Chapter 23: Respiratory System Interactive Lecture Guide

Comprehensive vocabulary flashcards covering the six modules of Chapter 23 Respiratory System, including respiratory anatomy, ventilatory mechanics, neural and chemical control, lung volumes and capacities, partial pressures, and gas transport mechanisms.

Conducting zone

The respiratory structures that move, warm, and filter incoming air without participating in gas exchange.

Respiratory zone

The region of the respiratory system containing structures such as respiratory bronchioles and alveoli where actual gas exchange occurs.

Respiratory membrane

A thin alveolar-capillary barrier situated between alveolar air and pulmonary capillary blood that permits gas diffusion.

Pulmonary surfactant

A substance secreted in the lungs whose primary function is to reduce alveolar surface tension, preventing alveolar collapse.

Elastic recoil

The passive recoil property of the lungs and chest wall that reduces thoracic volume after inspiratory muscles relax, making normal expiration passive.

Muscles of forced expiration

The internal intercostals and abdominal muscles, which contract to actively depress the ribs and increase intra-abdominal pressure during forceful exhalation.

Boyle’s law

The gas law dictating that pressure is inversely related to volume; when thoracic and alveolar volume increases during inspiration, alveolar pressure decreases below atmospheric pressure, causing air to enter.

Pre-Bötzinger complex

A pacemaker structure located in the medulla oblongata that is essential for generating the basic respiratory rhythm.

Medulla oblongata (respiratory control)

The primary brainstem autonomic controller that generates, maintains, and adjusts the basic automatic rhythm of breathing.

Pons (respiratory control)

The brainstem region containing the pontine respiratory group that regulates and smooths the transitions between inspiration and expiration.

Cerebral cortex (respiratory control)

The higher brain region that enables temporary voluntary conscious control of breathing.

Chemoreflex

The reflex adjustment of ventilation mediated by chemoreceptors, where a rise in $CO_2$ accompanied by a falling pH acts as the strongest routine chemical stimulus to increase respiration.

Hering–Breuer inflation reflex

A protective stretch reflex initiated by pulmonary receptors whose primary function is to prevent excessive lung inflation.

Residual volume (RV)

The volume of air that remains inside the lungs even after a maximal forced exhalation ($1{,}200\,mL$).

Vital capacity (VC)

The maximum volume of air exhaled after maximal inhalation, calculated by the formula $VC = IRV + TV + ERV$ ($3{,}000\,mL + 500\,mL + 1{,}100\,mL = 4{,}600\,mL$).

Total lung capacity (TLC)

The total volume of air contained within the lungs after a maximal inhalation effort, calculated as $TLC = VC + RV$ ($4{,}600\,mL + 1{,}200\,mL = 5{,}800\,mL$).

External respiration

The exchange of respiratory gases occurring in the lungs, where oxygen diffuses down its partial-pressure gradient from the alveoli into pulmonary capillary blood.

Internal respiration

The exchange of respiratory gases occurring in systemic body tissues, where oxygen diffuses from systemic capillary blood into tissue cells.

Hemoglobin saturation capacity

The binding capacity of one hemoglobin molecule, which can bind up to four molecules of oxygen when fully saturated.

7–23–70 pattern of $CO_2$ transport

The distribution pattern of carbon dioxide transport in blood: $7\%$ dissolved in plasma, $23\%$ bound to hemoglobin (carbaminohemoglobin), and $70\%$ transported as bicarbonate.

Carbonic anhydrase

An enzyme inside erythrocytes that catalyzes the reversible conversion of $CO_2$ and $H_2O$ into carbonic acid ($H_2CO_3$).

Chloride shift

The ionic exchange in systemic capillaries where bicarbonate ($HCO_3^-$) exits the erythrocyte into plasma while chloride ($Cl^-$) enters the red blood cell to maintain electrical neutrality.

Factors promoting oxygen unloading

Physiological tissue conditions—specifically higher $CO_2$, lower pH (acidosis), and higher temperature—that weaken hemoglobin's affinity for oxygen and facilitate oxygen release.