Respiratory System Study Guide - TBL #2 Practice Flashcards

These flashcards cover the key concepts of the respiratory system including anatomy, mechanics, gas exchange, and pathology as outlined in the TBL #2 Study Guide.

What generations of the airway tree constitute the conducting zone?

Generations $0-16$

Which structures are included in the conducting zone?

Trachea, bronchi, bronchioles, and terminal bronchioles

What are the primary functions of the conducting zone?

Warms, humidifies, and filters air, but does not participate in gas exchange

What is the typical volume of the anatomic dead space?

About $150\,mL$

What generations of the airway tree constitute the respiratory zone?

Generations $17-23$

Which structures make up the respiratory zone (acinus)?

Respiratory bronchioles, alveolar ducts, and alveoli

Which structure marks the end of the conducting zone?

Terminal bronchioles

Which structure marks the start of the respiratory zone?

Respiratory bronchioles

What type of epithelium is found in the conducting zone?

Pseudostratified ciliated columnar epithelium, which becomes cuboidal near terminal bronchioles

What type of epithelium is found in the alveoli?

Simple squamous epithelium

Where does smooth muscle end in the airway tree?

At the terminal bronchioles

Up to which point is cartilage present in the airway tree?

Through the bronchi

What are the stem cells of the conducting zone?

Basal cells and club (Clara) cells

Which cells in the conducting zone secrete mucus?

Goblet cells

What percentage of the alveolar surface is covered by Type I pneumocytes?

$$97\%$$

What are the functions of Type II pneumocytes?

Produce surfactant and act as stem cells

What is the role of alveolar macrophages?

Phagocytosis of debris in the alveoli

What is the mucociliary escalator?

The process of filtration via mucus and cilia to clear the airways

What genetic mutation causes cystic fibrosis?

Mutation in the $CFTR$ (cystic fibrosis transmembrane conductance regulator) gene

What is the inheritance pattern of cystic fibrosis?

Autosomal recessive

What electrolyte imbalance occurs in the mucus of CF patients?

Chloride cannot exit cells, pulling sodium and water in and thickening the mucus

Which drug is mentioned as a treatment for CF that reopens chloride channels?

$$Ivacaftor$$

What is the underlying defect in Kartagener syndrome?

A dynein arm defect causing immotile cilia

What are the clinical signs of Kartagener syndrome?

Chronic sinusitis, bronchiectasis, infertility, and situs inversus

Why does Kartagener syndrome cause situs inversus?

Cilia normally direct organ lateralization in the embryo

Is inspiration active or passive at rest?

Active (requires $ATP$)

Is expiration active or passive at rest?

Passive (driven by elastic recoil)

What is the primary muscle of inspiration, and what is its nerve supply?

The diaphragm, supplied by phrenic nerve roots $C3-C5$

Which muscles are involved in primary inspiration?

Diaphragm and external intercostals

Which muscles are used for forced or labored inspiration?

Sternocleidomastoid and scalenes

Which muscles are used for forced expiration?

Internal intercostals, rectus abdominis, and transverse abdominis

What is the mnemonic for the phrenic nerve roots?

$$C3, 4, 5\text{ keep the diaphragm alive}$$

What do atmospheric, alveolar, and intrapleural pressures represent?

Atmospheric = zero reference; Alveolar = inside alveoli; Intrapleural = in pleural space (normally negative)

What is the formula for transpulmonary pressure (TPP)?

$$TPP = \text{Alveolar pressure} - \text{Intrapleural pressure}$$

What happens if the transpulmonary pressure becomes zero or negative?

The lung collapses (atelectasis)

According to Boyle's law, what is the relationship between pressure and volume?

$$P_1 \times V_1 = P_2 \times V_2$$

What happens to intrapleural pressure during inspiration?

It becomes more negative

During inspiration, how does alveolar pressure change before air flows in?

Alveolar volume rises, causing alveolar pressure to drop below atmospheric pressure

During what activities can intrapleural pressure become positive?

Coughing, sneezing, vomiting, and straining

What is Functional Residual Capacity (FRC)?

The resting end-expiratory point where inward lung elastic recoil balances outward chest wall spring

At what point is pulmonary vascular resistance (PVR) at its minimum?

At functional residual capacity (FRC)

What is the equation for Minute Ventilation ($\dot{V}_E$)?

$$\dot{V}_E = VT \times RR$$

What is the equation for Alveolar Ventilation ($\dot{V}_A$)?

$$\dot{V}_A = (VT - VD) \times RR$$

What are the normal values for Respiratory Rate (RR) and Tidal Volume (VT)?

$RR = 12-20\text{ breaths/min}$; $VT \approx 500\,mL/breath$ (or $6-8\,mL/kg$)

What is the difference between minute ventilation and alveolar ventilation?

Minute ventilation includes dead space air, while alveolar ventilation only counts air contributing to gas exchange

What is the definition of Compliance (C)?

$$C = \frac{\Delta V}{\Delta P}$$

How does surfactant affect lung compliance?

Surfactant increases compliance by reducing surface tension

What is the normal compliance value for the combined lung and chest wall system?

$$0.13\,L/cmH_2O$$

What is the normal compliance value for the lungs alone?

$$0.22\,L/cmH_2O$$

Conditions like emphysema and normal aging cause what change in compliance?

Increased compliance (easier to fill, less elastic recoil)

Conditions like pulmonary fibrosis, pneumonia, and ARDS cause what change in compliance?

Decreased compliance (stiffer lung, harder to fill)

What is hysteresis in respiratory physiology?

The difference in the pressure-volume curve between inflation and deflation of the same breath

Why is inflating the lung harder than deflating it?

