Gas Exchange Flashcards
Be able to explain how the structure of the alveoli is adapted to its function
– 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
Be able to explain how the structure of the type I and type II pneumocytes is adapted to its function
– 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)
• Note: these cells can divide and make both type I and type II pneumocytes if needed
Inspiration
a. Diaphragm muscles contract (flatten downwards) and external (on outside) intercostal muscles contract (pull ribs up and out)
b. 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
a. 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)
b. Thoracic cavity volume and lung volume decrease (pressure of air in lungs rises above atmospheric pressure – air rushes out to equalize)
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.
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)
• A ventilation system allows continuous cycling of the air in the lungs with the air in the atmosphere to maintain concentration gradients between the alveoli and the capillaries for gas exchange
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)
Be able to explain the causes and consequences of emphysema.
Emphysema is a chronic/progressive disease where the walls of the alveoli are damaged (feeling of shortness of breath) - a form of COPD (chronic obstructive pulmonary disease)
– 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
Be able to explain the causes and consequences of lung cancer.
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
– 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
Be able to explain the effects of increased exercise on ventilation rate (and tidal volume)
Exercise increases metabolism (cell resp.) and decreases blood pH (more CO2), which ↑demand for oxygen; this causes ↑ventilation rate (more breaths per minute), and/ or ↑ tidal volume (amount of air exchanged with each breath)
Be able to explain how to use a spirometer to measure ventilation rate.
Spirometer (measures volume of gas expelled per breath) - Note: changes in
volume are shown as increasing (breathing in) or decreasing (breathing out)
over time on a graph and each breath is one “wave” (shows tidal volume)
