Respiratory System

• Trachea


  Stiff tube leading from oral cavity
• Bronchi


  The two branches of the trachea, each leading to a lung
• Bronchioles


  Network of smaller passages surrounded by bronchiolar smooth muscle
• Alveolar ducts


  Tubes that connect bronchioles to alveoli
• Alveoli


  Clusters of sack-like tubes at the end of each alveolar duct where gas exchange occurs
• Respiratory pathway


  Trachea -> bronchi -> bronchioles-> alveolar ducts -> alveoli
• Which parts of respiratory pathway have rings of cartilage?

  Trachea and bronchi
• Type 1 cell lining of alveolus

  Align lumen of each alveolus; where gas exchange occurs; more flat than endothelial cells
• Type 2 cell lining of alveolus

  Rounded; secretory cell (secretes compound surfactant)
• How many layers of cells does alveoli have?

  Single layer of cells (similar to capillaries) which allows for efficient exchange of gases between alveoli airspace and interstitial fluid
• Purpose of pleural cavity


  Fluid filled sac that surrounds each lung and protects lungs against injury. Also allows lungs to inflate
• Two membranes of pleura cavity

  Parietal and visceral pleura
• Steps of gas exchange during respiration

  ventilation -> gas exchange between alveoli and blood -> gas transport -> gas exchange between to blood and cells -> cellular respiration
• ventilation


  exchange of air between atmosphere and lungs
• diffusion


  between alveolar air and blood
• transport


  through the blood
• exchange


  of O2 and CO2 between blood and cells
• utilization


  of O2 and formation of CO2 in cells
• inspiration


  breathing in where Palv < Patm to let air to come in
• expiration


  breathing out where Palv > Patm to force air out
• Equation of flow rate

  F = (Palv - Patm) / R

  Palv is alveolar pressure

  Patm is atmospheric pressure

  R is resistance which is inversely proportional
• Compression


  Exhalation where decrease in volume of thoracic cavity causes increase in alveolar pressure
• Decompression


  Inhalation where increase in volume of thoracic cavity causes decrease in alveolar pressure allowing air to enter the lungs
• P ip


  intrapleural pressure
• P tp


  transpulmonary pressure
• P cw


  chest wall pressure
• Which pressure must always be lower than P alv or lungs will collapse?

  P ip (intrapleural pressure)
• What does elastic recoil maintain when lungs are at rest?

  a negative intraplural pressure
• Respiratory pump


  action of chest expands to allow lungs to fill with air; helps pull blood into heart through veins
• What is surfactant regulated by?

  stretching of alveoli during inspiration and production is stimulated by cortisol
• What is surfactant secreted by?

  Type II alveolar cells
• What effect does surfactant have on alveolar diameter?

  Selectively reduces tension on smaller alveoli which prevents it from shrinking and expelling contents/air into forming larger alveoli
• What size of alveoli has more efficient gas exchange?

  small alveoli because has greater surface area to volume ratio
• Respiratory distress syndrome


  Common in infants born before week 37

  Results from immature type II alveolar cells which has deficiency of surfactant

  "Ground glass" opacity of lungs

  Decreased compliance so takes greater transpulmonary pressure difference to inflate lungs
• Lung diseases associated with increased resistance to airflow

  Asthma: bronchioconstriction

  Chronic obstructive pulmonary disease (COPD): Chronic bronchitis (excessive mucous) and Emphysema (destruction of lung tissue due to smoking or air pollution)
• relationship of CO2 and carbonic anhydrase

  CO2 + H2O <---carbonic anhydrase---> H2CO3 <-----> H+ + HCO3-

  
  

  Carbonic anhydrase catalyzes both the forward and reverse reactions. Direction depends on the relative concentration of CO2 and HCO3-
• What is CO2 carried as or by?

  60% of CO2 produced is carried as HCO3-

  Remaining CO2 is either free in solution or bound to hemoglobin
• CO2 production by tissue shifts the equilibrium which way?

  shifts to form more HCO3-
• In the lungs, the equilibrium of CO2 is shifted which way?

  CO2 is being removed from the body so reaction is driven towards the formation of CO2
• What coordinates the autonomic control of breathing?

  medullary respiratory center