respiratory system functions

Nasal cavity

Air-filled space that warms, moistens, and filters incoming air; lined with mucous membranes and cilia that trap particles and move debris toward the throat for removal.

External nares (nostrils)

Openings that allow air to enter the nasal cavity; contain hairs (vibrissae) that filter large particles from inhaled air.

Nasal septum

Divides the nasal cavity into right and left sides; helps direct airflow and supports proper air conditioning (warming, humidifying, filtering).

Hard palate

Forms the floor of the nasal cavity and separates it from the oral cavity; allows simultaneous breathing and chewing.

Conchae (superior, middle, inferior)

Bony projections that increase surface area and create air turbulence, enhancing warming, humidifying, and filtering of inhaled air.

Pharynx

Muscular passageway that connects nasal and oral cavities to the larynx and esophagus; functions in both respiration and digestion.

Nasopharynx

Upper portion of the pharynx behind the nasal cavity; conducts air only and contains openings for auditory tubes.

Oropharynx

Middle portion of the pharynx; passageway for both air and food.

Laryngopharynx

Inferior portion of the pharynx; directs air to the larynx and food to the esophagus.

Larynx

Voice box that maintains an open airway, routes air and food appropriately, and produces sound via vocal cords.

Epiglottis

Elastic cartilage that covers the laryngeal inlet during swallowing to prevent food and liquid from entering the airway.

Thyroid cartilage

Largest cartilage of the larynx; forms the 'Adam's apple' and protects the vocal cords.

Cricothyroid membrane

Connective tissue between thyroid and cricoid cartilage; allows flexibility and is an emergency airway access point.

Cricoid cartilage

Ring-shaped cartilage that forms the base of the larynx; maintains airway patency.

Arytenoid cartilage

Paired cartilages that anchor vocal cords and control their tension and position for sound production.

Vestibular folds (false vocal cords)

Do not produce sound; help close the glottis during swallowing to protect the airway.

Vocal folds (true vocal cords)

Produce sound by vibrating as air passes through; pitch depends on tension and length.

Glottis

Opening between the vocal folds; controls airflow and is essential for sound production.

Trachea

Airway that conducts air from the larynx to the bronchi; reinforced with C-shaped cartilage rings to keep it open.

Trachealis muscle

Smooth muscle that connects the open ends of tracheal cartilage rings; contracts during coughing to expel air and debris.

Primary bronchus

First branches from the trachea entering each lung; conducts air into the lungs (right is wider and more vertical).

Secondary bronchus

Branches of primary bronchi that supply each lobe of the lungs.

Tertiary bronchus

Further branches that supply specific bronchopulmonary segments within each lung.

Right lung

Has three lobes (superior, middle, inferior); larger and more vertical than left lung.

Left lung

Has two lobes (superior and inferior); smaller due to space taken by the heart.

Superior lobe (right lung)

Upper portion of right lung involved in gas exchange.

Middle lobe (right lung)

Unique to right lung; contributes to gas exchange.

Inferior lobe (right lung)

Largest lobe; major site of gas exchange.

Oblique fissure (right lung)

Separates inferior lobe from superior and middle lobes.

Horizontal fissure (right lung)

Separates superior and middle lobes.

Superior lobe (left lung)

Upper lobe of left lung; includes the lingula.

Cardiac notch

Indentation in left lung that accommodates the heart.

Inferior lobe (left lung)

Lower lobe; major area for gas exchange.

Oblique fissure (left lung)

Separates superior and inferior lobes.

Diaphragm

Primary muscle of breathing; contraction increases thoracic volume (inspiration), relaxation decreases volume (expiration).

External intercostal muscles

Elevate ribs during inspiration, increasing thoracic volume.

Internal intercostal muscles

Depress ribs during forced expiration, decreasing thoracic volume.

Phrenic nerve

Innervates the diaphragm; essential for initiating breathing by stimulating diaphragm contraction.