Gas Exchange in Alveoli

Question 1

Alveoli

Answer 1

• millions of microscopic air sacs where gas exchange occurs

- surrounded by a network of capillaries

Question 2

Walls made from

Answer 2

• singler layer of thin flat cells

- alveolar epithelium

Question 3

capillaries made from

Answer 3

-capillary endothelium

Question 4

alveoli walls contain

Answer 4

-protein called elastin

0helps alveoli return/recoil to normal shape after inhaling and exhaling

Question 5

Movement of O2 + CO2

Answer 5

• air moves down trachea, bronchi and bronchioles into the alveoli
• movement down pressure gradient
• oxygen then moves into blood where it can be transported around the body
• down diffusion gradient
• CO2 moves down its own diffusion gradient and pressure gradient in the opposite direction of oxygen and is breathed out

Question 6

Gas exchange in alveoli

Answer 6

• O2 diffuses out of the alveoli across alveolar epithelium and capillary endothelium into compound called haemoglobin into the blood
• CO2 diffuses into alveoli from blood

Question 7

Gradients

Answer 7

• pressure gradient = trachea - bronchi - bronchioles -alveoli
• diffusion gradient = alveolar epithelium - capillary endothelium - blood

Question 8

Factors affecting rate of diffusion

Answer 8

• thin exchange surface are so alveolar epithelium is only one cell thick so there’s a short diffusion pathway
• large surface area so millions of alveoli so large surface area for gas exchange
• steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries increases rate of diffusion as its constantly maintained by the flow of blood and ventilation