Across
- 3. Thin layer of cells lining the alveoli
- 6. Basic unit of life; red ones carry oxygen
- 9. Type of fibres in alveoli walls that allow them to stretch and recoil
- 10. Movement of molecules from high to low concentration
- 13. Protein in red blood cells that binds oxygen
- 14. Gas needed by cells for respiration, absorbed in alveoli
- 16. Tiny air sacs in the lungs where gas exchange takes place
- 17. Organs that contain millions of alveoli
Down
- 1. Tiny blood vessels surrounding alveoli for gas diffusion
- 2. Steep concentration difference that drives diffusion
- 4. Thin barrier through which gases diffuse
- 5. Fluid that carries gases, nutrients, and waste
- 7. Process where oxygen enters blood and carbon dioxide leaves
- 8. Breathing movements that refresh air in the lungs
- 11. Color of blood cells that transport oxygen
- 12. Structures in alveoli walls that help prevent bursting
- 15. Oxygen and carbon dioxide are examples of this