More pressure is needed to overcome alveolar surface tension at the start of inspiration

In an obstructive disease like emphysema, what happens to the slope of the compliance curve?

The slope becomes steeper (abnormally high compliance)

In a restrictive disease like fibrosis, what happens to the slope of the compliance curve?

The slope becomes flatter (abnormally low compliance)

What is the primary component of surfactant?

Dipalmitoylphosphatidylcholine ($DPPC$)

When do Type II pneumocytes begin secreting surfactant, and when are mature levels reached?

Starting around $20-22\text{ weeks}$; mature levels by $\approx 35\text{ weeks}$ gestation

Which hormones stimulate surfactant synthesis?

Cortisol, thyroxine, and prolactin

Which hormone inhibits surfactant synthesis?

Insulin

What is the Law of Laplace for a sphere (alveolus)?

$$\text{Collapsing pressure} = \frac{2 \times \text{Surface tension}}{\text{Radius}}$$

Why do smaller alveoli have a higher tendency to collapse?

Smaller radius leads to a higher collapsing pressure for a given surface tension

What causes Neonatal Respiratory Distress Syndrome (NRDS)?

Surfactant deficiency leading to high surface tension and alveolar collapse

What is the classic finding on a chest X-ray for NRDS?

Ground-glass appearance

Why are infants of diabetic mothers at higher risk for NRDS?

High fetal insulin suppresses surfactant production

What amiotic fluid screening test predicts NRDS?

$Lecithin/sphingomyelin$ ($L/S$) ratio; $<1.5$ predicts NRDS ($\ge 2$ is reassuring)

What is the prenatal treatment to prevent NRDS?

Maternal glucocorticoids (e.g., betamethasone, dexamethasone)

What are the complications of high supplemental oxygen in newborns (RIB mnemonic)?

Retinopathy of prematurity, Intraventricular hemorrhage, and Bronchopulmonary dysplasia

What is the basic equation for Airflow ($\dot{Q}$)?

$$\dot{Q} = \frac{\Delta P}{R}$$

What is Poiseuille's Law for airway resistance (R)?

$$R = \frac{8 \times \eta \times l}{\pi \times r^4}$$

By what factor does resistance drop if the airway radius doubles?

A factor of $16$ ($2^4$)

Where in the airway tree is resistance highest?

In the medium-sized bronchi

Why is resistance low in the terminal bronchioles?

Because they are arranged in parallel, which lowers total combined resistance

How does mean arterial pressure compare between the pulmonary and systemic circulations?

Pulmonary is low pressure ($\approx 15\,mmHg$); systemic is high pressure ($\approx 90-100\,mmHg$)

What is the pulmonary vascular response to hypoxia?

Vasoconstriction (hypoxic pulmonary vasoconstriction)

What is the systemic vascular response to hypoxia?

Vasodilation

What is the adaptive purpose of hypoxic pulmonary vasoconstriction?

It redirects blood away from poorly ventilated alveoli toward better-ventilated ones to optimize V/Q matching

What can chronic hypoxic vasoconstriction lead to?

Pulmonary hypertension and right heart strain (cor pulmonale)

Where in the brainstem is the automatic breathing rhythm generated?

Medulla oblongata

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

Sets the basic inspiratory rhythm and receives sensory input via CN IX and CN X

When is the ventral respiratory group (VRG) activated?

During forced inspiration and forced (active) expiration

What is the role of the pneumotaxic center in the pons?

Inhibits inspiration and limits tidal volume, speeding the rate

What is the role of the apneustic center in the pons?

Promotes inspiration and prolongs inspiratory bursts

Where are central chemoreceptors located, and what is their primary stimulus?

Ventral surface of the medulla; stimulated by $H^+$ in the CSF (driven by $CO_2$)

Where are peripheral chemoreceptors located?

Carotid bodies (carotid bifurcation) and aortic bodies (aortic arch)

What is the primary stimulus for peripheral chemoreceptors?

Decreased $PaO_2$ (especially below $60\,mmHg$)

Which nerves carry afferent signals from the carotid and aortic bodies?

$CN\,IX$ (carotid bodies) and $CN\,X$ (aortic bodies)

Why should you be cautious giving high supplemental oxygen to chronic $CO_2$ retainers?

It can blunt their hypoxic drive, which has become their dominant stimulus for breathing

What is the Hering-Breuer reflex?

A protective stretch reflex where airway receptors inhibit inspiration to prevent over-distension

Describe Kussmaul breathing and its typical cause.

Deep, rapid, labored breathing; caused by severe metabolic acidosis (e.g., DKA)

Describe Cheyne-Stokes breathing.

Cyclic crescendo-decrescendo pattern alternating with apnea

What are typical causes of Cheyne-Stokes breathing?

Central sleep apnea, congestive heart failure, and CNS injury

Describe Biot (ataxic) breathing and its significance.

Irregular, unpredictable breaths with apnea; indicates severe brainstem/medullary damage

Which lung volume cannot be measured by spirometry?

Residual Volume ($RV$)

What is Inspiratory Capacity (IC) composed of?

$$IC = IRV + VT$$

What is Functional Residual Capacity (FRC) composed of?

$$FRC = RV + ERV$$

What is Vital Capacity (VC) composed of?

$$VC = IRV + VT + ERV$$

What is the formula for Total Lung Capacity (TLC)?

$TLC = VC + RV$ (or $IRV + VT + ERV + RV$)

What is a normal FEV1/FVC ratio?

$$70-80\%$$

In obstructive disease, what happens to the FEV1/FVC ratio?

It decreases ($<70\%$)

In restrictive disease, what happens to the FEV1/FVC ratio?

It is normal or increased ($\ge 70\%$)