BISC 101 Lecture Notes - Lecture 17: Countercurrent Exchange, Gas Exchange, Intercostal Muscle

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 101
• Professor: Tony Williams

Document Summary

Air filled tubes (tracheae) branch throughout body + air sacs. Smallest (tracheoles) reach individual cells (fluid filled tips) Rely on diffusion (small insects) or pumping movements of body. Openings of trachea (spiracles) regulate air flow and water loss. Respiratory system branches repeatedly from largest airway (trachea) to smallest (bronchioles-no gas exchange here) Bronchioles terminate in divided alveoli (site of gas exchange-diffusion) Ventilation occurs by changing the volume and pressure of chest cavity. Exhalation: diaphragm and muscles relax (air out) Homeostatic control of breathing: active muscle tissue uses o2 (po2 decreases) and produces co2 (pco2 increases)-regulation relies on changes in pco2 and ph. Partial pressure gradients of o2 and co2 drive diffusion of gases at different points in the circulatory system. Carbon dioxide has high solubility in blood (200ml co2/liter blood) = 20 times higher than o2; so co2 transport relatively easy.