Detailed Notes on the Respiratory System

Key Concepts of the Respiratory System

General Aspects of the Respiratory System

• Cells utilize oxygen (O2) and release carbon dioxide (CO2).
• The respiratory system is crucial for gas exchange.
• The cardiovascular system transports gases in the blood.
• Failure of either system results in rapid cell death due to oxygen starvation.

Structure and Function of the Respiratory System

• Airflow Pathway: air travels from bronchi to bronchioles and finally to alveoli.
• Divisions of the Respiratory System:
  • Conducting Division: channels airflow from nostrils to bronchioles (no gas exchange).
  • Respiratory Division: includes alveoli and gas-exchange regions.
• Tracts:
  • Upper Respiratory Tract: includes organs from the nose to the larynx.
  • Lower Respiratory Tract: includes organs from the trachea to the lungs.

Anatomy of the Nose

• Functions of the Nose:
  • Warms, cleanses, and humidifies inhaled air.
  • Detects odors.
  • Acts as a resonating chamber to amplify voice.
• Structure:
  • Bony Support: nasal bones and maxillae create the superior half; lateral and alar cartilages form the inferior half.
  • Ala Nasi: dense connective tissue that forms the flared lateral wall of nostrils.

Nasal Cavity and Rhinoplasty

• Nasal Cavity: extends from nostrils to choanae; divided by a nasal septum into left and right chambers.
• Rhinoplasty: surgical procedure to alter the nose; may involve reshaping cartilage and repositioning bones.

Histology of the Nasal Cavity

• Mucosa: lined by olfactory mucosa (for smell) and respiratory mucosa (ciliated pseudostratified epithelium).
• Defensive Role: mucus traps particles; lysozyme destroys bacteria; plasma cells produce IgA antibodies.
• Cila Functionality: cilia transport debris-laden mucus to the pharynx (mucociliary ladder).
• Erectile Tissue: helps to shift air flow between nostrils, preventing dryness.

Pharynx Structure

• Regions:
  • Nasopharynx: lined with pseudostratified epithelium, connects to auditory tubes, contains pharyngeal tonsil.
  • Oropharynx: lined with stratified squamous epithelium, contains palatine and lingual tonsils.
  • Laryngopharynx: also lined with stratified squamous epithelium, extends from hyoid bone to larynx.

Larynx Functionality

• Components: epiglottis (covers glottis) and vocal cords (produce sound).
• Controls airflow; intrinsic muscles adjust vocal cord tension for pitch variation.
• Speech Production: requires collaboration with the pharynx and oral cavity; controlled by tension on vocal cords (tighter = higher pitch).

Trachea and Bronchial Tree

• Structure: rigid tube, approximately 4.5 in. long; supported by C-shaped cartilaginous rings.
• Trachealis Muscle: allows adjustment of airflow; lined with ciliated pseudostratified epithelium.
• Bronchial Tree Structure: divides into primary bronchi (right and left), secondary (lobar) bronchi, and tertiary (segmental) bronchi.
• Bronchioles: lack cartilage but have smooth muscle; function in air passage.

Alveoli and Gas Exchange

• Types of Alveolar Cells: Type I (for gas exchange), Type II (secretes surfactant).
• Respiratory Membrane: thin (0.5 microns); essential for efficient gas exchange; consists of four layers.
• Blood Supply: receives both pulmonary and bronchial blood supply; pulmonary arteries deliver deoxygenated blood; bronchial arteries supply oxygenated blood to lung tissue.

Mechanics of Breathing

• Inspiration: diaphragm and intercostal muscles contract, decreasing intrapleural pressure, leading to lung expansion and air influx.
• Expiration: can be passive (lung elasticity) or active (using muscles to push air out).
  • Forced expiration: involves abdominal and internal intercostal muscles.

Ventilation Control and Regulation

• Controlled by neurons in medulla oblongata and pons; involuntary and voluntary control of breathing.
• Chemical Regulation: primarily influenced by CO2 levels; central and peripheral chemoreceptors monitor blood chemistry (pH, CO2, O2).

Gas Exchange and Transport

• Alveolar Gas Exchange: involves diffusion; influenced by partial pressures and solubility. O2 is loaded into the blood, CO2 is unloaded.
• Oxygen Transport: 98.5% bound to hemoglobin as oxyhemoglobin; factors affecting release include pH (Bohr effect) and temperature.
• Carbon Dioxide Transport: primarily as bicarbonate ions in plasma, bound to hemoglobin, or dissolved in blood.

Lung Diseases and Disorders

• COPD (Chronic Obstructive Pulmonary Disease): includes chronic bronchitis (mucus overproduction) and emphysema (destruction of alveoli).
• Asthma: inflammatory disorder; broncho-reactivity; reversible.
• Lung Cancer: associated with smoking; includes multiple types, such as squamous cell carcinoma and adenocarcinoma.

Summary of Breathing Patterns and Conditions

• Common Terms:
  • Eupnea (normal breathing), Apnea (temporary cessation), Dyspnea (difficult breathing), Tachypnea (rapid breathing).
• Clinical Application: vital signs and imaging vital for assessing respiratory health; understanding lung capacity through spirometry and interpreting respiratory physiology helps in diagnosing respiratory maladies.