Respiratory Terms

Bronchioles

Small, branch-like airways that branch off of the bronchi. Lack cartilage rings. Regulate airflow and transport air to the alveoli.

Alveoli

Tiny air sacs at the ends of the alveolar ducts in the lungs, composed of a single layer of squamous epithelial cells. Serves as the sites of gas exchange where oxygen diffuses into the blood, and carbon dioxide diffuses out.

Alveolar Duct

Small passages leading from bronchioles to alveolar sacs in the lungs. Direct air into alveolar sacs

Alveolar Sac

Clusters of alveoli, located at the end of alveolar ducts Facilitate gas exchange between air and blood.

Alveolar Surfactant

A lipid-protein substance, coating the alveoli. Reduces surface tension, preventing alveolar collapse.

Epiglottis

A flap of cartilage, located at the entrance of the larynx. Prevents food and liquid from entering the trachea during swallowing.

Glottis

Opening between the vocal cords, located in the larynx. Allows air to pass through the vocal cords for sound production.

Conchae

Bony projections along the lateral walls of the nasal cavity. Warm, moisten, and filter incoming air.

Ciliated Epithelia

Epithelial cells with cilia, lining the trachea and bronchi. Move mucus and trap particles upward toward the throat for swallowing.

Pharynx

Muscular passageway that extends from the nasal cavity to the larynx. Transports air and food; divides into nasopharynx, oropharynx, and laryngopharynx.

Larynx

The cartilaginous “voice box” located between the pharynx and trachea. Directs air into the trachea and houses the vocal cords for sound production.

Trachea

Windpipe supported by cartilaginous rings, extending from the larynx and bifurcates into the bronchi. Provides a clear airway for air to travel to the lungs.

Diffusion

The movement of gases from an area of high concentration to low concentration. Allows oxygen to move from alveoli into blood and carbon dioxide to move out.

Intercostal Muscles

Within the thoracic cage, muscles between the ribs. Aids in breathing by expanding and contracting the rib cage.

Diaphragm

Dome-shaped sheet of muscle, separating the thoracic and abdominal cavities. Contracts to increase thoracic volume, creating negative pressure for inhalation.

Visceral Pleura

Thin membrane covering the lungs, adhering the lung surface. Reduces friction and keeps lungs inflated.

Parietal Pleura

Outer membrane lining the thoracic cavity, attaching to the chest wall. Provides structural support and forms the pleural cavity.

Pleural Fluid

Lubricating fluid, found in the pleural cavity between visceral and parietal pleura. Reduces friction and maintains lung attachment to the thoracic wall.

Respiratory Volumes

  1. Tidal Volume: Amount of air inhaled/exhaled during normal breathing (~500 mL)
  2. Inspiratory Reserve Volume (IRV): Additional air that can be inhaled beyond tidal volume (~3100 mL)
  3. Expiratory Reserve Volume (ERV): Air forcibly exhaled after tidal volume (~1200 mL)
  4. Residual Volume: Air remaining in the lungs after forced exhalation (~1200 mL)

Dalton’s Law of Partial Pressures

States that the total pressure of a gas mixture equals the sum of the partial pressures of its individual gases.

Henry’s Law

States that gases dissolve in liquids in proportion to their partial pressures.