Chapter 42: Gas Exchange and Circulation
42.1 The Respiratory and Circulatory Systems
● Ventilation, the movement of air or water through a specialized gas exchange
organ, such as a lung or gill.
● Diffusion αt the respiratory surface, where 02 moves from 1e air or water into
the blood and C02 moves from 1e blood into 1e air or water, along their
concentration gradients.
● Circultion, the transport of dissolved 02 and C02 throughout the body-along with
nutrients, wastes, and other types of molecules-via the circulatory system.
● Diffusion in the tissues, where 02 moves from the blood into the tissues and C02
moves from the tissues into the blood, along their concentration gradients.
● Cellulαr respirαtion, the cell’s use of 02 and production of C02.
○ In tissues, where cellular respiration has led to low 02 levels and high C02
levels, gas exchange occurs between blood and cells.
42.2 Air and Water as Respiratory Media
● Partial pressure is the press of a particular gas in a mixture of gases.
42.3 Organs of Gas Exchange
● Fick’s law of diffusion, states that the rate of diffusion of a gas depends on five
parameters:
○ Solubility of the gas in the aqueous film lining the gas exchange surface
○ Temperature
○ Surface area available for diffusion
○ The difference in partial pressures of the gas across the gas exchange
surface
○ The thickness of the gas-exchange surface
● A tube known as the trachea (not to be confused with the tracheae of insects)
carries the inhaled air to narrower tubes called bronchi.
● The bronchi branch off into yet narrower tubes，the bronchioles.
● Lungs are internal organs that are used for gas exchange.
● The lungs of mammals, in contrast, are finely divided into tiny sacs called alveoli.
● One mechanism for pumping air is positive pressure ventilation, used by frogs
and some other amphibians.
42.1 The Respiratory and Circulatory Systems
● Ventilation, the movement of air or water through a specialized gas exchange
organ, such as a lung or gill.
● Diffusion αt the respiratory surface, where 02 moves from 1e air or water into
the blood and C02 moves from 1e blood into 1e air or water, along their
concentration gradients.
● Circultion, the transport of dissolved 02 and C02 throughout the body-along with
nutrients, wastes, and other types of molecules-via the circulatory system.
● Diffusion in the tissues, where 02 moves from the blood into the tissues and C02
moves from the tissues into the blood, along their concentration gradients.
● Cellulαr respirαtion, the cell’s use of 02 and production of C02.
○ In tissues, where cellular respiration has led to low 02 levels and high C02
levels, gas exchange occurs between blood and cells.
42.2 Air and Water as Respiratory Media
● Partial pressure is the press of a particular gas in a mixture of gases.
42.3 Organs of Gas Exchange
● Fick’s law of diffusion, states that the rate of diffusion of a gas depends on five
parameters:
○ Solubility of the gas in the aqueous film lining the gas exchange surface
○ Temperature
○ Surface area available for diffusion
○ The difference in partial pressures of the gas across the gas exchange
surface
○ The thickness of the gas-exchange surface
● A tube known as the trachea (not to be confused with the tracheae of insects)
carries the inhaled air to narrower tubes called bronchi.
● The bronchi branch off into yet narrower tubes，the bronchioles.
● Lungs are internal organs that are used for gas exchange.
● The lungs of mammals, in contrast, are finely divided into tiny sacs called alveoli.
● One mechanism for pumping air is positive pressure ventilation, used by frogs
and some other amphibians.
