MCAT Biological and Biochemical Foundations of Living Systems Flashcards: 3b Respiratory System Gas Exchange

What this deck covers

This deck focuses on 3b Respiratory System Gas Exchange, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Biological and Biochemical Foundations of Living Systems.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: State the law that relates alveolar pressure to surface tension and radius.

Answer: $P=frac{2T}{r}$ (Laplace law). It shows pressure required to prevent collapse is inversely proportional to radius and directly to tension.

Flashcard 2: What type of epithelium lines most of the trachea and primary bronchi?

Answer: Pseudostratified ciliated columnar epithelium with goblet cells. This specialized epithelium traps debris in mucus and uses cilia to propel it out of the airways.

Flashcard 3: What is the direction of $O_2$ diffusion at the alveolus when $P_{A O_2}>P_{a O_2}$?

Answer: $O_2$ diffuses from alveoli into pulmonary capillary blood. Gases diffuse down partial pressure gradients, from higher alveolar to lower blood levels.

Flashcard 4: What is the primary muscle of inspiration in quiet breathing?

Answer: Diaphragm. Its contraction flattens and enlarges the thoracic cavity, reducing pressure for air inflow.

Flashcard 5: What is the Bohr effect in one sentence?

Answer: Increased $CO_2$ or $H^+$ decreases hemoglobin $O_2$ affinity (right shift). It shifts the oxygen-hemoglobin dissociation curve rightward, aiding O2 release in acidic tissues.

Flashcard 6: What is the Haldane effect in one sentence?

Answer: Oxygenation of hemoglobin decreases $CO_2$ carrying capacity, promoting $CO_2$ unloading. It describes how oxygen binding reduces hemoglobin's CO2 affinity, facilitating release in lungs.

Flashcard 7: What is the primary function of cilia and mucus in the conducting airways?

Answer: Mucociliary escalator clears particles and pathogens from airways. Cilia beat to move mucus-trapped debris upward for expulsion, protecting lower airways.

Flashcard 8: What is the major immune cell type that patrols alveoli and removes debris?

Answer: Alveolar macrophages. They phagocytose inhaled particles and microbes to maintain alveolar sterility.

Flashcard 9: Which cartilage structure prevents tracheal collapse during inspiration?

Answer: C-shaped hyaline cartilage rings. These rings provide rigid support to maintain airway patency while allowing esophageal expansion.

Flashcard 10: Which alveolar cell type forms most of the gas-exchange surface?

Answer: Type I pneumocytes (type I alveolar cells). Their thin, squamous structure minimizes diffusion distance for efficient gas exchange.

Flashcard 11: What is the correct anatomical order of airflow from nose to gas-exchange surface?

Answer: Nasal cavity pharynx larynx trachea bronchi bronchioles alveoli. This sequence follows the path of inspired air through the respiratory tract to the site of diffusion.

Flashcard 12: What is the main effect of surfactant on alveoli?

Answer: Decreases surface tension and reduces alveolar collapse. Surfactant lowers surface tension proportionally more in smaller alveoli, stabilizing them per Laplace's law.

Flashcard 13: What is transpulmonary pressure defined as, in terms of lung and pleural pressures?

Answer: $P_{tp}=P_{alv}-P_{ip}$. It represents the pressure gradient that maintains lung expansion against elastic recoil.

Flashcard 14: What is the functional difference between conducting zone and respiratory zone?

Answer: Conducting: air transport; Respiratory: gas exchange (alveoli). Conducting zone conditions and transports air, while respiratory zone enables oxygen and carbon dioxide diffusion.

Flashcard 15: Which alveolar cell type produces pulmonary surfactant?

Answer: Type II pneumocytes (type II alveolar cells). These cells secrete surfactant to lower alveolar surface tension and prevent collapse.

Flashcard 16: What is intrapleural pressure relative to atmospheric pressure under normal conditions?

Answer: Negative relative to atmospheric pressure. This subatmospheric pressure opposes lung recoil, keeping alveoli inflated.

Flashcard 17: What enzyme in red blood cells catalyzes $CO_2+H_2OH_2CO_3$?

Answer: Carbonic anhydrase. It accelerates CO2 hydration to carbonic acid, enabling bicarbonate formation for transport.

Flashcard 18: What is lung compliance, stated as a simple formula relating volume and pressure?

Answer: $C=frac{Delta V}{Delta P}$. It quantifies lung distensibility as volume change per unit pressure change.

Flashcard 19: Identify the primary form in which $CO_2$ is transported in blood.

Answer: Bicarbonate ($HCO_3^-$) in plasma. Most CO2 is converted to bicarbonate for soluble transport, minimizing blood pH changes.

Flashcard 20: What is the name of the airway branch where cartilage disappears and smooth muscle predominates?

Answer: Bronchioles. Absence of cartilage allows smooth muscle to control airway diameter for regulating airflow resistance.

Flashcard 21: What is the relationship between thoracic volume and intrapulmonary pressure (Boyle law)?

Answer: As volume increases, pressure decreases; as volume decreases, pressure increases. Boyle's law dictates inverse relationship between volume and pressure in a closed system at constant temperature.

Flashcard 22: Which variable increases diffusion rate across the alveolar membrane: increased thickness or increased area?

Answer: Increased area increases diffusion rate. Fick's law states diffusion rate is directly proportional to surface area and inversely to membrane thickness.

Flashcard 23: Which muscles are most associated with forced expiration?

Answer: Internal intercostals and abdominal muscles. They contract to decrease thoracic volume, increasing pressure to expel air forcefully.

Flashcard 24: Identify what happens to intrapleural pressure during inspiration.

Answer: It becomes more negative. Thoracic expansion during inspiration further lowers intrapleural pressure to inflate lungs.

Flashcard 25: What is the direction of $CO_2$ diffusion at the alveolus when $P_{a CO_2}>P_{A CO_2}$?

Answer: $CO_2$ diffuses from blood into alveoli. Diffusion follows the partial pressure gradient from higher in blood to lower in alveoli for exhalation.