Respiratory_System

Upper respiratory tract

Includes nose, nasal cavity, paranasal sinuses, and nasopharynx.

Lower respiratory tract

Consists of trachea, bronchial tree, and lungs.

Conducting zone

Includes nose, pharynx, larynx, trachea, bronchi, and up to terminal bronchioles.

Respiratory zone

Includes respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Respiratory mucosa

Pseudostratified columnar ciliated epithelium lining most of the respiratory system.

Cilia

Hair-like structures on mucosal cells that move mucus upward to pharynx.

Nasal septum

Separates interior of the nose into two cavities.

Bony hard palate

Formed by the maxillae and palatine bones, separates oral and nasal cavities.

Pharynx

Shared passageway for food and air, divided into nasopharynx, oropharynx, and laryngopharynx.

Larynx

Framework formed by several pieces of cartilage; responsible for voice production.

Vocal cords

True cords that stretch across the larynx for voice production.

Trachea

Tube extending from larynx about 4.5 inches long; passageway for air.

Bronchi

Branches of trachea leading to each lung, further subdividing into bronchioles.

Alveoli

Microscopic air sacs where gas exchange occurs.

Type I alveolar cell

Typical cell making up the walls of the alveoli.

Type II alveolar cells

Cells that produce surfactant to reduce surface tension in alveoli.

Pleura

Moist membrane lining the chest cavity and covering lungs, reducing friction.

Pulmonary ventilation

The process of breathing.

External respiration

Exchange of gases in lungs; oxygen enters blood, carbon dioxide exits.

Internal respiration

Exchange of gases at the tissue level; oxygen exits blood, carbon dioxide enters.

Medulla oblongata

Brain structure that controls the basic rhythm of breathing.

Chemoreceptors

Sensory receptors that detect changes in CO₂, O₂, and pH to adjust respiration.

Mechanoreceptors

Receptors that prevent lung overinflation and respond to physical irritants.

Cerebrum

Higher brain center influencing respiration.

Hypothalamus

Brain region involved in regulating breathing patterns.