Exchange surfaces and Breathing

Question 1

Why is there a need for exchange surfaces?

Answer 1

• Diffusion alone can not meet the oxygen demands of a multicellular organism
• So we need lots of exchange of O2 and CO2

Question 2

What are the features of an effective exchange system?

Answer 2

• Increased SA:V (more particles can diffuse at once)
• Thin layer ( reduces diffusion distance)
• Good blood supply (Maintaining a steep concentration gradient)
• Good ventilation (flow of water / air)

Question 3

What happens to air when it enters through the nasal cavity?

Answer 3

• Becomes warmer (close to body temp)
• Traps dust / bacteria via mucus
• increases humidity of the air

Question 4

What is the role of cartilage in the trachea?

Answer 4

• stops the trachea and bronchi from collapsing (provides structure to the trachea and bronchi)
• incomplete cartilage rings so that food can pass easily down the oesophagus

Question 5

What is the function of the ciliated epithelium?

Answer 5

• found in the trachea
• waft mucus produced by the goblet cells
• waft dirt/microorganisms away from the lungs
• most of it goes into the throat where it is swallowed

Question 6

What are the effects of cigarettes on the cillia?

Answer 6

-stop the beating of the cilia

Question 7

What is the function of the goblet cells?

Answer 7

• secrete mucus onto the lining of the trachea

- this is to trap dust and microorganisms

Question 8

What is the function of smooth muscle cells?

Answer 8

-to constrict the bronchioles

Question 9

What is the function of elastic fibres?

Answer 9

• allow the alveoli to stretch as air is drawn in
• also when recoiling help squeeze air out
• helps with the elastic recoil of the lungs

Question 10

Where can gaseous exchange happen?

Answer 10

• bronchioles & alveoli

- through flattened (pavement cells)

Question 11

Inspiration

Answer 11

• Diaphragm contracts and flattens
• External Intercostal muscles contract moving the ribcage up and out
• this increases the thoracic volume
• therefore decreasing thoracic pressure which is now lower than the external pressure
• This draws air in through the nasal cavity the trachea bronchi bronchioles and into the alveoli for gas exchange
• Until the difference in pressure is equal

Question 12

Expiration

Answer 12

• Diaphragm relaxes and moves up
• External intercostal muscles relax moving the ribcage down and in
• This decreases thoracic volume
• This increases thoracic pressure compared to the external pressure
• Air moves out of the lungs
• Until the difference in pressure is equal

Question 13

When do the internal intercostal muscles contract?

Answer 13

-During forced exhalation

Question 14

What is used to measure lung capacity?

Answer 14

• Spirometer (Need to know)

- Peak flow meter

Question 15

Tidal volume

Answer 15

-Volume of air that moves in and out of the lungs

Question 16

Vital capacity

Answer 16

-The volume of air that can be breathed in after the strongest possible exhalation

Question 17

Breathing rate

Answer 17

-number of breaths per minute

Question 18

ventilation rate

Answer 18

tidal volume * breathing rate

Question 19

Why is a nose clip used?

Answer 19

• to keep the volume of air breathed by the patient the same

Question 20

Why is there soda lime?

Answer 20

• to absorb the CO2 from the subject

Question 21

How does air enter insects?

Answer 21

-through spiracles in the thorax and the abdomen of insects

Question 22

Why does the spiracle need to be closed most of the time?

Answer 22

• when the insect is at rest to prevent water loss

- spiracles are controlled by sphincters

Question 23

What tube carries the air into the body?

Answer 23

-tracheae

Question 24

What makes the tracheae impermeable to gasses?

Answer 24

-chitin spirals

Question 25

What gives large surface area for gas exchange in insects?

Answer 25

-tracheoles

Question 26

Explain the gaseous exchange in insects

Answer 26

• air enters through spiracles
• Abdominal movement pushing oxygen through tracheae
• air goes through the tracheae into the tracheoles where gaseous exchange takes place
• O2 dissolves into the water lining the tracheoles
• tracheal fluid limits the penetration of gases
• When the insect is active it produces lactic acid due to anaerobic respiration
• This draws the tracheal fluid out of tracheoles
• increasing SA and more gas exchange

Question 27

Ventilation in bony fish: (how does water enter the buccal cavity?)

Answer 27

1. Mouth opens and buccal cavity expands (Lowered)
2. This increases Buccal Volume and decreases Buccal pressure
3. Water moves into the buccal cavity down a pressure gradient

Question 28

Ventilation in bony fish: (how does water travel from the buccal cavity to the opercular cavity?)

Answer 28

4. Floor of the buccal cavity moves up Opercular cavity expands (valves shut) (at the same time as the buccal cavity being moved up)
5. This increases the opercular volume and decreases opercular pressure while the pressure in the buccal cavity increases
6. Therefore Water moves from the buccal cavity to the opercular cavity OVER THE GILLS down a pressure gradient

Question 29

Ventilation in bony fish: (how does water leave the opercular cavity?)

Answer 29

7. Buccal cavity and opercular cavity both constrict
8. This decreases buccal and opercular volume increasing the pressure on both the buccal and opercular cavity
9. Water LEAVES the OPERCULAR cavity to outside down a pressure gradient

Question 30

Effective gas exchange in water

Answer 30

• tips of adjacent gill filaments overlap slowing water down

- Countercurrent exchange system

Question 31

Explain the countercurrent exchange system in fish

Answer 31

• blood in the gills and water flow in opposite directions
• This MAINTAINS a concentration gradient for oxygen to diffuse across
• so a Much higher oxygen saturation in the blood is achieved