Breathing System

• Parts of the system (lungs and ribs):

  intercostal muscles

  brochiole

  bronchus

  alveoli

  diaphragm

  heart

  cartilage rings

  trachea

  lungs
• Ventilation:

  Air high in oxygen is continually entering the alveoli

  Air low is continually removed
• Pathway of oxygen entering alveoli…

  diffuses through alveolar epithelium

  through capillary epithelium

  into the blood
• Intercostal Muscles:

  -antagonistic muscle pair

  -includes internal and external muscles
• Breathing In:

  diaphragm flattens

  lungs move up and out

  downward pressure gradient

  low pressure in lungs
• Breathing Out:

  diaphragm curves

  upward pressure gradient

  high pressure in lungs
• tidal volume = volume of air taken in at each breath
• ventilation rate = 60 seconds/ timer for one breath
• pulmonary ventilation = tidal volume x ventilation rate
• Tidal Volume:

  breathing in and out at rest
• Spirometer Tracing:

  measures volume of air in and out of the lungs
• Alveolus-

  thin layer of flattened cells for a short diffusion distance

  epithelial cells are squamous (squashed)

  blood entering contains a low concentration of oxygen, and a high concentration of carbon dioxide

  blood leaving contains a high concentration of oxygen, and a low concentration of carbon dioxide

  elastic tissue recalls to expel air
• What do alveoli provide?

  large s.a. for gas exchange
• what does oxygen always diffuse?

  across

  through the phospholipid bilayer
• Features that increase diffusion in lungs....

  large s.a.:volume ratio

  a thin surface so short diffusion pathway

  a diffusion gradient
• to shorten diffusion distance...

  flattened alveolar epithelium cells

  blood capillaries close to alveolar epithelium

  capillary endothelium is one cell thick
• to increase s.a: volume ratio...

  alveolar epithelium wall folded

  many alveoli and capillaries (branched)
• to maintain diffusion gradient...

  circulation comes away blood with high concentration of oxygen, replaces with low concentration

  lung ventilation brings in air with high oxygen concentration
• what happens during inspiration?

  thoracic cavity expands

  external intercostal muscles contract

  diaphragm contracts then flattens

  rib cage lifts up and out

  volume of thoracic increases

  pressure decreases

  air moves down pressure gradient into lungs
• what happens during expiration?

  external intercostal muscles relax (internal contract)

  ribcage drops down and in

  diaphragm relaxes and lifts up

  volume of thorax decreases, pressure increases

  air moves down pressure gradient, out of lungs