adaptations of the alveoli

Question 1

how is the surface area of the alveoli adapted

Answer 1

-their surface area is enormous (around 70m2)
-area for movement of gases is sufficiently large enough for gas exchange

Question 1

what are the features of an alveoli that make them efficient for gas exchange

Answer 1

-large surface area
-permeable barrier (most lining)
-thin barrier
-good blood supply

Question 2

what 3 ways does moist lining help the alveoli

Answer 2

(1) provides surfactant coat
(2) carbon dioxide and oxygen can dissolve in the small moist lining
(3) stops the alveolus from drying and cracking

Question 3

what is the role of the surfactant coat of the alveoli and how is it produced

Answer 3

-produced by lungs
-reduces cohesion forces between water molecules which could make alveoli collapse

Question 4

how does the moist lining stop the alveoli from drying and cracking

Answer 4

-provides a lubricant on the inside of the epithelial lining

Question 5

how does the alveoli have a thin barrier

Answer 5

(1) Alveolar wall is one cell thick
(2) Capillary wall is one cell thick
(3) Capillaries are close in contact with the alveolus wall
(4) Capillaries are very narrow so RBC can only move down in single file

Question 6

how are the alveolar wall and capillary wall only one cell thick

Answer 6

-both made from squamous cells which are flattened and very thin

Question 7

why is the capillaries being narrow an advantage to the alveoli

Answer 7

-RBC can only move in single file
-RBC squeezed against walls
-puts them closer to air in alveoli
-slows down their rate of flow (more time for gases to diffuse)

Question 8

How does a good blood supply provide an advantage to the alveoli

Answer 8

-constant supply of blood from capillaries maintains a steep conc grad
-blood transporting O2 away from lungs has a lower concentration in blood than alveoli
-Conc transporting CO2 to the lungs has a higher conc in blood than alveoli