Fill in the blanks
1. The tiny holes in the lungs are called __________, also known as __________.
2. The air sacs are surrounded by very tiny blood vessels called __________.
3. Both the air sac walls and capillary walls are made of a __________ layer of __________.
4. The process where oxygen and carbon dioxide move between the air sacs and blood is called
__________.
5. Blood arriving at the lungs from the body has __________ oxygen and __________ carbon
dioxide.
6. Oxygen moves from the air sacs into the blood because there is more oxygen in the
__________ than in the __________.
7. In the red blood cells, oxygen combines with a substance called __________.
8. Carbon dioxide moves from the __________ into the __________ during gas exchange.
Circle the correct answer
1. Another name for an air sac is:
a) capillary
b) alveolus
c) artery
2. The air sac walls are:
a) thick
b) made of two layers
c) one cell thick
3. Diffusion happens when:
a) gases move from high to low concentration
b) blood is pumped
c) muscles contract
4. The blood that arrives at the lungs has:
a) lots of oxygen
b) no carbon dioxide
c) little oxygen and a lot of carbon dioxide
5. Oxygen from the air enters the:
a) stomach
b) blood
c) lungs
6. Capillaries are:
a) thick blood vessels
alveoli
b) found in the heart
7. Oxygen combines with:
a) platelets
b) white blood cells
c) tiny blood vessels around the
c) haemoglobin
Short Answer Questions
1. What are air sacs also called?
2. What surrounds the air sacs in the lungs?
3. How many layers of cells make up the wall of an air sac?
4. What is the function of the capillaries around the alveoli?
5. What happens to oxygen inside the alveoli?
6. What happens to carbon dioxide in the blood at the alveoli?
7. What is the name of the process by which gases move between the air sacs and the blood?
8. Why does oxygen move from the air sac into the blood?
9. What happens to oxygen once it enters the blood?
10. Why does carbon dioxide leave the blood and enter the air sac?