Which of the following are parts of the respiratory system?

(You may select more than one answer)

• mouth

• windpipe

• heart

• lungs

• blood

What is the percentage of the following gases in the air that we breathe in?

• 0.04 %

• water vapour and other gases

• 78 %

• nitrogen

• 21 %

• oxygen

• 0.96 %

• carbon dioxide

The air that we exhale still contains about _____ % of oxygen.

Gaseous exchange in a human takes place at the _____ _____ in the lungs.

Arrange the circulation in a human by ordering the following correctly.

• deoxygenated blood returns to the heart

• absorbed by blood

• blood travels to heart

• oxygen in air sacs

• heart pumps oxygenated blood

The air sacs are covered with numerous tiny blood vessels called ___________.

• arteries

• veins

• capillaries

• red blood cells

How are our air sacs adapted for gaseous exchange?

(You may select more than one answer)

• They are thick to absorb more oxygen.

• Their high numbers increase the surface area for gaseous exchange.

• They are surrounded with blood vessels to exchange oxygen and carbon dioxide.

• They trap dust and dirt so clean air enters the blood.

​ Which of the following are not transported in the tubes in plants?

(You may choose more than one answer)

• water

• mineral salts

• carbon dioxide

• oxygen

• food

_____________ leaves the blood at the lungs.

• Carbon dioxide only

• Carbon dioxide and water

• Oxygen

• Nitrogen

Our lungs expand when we inhale and contract when we exhale.

• True

• False