Transcript day 3 gas exchange

Gas Exchange
Gills
Alveoli
Why do we need a
respiratory system?
 Need O2 (IN)

for cellular respiration

to make ATP
food
CO2
O2
 Need CO2 (OUT)

waste product from cellular respiration
ATP
What’s needed for gas exchange?


need high surface area

maximize gas exchange

gases move across by diffusion
need moist membrane

maintains cell membrane structure

gases only diffuse in water
Gas exchange
has many forms
one-celled
insects
amphibians
fish
echinoderms
mammals
Gills: Countercurrent
 Water carrying gas flows
in one direction,
blood flows in opposite
direction


maintains diffusion gradient
over whole length of gill
capillary
maximizing O2 transfer from
water to blood
Tracheal System
 air tubes branching throughout
body
 gas exchanged by diffusion
across moist cells lining terminal
ends, not through open
circulatory system
Gas Exchange
in Humans
 Concentration gradient & pressure drives movement of gases
into & out of blood at both lungs & body tissue
 both oxygen and carbon dioxide diffuse from an area of high
concentration to an area of lower concentration
 (see fig 11.9 page 452)
capillaries in lungs
capillaries in muscle
O2
O2
O2
O2
CO2
CO2
CO2
CO2
blood
lungs
blood
body
How Blood Transports Gases
- Both O2 and CO2 are transport by
blood.
- About 99% of O2 is carried by
hemoglobin (protein in red blood cells)
- About 23% of CO2 is carried by
hemoglobin 77% is carried by blood
fluid
- When CO2 reaches the lungs, it
diffuses into the air in the alveoli
see figure 11.10 (page 453)