Human gas exchange

Question 1

Ventilation

Answer 1

(breathing) air drawn into & out of lungs
- involves diaphragm
- antagonistic interaction between external & internal intercostal muscles

Question 2

Inspiration?

Answer 2

• external intercostal muscles contract & internal relax, pulls ribs upwards & outwards (rise)
• diaphragm contracts (to become flatter & pushes organs down)
• vol of chest cavity/lungs increases
• pressure in chest cavity/lungs drops below atm. pressure
• air containing O2 is sucked thru mouth, air moves into lungs (down pressure gradient)

Question 3

Expiration?

Answer 3

• external intercostal muscles relax & internal contract, pulls ribs downwards & inwards (fall)
• diaphragm relaxes (pushed back up by displaced organs underneath)
• vol of chest cavity/lungs decreases
• pressure in chest cavity/lungs rises above atm. pressure
• air moves out of lungs (down pressure gradient), air forced out thru mouth removing waste CO2

Question 4

Main Adaptations of alveolar epithelium?

Answer 4

• gas exchange happens between epithelium & blood
  1. millions of alveoli in each lung - creates very large SA for exchange
  2. alveoli epithelium cells r very thin - minimise diffusion distance
  3. each alveolus surrounded by network of capillaries to remove exchanged gases so - maintains conc. gradient

Question 5

Extra adaptations of alveolar epithelium?

Answer 5

• capillary walls r also thin asw ( 1 cell thick)
• moist surfaces for gases to dissolve b4 diffuse
• lungs r constantly ventilated - also maintains conc. gradient
• capillaries r so narrow so - RBCs squashed against capillary wall - slows flow of blood so - time for diffusion to occur

Question 6

Pulmonary ventilation rate?

Answer 6

= tidal vol x breathing rate
- tidal vol (vol of air normally taken in at each breath when body at rest)
- aka the total vol of air moved into lugs during 1 min (dm^3min^-1)

Question 7

Pulmonary surfactant - maintaining structure of alveoli?

Answer 7

*when air press inside lungs drop - tendency for lungs to collapse - cartilage keeps trachea & bronchi open but - alveoli lack structural support…

• a phospholipid that coats surfaces of lungs
• has low surface tension
• w/o it - watery lining of alveoli would create surface tension - would cause them to collapse

Question 8

Lung structure?

Answer 8

• tissue is elastic - lungs recoil & regain OG shape when not actively expanded - recoil plays major part in pushing air out of lungs
• surrounding each lung & lining thorax - pleural membranes
• between: pleural cavity which contains pleural fluid
• fluid acts acts as lubricant - allows friction free movement against inner wall of thorax during ventilation

Question 9

Spirometer trace & Respiratory volumes?

Answer 9

• tidal vol - vol of air at rest
• vital capacity - max vol of air can inhale/exhale
• residual vol - vol of air left in lungs after strongest exhalation
• total lung capacity - viral capacity + residual capacity

Question 10

always state for correlation graphs - evaluate?

Answer 10

correlation doesn’t prove causation - other factors e.g. genetics/pollution could cause deaths
others:
- no correlation coefficient statistic to know if correlation is significant
- data overlaps