Ch 22

• All body processes directly or indirectly require ATP
• Respiratory system consists of system of tubes that delivers air to lungs
• Respiration


  Term used to refer to ventilation of lungs (breathing)
• Principal organs of respiratory system

  • Nose
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Ventilation


  Act of breathing; moving air in, out of lungs
• Functions of nose and nasal cavity

  • Passageway for air
  • Mucosal membrane has rich blood supply
  • Warms, cleanses, humidifies inhaled air
  • Mucus traps particles, microbes
  • Hairs trap particles
  • Detects odors
  • Serves as resonating chamber that amplifies voice
• Regions of pharynx


  • Nasopharynx: posterior to nasal cavity through posterior to oral cavity
  • Oropharynx: posterior to oral cavity
  • Laryngopharynx: epiglottis to esophagus
• Larynx


  • Cartilaginous chamber
  • Primary function: to keep food, drink out of airway
• Trachea is a rigid tube anterior to esophagus
• Bronchial tree is a branching system of air tubes in each lung from trachea to deep into lung interior
• 150 million alveoli in each lung, providing huge amount of surface for gas exchange
• Path of air flow

  Nose → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Terminal bronchioles → Respiratory bronchioles → Alveolar sac → Alveoli
• Visceral pleura


  Serous membrane that covers lungs
• Pulmonary ventilation


  Breathing: consists of repetitive cycle of inspiration (inhaling), expiration (exhaling)
• Muscles of quiet inspiration

  • Diaphragm
  • External intercostal muscles
• Normal quiet expiration


  Energy-saving (passive) process achieved by elasticity of lungs, thoracic cage
• Accessory muscles of respiration


  • Forced inspiration: Sternocleidomastoid, pectoralis major, pectoralis minor, serratus anterior muscles, and other thoracic, lumbar muscles
  • Forced expiration: Rectus abdominis, internal intercostals, other lumbar, abdominal, pelvic muscles
• Respiratory centers


  Automatic, unconscious cycle of breathing controlled by respiratory centers in medulla oblongata, pons
• Central chemoreceptors


  Brainstem neurons respond to changes in pH of cerebrospinal fluid
• Stretch receptors


  Found in smooth muscles of bronchi, bronchioles, and in visceral pleura, respond to inflation of lungs
• Voluntary control over breathing originates in cerebrum
• Respiratory airflow


  Governed by same principles of flow, pressure, resistance as blood flow
• Boyle's law


  At constant temperature, pressure of a given quantity of gas is inversely proportional to its volume
• Breathing


  1. Passive process

  2. Recoil of lungs compresses them

  3. Volume of thoracic cavity decreases

  4. Raises intrapulmonary pressure above atmospheric pressure

  5. Air flows down pressure gradient, out of lungs
• Forced breathing


  1. Accessory muscles decreases thoracic cavity and lung volume even more

  2. Raises intrapulmonary pressure to force more air out
• Respiratory Cycle


  1. At rest, atmospheric and intrapulmonary pressures are equal, and there is no airflow

  2. Ribs swing upward like bucket handles during inspiration

  3. Inspiration

  4. Expiration

  5. Pause

  6. Ribs swing downward like bucket handles during expiration

  7. In inspiration, the thoracic cavity expands laterally, vertically, and anteriorly; intrapulmonary pressure drops 1 cm below atmospheric pressure, and air flows into the lungs

  8. In expiration, the thoracic cavity contracts in all three directions: intrapulmonary pressure rises 1 cm above atmospheric pressure, and air flows out of the lungs
• Pneumothorax


  Presence of air in pleural cavity
• Pneumothorax


  1. Thoracic wall is punctured

  2. Inspiration sucks air through wound into pleural cavity

  3. Pleural cavity becomes air-filled cavity

  4. Loss of negative intrapleural pressure allows lungs to recoil, collapse
• Airway resistance


  Increasing resistance decreases airflow
• Factors influencing airway resistance

  • Bronchiole diameter
  • Pulmonary compliance
• Bronchodilation


  Increase in diameter of bronchus or bronchiole increases air flow
• Bronchoconstriction


  Decrease in diameter of bronchus or bronchiole decreases airflow
• Suffocation can occur from extreme bronchoconstriction brought about by anaphylactic shock, asthma
• Pulmonary compliance


  Ease of lung expansion
• Compliance reduced by lung diseases that cause stiffening due to scar tissue
• Surfactant


  Secreted by great cells of alveoli, disrupts hydrogen bonds between water molecules, reducing surface tension (caused by water cohesion)
• Infant respiratory distress syndrome (IRDS): premature babies lacking surfactant treated w/ artificial surfactant until they can make their own
• Anatomic dead space


  Conducting zone where there is no gas exchange
• Physiologic (total) dead space

  In pulmonary diseases, some alveoli may be unable to exchange gases
• If a person inhales 500 mL of air, 150 mL stays in anatomical dead space, then 350 mL reaches alveoli