Chapter 22: The Respiratory System

Overview of the Respiratory System

• Comprised of a tract: elongated passage or pathway.
• Function: series of air distribution or air conduction tubes.
• Often described as a "respiratory tree":
  • Trachea (windpipe) = trunk/base
  • Bronchi = branches
  • Alveoli = leaves

Subdivisions

• Upper Respiratory Tract:
  • Larynx and any superior respiratory organ.
  • Includes nasal cavity and pharynx (throat).
• Lower Respiratory Tract:
  • Trachea and any inferior respiratory organ.
  • Includes lungs, primary bronchi, alveoli.

Mucous Membrane

• Respiratory tract is lined with mucosa.
• Purpose: to trap and remove inhaled irritants.

Purpose of Respiration

1. Supply oxygen for aerobic respiration (ATP production).
2. Eliminate carbon dioxide waste from biochemical reactions.

• Uses diffusion: passive transport of molecules down concentration gradients.

Gas Exchange Process

• Oxygen:
  • Higher concentration in alveoli than blood → diffuses into blood.
• Carbon Dioxide:
  • Higher concentration in blood than alveoli → diffuses into alveoli for exhalation.

Alveoli and Gas Exchange

• Alveoli: microscopic air sacs for gas exchange.
• Lined with simple squamous epithelium (thin, single-layered cells).
• High surface area for efficient gas diffusion.

Epithelium Types

• Pseudostratified Columnar Epithelium:
  • Found in trachea & nasal cavity, with cilia and goblet cells.
  • Known as "respiratory epithelium."
• Stratified Squamous Epithelium:
  • Found in areas subject to abrasion (e.g., inferior pharynx).
• Simple Columnar Epithelium:
  • Lining of primary bronchi.
• Simple Cuboidal Epithelium:
  • Found in bronchioles.

Respiratory Mucosa

• Combination of respiratory epithelium and underlying connective tissue (loose areolar tissue).
• Functions to trap and move irritants via mucus and cilia.

Structures of the Respiratory System

• Trachea:
  • Reinforced by C-shaped hyaline cartilage rings.
  • Trachealis muscle completes the ring at the posterior aspect.
  • Cricoid cartilage: complete ring of cartilage.
• Bronchi & Bronchioles:
  • Transition from primary bronchi to bronchioles.
  • Lined with different epithelial cells as they decrease in size.

Lung Anatomy

• Right Lung: 3 lobes (superior, middle, inferior), divided by horizontal and oblique fissures.
• Left Lung: 2 lobes (superior, inferior), divided by oblique fissure.

Nervous System Effects

• Parasympathetic Nervous System:
  • Promotes Bronco-constriction (energy conservation, decreased breathing).
• Sympathetic Nervous System:
  • Promotes Bronco-dilation (adrenaline release, increased breathing).

Surface Tension in Alveoli

• Alveoli lined with water, can lead to surface tension problems.
• Surfactant reduces surface tension, prevents alveolar collapse.
• Premature infants may require synthetic surfactant.

The Pleura

• Visceral Pleura: Covers lung surface.
• Parietal Pleura: Lines thoracic cavity.
• Pleural Cavity: Contains fluid to reduce friction.

Nasal Cavity and Sinuses

• Nasal Septum: Bone partition subdividing nasal cavity.
• Paranasal Sinuses: Located within skull bones (frontal, maxillary, sphenoid, ethmoid).

Olfactory Epithelium

• Specialized epithelium for smell located in the nasal cavity.

Larynx and Pharynx

• Larynx: Voice box, reinforced by cartilage.
• Pharynx: Divided into nasopharynx, oropharynx, and laryngopharynx for airflow and food passage.