Functions of the Respiratory System

Functions of the Respiratory System

• Supplies body with oxygen (O2) and eliminates carbon dioxide (CO2).
• Enables speech and other vocalizations.

Respiratory Zone vs. Conducting Zone, Upper vs. Lower Respiratory

• Conducting zone (nose to terminal bronchioles): warms, humidifies, and filters incoming air.
• Respiratory zone (respiratory bronchioles to alveoli): site of gas exchange.
• Upper respiratory tract: Nose, nasal cavity, pharynx.
• Lower respiratory tract: Larynx, trachea, bronchi, lungs.

Anatomy

Bronchioles

• Terminal bronchioles: End of conducting zone.
• Respiratory bronchioles: Start of respiratory zone.

Alveolar Ducts and Alveoli

• Alveoli: Tiny air sacs for gas exchange.
  • Type I cells: Main site of gas exchange.
  • Type II cells: Produce surfactant.
  • Macrophages: Phagocytize inhaled particles.
  • Alveolar fluid: Surrounds alveoli, important for gas exchange.

Lungs

• Bronchopulmonary segments: Lobules with independent blood supply.
• Lobules: Small compartments of lung tissue.

Respiratory Membrane

• 4 layers: Alveolar and capillary endothelia, their fused basal laminas.
• Characteristics: Thin for efficient diffusion.

Blood Flow Through Heart and Lungs (Pulmonary Circulation)

• Oxygen-poor blood pumped from right ventricle to pulmonary arteries to lungs.
• Oxygen-rich blood returns to left atrium via pulmonary veins.

Pulmonary Ventilation (Breathing)

• Boyle's Law: Pressure of a gas is inversely proportional to its volume.
• Inhalation (Inspiration): Thoracic cavity expands, decreasing pressure, causing air to flow in.
• Exhalation (Expiration): Thoracic cavity recoils, increasing pressure, forcing air out.

Muscles Used in Breathing

• Quiet breathing: Primarily diaphragm and intercostals.
• Labored breathing: Accessory muscles (sternocleidomastoid, scalene).

Factors Affecting Breathing

• Surface tension: Surfactant reduces tension in alveoli.
• Compliance: Ease with which lungs expand.
• Airway resistance: Resistance to airflow in airways.

External Respiration

• Occurs in alveoli.
• Dalton's Law: Total pressure of a mixture of gases is the sum of the individual pressures.
• Henry's Law: Amount of gas that dissolves in a liquid is proportional to its partial pressure.
• Diffusion of O2 and CO2: High pressure to low pressure.
• Factors affecting diffusion rate: Surface area, thickness of respiratory membrane, partial pressure difference.

Internal Respiration

• Occurs in body tissues.
• Blood → tissues: O2 diffuses out; CO2 diffuses in.

Oxygen Carried in Blood

• Dissolved: 1.5%.
• Hemoglobin (Hb): 98.5%

Hemoglobin Structure

• Complex protein with 4 heme groups, each containing an iron atom.

Factors Determining O2 Binding to Hemoglobin

• Partial pressure of O2 (PO2), temperature, pH, BPG (2,3-bisphosphoglycerate).

Carbon Dioxide Carried in Blood

• Plasma: 7%.
• Hemoglobin: 23%.
• Bicarbonate ion (HCO3-): 70%.

Control of Breathing

• Respiratory Center in Brain: Medulla and pons.

  • Medulla: Controls basic rhythm of breathing.
  • Pons: Modifies and smooths breathing rhythm.

• Regulation of Breathing: Other parts of brain, chemoreceptors, proprioceptors.

• Chemoreceptors: Detect changes in blood gas levels (O2, CO2).

• Proprioceptors: Detect body movement.

Other Factors Influencing Breathing Rate

• Emotions, pain, metabolic rate.

Effects of Exercise, Aging, and Smoking on Breathing

• Exercise: Increases breathing rate and depth.
• Aging: Decreases lung elasticity, reducing vital capacity.
• Smoking: Damages alveoli and airways, impairing gas exchange.

Diseases/Disorders of the Respiratory System

• Asthma: Inflammation and constriction of airways.
• COPD (Emphysema, Chronic Bronchitis, Lung Cancer): Progressive lung diseases.
• Coryza: Common cold.
• Influenza: Flu.
• Pneumonia: Infection of lung tissue.
• Tuberculosis: Bacterial infection of lungs.
• Cystic Fibrosis: Genetic disorder affecting mucus production.

Miscellaneous

• Capillaries: Tiny blood vessels surrounding alveoli for gas exchange.
• Chloride shift: Movement of chloride ions to maintain electrical balance during CO2 transport.
• Anemia: Reduced oxygen-carrying capacity of blood.
• CO poisoning: CO binds to hemoglobin, preventing O2 binding.
• Hypoxia: Inadequate oxygen delivery to tissues (various types).
• Patency: Openness of a passage.
• Eupnea: Normal breathing.
• Apnea: Temporary cessation of breathing.
• Dyspnea: Difficulty breathing.
• Tachypnea: Rapid breathing.

Explore the essential functions of the respiratory system, including oxygen supply and carbon dioxide elimination. Understand the differences between the conducting and respiratory zones, and the anatomy of bronchioles and alveoli, key structures facilitating gas exchange.