Respiratory System – Key Vocabulary

Overview

• Cells consume O2 and produce CO2 + free radicals ➜ body must remove wastes and continually resupply O_2.
• Respiratory system PRIMARY functions
  • Supply body with O2, dispose CO2.
  • Secondary: olfaction & speech production.
• FOUR integrated processes (collectively “respiration”)
  1. Pulmonary ventilation (breathing): inspiration + expiration.
  2. External respiration: gas exchange lungs ↔ blood (diffusion).
  3. Transport of respiratory gases (cardiovascular job): O2 to tissues, CO2 to lungs.
  4. Internal respiration: blood ↔ tissue cell diffusion; cornerstone of cellular (metabolic) respiration.
• Respiratory + circulatory systems are tightly coupled; failure of either ➜ cellular hypoxia.

Functional Anatomy – Macroscopic Map

• Organs (superior ➜ inferior): Nose → Paranasal sinuses → Pharynx → Larynx → Trachea → Bronchi (& branches) → Lungs (alveoli).
• Upper respiratory system: nose → larynx (inclusive).
• Lower respiratory system: larynx → alveoli (plus respiratory muscles sometimes grouped separately).

Upper Respiratory System

Nose & Paranasal Sinuses

• Only externally visible respiratory organ.
• 5 key functions: airway, moisten/warm air, filter/clean air, resonance for speech, house olfactory receptors.

External Nose anatomy

• Surface landmarks: root (between brows), bridge, dorsum nasi, apex; openings = nares bordered by alae.
• Framework: nasal + frontal bones (bridge/root), maxillary bones (lateral), hyaline cartilages (septal, alar, lateral processes) inferiorly.

Nasal Cavity Details

• Divided by nasal septum (septal cartilage + vomer + perpendicular plate of ethmoid).
• Posterior communication with nasopharynx through posterior nasal apertures (choanae).
• Roof: ethmoid + sphenoid bones. Floor: palate (hard anterior, soft posterior).
• Vestibule (area superior to nostril) lined with skin, sebaceous/sweat glands, vibrissae (filter coarse particles).
• Remainder lined by:
  • Olfactory mucosa (superior slit): olfactory epithelium.
  • Respiratory mucosa: pseudostratified ciliated columnar epithelium with goblet cells; rests on seromucous glands (~1 L mucus/day containing lysozyme & defensins).
• Ciliated cells sweep mucus posteriorly; cold ➜ ciliary sluggishness ➜ “runny nose.”
• Rich capillary/venous plexus warms air; superficial vessels prone to epistaxis.
• Nasal Conchae (superior, middle, inferior): mucosa-covered baffles creating turbulence; inferior grooves = meatuses.
  • Functions: filter (>6\mu m particles caught), warm, moisten inhaled air; reclaim heat & moisture during exhalation.
• Paranasal Sinuses (frontal, sphenoid, ethmoid, maxillary): lighten skull, warm/moisten air, mucus drains into cavity; blockage ➜ sinusitis/sinus headache.

Pharynx (throat)

• Funnel from skull base to C_6 (~13 cm).
• 3 regions:
  1. Nasopharynx (air only): pseudostratified epithelium, pharyngeal tonsil (adenoids), pharyngotympanic tube openings + tubal tonsil; soft palate/uvula close during swallow.
  2. Oropharynx (food+air): stratified squamous epithelium; isthmus of fauces doorway; palatine & lingual tonsils.
  3. Laryngopharynx (food+air): stratified squamous; diverging pathways— anterior larynx (air), posterior esophagus (food); during swallow “food has right-of-way.”
• Protective mechanisms: tonsils, sneeze reflex, ciliary escalator.

Lower Respiratory System

Conducting vs Respiratory Zones

• Conducting zone: rigid conduits nose → terminal bronchioles; warm, humidify, cleanse air.
• Respiratory zone: site of gas exchange—respiratory bronchioles, alveolar ducts, alveoli (microscopic).

Larynx (voice box)

• Extends C3–C6 (~5 cm). Attaches to hyoid; opens into laryngopharynx; continuous with trachea.
• Functions: patent airway, switching route (epiglottis) for air/food, voice production.
• Cartilages (9): thyroid (Adam’s apple), cricoid, epiglottis (elastic “guardian”), paired arytenoid (anchor vocal cords), cuneiform, corniculate.
• Vocal ligaments form vocal folds (true cords)—pearlescent, avascular; opening = glottis. Superior vestibular folds (false cords) close glottis during swallow.
• Epithelium: superior stratified squamous; below cords pseudostratified ciliated (cilia beat upward).
• Voice: pitch = tension/length; loudness = air force; resonance chambers = pharynx, oral/nasal/sinus cavities; articulation by tongue, soft palate, lips.
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