RESPIRATORY SYSTEM

RESPIRATORY SYSTEM 1 (lecture 13)

what's the respiratory system doing?

• internal respiration:
  • happening in cells
  • mitochondria uses oxygen for ATP production (energy)
  • produces carbon dioxide

• external respiration:
  • movement of gases between environment and cells

common features of a respiratory membrane

• thin membranes

• moist membranes

• large surface area

evolution of respiration

• O2 levels in atmosphere dropped thousands of years ago
  • caused loss of massive biodiversity
  • changes in various organisms

• different respiratory structures evolved in vertebrate species

• some species don't completely depend on lungs
  • use skin, gills, trachea

• diffusion of gases works well over short distances (1-2cm)

• ↑ unicellular/small multicellular organisms have:
  • low metabolic demands
  • large surface area relative to body mass

• complexity increases with organism size
  • linked with complex cardiovascular system

• complex organisms use:
  • diffusion of gases
  • bulk flow (gases flow through fluid like blood)

aquatic organisms

• oxygen doesn't dissolve well in water

• aquatic organisms use specialized respiratory system (gills) to compensate
  • large surface area
  • localized system - completely dependent on them for their survival

• gills characteristics:
  • thin, translucent membranes
  • have protective flap/coverings
  • water flow maintained by swimming or buccal muscles
  • countercurrent flow (water and blood flow in opposite directions)
  • ↑ maintains small but constant gradient for gas exchange

• some fish developed air breathing by evolutionary processes

amphibians

• transitional characteristics for air and water breathing

• use lungs, gills, and or skin exchange

• breathing process:
  • air in through buccal (oral ) cavity
  • mouth closes
  • air out when buccal cavity contracts

• slow breathing pace (low metabolic rates)

• more terrestrial species have more developed lungs

reptiles

• evolved suction pumps for air intake

• separate muscles for eating and breathing

• breathing cycles:
  • inspiratory (ribs out, decreasing pressure)
  • expiratory (ribs in, increasing pressure)

• muscle variability among species

birds

• increased metabolic rate = higher gas exchange requirements

• stiff lungs (volume doesn't change)

• use air sacs for pressure changes

• constant opposite flow of air and blood in lungs
  • counterflow = continuous gas exchange
  • maximum efficiency at high altitudes

• avian hemoglobin = high oxygen affinity

mammalian organisms

• lungs have greater surface area
  • numerous air-filled alveoli
  • dense capillary network

  

• upper and lower respiratory tract

  • upper tract:
    • humidifies, warms, moistens air

  • lower tract:
    • all gas exchange occurs here

• structures for air flow pressure gradient:
  • diaphragm
  • intercostal muscles
  • abdominal muscles

• lung sits within pleural sac reduces friction and aids lung inflation

upper respiratory tract

1. nasal cavities

2. oral cavity

3. pharynx

4. larynx

   
   

   

   
   

   1) nasal cavities

   • key features:

     • ciliated epithelium with mucous-producing goblet cells

     • extensive mucous membrane surface

   • main functions:

     • warm and humidify air

     • clean air by trapping particles (hairs, mucus, and cilia)

     • sense of smell

     
     

     2. oral cavity

   • key features:

     • large diameter

     • low-resistance passage

   • main functions:

     • important during exercise or nasal obstruction

     • limited warming, humidifying, or cleaning of air

       
       

       3. pharynx

   • key features:

     • muscular tube

   • main functions:

     • transports air, food, and water

     • roles in cough reflex and vocalization

       
       

       4. larynx

   • key features:

     • muscular tube with cartilage

     • complex structure

   • main functions:

     • keeps airway open

     • prevents food from entering airway

     • produces voice

lower respiratory tract

conduction zone:
• large structures up to respiratory bronchioles
• cartilage rings provide support, preventing collapse during exhalation
• smooth muscle in bronchioles controls airway resistance
• functions: delivering, bulk flow, air conditioning

• has goblet cells producing mucous - which move towards pharynx for swallowing.

respiratory zone:
• terminal bronchioles and alveoli
• site of gas exchange

• includes respiratory bronchioles + alveoli

• gas exchange maximized by:

  • large SA

  • thin walls

  • no cartilage

  • no goblet cells

  • little to no cilia

blood transport of gases

• the solubility of oxygen in dilute solutions is low

• PO₂ formation helps to keep the o2 concentration in blood low to maintain the oxygen diffusion gradient

• metalloproteins ( proteins with metal ions?) act as GASEOUS oxygen binding proteins

  • hemoglobin

  • hemocyanin

  • hemerythrin

    hemoglobin is the binding protein in vertebrates

    • red color when o2 binds

    • contained within RBCs.

summary of homeostasis in respiratory system

• blood gas homeostasis (o2, co2) is achieved by respiratory and/or cardiovascular changes

  • CO2, O2 are regulated variables

  • blood oxygen and co2 detected by chemoreceptors

  • cardiovascular + respiratory control centers in the medulla = control centers ( are often connected)

  • changes in the airway diameter are controlled through other mechanisms ( autonomic control of bronchiles and essential (intrinsic ) mechanisms)

RESPIRATORY SYSTEM 2 ( lecture 14)

introduction to gases and flow

• air is a mixture of gases

  • 78% nitrogen

  • 21% oxygen

  • 0.033% carbon dioxide

    - the partial pressure of that gas = the % of that gas in air composition

• water vapor is also present in the air, diluting it

  • water vapor is dependent on humidity

  • air inside your lungs is more humid than the air outside of your lungs

  
  

diffuses of gasses across respiratory membranes

there are essentially two types of flow

• gas exchange depends on a respiratory membrane

• diffusion rate is :

  proportional to the following:

  • SA

  • diffusion coefficient

  • the strength of the partial pressure gradient

    
    

    
    

  • inversely proportional to:

  • to the membrane thickness

what is the diffusion coefficient?

• it is property of a gas that depends on:

  • solubility ( the more soluble the gas is, the quicker it diffuses - it has a high coefficient )

  • molecular weight ( the smaller the gas is, the quicker it diffuses - it has a high coefficient)

recall that in order for a gas to pass into a cell it has to go through a liquid first.

• co2 has a higher diffusion coefficient than 02 in water, despite it having a higher molecular weight.

  

partial pressure gradient

• the partial pressure - the pressure exerted by an individual gas in a mixture

• partial pressure gradient is the only factor impacting diffusion rate that changes physiological conditions in the short term

• gas flows from high pp to low pp between two areas

  • larger pp gradient = higher flow

  • to get the partial pressure when given the conc, times the conc by 760 mm Hg

  • conc x mmHg = pp

    

summary of what determines the respiratory gas diffusion rate?

bulk flow of gases in the airways

special properties of gas flow in the airways