Outline - 4, BIO 3360, Respiration IV - Water Breathing Animals
I. Respiration in Water Breathing Animals
A. Issues to overcome
1. Water has lower oxygen content than air
2. More ventilation is needed to provide the same amount of oxygen
3. Water is higher density and higher viscosity than air
4. More energy required to move water than air
5. Diffusion rate of oxygen is slower in water than air.
B. Integumentary exchange - thin skin, large surface area, convection
C. External gills - protected or unprotected
D. Internal gills - within body contour
1. Ventilation - unidirectional - not tidal; In through mouth or spiracle and out across gills
E. Gas transport - involves gases moving from high to low pressure, gill perfusion, gill diffusion, circulation, tissue diffusion
1. Gill filaments are covered with gill lamellae to increase surface area
2. Countercurrent mechanism
water and blood move in parallel tubes in the opposite direction ensuring concentration gradient