8.2 Breathing and Gas Exchange

Which of the following happens during inhalation?

• Intercostal muscles contract

• Diaphragm relaxes

• Rib cage moves up and out

• Volume of the chest increases

Answer explanation

When the diaphragm relaxes, it becomes dome-shaped

Which adaptation increases the surface area for gas exchange at the alveoli?

• There are lots of tiny alveoli

• The walls of the alveoli are one cell thick

• The alveoli have a good blood supply

• Oxygen-rich air is breathed in and carbon dioxide-rich air is breathed out

What causes air to move out of the respiratory system when a person exhales?

• Increased pressure in the chest

• Increased volume in the chest

• The upward and outward movement of the rib cage

• Contraction of the diaphragm

Answer explanation

High pressure in the chest forces the air to move out

Why are the walls of the capillaries and alveoli one cell thick?

• To increase the surface area for gas exchange

• To decrease the distance travelled by the gases

• To maintain a concentration gradient between the capillary and the alveolus

Which statement is correct about inhalation?

• Decreased volume in the chest leads to increased pressure

• Increased volume in the chest leads to decreased pressure

• Decreased volume in the chest leads to decreased pressure

• Increased volume in the chest leads to increased pressure

A person inflates a balloon by exhaling into it. How will the air in the balloon differ from the atmospheric air?

• It will contain more oxygen

• It will contain less carbon dioxide

• It will contain less oxygen

• It will contain the same amount of nitrogen

During inhalation...

• Pressure in the chest increases

• Volume in the chest increases

• Muscles are contracted

• Rib cage moves down and in

Which statement explains the difference in oxygen concentration between inhaled air and exhaled air?

• Oxygen diffuses into the blood stream

• Oxygen diffuses out of the blood stream

• Inhaled air contains more oxygen

• Exhaled air contains less oxygen

How does the respiratory system maintain a concentration gradient between the alveolus and the capillary?

• Breathing in oxygen-rich air and breathing out oxygen-poor air

• Walls of the capillary and alveolus are one cell thick

• Numerous, tiny alveoli

• Continuous movement of blood

Which of these is in the right order to explain exhalation?

• Muscles relax -> volume decreases -> pressure increases

• volume increases -> muscles relax -> pressure increases

• Pressure increases -> volume decreases -> muscles relax

• muscles relax -> pressure increases -> volume decreases

Answer explanation

Muscles create volume changes which affect the pressure of the gases