CH 23 respiratory system

• major function of the respiratory system is to supply the body with oxygen and dispose of carbon dioxide
• other functions

  • olfactory sensations
  • regulation of blood pH
  • production of sound (speech)
  • removal of some water and heat in ehxaled
  • protection against the entrance of pathogens
• the respiratory system can be divided into:

  • conducting portion
  • respiratory portion
• conduction portion:

  • from nostrils to bronchioles
  • passageways that conduct air
• generally functions to warm, moistens, cleanse(filter) incoming air

  conduction portion
• actual site of gas exchange

  respiratory portion
• the respiratory portion includes the alveoli
• respiratory zone:

  respiratory bronchiole + alveolar duct + alveolar sac + alveolus
• Paired lungs are located in the thoracic cavity
• Each lung is cone-shaped; points up and broad base rests on diaphragm
• R lung has 3 lobes; L lung 2 lobes
• Parietal pleura lines the inner surface of the thoracic cavity
• Visceral pleura covers the external surface of each lung
• Space between the pleural and viscera pleura is the pleural cavity
• Respiratory bronchioles divide into alveolar ducts which lead into the alveolar sacs
• cluster of alveoli

  alveolar sacs
• Walls of alveoli is composed primarily of simple squamous epithelial cells, known as Type I alveolar cells
• Type I alveolar cells are surrounded by pulmonary capillaries
• respiratory membrane = Type 1 alveolar cell + fused basement membrane + endothelial cell of pulmonary capillary
• Gas exchange occurs across the respiratory membrane
• gas exchange:

  • O2 moves from the air in the alveoli into the blood
  • CO2 moves from the blood into the air in the alveoli
• Scattered throughout the alveolar epithelium are Type II alveolar cells which secrete alveolar fluid
• the alveolar fluid keeps surfaces moist
• alveolar fluid contains surfactant (detergent-like substance) made of phospholipids and proteins
• Surfactant acts to decrease surface tension and prevent collapse of the alveolus when exhaled
• surface tension is the force at air-water interface that opposes the expansion of the water surface (polar water molecules are more strongly attracted to each other than to gas molecules)
• surfactant decreases surface tension by disrupting hydrogen bonds among water molecules making it easier to expand the lungs
• surfactant is needed to overcome surface tension to expand lungs when we breathe
• if the hydrogen bonds are not bonded with each other, it is easier to expand our lungs
• A breathing disorder of premature newborns in which the alveoli do not remain open due to a lack of surfactant.

  Respiratory distress syndrome (RDS)
• what does COPD stand for?

  Chronic obstructive pulmonary disease
• type of respiratory disorder characterized by chronic and recurrent obstruction of airflow

  COPD
• principal types are emphysema and chronic bronchitis

  COPD
• characterized by destruction of the walls of the pulmonary alveoli producing abnormally large air spaces that remain filled with air during exhalation

  emphysema
• less surface area for gas exchange so oxygen diffusion across the damaged respiratory membrane is reduced


  emphysema
• characterized by excessive secretion of bronchial mucus accompanied by a productive cough

  chronic bronchitis
• increase in size and number of mucus glands and goblet cells in the airway epithelium

  chronic bronchitis
• thickened and excessive mucus narrows the airway and impairs ciliary function

  chronic bronchitis
• inhaled pathogens become embedded in airway secretions and multiply rapidly

  chronic bronchitis
• characterized by chronic airway inflammation and obstruction

  asthma