Unit 4- Gas Exchage In Humans

Question 1

What 3 features do organisms larger than 100 micrometers need to survive?

Answer 1

1) to be multicellular, where small cells can exchange materials quickly
2) a mass transport system, which uses energy to pump nutrient solutions quickly around large bodies, eg blood system
3) a specialised exchange system with a large surface area, eg gills, lungs

Question 2

What is Ficks law?

Answer 2

Rate of diffusion is directly proportional to (surface area x conc. gradient) divided by diffusion distance

Question 3

What does Ficks law tell us about what is needed to support a fast rate of diffusion?

Answer 3

• a large surface area
• a short diffusion distance/pathway
• a mechanism to maintain a high conc. gradient across the surface

Question 4

What is epithelial tissue?

Answer 4

The layer of cells covering all the external and internal surfaces of the body, and is also the site of exchange

Question 5

Give 3 examples of adapted epithelial cells:

Answer 5

• squamous epithelial, surrounding the alveoli and is very flat
• endothelium, lining the capillaries, also very flat
• columnar epithelium, lines the alimentary canal, cells have thick micro villi
• ciliates epithelium, lines the trachea and bronchi, secrete mucus for lubrication
• epidermis, lines outside layer of skin, is tough and impermeable

Question 6

What is the layer that surrounds the lungs called?

Answer 6

Pleural membrane

Question 7

Where does gas exchange occur?

Answer 7

The alveoli

Question 8

How is the human adapted for gas exchange?

Answer 8

• millions of alveoli provide a huge surface area
• walls of alveoli are composed of single flat squamous cell, so gas diffusion pathway is very short (squamous and capillary cell)
• high conc, gradient is maintained by blood flow and ventilation

Question 9

What also occurs in the alveoli but causes problems?

Answer 9

Water loss from the blood plasma, as it diffuses into the alveoli

Question 10

Why does the movement of water into the alveoli from the blood plasma cause problems?

Answer 10

Alveoli may collapse due tot he water surface tension, reducing surface area for gas exchange

Question 11

How does the body reduce the risk of water collapsing alveoli?

Answer 11

Epithelial cells secrete a soapy surfactant that reduces water surface tension, so it doesn’t collapse the alveoli

Question 12

What do epithelial cells in the bronchi do and what use is this??

Answer 12

• secrete mucus
• traps bacteria, which is swept to the throat by ciliates epithelial cells and then swallowed and the bacteria are killed by the acid

Question 13

What is ventilation?

Answer 13

• the movement of air over the gas exchange surfaces

Question 14

What is the pleural membrane attached to?

Answer 14

• outside, thorax

- inside, the lungs

Question 15

Why is the pleural fluid incompressible? And where is it found?

Answer 15

• so if the thorax moves the lungs also move in the same way

- in between the membranes in the pleural cavity

Question 16

Describe the process of inspiration:

Answer 16

• diaphragm contacts and flattens, the external intercostal muscles contract pulling rib cage out
• thorax volume increases, increasing volume of lungs and alveoli
• pressure in thorax decreases below atmospheric pressure
• air flows in from a high pressure to a low pressure

Question 17

Describe the process of expiration:

Answer 17

• The diaphragm relaxes curving up, and external intercostal muscle relax, rib cage falls
• decrease in thorax volume and also lung and alveoli so they shrink by elastic recoil
• pressure increases in alveoli above atmospheric pressure
• air flows out from a high pressure to a low pressure

Question 18

Describe what happen in expiration during exercise:

Answer 18

• abs contract pushing diaphragm upwards
• internal intercostal muscles contract pulling ribs down
• larger and faster expiration rate

Question 19

What is pulmonary ventilation:

Answer 19

The volume of air ventilating the air each minute

Question 20

What is the equation for the pulmonary ventilation?

Answer 20

Ventilation rate x tidal volume

Question 21

What is the equation for the ventilation rate?

Answer 21

Ventilation rate = 60/ (cycle time/s)

Question 22

What is the tidal volume?

Answer 22

The volume of air breathed in each individual breath

Question 23

Why is the Pulmonary ventilation increased during exercise?

Answer 23

• oxygen can diffuse from air to the blood faster

- CO2 can diffuse out the blood faster

Question 24

Differences between ventilation and gas exchange:

Answer 24

Gas exchange:
- uses diffusion, passive, slow
Ventilation:
- uses mass flow, requires ATP (muscle contraction), quick