Gas Exchange

Question 1

Be able to explain how the structure of the ventilation system is adapted to its function (including the structure of alveoli and type I and type II pneumocytes).

Answer 1

Trachea - Tube that allows air to travel into and out of the lungs to and from the atmosphere
Lungs - Take in fresh air (oxygen) from atmosphere and get rid of carbon dioxide from blood
Bronchi - Tubes (right and left) that carry air into lungs (from trachea) and out of lungs
Bronchioles - Smaller tubes that carry air to and from the alveoli (from the bronchi) - ↑SA
Alveoli - Clusters of air sacs (↑SA) at ends of bronchioles - Gas exchange with the blood (O2 and CO2)
Thin walls – surrounded by a single layer of epithelial cells (minimizes diffusion distance)
- capillary walls only one cell thick too
Rich capillary network surrounding each alveolus
– maintains high concentration gradient (O2/ CO2) between lungs and blood for diffusion
Increased SA:V ratio – small, spherical shape increases surface area while decreasing volume
Moist – cells lining each alveolus secrete fluids to allow gases to dissolve (dissolved oxygen diffuses easier into blood) and prevent alveoli from collapsing on themselves/ sticking together
Pneumocytes
Type I: squamous (flattened) and extremely thin to minimize diffusion distance and increase surface area for gas exchange
Note: these cells are amitotic(do not divide)
Type II: cuboidal with granules (store components to make surfactant); function is to secrete pulmonary surfactant - a liquid substance that reduces surface tension (ensuring all alveoli expand at the same rate and none of them collapse in on themselves due to unequal pressure)

Question 2

Be able to explain the antagonistic roles of the internal and external intercostal muscles, as well as the diaphragm and abdominal muscles in the processes of inspiration and expiration (and be able to explain the volume and pressure changes/ negative pressure mechanism caused by these muscles in the process of ventilation).

Answer 2

Inspiration
Diaphragm muscles contract (flatten downwards) and external (on outside) intercostal muscles contract (pull ribs up and out) Thoracic cavity volume and lung volume increase (pressure of air in lungs drops below atmospheric pressure – air rushes in through mouth or nasal passage to equalize)

Expiration
Diaphragm muscles relax (curves upward), abdominal wall muscles contract (pushing diaphragm up), external intercostal muscles relax (ribs fall), and internal (on inside) intercostal muscles contract (pulling ribs back down) Thoracic cavity volume and lung volume decrease (pressure of air in lungs rises above atmospheric pressure – air rushes out to equalize)

Question 3

Be able to explain the process of gas exchange in the alveoli of the lungs and the role of the ventilation system in maintaining concentration gradients of CO2 and O2 between the alveoli and the capillaries surrounding them.

Answer 3

Because gas exchange is a passive process (diffusion),
the lungs function to continually cycle fresh air into the alveoli (high O2 in alveoli allows diffusion of O2 into the blood and low CO2 in alveoli allows diffusion of CO2 out of blood and into alveoli). Ventilation system maintains a high concentration of O2 AND a low concentration of CO2 in the alveoli in the lungs
Ensures that O2 diffuses from the lungs through the alveoli walls INTO the blood (capillaries) and CO2 diffuses OUT of the blood (capillaries) through the alveoli walls and into the lungs (most cell respiration is aerobic – requires O2 and produces CO2)

Question 4

Be able to explain the causes and consequences of emphysema and lung cancer.

Answer 4

Emphysema is a chronic/progressive disease where the walls of the alveoli are damaged
- Consequences: Healthy alveoli turn into large, irregularly shaped structures with gaping holes, ↓ elasticity (so ↑ total lung volume at rest) ↓ SA, ↓O2 can reach the bloodstream
- Causes: tobacco/marijuana/fumes/coal dust/air pollution
Lung Cancer is a cancerous growth (uncontrolled cell division) within the lungs.
- Malignant cancer cells can take over healthy tissues of the bronchioles & alveoli – then eventually spread (metastasize) to the brain/bones/liver/adrenal gland
- Consequences: Lung tissues become dysfunctional can lead to internal bleeding, coughing up blood, wheezing, respiratory distress and weight loss
- Causes: carcinogens (smoking, asbestos)/air pollution/ certain infections/genetic predispositions

Question 5

Be able to define: ventilation, ventilation rate, tidal volume, cardiac cycle, cancer, inspiration, expiration, pneumocytes, gas exchange, respiration, cellular respiration, atrium, ventricle, artery, vein, pulmonary circulation, systemic circulation, myogenic, systole, diastole, atherosclerosis, occlusion, coronary heart disease

Question 6

Be able to explain the effects of increased exercise on ventilation rate (and tidal volume)

Question 7

Be able to explain how to use a spirometer to measure ventilation rate.

Question 8

Be able to use spirometer data to calculate ventilation rate and tidal volume and make conclusions using that data.