Explore how alveoli, ventilation and blood flow maintain oxygen and carbon-dioxide gradients for continuous gas exchange in IB Biology HL B3.1.1.
Adult humans may absorb more than five hundred litres of oxygen per day. Explain how gas exchange is maintained in the human respiratory system.
a. ventilation/inhaling brings fresh air/air with high oxygen concentration to the lungs OR ventilation/exhaling gets rid of stale air/air with high concentration of carbon dioxide
b. ventilation due to muscle contractions causing pressure/volume changes in the thorax
c. contraction of external intercostal muscles AND diaphragm occurs during inspiration OR contraction of internal intercostal muscles/abdomen wall muscles during «forced» expiration
d. alveoli surrounded by «many» capillaries
e. blood flow/pumping of heart «brings blood to/takes blood away from alveoli/lungs»
f. concentration gradients «of oxygen/ CO2 » maintained «by ventilation/blood flow»
g. O2 AND CO2 diffuse
h. CO2 from capillaries/blood/vessel to alveolus/air AND O2 from alveoli into capillaries/blood/vessel
i. large numbers of alveoli increase surface area
j. short distance so rapid diffusion/gas exchange
k. type I pneumocytes/alveolus wall/capillary walls are one cell thick/very thin
I. alveoli «lining» moist for dissolving of gases/rapid diffusion OR
type II pneumocytes keep the «lining of» the alveolus moist
m. type II pneumocytes secrete surfactant to reduce surface tension/prevents alveoli from collapsing