respiratory system

• Respiratory system functions


  • Exchange of gases between the atmosphere and the blood
  • Homeostatic regulation of body pH
  • Protection from inhaled pathogens and irritating substances
  • Vocalization

  
• Overview of external and cellular respiration

  1. CO2 from cells to lungs

  2. O2 from lungs to cells

  3. ATP production in cells

  
• Respiratory organs


  • Moist surfaces in which gases dissolve and diffuse
  • Increased surface area for gas exchange
  • Extensive blood flow
  • Thin, delicate structure

  
• Gills


  • Specialized extensions of tissue that project into water
  • Increase surface area for diffusion
  • External gills are not enclosed within body structures
  • Found in immature fish and amphibians
  • Must be constantly moved to ensure contact with oxygen-rich fresh water
  • Are easily damaged

  
• Gill structure


  • Gills of bony fishes are located between the oral (buccal or mouth) cavity and the opercular cavities
  • These two sets of cavities function as pumps that alternately expand to move water into the mouth, through the gills, and out of the fish through the open operculum or gill cover

  
• Gill structure


  • Lamella
  • Gill filaments
  • Gill arch
• Lungs


  • Gills were replaced in terrestrial animals by lungs
  • The lung system involves moving air through a branched tubular passage
  • A two-way flow system (except birds)
  • Lungs of amphibians are formed as saclike outpouchings of the gut
  • Frogs have positive pressure breathing
  • Reptiles have negative pressure breathing (mammals also)

  
• Lungs move with thoracic cavity
• Inhalation


  1. Contraction of the external intercostal muscles expands the rib cage

  2. Contraction of the diaphragm expands the volume of thorax and lungs

  3. Produces negative pressure which draws air into the lungs

  
• Exhalation


  1. Diaphragm relaxes (moves up)

  2. Rib cage gets smaller as rib muscles relax
• Control of breathing in humans

  • The main breathing control center consists of neural circuits in the medulla oblongata, near the base of the brain
  • The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid
  • The medulla adjusts breathing rate and depth to match metabolic demands

  
• Rising level of CO2 in tissues

  Lowers blood pH
• Lowered blood pH


  Signals from medulla to rib muscles and diaphragm increase rate and depth of ventilation
• Increased ventilation


  CO2 level decreases
• Hemoglobin


  • Consists of four polypeptide chains
  • Loads up on oxygen in the lungs
  • Transports oxygen through the blood
  • Unloads oxygen at the body's cells

  
• Hemoglobin structure


  • A molecule of hemoglobin

  
• CO2 transport


  1. From blood to lungs

  2. From tissues to blood
• O2 transport


  1. From blood to tissues

  2. From lungs to blood