BIO202H5 Lecture Notes - Lecture 1: Countercurrent Exchange, Gill, Buccal Pumping
Document Summary
Ficks law- when an organism has a large surface area than volume- it implies that there is a short path length from external environment to internal cells, meaning that diffusion will solve the purpose. Greater volume relative to surface area requires specialized tissue to aid in acquiring oxygen. Ventilation is the gas exchange with the environment and perfusion is gas delivery within the body: animals use oxygen from the environment surrounding them and release carbon dioxide. This increases the concentration of oxygen in their body in comparison to the concentration of oxygen in the environment. Hence, the concentration gradient increases and diffusion is maximized: ventilation increases p1 due to the gas exchange past the respiratory surface, whereas, perfusion decreases p2 due to the movement of body fluids (blood) Concurrent exchange is when water flows in opposite direction of the blood flow, maximizing the concentration gradient (p1-p2: oxygen from the water diffuses into the blood raising its oxygen content.
