repiratory critical fast

Trace the pathway of air into the respiratory system.

Air enters through the nose or mouth → nasal cavity → pharynx (nasopharynx → oropharynx → laryngopharynx) → larynx → trachea → primary bronchi → secondary bronchi → tertiary bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → alveoli.

Functional difference between conducting and respiratory zones.

The conducting zone moves air and conditions it (warms, humidifies, filters) but does not perform gas exchange, while the respiratory zone is where gas exchange occurs in the alveoli.

Why stratified squamous in oropharynx/laryngopharynx?

These regions handle both food and air, so nonkeratinized stratified squamous epithelium protects against abrasion from food, unlike pseudostratified ciliated epithelium which is better for moving mucus.

Why C-shaped cartilage rings in trachea?

They keep the airway open (prevent collapse) while allowing flexibility, and the open posterior side allows the esophagus to expand during swallowing.

Histology changes as diameter decreases.

Epithelium changes from pseudostratified ciliated columnar → simple cuboidal → simple squamous (alveoli); cartilage decreases and disappears; smooth muscle increases; cilia and goblet cells are lost.

Terminal vs respiratory bronchioles.

Terminal bronchioles are part of the conducting zone (no gas exchange), while respiratory bronchioles are part of the respiratory zone and begin gas exchange.

Difference between right and left primary bronchi.

The right bronchus is wider, shorter, and more vertical, making it easier for objects to enter; the left is narrower and more angled due to the heart.

How volume and pressure changes cause ventilation.

Air moves from high to low pressure. When thoracic volume increases, pressure decreases and air flows in (inhalation); when volume decreases, pressure increases and air flows out (exhalation).

9. Differentiate pressures.

• Atmospheric pressure (Patm): pressure of air outside the body

• Intrapulmonary pressure (Ppul): pressure inside alveoli

• Intrapleural pressure (Pip): pressure in pleural cavity (always negative to keep lungs expanded)

Role of surfactant & lack of it.

Surfactant reduces surface tension and prevents alveoli from collapsing (atelectasis). Without it, alveoli collapse, making ventilation difficult and reducing gas exchange.

Equal exchange of O₂ and CO₂ despite gradient differences.

Even though O₂ has a steeper gradient, CO₂ is more soluble in blood, so it diffuses just as efficiently as oxygen.

Hyperventilation effects

Hyperventilation decreases CO₂ levels in the blood, which increases blood pH (respiratory alkalosis).

Muscles used in deep breath (blowing up a balloon).

Diaphragm and external intercostals contract to increase volume, while accessory muscles (sternocleidomastoid, scalenes, pectoralis minor) assist in expanding the thoracic cavity.

What happens when CO₂ rises (holding breath)?

Rising CO₂ increases acidity (lowers pH), which stimulates chemoreceptors and the medulla to trigger breathing; eventually, the body forces breathing to resume.