve volume, Residual volume.
55What capacity includes all four lung volumes?
Total lung capacity (TLC = TV + IRV + ERV + RV).
56What is required to reinflate a lung after a pneumothorax?
Restoring negative intrapleural pressure using a chest tube and vacuum.
57What role does surface tension play in lung collapse?
Water in the alveoli promotes collapse unless counteracted by residual volume and surfactant.
58What is the approximate inspiratory reserve volume in males?
~3000 mL.
59Can spirometry measure residual volume? Why or why not?
No; because it cannot measure air that stays in the lungs and doesn’t leave the airway.
60What is lung compliance?
The ability of the lung to stretch or expand.
61 What conditions lower lung compliance?
Fibrosis, restrictive lung disease, inadequate surfactant.
62What is elastance?
The ability of the lung to return to its resting volume after stretching.
63What does surfactant do?
Reduces surface tension in alveoli, increasing compliance.
64What cells produce surfactant?
Type II alveolar cells (pneumocytes).
65What is the Law of LaPlace formula?
P=
r
2T
66In the Law of LaPlace, what happens if radius decreases?
Pressure increases
67How does surfactant stabilize alveoli of different sizes?
It reduces surface tension more in smaller alveoli.
68What is total pulmonary ventilation (TPV)?
Ventilation rate × tidal volume = ~6000 mL/min
69What is alveolar ventilation (AV)?
Ventilation rate × (tidal volume - dead space) = ~4200 mL/min
70What is dead space?
The volume of air (~150 mL) not involved in gas exchange.
71What are the Pores of Kohn and Canals of Lambert?
Structures that allow air exchange between alveoli.
72What is eupnea?
Normal quiet breathing.
73What is dyspnea?
Difficulty breathing; subjective discomfort.
74What happens to alveolar PO₂ and PCO₂ during hyperventilation?
PO₂ increases, PCO₂ decreases.
75Why does only about 13-14% of air in a breath reach alveoli as fresh air?
Because of residual air and dead space mixing.
76What two local factors influence alveolar gas exchange efficiency?
Bronchial airflow (ventilation) and arteriole blood flow (perfusion).
77What happens if alveolar PO₂ decreases and PCO₂ increases?
Arterioles constrict to reduce blood flow to that alveolus.
78What does high CO₂ in exhaled air do to bronchioles?
Causes bronchodilation to enhance CO₂ removal.
79How does pulmonary circulation respond to low alveolar O₂?
Pulmonary arteries constrict (vasoconstriction) to redirect blood to better ventilated areas.
80What is Zone 1 of the lung?
Apex – low blood flow, high PO₂, high pH (~7.5).
81What is Zone 3 of the lung?
Base – high perfusion and ventilation, but lower PO₂ and pH.
82What is the difference in spirometry between obstructive and restrictive lung diseases?
Obstructive: ↓ FEV₁/FVC.
Restrictive: ↓ FVC, normal FEV₁/FVC.
83How does pneumonia affect gas exchange?
Alveoli fill with fluid → ↓ surface area and ↑ diffusion barrier.
84What causes airflow limitation in bronchitis?
Mucus build-up increases resistance and narrows airways.
85Why is emphysema bad for gas exchange?
It destroys alveolar walls, reducing surface area for exchange.
86What happens to bronchioles and pulmonary arteries with increased CO₂?
Bronchioles dilate; pulmonary arteries constrict.
87Why is perfusion higher at the base of the lung?
Gravity increases hydrostatic pressure, enhancing blood flow.
88What is the partial pressure of O₂ in dry air?
160 mm Hg
89Normal arterial PO₂ and PCO₂?
PO₂: 95–100 mm Hg, PCO₂: 40 mm Hg
90Why does CO₂ diffuse faster than O₂?
It is 20x more soluble in plasma.
91How many O₂ molecules can one hemoglobin bind?
4 (1 per heme group)
92What percentage of oxygen is bound to hemoglobin?
About 98%
93What factors shift the hemoglobin O₂ affinity?
pH, temperature, CO₂ (Bohr effect)
94Define hypoxic hypoxia.
Low arterial PO₂, e.g., high altitude, hypoventilation.
95What causes anemic hypoxia?
Low hemoglobin or altered Hb-O₂ binding (e.g., CO poisoning).
96What is histotoxic hypoxia?
Cells can’t use O₂, often due to cyanide poisoning.
97What disease decreases surface area for diffusion?
Emphysema
98How does pulmonary edema affect diffusion?
Increases diffusion distance due to fluid buildup.
99Why does asthma reduce PO₂?
Increased airway resistance limits ventilation.
100What is the primary factor affecting gas exchange?
The concentration (partial pressure) gradient
101How does surface area affect gas diffusion?
More surface area = more efficient diffusion.
102How does distance influence gas diffusion?
Greater distance = slower diffusion (inversely proportional to distance²)
103What % of oxygen in the blood is bound to hemoglobin?
Over 98%.
104What is Fick's equation?
QO₂ = Cardiac Output × (Arterial [O₂] – Venous [O₂]).
105Q: What is the average resting oxygen consumption (QO₂)?
250 mL/min.
106What increases hemoglobin’s affinity for O₂?
Low temperature, high pH, low PCO₂, low 2,3-BPG.
107 What decreases hemoglobin’s affinity for O₂?
High temperature, low pH, high PCO₂, high 2,3-BPG.
108What is the Bohr effect?
↓ pH and ↑ CO₂ cause hemoglobin to release oxygen.
109What causes a right shift in the Hb-O₂ curve?
↑ Temp, ↑ CO₂, ↓ pH, ↑ 2,3-BPG.
110What does a left shift in the Hb-O₂ curve indicate?
Hb has higher O₂ affinity, holds onto O₂ longer.
111What is P50?
PO₂ at which hemoglobin is 50% saturated (analogous to Km).
112Why does fetal Hb have higher O₂ affinity?
To extract O₂ from maternal blood efficiently.
113What protein stores oxygen in muscle?
Myoglobin
114What are the 3 forms of CO₂ transport in blood?
Dissolved (7%), bicarbonate (70%), bound to Hb (23%).
115Where is carbonic anhydrase found?
Inside red blood cells.
116 What is the Haldane effect?
Deoxygenated Hb binds CO₂ more readily.
117What does 2,3-BPG do to Hb?
Decreases affinity for O₂; promotes O₂ release.
118What happens to 2,3-BPG in stored blood?
It decreases → Hb holds onto O₂ more tightly.
119What metabolism do RBCs use to produce 2,3-BPG?
Anaerobic glycolysis.
120What are the three main forms of CO₂ transport in the blood?