4.3 Gas exchange in mammals

Question 1

What are three features an organism must have to maximise gas exchange ?

Answer 1

• A large SA:V ratio compared to the small SA:V ratio of an organism as a whole
• Thin, permeable membranes for short diffusion distance and allow free passage of substances
• Maintaining a steep concentration gradient

Question 2

Where are the two lungs found in the human body?

Answer 2

Thorax/chest cavity

Question 3

What do hairs in the nasal cavity do and what else does it do?

Answer 3

Trap dust particles and other pathogens, warms and moistens the air before it enters the lungs

Question 4

What are three adaptations of the Trachea

Answer 4

• Walls of trachea contain cartilage which prevents the walls of the cartilage to collapse when we inhale
• Absence of a full ring of cartilage around the trachea allows food to pass down easily in the oesophogus
• Trachea walls are covered with ciliated epethelial cells and goblet cells.

Question 5

What do goblet cells do?

Answer 5

They secrete mucus which traps dust and pathogens

Question 6

What do ciliated epithelial cells do?

Answer 6

The cillia on the cell membrane beat to move the mucus up the throat, mucus then swallowed and dust particles and pathogens are digested by digestive enzymes in the stomach

Question 7

What do the bronchi split into to?

Answer 7

Bronchioles

Question 8

What do bronchioles do when their smooth muscle relaxes?

Answer 8

They widen allowing more air into the lungs

Question 9

What do the bronchioles lead to ?

Answer 9

Alveoli

Question 10

How are the alveoli adapted to maximise gas exchange ?

Answer 10

• Hundreds of millions of alveoli therefore providing a large SA:V ratio
• The wall of the alveoli and the surrounding capillaries are only one cell thick which allows for short diffusion distance
• Once blood is oxygenated, the blood is rapidly carried away from the alveoli via the capillaries ensuring a steep conc gradient, co2 is continuously brought to the alveoli in the bloodstream

Question 11

Why dont the alveoli collapse ?

Answer 11

The alveoli is coated with a special phospholipid called lung surfactant which makes breathing easier

Question 12

What are insects covered with which makes it difficult for gas exchange to occur

Answer 12

Exoskeleton made up of chitin

Question 13

What are the small openings called on the surface of the exoskeleton ? (abdomen area)

Answer 13

• Spiracles

Question 14

What are the spiracles controlled by ?

Answer 14

Sphincters

Question 15

When are the sphincters open and when are they closed ?

Answer 15

OPEN - When the insect needs oxygen
CLOSED - When it doesn’t need oxygen

Question 16

Why is it important the sphincters stay closed when it doesnt need oxygen

Answer 16

To prevent water loss

Question 17

What to the spiracles lead to?

Answer 17

The trachea, which extend down and along the insects body and they are 1mm thick.

Question 18

What are the trachae supported by to keep them open ?

Answer 18

Chitin spirals which hold the trachea open

Question 19

What since next to no gas exchange can occur in the trachea, what do they branch off into?

Answer 19

Tracheoles

Question 20

What is the difference between trachea and tracheoles

Answer 20

Tracheoles contain no chitin rings and are permeable to gases because of this.

Question 21

How is there a short diffusion distance in gas exchange of insects ?

Answer 21

Very short distance between the tracheoles and the cells of the insect

Question 22

How is there a large surface area for gas exchange in insects ?

Answer 22

• There a large amount of tracheoles which provide a large SA:V ratio

Question 23

What is the link between high levels of activity in a insect and tracheol fluid

Answer 23

• When insects do high levels of activity, the cells respire anaerobically and produce lactic acid
• This lowers the water potential of the cells which causes the tracheol fluid to move into the cells.
• This means that more air can move into the tracheoles and there more of the tracheoles are available for gas exchange

Question 24

Where are the gills kept on a fish

Answer 24

In the gill cavity covered by a bony flap called the operculum