unit 3, Human Gas Exchange

Question 1

what is the definition of gas exchange?

Answer 1

diffusion of oxygen from the air in the alveoli into the blood and the diffusion of carbon dioxide from the blood into the alveoli.

Question 2

what is the trachea and what structural adaptaions does it have?

Answer 2

wind pipe, it has cartilage rings that are tough to support and keep the trachea open

Question 3

what does the antagonistic interaction between the internal and external intercostal muscled do?

Answer 3

-contraction of the external intercostal muscle leeds to inspiration
-contraction of the internal intercostal muscle leeds to expiration

Question 4

during inspiration what does the following structures do?
-external intercostal muscle
-internal intercostal muscle
-diaphragm
-air pressure in lungs
-lung volume
-how air moves

Answer 4

-contracts, pulling the ribs up and out
-relax
-contracts downwards from dome position into a flatter position
-initally lower than atmosphere, increases slowly
-increases, to decrease the pressure
-air moves into lungs as there is a higher pressure in the atmosphere compared to the lung

Question 5

during expiration what does the following structures do?
-external intercostal muscle
-internal intercostal muscle
-diaphragm
-air pressure in lungs
-lung volume
-how air moves

Answer 5

-relax
-contracts, pulls ribs inwards and downwards
-relaxes and goes to dome positioon
-initially greater than atmosphere, drops slowly
-decrease, to increase pressure
-air moves out of lungs as there is a higher pressure in lungs compared to the atmosphere

Question 6

what happens in the alveoli for gas exchange?

Answer 6

02 diffuses into the capillary to make the deoxygenated blood oxygenated blood, whilst the c02 diffuses in to the alveoli.

Question 7

what is the structure of the alveoli?

Answer 7

• the alveoli is a tiny air sac
  -it is surrounded by a capillary, that has a layer around it calleed the epithelium
  -has a layer called the epithelium around it

Question 8

what are the adaptaions of the alveolar epithelium?

Answer 8

-tiny air sacs, there is 300 million in a lung, so very large surface area for gas exchange
-epithelium cell is thin, so there is a short diffusion pathway
-alveoli is surrounded by a capillary to remove echanged gases, to maintain a concentration gradient

Question 9

explain how changes to the lung tissue reduce efficiency of gas exhange

Answer 9

1)Alveolar walls thicken;
2)Longer diffusion pathway;
3)Scarred / fibrous tissue;
4)Reduces surface area (for gaseous exchange);

Question 10

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are not required. [4]

Answer 10

1. Trachea and bronchi and bronchioles;
2. Down pressure gradient;
3. Down diffusion gradient;
4. Across alveolar epithelium;
   Capillary wall neutral
5. Across capillary endothelium / epithelium;