exchange surfaces exam questions

Question 1

Describe the features of the lungs that make them effective organs for the exchange of gases. (5)

Answer 1

many alveoli to produce large surface area;
thin barrier- only two cells thick;
good blood supply-many capillaries;
to carry dissolved gases to and from the alveoli;
ventilation to refresh the air in the alveoli;
*elastic tissue to stretch and recoil to help expel air;

Question 2

Explain why the volume of air in the spirometer drops slowly over the first minute

Answer 2

oxygen is used in respiration;
carbon dioxide is released ( in respiration);
carbon dioxide is absorbed (by soda lime);

Question 3

Features of alveolous

Answer 3

large surface area to volume (ratio)
thinwall/short diffusion distance
squamous epithelium;
permeable;
Capillaries close to alveolous
*elastic tissue/recoil (after expansion);
surfactant;

Question 4

Function of cartilage

Answer 4

-prevents collapse and supports
-during inhalation, volume of thorax increase
-negative pressure

Question 5

Function of elastic fibres

Answer 5

Stretch during inhalation
Increases lung volume
recoils during exhalation for a more complete expulsion

Question 6

Why do mammals have large no. of alveoli?

Answer 6

generally larger
smaller SA:V
alveoli, gives increased area for gas exchang);
need for more oxygen due to, high metabolic activity
much respiration/more energy need;
high demand for carbon dioxide removal

Question 7

Describe the mechanism by which oxygen gets from alveolar space to the red blood cells.

Answer 7

Oxygen conc. is higher in lungs
diffusion down concentration gradient;
dissolves in the water film
crosses alveolar wall/endothelium

Question 8

Explain why bronchioles fill with mucus during asthma attack

Answer 8

Histamine secreted
mucus is not moved
more goblet cells produce more mucus
fewer cilia

Question 9

Explain why cross sectional area of air spaces in bronchioles decreases during asthma attack

Answer 9

thicker smooth muscle;
muscle contracts;
connective tissue, swells / enlarges
lining of bronchiole thrown into deeper folds

Question 10

Describe how spirometer would be used to measure tidal volume

Answer 10

-not breathe through nose
-breathes evenly
-measure height of waves
-measure 3 waves -> mean

Question 11

How does ventilation maintain steep diffusion gradient?

Answer 11

-increases po2 in air sac
-conc. of o2 is higher than in the blood
-decreases pCO2 in air sac
-conc of co2 is lower than in blood

Question 12

How is steep conc gradient maintained in lungs (other than ventilation)?

Answer 12

-continuous blood flow in capillaries
-brings more Co2 and takes away more O2
-O2 combines with Hb
-keep conc of O2 in blood low

Question 13

Why is it not possible to expel all air from the lungs?

Answer 13

-thorax cant be compressed completely
-trachea held open by cartilage
-bronchiole/alveoli held open by elastic fibres