2.2 Adaptations for gas exchange MAMMALS(+humans)

Question 1

What is the respiratory surface in mammals?

Answer 1

Internal lungs - offer protection and help prevent dessication

Question 2

how are lungs adapted for gas exchange

Answer 2

Millions of alveoli provide large surface area
Surfactant provides moist lining within alveoli so gases dissolve before diffusion

Walls of alveoli and surrounding capillaries one cell thick providing short diffusion pathway

Ventilation mechanism and circulatory system maintains concentration gradient at the respiratory surface

Question 3

Describe the process of inspiration in humans

Answer 3

-Diaphragm contracts and flattens
-The external intercostal muscles contract pulling the ribs up and out
-The outer pleural membrane, pulling out ribs

-The pressure in the pleural space decreases

-The inner pleural membrane, attached to the alveoli, moves out
-The alveoli expand, increasing their volume and reducing pressure inside below atmospheric pressure
-Air is sucked into the lungs

Question 4

What prevents the alveoli from collapsing during expiration?

Answer 4

Surfactant coating the inside, which reduces surface tension

Question 5

What term describes the type of breathing used by humans?

Answer 5

Negative pressure breathing
An increase in volume reduces the pressure within the lungs to below atmospheric pressure, sucking air in