Gas Exchange

Question 1

Describe and explain how the structure of alveoli is adapted for efficient gas exchange

Answer 1

• thin (alveolar) walls / one cell thick / thin epithelium / squamous epithelium
• short diffusion distance (between air and blood)
• elastic / elastic fibres
• stretch to increase SA / recoil to expel air
• surrounded by capillaries
• ref. to maintain diffusion / concentration gradient; of carbon dioxide and oxygen
• blood maintains concentration gradient
• large surface area for diffusion
• some cells secrete surfactant
• prevent collapse

Question 2

Explain the role of elastic fibres on the alveoli

Answer 2

• stretch / expand / lengthen on inspiration, recoil / shorten on expiration - R: contract/relax
• (stretch) to increase surface area/volume of air for diffusion/gas exchange
• (recoil) to (help) expel air / force air out
• prevent alveoli busting / breaking - R: collapsing

Question 3

Lungs

Answer 3

• site of gaseous exchange

• large surface area

• in the thoracic (chest) cavity

• surrounded by an airtight space between the pleural membranes

• the space contains a small amount of fluid to allow friction-free movement of the lunch expanding during ventilation (due to movement of the ribs and diaphragm)

Question 4

Small bronchioles

Answer 4

• contain no cartilage

• surrounded by smooth muscle - contract or relax to adjust diameter of airways

• during exercise smooth muscler relaxes - greater flow of air to alveoli

• can occur due to abserse of cartilage

Question 5

Cartilage in trachea and bronchi

Answer 5

• keeps airways open

• keeps air resistance low

• prevents trachea collapsing/bursting as air pressure charges during breathing

• in trachea - regular arrangements of C shaped rings of cartilage

• in bronchi - irregular blocks/plates of cartilage

Question 6

Order of air flow

Answer 6

Trachea, bronchi, bronchioles - in order to inflate lungs

Question 7

warming the air

Answer 7

• air that flows into trachea:

• warmed by body temperature

• moistened by evaporation from lining

Question 8

Protection needed against…

Answer 8

Unwanted particles
Eg. Bacteria, fungi, dust, pollen, said, viruses

Question 9

Unwanted particles are a treat to…

Answer 9

Proper functioning of the lungs

Question 10

Particles caught…

Answer 10

• larger than 5-10 um

• on hairs inside nose and mucus lining the nasal passages and airways