Respiratory System Overview

Structure and Function

• The respiratory system facilitates gas exchange, bringing oxygen into the body and removing carbon dioxide.
• It comprises the nose, pharynx, larynx, trachea, bronchi, and lungs.
• The lungs are the primary organs, containing millions of alveoli where gas exchange occurs.

Airflow and Ventilation

• Breathing involves inhaling and exhaling air.
• Inhalation is an active process; the diaphragm and intercostal muscles contract, expanding the thoracic cavity and decreasing pressure to draw air in.
• Exhalation is a passive process; these muscles relax, the thoracic cavity recoils, and pressure increases to force air out.
• Lung compliance and elasticity influence the ease of breathing, impacted by factors like lung tissue elasticity and the presence of surface tension.

Gas Exchange

• Oxygen diffuses from the alveoli into the capillaries surrounding them.
• Carbon dioxide diffuses from the capillaries into the alveoli to be exhaled.
• This exchange is facilitated by the high concentration gradient.
• Hemoglobin, a protein in red blood cells, binds to oxygen and transports it throughout the body.

Control of Respiration

• Respiration is controlled by the autonomic nervous system, specifically the respiratory centers in the brainstem.
• Chemoreceptors detect changes in blood oxygen and carbon dioxide levels and adjust breathing rate accordingly.
• Higher carbon dioxide levels and lower oxygen levels stimulate the respiratory centers to increase breathing.

Pulmonary Volumes and Capacities

• Lung volumes and capacities describe the amount of air moved during breathing.
• Tidal volume is the amount of air inhaled and exhaled during a normal breath; inspiratory reserve volume, expiratory reserve volume, and residual volume describe different quantities in lung capacity.
• These volumes and capacities can be determined during pulmonary function tests.

Respiratory Disorders

• Many conditions can affect the respiratory system.
  • Asthma involves airway inflammation and constriction, making breathing difficult.
  • Pneumonia is characterized by lung inflammation and fluid buildup, inhibiting gas exchange.
  • Chronic Obstructive Pulmonary Disease (COPD) encompasses conditions like chronic bronchitis and emphysema, leading to persistent airflow blockage.
  • Cystic fibrosis creates thick mucus that obstructs airways.
  • Lung cancer involves uncontrolled cell growth in the lungs.

Factors Influencing Respiration

• Physical factors like altitude and temperature can affect gas exchange.
• Exercise increases the body's demand for oxygen, resulting in increased breathing rate and depth.
• Age, certain medical conditions (like heart disease), obesity, and smoking also have implications for respiratory function.

Protection Mechanisms

• The respiratory system has protective mechanisms to filter the air and prevent infection.
  • Mucus and cilia line the airways, trapping and removing particles.
  • Cough reflex helps expel irritants.
  • Immune responses help neutralize pathogens.